WorldWideScience

Sample records for extreme flash floods

  1. Extreme flash floods in Barcelona County

    Directory of Open Access Journals (Sweden)

    A. Barrera

    2005-01-01

    Full Text Available In this paper the catastrophic and extraordinary floods occurring in Barcelona County (Catalonia, NE Spain are studied, in order to characterise the temporal evolution of extreme flash floods in that area and their main features. These events usually cause economical losses and major problems for undertaking daily activity in Barcelona city. This kind of floods is a very common feature in the North-east of Spain and they are recorded every year in some point of Catalonia. This contribution also shows the frequency of those events, within the framework of all the floods that have occurred in Barcelona since the 14th century, but also describes the flooded area, urban evolution, impacts and the weather conditions for any of most severe events. The evolution of flood occurrence shows the existence of oscillations in the earlier and later modern age periods that can be attributed to climatic variability, evolution of the perception threshold and changes in vulnerability. A great increase of vulnerability can be assumed for the period 1850-1900. The analysis of the time evolution for the Barcelona rainfall series (1854-2000 shows that no trend exists, although, due to the changes in urban planning, flash-floods impact has changed over this time. The number of catastrophic flash floods has diminished, although the extraordinary ones have increased.

  2. Assessment of Vulnerability to Extreme Flash Floods in Design Storms

    Directory of Open Access Journals (Sweden)

    Hyun Il Choi

    2011-07-01

    Full Text Available There has been an increase in the occurrence of sudden local flooding of great volume and short duration caused by heavy or excessive rainfall intensity over a small area, which presents the greatest potential danger threat to the natural environment, human life, public health and property, etc. Such flash floods have rapid runoff and debris flow that rises quickly with little or no advance warning to prevent flood damage. This study develops a flash flood index through the average of the same scale relative severity factors quantifying characteristics of hydrographs generated from a rainfall-runoff model for the long-term observed rainfall data in a small ungauged study basin, and presents regression equations between rainfall characteristics and the flash flood index. The aim of this study is to develop flash flood index-duration-frequency relation curves by combining the rainfall intensity-duration-frequency relation and the flash flood index from probability rainfall data in order to evaluate vulnerability to extreme flash floods in design storms. This study is an initial effort to quantify the flash flood severity of design storms for both existing and planned flood control facilities to cope with residual flood risks due to extreme flash floods that have ocurred frequently in recent years.

  3. Assessment of vulnerability to extreme flash floods in design storms.

    Science.gov (United States)

    Kim, Eung Seok; Choi, Hyun Il

    2011-07-01

    There has been an increase in the occurrence of sudden local flooding of great volume and short duration caused by heavy or excessive rainfall intensity over a small area, which presents the greatest potential danger threat to the natural environment, human life, public health and property, etc. Such flash floods have rapid runoff and debris flow that rises quickly with little or no advance warning to prevent flood damage. This study develops a flash flood index through the average of the same scale relative severity factors quantifying characteristics of hydrographs generated from a rainfall-runoff model for the long-term observed rainfall data in a small ungauged study basin, and presents regression equations between rainfall characteristics and the flash flood index. The aim of this study is to develop flash flood index-duration-frequency relation curves by combining the rainfall intensity-duration-frequency relation and the flash flood index from probability rainfall data in order to evaluate vulnerability to extreme flash floods in design storms. This study is an initial effort to quantify the flash flood severity of design storms for both existing and planned flood control facilities to cope with residual flood risks due to extreme flash floods that have ocurred frequently in recent years.

  4. A European precipitation index for extreme rain‐storm and flash flood early warning

    National Research Council Canada - National Science Library

    Alfieri, L; Thielen, J

    2015-01-01

    .... Despite recent notable advances in weather forecasting, most operational early warning systems for extreme rainstorms and flash floods are still based on rainfall measurements from rain gauges...

  5. Floods and Flash Flooding

    Science.gov (United States)

    Floods and flash flooding Now is the time to determine your area’s flood risk. If you are not sure whether you ... If you are in a floodplain, consider buying flood insurance. Do not drive around barricades. If your ...

  6. A European precipitation index for extreme rain-storm and flash flood early warning

    OpenAIRE

    ALFIERI LORENZO; THIELEN DEL POZO Jutta

    2012-01-01

    Extreme rain-storms are known for triggering devastating flash floods in various regions of Europe and particularly along the Mediterranean coasts. Despite recent notable advances in weather forecasting, most operational early warning systems for extreme rainstorms and flash floods are based on rainfall estimation, rather than on forecasts. As a result, warning lead times are bounded to few hours and warnings are usually issued when the event is already taking place. This work proposes a n...

  7. Climate change impact assessment of extreme precipitation on urban flash floods – case study, Aarhus, Denmark

    DEFF Research Database (Denmark)

    Madsen, Henrik; Sunyer Pinya, Maria Antonia; Rosbjerg, Dan

    Climate change is expected to cause more intense extreme rainfall events, which will have a severe impact on the risk of flash floods in urban areas. An assessment study was performed for the city of Aarhus, Denmark, analysing different methods of statistical downscaling of climate model projecti......Climate change is expected to cause more intense extreme rainfall events, which will have a severe impact on the risk of flash floods in urban areas. An assessment study was performed for the city of Aarhus, Denmark, analysing different methods of statistical downscaling of climate model...... considered. Urban flooding in Aarhus was simulated with a model that dynamically couples a hydraulic model of the drainage system and a 2D overland flow model. Scenarios representing current and future climate including uncertainties in the climate projections were analysed using synthetic design storms...

  8. Processes and Geomorphological Impacts of an Extreme Flash Flood Event in SE Spain

    Science.gov (United States)

    Hooke, J.

    2015-12-01

    A major flash flood event took place on 28 September, 2012 in SE Spain, resulting in 10 fatalities and much damage to infrastructure regionally. The flood affected long-term monitoring sites in two catchments in which morphological changes and flow dynamics of these ephemeral channels were being measured. Thus detailed data on channel state prior to the flood were available. The flood event in the Nogalte catchment was extreme in its peak flow, rate of rise and unit runoff. The catchment has steep relief and much bare soil under almond groves, resulting in high sediment supply. The channel is confined in places, but mostly wide and braided, composed of loose gravel and occupying much of the valley floor. Flow was spatially continuous, with high connectivity throughout the catchment. The flood effects were net depositional in the monitored sites, with massive sedimentation on the channel bars. Vegetation was destroyed. Bank erosion and destruction of embankments took place in some locations. Hydraulic calculations indicate very high velocities, stream power and Froude numbers. Modelling and field evidence demonstrate extremely high sediment competence and sediment loadings. The influence of the event dynamics on processes and net outcomes is discussed. The impacts are compared with other events in this and neighbouring catchments. Overall, the event in the Nogalte did not alter the morphology markedly in spite of its extreme characteristics. It is suggested that these valley floors are adapted to this type of flash flood but that flows of such force and magnitude need to be allowed for in management in such an environment.

  9. Geomorphological factors of flash floods

    Science.gov (United States)

    Kuznetsova, Yulia

    2016-04-01

    Growing anthropogenic load, rise of extreme meteorological events frequency and total precipitation depth often lead to increasing danger of catastrophic fluvial processes worldwide. Flash floods are one of the most dangerous and less understood types of them. Difficulties of their study are mainly related to short duration of single events, remoteness and hard access to origin areas. Most detailed researches of flash floods focus on hydrological parameters of the flow itself and its meteorological factors. At the same time, importance of the basin geological and geomorphological structure for flash floods generation and the role they play in global sediment redistribution is yet poorly understood. However, understanding and quantitative assessment of these features is a real basis for a complete concept of factors, characteristics and dynamics of flash floods. This work is a review of published data on flash floods, and focuses on the geomorphological factors of the phenomenon. We consider both individual roles and interactions between different geomorphological features (the whole basin parameters, characteristics of the single slopes and valley bottom). Special attention is paid to critical values of certain factors. This approach also highlights the gaps or less studied factors of flash floods. Finally, all data is organized into a complex diagram that may be used for flash floods modeling. This also may help to reach a new level of flash flood predictions and risk assessment.

  10. Towards a detailed knowledge about Mediterranean flash floods and extreme floods in the catchments of Spain, France and Italy

    Science.gov (United States)

    Duband, D.

    2009-09-01

    It is important to remember that scientific research programs of the European Commission and contributors had implemented a multidisciplinary (geography, history, meteorology, climatology, hydrology, geomorphology, geology, paleohydrology, sociology, economy......) better knowledge and more understanding of the physical risk assessment of disastrous floods (particularly flash floods) with rising factors of vulnerability and perhaps climate change at the end of the XX1 century, in the triangular geographical area Zaragosa (Spain)-Orléans (France)-Firenze (Italy). With reference to historical floods events observed from last two centuries in Spain (Catalonia), France (Languedoc Roussillon - Provence Alpes Cote d’Azur-Corse-Rhone Alpes -Auvergne- Bourgogne) and in Italy (Ligurie - Piemont - Lombardie) we lay particular stress on a detailed understanding of the spatial and temporal scales of the physical dynamic process being at the origin of locals or extensive flash floods. This study requires to be based on the meteorology (atmospheric circulation patterns ,on west Europe- Atlantic and Mediterranean sea) responsible, with relief and sea surface temperature, of high precipitations (amounts, intensities), air temperature, discharges of high floods, observed in the past ,on large and coastal rivers. We will take example of the Rhone river catchments, in connexion with Po-Ebre-Loire-Seine rivers, based on the studies of thirty high historical floods occurred from 1840 to 2005, and characteristics of Oceanic and Mediterranean weather situations, sometime alternated. Since recent years we have the daily mean sea level pressure dataset (EMSLP) reconstructions for European-North Atlantic Region for the period 1850-2006. So it is now possible to allow us the selection in the complete meteorological dataset during 1950- 2009 period by an analog method (like operational daily applications from 1969, at Electricity of France) to select weather situations similar to

  11. Characteristics of the extreme rainfall event and consequent flash floods in W Slovenia in September 2007

    Directory of Open Access Journals (Sweden)

    S. Rusjan

    2009-06-01

    Full Text Available During a weather front that passed over large parts of Slovenia on 18.9.2007, extreme rainfall events were triggered causing several severe flash floods with six casualties. Out of 210 municipalities in Slovenia, 60 were reporting flood damages, and the total economic flood damage was later estimated at close to 200 million Euro; highest damage was claimed by Železniki municipality in NW Slovenia. The main purpose of the study presented in this paper was to put together available meteorological and hydrological data in order to get better insight into temporal and spatial dynamics and variability of the flash flood event along the Selška Sora River flowing through the town of Železniki. The weather forecast by the Environmental Agency of the Republic of Slovenia (ARSO lead to early warning of floodings but has underestimated rainfall amounts by a factor of 2. Also meteorological radar underestimated ground rainfall as much as by 50%. During that day, in many rainfall gauging stations operated by ARSO in the area under investigation, extreme rainfall amounts were measured, e.g. 303 mm in 24 h or 157 mm in 2 h. Some of the measured rainfall amounts were the highest registered amounts in Slovenia so far. Statistical analysis using Gumble distribution was performed and rainfall return periods were estimated. When assessing rainfall return periods, a question of the sampling error as a consequence of short rainfall records used was raised. Furthermore, measured rainfall data were used to reconstruct hydrographs on selected water stations along the Selška Sora River. The cumulative areal precipitation for the Selška Sora River catchment upstream of Železniki amounted to 219 mm, while the modeled effective precipitation used to simulate the hydrograph peak was only 57 mm. The modeled direct runoff coefficient therefore amounts to 0.26. Surprisingly low value is mainly caused by the applied unit hydrograph method that seeks to meet the peak

  12. Estimation of extreme flash flood evolution in Barcelona County from 1351 to 2005

    Directory of Open Access Journals (Sweden)

    A. Barrera

    2006-01-01

    Full Text Available Every year, flash floods cause economic losses and major problems for undertaking daily activity in the Catalonia region (NE Spain. Sometimes catastrophic damage and casualties occur. When a long term analysis of floods is undertaken, a question arises regarding the changing role of the vulnerability and the hazard in risk evolution. This paper sets out to give some information to deal with this question, on the basis of analysis of all the floods that have occurred in Barcelona county (Catalonia since the 14th century, as well as the flooded area, urban evolution, impacts and the weather conditions for any of most severe events. With this objective, the identification and classification of historical floods, and characterisation of flash-floods among these, have been undertaken. Besides this, the main meteorological factors associated with recent flash floods in this city and neighbouring regions are well-known. On the other hand, the identification of rainfall trends that could explain the historical evolution of flood hazard occurrence in this city has been analysed. Finally, identification of the influence of urban development on the vulnerability to floods has been carried out. Barcelona city has been selected thanks to its long continuous data series (daily rainfall data series, since 1854; one of the longest rainfall rate series of Europe, since 1921 and for the accurate historical archive information that is available (since the Roman Empire for the urban evolution. The evolution of flood occurrence shows the existence of oscillations in the earlier and later modern-age periods that can be attributed to climatic variability, evolution of the perception threshold and changes in vulnerability. A great increase of vulnerability can be assumed for the period 1850–1900. The analysis of the time evolution for the Barcelona rainfall series (1854–2000 shows that no trend exists, although, due to changes in urban planning, flash-floods impact

  13. The 20 February 2010 Madeira flash-floods: synoptic analysis and extreme rainfall assessment

    Directory of Open Access Journals (Sweden)

    M. Fragoso

    2012-03-01

    Full Text Available This study aims to characterise the rainfall exceptionality and the meteorological context of the 20 February 2010 flash-floods in Madeira (Portugal. Daily and hourly precipitation records from the available rain-gauge station networks are evaluated in order to reconstitute the temporal evolution of the rainstorm, as its geographic incidence, contributing to understand the flash-flood dynamics and the type and spatial distribution of the associated impacts. The exceptionality of the rainstorm is further confirmed by the return period associated with the daily precipitation registered at the two long-term record stations, with 146.9 mm observed in the city of Funchal and 333.8 mm on the mountain top, corresponding to an estimated return period of approximately 290 yr and 90 yr, respectively. Furthermore, the synoptic associated situation responsible for the flash-floods is analysed using different sources of information, e.g., weather charts, reanalysis data, Meteosat images and radiosounding data, with the focus on two main issues: (1 the dynamical conditions that promoted such anomalous humidity availability over the Madeira region on 20 February 2010 and (2 the uplift mechanism that induced deep convection activity.

  14. Impact of agricultural management on pluvial flash floods - Case study of an extreme event observed in Austria in 2016

    Science.gov (United States)

    Lumassegger, Simon; Achleitner, Stefan; Kohl, Bernhard

    2017-04-01

    Central Europe was affected by extreme flash floods in summer 2016 triggered by short, high-intensity storm cells. Besides fluvial runoff, local pluvial floods appear to increase recently. In frame of the research project SAFFER-CC (sensitivity assessment of critical condition for local flash floods - evaluating the recurrence under climate change) surface runoff and pluvial flooding is assessed using a coupled hydrological/2D hydrodynamic model for the severely affected municipality of Schwertberg, Upper Austria. In this small catchment several flooding events occurred in the last years, where the most severe event occurred during summer 2016. Several areas could only be reached after the flood wave subsided with observed flood marks up to one meter. The modeled catchment is intensively cultivated with maize, sugar beets, winter wheat and soy on the hillside and hence highly vulnerable to water erosion. The average inclination is relatively steep with 15 % leading to high flow velocities of surface runoff associated with large amounts of transported sediments. To assess the influence of land use and soil conservation on flash floods, field experiments with a portable irrigation spray installation were carried out at different locations. The test plots were subjected to rainfall with constant intensity of 100 mm/h for one hour. Consecutively a super intense, one hour lasting, rainfall hydrograph was applied after 30 minutes at the same plots, ranging from 50 mm/h to 200 mm/h. Surface runoff was collected and measured in a tank and water samples were taken to determine the suspended material load. Large differences of runoff coefficients were determined depending on the agricultural management. The largest discharge was measured in a maize field, where surface runoff occurred immediately after start of irrigation. The determined runoff coefficients ranged from 0.22 for soy up to 0.65 for maize for the same soil type and inclination. The conclusion that runoff is

  15. Atmospheric Rivers, Floods, and Flash Floods in California

    Science.gov (United States)

    Skelly, Klint T.

    Atmospheric Rivers (ARs) are long (>2000 km), narrow (<1000 km) corridors of enhanced vertically integrated water vapor (IWV) and enhanced IWV transport (IVT). The landfall of ARs along the U.S. West Coast have been linked to extreme precipitation and flooding/flash flooding in regions of complex topography. The objective of this study is to investigate the relationship between a 10 water-year (2005-2014) climatology of floods, flash floods, and landfalling ARs. The ARs in this study are defined using IVT following the Rutz et al. (2013) methodology, whereas floods and flash floods are identified by the National Centers for Environmental Information (NCEI) Storm Events Database. The results of this study indicate that landfalling ARs are present on a majority of days that there are floods in northern California. Landfalling ARs are predominantly present on a majority of days that there are flash flood reports during the cold-season (November-March); however, the North American monsoon is present on days that there are flash flood reports during the warm-season (April-October). Two exemplary case studies are provided to illustrate the hydrologic impact of landfalling ARs. The first case study illustrated a flood event that occurred in associated with three landfalling ARs that produced 800 mm in regions over the Russian River watershed in northern California and the second case study illustrated a flash flood event that occurred in association with a landfalling AR that produced ˜225 mm of precipitation in regions over the Santa Ynez xii watershed in which produced a flash flood over the southern portions of Santa Barbara County in southern California.

  16. Using an extended 2D hydrodynamic model for evaluating damage risk caused by extreme rain events: Flash-Flood-Risk-Map (FFRM) Upper Austria

    Science.gov (United States)

    Humer, Günter; Reithofer, Andreas

    2016-04-01

    Using an extended 2D hydrodynamic model for evaluating damage risk caused by extreme rain events: Flash-Flood-Risk-Map (FFRM) Upper Austria Considering the increase in flash flood events causing massive damage during the last years in urban but also rural areas [1-4], the requirement for hydrodynamic calculation of flash flood prone areas and possible countermeasures has arisen to many municipalities and local governments. Besides the German based URBAS project [1], also the EU-funded FP7 research project "SWITCH-ON" [5] addresses the damage risk caused by flash floods in the sub-project "FFRM" (Flash Flood Risk Map Upper Austria) by calculating damage risk for buildings and vulnerable infrastructure like schools and hospitals caused by flash-flood driven inundation. While danger zones in riverine flooding are established as an integral part of spatial planning, flash floods caused by overland runoff from extreme rain events have been for long an underrated safety hazard not only for buildings and infrastructure, but man and animals as well. Based on the widespread 2D-model "hydro_as-2D", an extension was developed, which calculates the runoff formation from a spatially and temporally variable precipitation and determines two dimensionally the land surface area runoff and its concentration. The conception of the model is to preprocess the precipitation data and calculate the effective runoff-volume for a short time step of e.g. five minutes. This volume is applied to the nodes of the 2D-model and the calculation of the hydrodynamic model is started. At the end of each time step, the model run is stopped, the preprocessing step is repeated and the hydraulic model calculation is continued. In view of the later use for the whole of Upper Austria (12.000 km²) a model grid of 25x25 m² was established using digital elevation data. Model parameters could be estimated for the small catchment of river Ach, which was hit by an intense rain event with up to 109 mm per hour

  17. "Know What to Do If You Encounter a Flash Flood": Mental Models Analysis for Improving Flash Flood Risk Communication and Public Decision Making.

    Science.gov (United States)

    Lazrus, Heather; Morss, Rebecca E; Demuth, Julie L; Lazo, Jeffrey K; Bostrom, Ann

    2016-02-01

    Understanding how people view flash flood risks can help improve risk communication, ultimately improving outcomes. This article analyzes data from 26 mental models interviews about flash floods with members of the public in Boulder, Colorado, to understand their perspectives on flash flood risks and mitigation. The analysis includes a comparison between public and professional perspectives by referencing a companion mental models study of Boulder-area professionals. A mental models approach can help to diagnose what people already know about flash flood risks and responses, as well as any critical gaps in their knowledge that might be addressed through improved risk communication. A few public interviewees mentioned most of the key concepts discussed by professionals as important for flash flood warning decision making. However, most interviewees exhibited some incomplete understandings and misconceptions about aspects of flash flood development and exposure, effects, or mitigation that may lead to ineffective warning decisions when a flash flood threatens. These include important misunderstandings about the rapid evolution of flash floods, the speed of water in flash floods, the locations and times that pose the greatest flash flood risk in Boulder, the value of situational awareness and environmental cues, and the most appropriate responses when a flash flood threatens. The findings point to recommendations for ways to improve risk communication, over the long term and when an event threatens, to help people quickly recognize and understand threats, obtain needed information, and make informed decisions in complex, rapidly evolving extreme weather events such as flash floods.

  18. Machine Learning Predictions of Flash Floods

    Science.gov (United States)

    Clark, R. A., III; Flamig, Z.; Gourley, J. J.; Hong, Y.

    2016-12-01

    This study concerns the development, assessment, and use of machine learning (ML) algorithms to automatically generate predictions of flash floods around the world from numerical weather prediction (NWP) output. Using an archive of NWP outputs from the Global Forecast System (GFS) model and a historical archive of reports of flash floods across the U.S. and Europe, we developed a set of ML models that output forecasts of the probability of a flash flood given a certain set of atmospheric conditions. Using these ML models, real-time global flash flood predictions from NWP data have been generated in research mode since February 2016. These ML models provide information about which atmospheric variables are most important in the flash flood prediction process. The raw ML predictions can be calibrated against historical events to generate reliable flash flood probabilities. The automatic system was tested in a research-to-operations testbed enviroment with National Weather Service forecasters. The ML models are quite successful at incorporating large amounts of information in a computationally-efficient manner and and result in reasonably skillful predictions. The system is largely successful at identifying flash floods resulting from synoptically-forced events, but struggles with isolated flash floods that arise as a result of weather systems largely unresolvable by the coarse resolution of a global NWP system. The results from this collection of studies suggest that automatic probabilistic predictions of flash floods are a plausible way forward in operational forecasting, but that future research could focus upon applying these methods to finer-scale NWP guidance, to NWP ensembles, and to forecast lead times beyond 24 hours.

  19. Karst flash floods: an example from the Dinaric karst (Croatia

    Directory of Open Access Journals (Sweden)

    O. Bonacci

    2006-01-01

    Full Text Available Flash floods constitute one of the deadliest and costliest natural disasters worldwide. This paper explains the karst flash flood phenomenon, which represents a special kind of flash flood. As the majority of flash floods karst flash floods are caused by intensive short-term precipitation in an area whose surface rarely exceeds a few square kilometres. The characteristics of all flash floods are their short duration, small areal extent, high flood peaks and rapid flows, and heavy loss of life and property. Karst flash floods have specific characteristics due to special conditions for water circulation, which exist in karst terrains. During karst flash floods a sudden rise of groundwater levels occurs, which causes the appearance of numerous, unexpected, abundant and temporary karst springs. This paper presents in detail an example of a karst flash flood in the Marina bay (Dinaric karst region of Croatia, which occurred in December 2004.

  20. Flash Flooding - Ways That Science and Adaptation Reduce Losses

    Science.gov (United States)

    Gruntfest, E.

    2014-12-01

    Flash flood vulnerability is increasing. Predictability is more difficult as more flooding results after wildfires destroy hillside vegetation. Recent extreme events have occurred outside of seasonal norms with well beyond expected precipitation rates, and with unusual storm behavior where precipitation rates increase at the end of a storm. Engineers, social scientists, physical scientists, planners, emergency managers and others must collaborate in new ways to keep losses from rising. For example improved detection using cameras and gages must be complemented by understanding why people drive through flooded roads and what can be done to reduce the number of people on flooded roadways. Case studies of successful collaborations will be provided along with discussion of challenges and opportunities for expanding the innovative flash flood risk reduction strategies.

  1. Concepts and approaches to study disruption and change of everyday life during flash flood events.

    NARCIS (Netherlands)

    Jeuring, Jelmer

    2013-01-01

    Concepts and approaches to study disruption and change of everyday life during flash flood events. The dynamics of extreme precipitations and consequential flash-floods in Southern France lead to important variations in vulnerability of people and property across space and time. In turn, these event

  2. Mental models of flash floods and landslides.

    Science.gov (United States)

    Wagner, Klaus

    2007-06-01

    Perceptions of flash floods and landslides were analyzed in four communities of the Bavarian Alps using the mental model approach. Thirty-eight qualitative interviews, two telephone surveys with 600 respondents, and two onsite interviews (74/95 respondents) were conducted. Mental models concerning flash floods are much better developed than those for landslides because the key physical processes for flash floods are easier for the general public to recognize and understand. Mental models are influenced by the local conditions. People who have a better knowledge about the hazards are those who use many different sources to inform themselves, express fear about natural hazards, or have previous experience with hazards. Conclusions for how to improve information for the general public are discussed.

  3. RURAL FLASH-FLOOD BEHAVIOR IN GOUYAVE WATERSHED, GRENADA, CARIBBEAN ISLAND

    Directory of Open Access Journals (Sweden)

    Rahmat Aris Pratomo

    2016-10-01

    Full Text Available Flash-flood is considered as one of the most common natural disasters in Grenada, a tropical small state island in Caribbean Island. Grenada has several areas which are susceptible to flooding. One of them is Gouyave town which is located in the north-west of Grenada. Its land-use types are highly dominated by green areas, especially in the upper-part of the region. The built-up areas can only be found in the lower-part of Gouyave watershed, near the coastal area. However, there were many land conversions from natural land-use types into built-up areas in the upper-part region. They affected the decrease of water infiltration and the increase of potential run-off, making these areas susceptible to flash-flood. In addition, it is also influenced by the phenomenon of climate change. Changes in extreme temperature increase higher potential of hurricanes or wind-storm, directly related to the potential escalation of flash-flood. To develop effective mitigation strategies, understanding the behavior of flash-flood is required. The purpose of this paper was to observe the behavior of flash-flood in Gouyave watershed in various return periods using OpenLISEM software. It was used to develop and analyse the flash-flood characteristics. The result showed that the climatic condition (rainfall intensity and land-use are influential to the flash-flood event. Flash-flood occurs in 35 and 100 years return period. Flash-flood inundates Gouyave’s area in long duration, with below 1 m flood depth. The flood propagation time is slow. This condition is also influenced by the narrower and longer of Gouyave basin shape. To develop flash-flood reduction strategies, the overall understanding of flash-flood behavior is important. If the mitigation strategy is adapted to their behavior, the implementation will be more optimum.

  4. Flash flood hazard mapping: a pilot case study in Xiapu River Basin, China

    Directory of Open Access Journals (Sweden)

    Da-wei Zhang

    2015-07-01

    Full Text Available Flash flood hazard mapping is a supporting component of non-structural measures for flash flood prevention. Pilot case studies are necessary to develop more practicable methods for the technical support systems of flash flood hazard mapping. In this study, the headwater catchment of the Xiapu River Basin in central China was selected as a pilot study area for flash flood hazard mapping. A conceptual distributed hydrological model was developed for flood calculation based on the framework of the Xinanjiang model, which is widely used in humid and semi-humid regions in China. The developed model employs the geomorphological unit hydrograph method, which is extremely valuable when simulating the overland flow process in ungauged catchments, as compared with the original Xinanjiang model. The model was tested in the pilot study area, and the results agree with the measured data on the whole. After calibration and validation, the model is shown to be a useful tool for flash flood calculation. A practicable method for flash flood hazard mapping using the calculated peak discharge and digital elevation model data was presented, and three levels of flood hazards were classified. The resulting flash flood hazard maps indicate that the method successfully predicts the spatial distribution of flash flood hazards, and it can meet the current requirements in China.

  5. FLASH FLOODS IN THE ILIŞUA BASIN

    Directory of Open Access Journals (Sweden)

    G. HOGNOGI

    2011-03-01

    Full Text Available Flash Floods in the Ilişua Basin. The Ilişua Valley is a right tributary of the Someşu Mare Valley and has its spring in the south-western part of the Tibleş Mountains. It is a perennial river, and its maximum flow sometimes exceeds the national multi-anual average. One manifestation of this high flow is represented by two types of flash floods: the ones caused by heavy rainfall and the ones caused by the both heavy precipitation and the melting of snow. These two types of flash floods have specific characteristics not only in terms of causes but also in the happening, the impact area and the scale or proportions of damage. These features are further explained in the analysis of two flash floods that have taken place on May 12-17, 1970 and June 20-21, 2006. The occurence of these extreme hydrological phenomena in the basin and their impact upon nature, people and infrastructure makes the need of more hydrological survey a fact.

  6. Flash floods: forecasting and warning

    National Research Council Canada - National Science Library

    Sene, Kevin

    2013-01-01

    .... Floods of this type are often characterised by fast flowing deep water and a high debris content which - combined with the short lead time available for warnings - add to the risk to people and property...

  7. Flash flood modeling with the MARINE hydrological distributed model

    Directory of Open Access Journals (Sweden)

    V. Estupina-Borrell

    2006-11-01

    Full Text Available Flash floods are characterized by their violence and the rapidity of their occurrence. Because these events are rare and unpredictable, but also fast and intense, their anticipation with sufficient lead time for warning and broadcasting is a primary subject of research. Because of the heterogeneities of the rain and of the behavior of the surface, spatially distributed hydrological models can lead to a better understanding of the processes and so on they can contribute to a better forecasting of flash flood. Our main goal here is to develop an operational and robust methodology for flash flood forecasting. This methodology should provide relevant data (information about flood evolution on short time scales, and should be applicable even in locations where direct observations are sparse (e.g. absence of historical and modern rainfalls and streamflows in small mountainous watersheds. The flash flood forecast is obtained by the physically based, space-time distributed hydrological model "MARINE'' (Model of Anticipation of Runoff and INondations for Extreme events. This model is presented and tested in this paper for a real flash flood event. The model consists in two steps, or two components: the first component is a "basin'' flood module which generates flood runoff in the upstream part of the watershed, and the second component is the "stream network'' module, which propagates the flood in the main river and its subsidiaries. The basin flash flood generation model is a rainfall-runoff model that can integrate remotely sensed data. Surface hydraulics equations are solved with enough simplifying hypotheses to allow real time exploitation. The minimum data required by the model are: (i the Digital Elevation Model, used to calculate slopes that generate runoff, it can be issued from satellite imagery (SPOT or from French Geographical Institute (IGN; (ii the rainfall data from meteorological radar, observed or

  8. Looking for Similarities Between Lowland (Flash) Floods

    Science.gov (United States)

    Brauer, C.; Teuling, R.; Torfs, P.; Hobbelt, L.; Jansen, F.; Melsen, L.; Uijlenhoet, R.

    2012-12-01

    On 26 August 2010 the eastern part of The Netherlands and the bordering part of Germany were struck by a series of rainfall events. Over an area of 740 km2 more than 120 mm of rainfall were observed in 24 h. We investigated the unprecedented flash flood triggered by this exceptionally heavy rainfall event (return period > 1000 years) in the 6.5 km2 Hupsel Brook catchment, which has been the experimental watershed employed by Wageningen University since the 1960s. This study improved our understanding of the dynamics of such lowland flash floods (Brauer et al., 2011). These observations, however, only show how our experimental catchment behaved and the results cannot be extrapolated directly to different floods in other (neighboring) lowland catchments. Therefore, it is necessary to use the information collected in one well-monitored catchment in combination with data from other, less well monitored catchments to find common signatures which could describe the runoff response during a lowland flood as a function of catchment characteristics. Because of the large spatial extent of the rainfall event in August 2010, many brooks and rivers in the Netherlands and Germany flooded. With data from several catchments we investigated the influence of rainfall and catchment characteristics (such as slope, size and land use) on the reaction of discharge to rainfall. We also investigated the runoff response in these catchments during previous floods by analyzing the relation between storage and discharge and the recession curve. In addition to the flood in August 2010, two other floods occurred in The Netherlands in recently. The three floods occurred in different parts of the country, after different types of rainfall events and with different initial conditions. We selected several catchments during each flood to compare their response and find out if these cases are fundamentally different or that they were produced by the same underlying processes and can be treated in a

  9. Advances in flash flood monitoring using UAVs

    Science.gov (United States)

    Perks, Matthew; Russell, Andrew; Large, Andrew

    2016-04-01

    UAVs have the potential to capture information about the earth's surface in dangerous and previously inaccessible locations. Through image acquisition of flash flood events and subsequent object-based analysis, highly dynamic and oft-immeasurable hydraulic phenomenon may be quantified at previously unattainable spatial and temporal resolutions. The potential for this approach to provide valuable information about the hydraulic conditions present during dynamic, high-energy flash floods has until now not been explored. In this paper we adopt a novel approach, utilising the Kande-Lucas-Tomasi (KLT) algorithm to track features present on the water surface which are related to the free-surface velocity. Following the successful tracking of features, a method analogous to the vector correction method has enabled accurate geometric rectification of velocity vectors. Uncertainties associated with the rectification process induced by unsteady camera movements are subsequently explored. Geo-registration errors are relatively stable and occur as a result of persistent residual distortion effects following image correction. The apparent ground movement of immobile control points between measurement intervals ranges from 0.05 - 0.13m. The application of this approach to assess the hydraulic conditions present in Alyth Burn, Scotland during a 1:200 year flash flood resulted in the generation of an average 4.2 measurements/m2 at a rate of 508 measurements/s. Analysis of these vectors provide a rare insight into the complexity of channel-overbank interactions during flash floods. The uncertainty attached to the calculated velocities is relatively low with a spatial average across the area of ± 0.15m/s. Little difference is observed in the uncertainty attached to out-of-bank velocities (± 0.15m/s), and within-channel velocities (± 0.16m/s), illustrating the consistency of the approach.

  10. Modeling on Flash Flood Disaster Induced by Bed Load

    Institute of Scientific and Technical Information of China (English)

    CAO Shuyou; LIU Xingnian; HUANG Er; YANG Keiun

    2008-01-01

    Flash floods result from a complex interaction among hydro-meteorological, hydrologi-cal, and hydraulic processes across various spatial and temporal scales. Sichuan Province suffers flash floods frequently owing to mountain weather and topography. A flash flood and gravel bed load transport are two key relative problems in mountain river engineering. Bed materials are often encountered in alternate scouring and deposition in mountain fluvial processes during a flash flood.In this circumstance, CRS-1 bed load numerical model jointly with scale physical model is em-ployed to predict water level and gravel bed scour and deposition for design of flood control dykes and flash flood disaster mitigation. A case study on the mechanism of a flash flood disaster in-duced by bed load transport for a hydropower station in Sichuan Province is conducted. Finally,suggestions to protect the hydropower station are proposed.

  11. Modelling (flash) floods in a Dutch lowland catchment

    Science.gov (United States)

    Brauer, C. C.; Teuling, A. J.; Overeem, A.; van der Velde, Y.; Hazenberg, P.; Warmerdam, P. M. M.; Kloosterman, P.; Uijlenhoet, R.

    2012-04-01

    On 26 August 2010 the eastern part of The Netherlands and the bordering part of Germany were struck by a series of rainfall events. We investigated the unprecedented flash flood triggered by this exceptionally heavy rainfall event (return period > 1000 years) in the 6.5 km2 Hupsel Brook catchment, which has been the experimental watershed employed by Wageningen University since the 1960s. This study improved our understanding of the dynamics of such lowland flash floods and the results have been published in HESS (Brauer et al., 2011). During this extreme event some thresholds became apparent that do not play a role during average conditions and are not incorporated in rainfall-runoff models. We present a detailed analysis of this extreme event, focusing on (1) the measured soil moisture, groundwater and discharge response of the catchment, (2) the thresholds we found, (3) the manner in which these processes and thresholds are incorporated in some well-known conceptual hydrological models and (4) how well these models are able to simulate the rainfall-runoff processes during the 2010 flash flood.

  12. A new French flash flood warning service

    Directory of Open Access Journals (Sweden)

    de Saint-Aubin Céline

    2016-01-01

    Full Text Available The French State services in charge of flood forecasting supervise about 22,000 km among the 120,000 km of the French rivers within a warning procedure called Vigilance Crues (http://www.vigicrues.gouv.fr. Some recent dramatic flood events on small watershed not covered by Vigilance Crues highlight the need for a new warning procedure to anticipate violent flash floods that regularly affect rapid river-basins. Thus the concept emerged of an automatic warning service specifically dedicated to local crisis managers. This service will be less elaborated than Vigilance Crues, probably with false alarms and missed events sometimes, but it will deliver a first information. The generation of the warning is based on a simple rainfall-runoff hydrological model developed by Irstea on all French rivers, fed with radar-gauge rainfall grids provided by Meteo-France. Every fifteen minutes, the hydrological model estimates the discharges on the rivers eligible to the service and determine if certain thresholds corresponding to a high or very high flood are likely to be exceeded. The last step of the real-time system is to determine which municipalities are concerned with flood risk and send them an automatic warning by voice call, optionally by sms or email. A specific web interface is available for users to monitor the evolution of the flood risk on maps that are updated every 15 minutes. This new flash flood warning service will be operational early 2017 as a free service for about 8,000 French municipalities.

  13. Flash Flooding and 'Muddy Floods' on Arable Land

    Science.gov (United States)

    Boardman, J.

    2012-04-01

    Flash flooding is often associated with upland, grazed catchments. It does, however, occur in lowland arable-dominated areas. In southern England, notable examples have occurred at Rottingdean (Brighton) in 1987, at Faringdon (Oxfordshire) in 1993 and at Breaky Bottom vineyard (near Brighton) in 1987 and 2000. All resulted in damage to nearby property. Runoff was largely from recently cultivated ground. The characteristics of such floods are: Rapid runoff from bare soil surfaces. Saturated excess overland flow is likely in the early parts of storms but high intensity rainfall on loamy soils results in crusting and Hortonian overland flow; High rates of erosion; Sediment transport to downvalley sites causing property damage ('muddy flooding'). Muddy floods are known from several areas of Europe e.g. Belgium, northern France, South Limburg (Netherlands) and Slovakia (Boardman et al 2006). In other areas they occur but have gone unreported or are classified under different terms. The necessary conditions for occurrence are areas of arable land which is bare at times of the year when there is a risk of storms. For muddy floods to cause damage (and hence be reported), vulnerable property must lie downstream from such areas of arable land. In some areas the incidence of muddy floods relates to autumn and early winter rainfall and winter cereal crops (e.g. southern England). In continental Europe, flooding is more common in summer and is associated with convectional storms and land uses including sugar beet, maize and potatoes. Predictions of increased numbers of high-intensity storms with future climate change, suggest that arable areas will continue to generate both flash floods and muddy floods.

  14. THE FREQUENCY OF OCCURRENCE OF FLASH FLOODS ON THE RIVERS IN THE LAND OF DORNA

    Directory of Open Access Journals (Sweden)

    MIHALCA Izabela Amalia

    2015-06-01

    Full Text Available Flash floods are extreme natural phenomena that determine numerous property damage and loss of human life on both global and local level. In order to highlight not only the frequency of occurrence of floods on the rivers in the Land of Dorna but also their effects on the community, we set ourselves to perform a secondary analysis of data provided by Siret River Basin Administration. As a result, one can observe that the highest frequency of occurrence of flash floods in the region of Dorna is in the spring. During the same period of time (from 1993 to 2003 there were recorded only significant property damages after the flash floods. At the end of this paper we suggested a series of coherent measures in order to combat the negative effects of flash floods.

  15. Flash flood swift water rescues, Texas, 2005–2014

    Directory of Open Access Journals (Sweden)

    Vaidehi Shah

    2017-01-01

    Full Text Available Although rainfall patterns are complex and difficult to predict, climate models suggest precipitation in Texas will occur less frequently and with greater intensity in the future. In combination with rapid population growth and development, extreme rainfall events are likely to lead to flash floods and necessitate swift water rescues. Swift water rescues are used to retrieve person(s from swift water flowing at a rate of 1 knot or greater. Data were obtained from the Texas Fire Marshal’s Office and analyzed to describe spatial and temporal characteristics of rescues. Between 2005 and 2014, 3256 swift water rescues were reported from 136 of 254 (54% counties. Over half (54.6%, n = 1777 occurred in counties known as Flash Flood Alley, which includes Texas’ largest and fastest growing cities. Less than 1.0% (n = 18 were reported from 49 counties designated as completely rural, or with an urban population less than 2500. Increases in swift water rescues were seen between March and September and during major weather events such as tropical storms. Because county-level data was utilized and demographic data was missing in all but 2% (n = 47 of the incidents, our ability to identify populations at risk or target interventions in the future using this data is limited. Despite the frequency of flash flood events and swift water rescues in Texas, knowledge gaps persist that should be addressed through the conduct of interdisciplinary research by epidemiologists and climatologists and by disseminating evidence-based health education and safety programs, particularly in rapidly growing counties that make up Texas’ Flash Flood Alley.

  16. A Bayesian Network approach for flash flood risk assessment

    Science.gov (United States)

    Boutkhamouine, Brahim; Roux, Hélène; Pérès, François

    2017-04-01

    Climate change is contributing to the increase of natural disasters such as extreme weather events. Sometimes, these events lead to sudden flash floods causing devastating effects on life and property. Most recently, many regions of the French Mediterranean perimeter have endured such catastrophic flood events; Var (October 2015), Ardèche (November 2014), Nîmes (October 2014), Hérault, Gard and Languedoc (September 2014), and Pyrenees mountains (Jun 2013). Altogether, it resulted in dozens of victims and property damages amounting to millions of euros. With this heavy loss in mind, development of hydrological forecasting and warning systems is becoming an essential element in regional and national strategies. Flash flood forecasting but also monitoring is a difficult task because small ungauged catchments ( 10 km2) are often the most destructive ones as for the extreme flash flood event of September 2002 in the Cévennes region (France) (Ruin et al., 2008). The problem of measurement/prediction uncertainty is particularly crucial when attempting to develop operational flash-flood forecasting methods. Taking into account the uncertainty related to the model structure itself, to the model parametrization or to the model forcing (spatio-temporal rainfall, initial conditions) is crucial in hydrological modelling. Quantifying these uncertainties is of primary importance for risk assessment and decision making. Although significant improvements have been made in computational power and distributed hydrologic modelling, the issue dealing with integration of uncertainties into flood forecasting remains up-to-date and challenging. In order to develop a framework which could handle these uncertainties and explain their propagation through the model, we propose to explore the potential of graphical models (GMs) and, more precisely, Bayesian Networks (BNs). These networks are Directed Acyclic Graphs (DAGs) in which knowledge of a certain phenomenon is represented by

  17. Recent precipitation trends, flash floods and landslides in southern Brazil

    Science.gov (United States)

    Ávila, Alvaro; Justino, Flavio; Wilson, Aaron; Bromwich, David; Amorim, Marcelo

    2016-11-01

    In order to understand the rising number of flash floods and landslides in the densely populated region of southeastern Brazil, this study analyzes the spatial and temporal changes in precipitation from 1978 to 2014. We focus on the sensitivity of mountainous regions, specifically the Rio de Janeiro (RJMR) and Santa Catarina (SCMR) regions. Daily rainfall observations are aggregated into annual and seasonal indexes, and RClimdex is used to evaluate a suite of precipitation and extreme event indexes. Results show positive annual and seasonal precipitation trends during all seasons except for the winter season in the RJMR. Diverse change points in their time series, spatial differences in the trends at individual stations, and trends associated with elevation suggest that despite the close proximity of these two regions, climate impacts are not uniform across all of southeastern Brazil. The majority of precipitation-related indexes present positive trends, especially in the extreme precipitation indexes (PRCPTOT, RX1day, Rx5day and R30 mm). Statistically significant positive correlations are discovered between landslides/flash floods events and annual maximum 1-day and 5-day consecutive precipitation, and these indexes may be useful indicators of natural hazard events for this region.

  18. Simulated CONUS Flash Flood Climatologies from Distributed Hydrologic Models

    Science.gov (United States)

    Flamig, Z.; Gourley, J. J.; Vergara, H. J.; Kirstetter, P. E.; Hong, Y.

    2016-12-01

    This study will describe a CONUS flash flood climatology created over the period from 2002 through 2011. The MRMS reanalysis precipitation dataset was used as forcing into the Ensemble Framework For Flash Flood Forecasting (EF5). This high resolution 1-sq km 5-minute dataset is ideal for simulating flash floods with a distributed hydrologic model. EF5 features multiple water balance components including SAC-SMA, CREST, and a hydrophobic model all coupled with kinematic wave routing. The EF5/SAC-SMA and EF5/CREST water balance schemes were used for the creation of dual flash flood climatologies based on the differing water balance principles. For the period from 2002 through 2011 the daily maximum streamflow, unit streamflow, and time of peak streamflow was stored along with the minimum soil moisture. These variables are used to describe the states of the soils right before a flash flood event and the peak streamflow that was simulated during the flash flood event. The results will be shown, compared and contrasted. The resulting model simulations will be verified on basins less than 1,000-sq km with USGS gauges to ensure the distributed hydrologic models are reliable. The results will also be compared spatially to Storm Data flash flood event observations to judge the degree of agreement between the simulated climatologies and observations.

  19. Flash floods in Europe: state of the art and research perspectives

    Science.gov (United States)

    Gaume, Eric

    2014-05-01

    Flash floods, i.e. floods induced by severe rainfall events generally affecting watersheds of limited area, are the most frequent, destructive and deadly kind of natural hazard known in Europe and throughout the world. Flash floods are especially intense across the Mediterranean zone, where rainfall accumulations exceeding 500 mm within a few hours may be observed. Despite this state of facts, the study of extremes in hydrology has essentially gone unexplored until the recent past, with the exception of some rare factual reports on individual flood events, with the sporadic inclusion of isolated estimated peak discharges. Floods of extraordinary magnitude are in fact hardly ever captured by existing standard measurement networks, either because they are too heavily concentrated in space and time or because their discharges greatly exceed the design and calibration ranges of the measurement devices employed (stream gauges). This situation has gradually evolved over the last decade for two main reasons. First, the expansion and densification of weather radar networks, combined with improved radar quantitative precipitation estimates, now provide ready access to rainfall measurements at spatial and temporal scales that, while not perfectly accurate, are compatible with the study of extreme events. Heavy rainfall events no longer fail to be recorded by existing rain gauge and radar networks. Second, pioneering research efforts on extreme floods, based on precise post-flood surveys, have helped overcome the limitations imposed by a small base of available direct measured data. This activity has already yielded significant progress in expanding the knowledge and understanding of extreme flash floods. This presentation will provide a review of the recent research progresses in the area of flash flood studies, mainly based on the outcomes of the European research projects FLOODsite, HYDRATE and Hymex. It will show how intensive collation of field data helped better define

  20. Heavy rainfall induced flash flood management

    Science.gov (United States)

    Weiler, Markus; Steinbrich, Andreas; Stölzle, Michael; Leistert, Hannes

    2016-04-01

    Heavy rain induced flash floods are still a serious hazard. In context of climate change even a rise of threat potential of flash flood must be suspected. To improve prediction of endangered areas hydraulic models was developed in the past that implement topography information in heigh resolution, gathered by laser scan applications. To run such models it is crucial to estimate the runoff input spatial distributed. However, this information is usually derived with relatively simple models lacking the process rigour that is required for prediction in engaged basins. Though available rain runoff models are able to model runoff response integral for measured catchments they do not indicate the spatial distribution of processes. Moreover they are commonly calibrated to measured runoff data and not applicable in other environments. Since runoff generation is commonly not measured, a calibration on it is hardly possible. In this study, we present a new approach for quantification of runoff generation in height spatial and temporal resolution. A suited model needs to work without calibration in every given environment under any given conditions. It is possible to develop such a model by combining spatial distributed input data of land surface properties (e.g. soil, geology, land use, …) with worldwide findings of runoff generation research. We developed such a model for the state of Baden-Württemberg, what has an extensive pool of spatial data. E.g. a digital elevation model of 1*1m² resolution, degree of sealing of the earth surface in 1*1m² resolution, soil properties (1:50.000) and geology (1:200.000). Within the state of Baden-Württemberg different regions are situated, with distinct environmental characteristics concerning as well climate, soil properties, land use, topography and geology. The model was tested and validated by modelling 36 observed flood events in 13 mesoscale catchments representing the different regions of Baden-Württemberg as well as by

  1. Impact of rainfall spatial variability on Flash Flood Forecasting

    Science.gov (United States)

    Douinot, Audrey; Roux, Hélène; Garambois, Pierre-André; Larnier, Kevin

    2014-05-01

    According to the United States National Hazard Statistics database, flooding and flash flooding have caused the largest number of deaths of any weather-related phenomenon over the last 30 years (Flash Flood Guidance Improvement Team, 2003). Like the storms that cause them, flash floods are very variable and non-linear phenomena in time and space, with the result that understanding and anticipating flash flood genesis is far from straightforward. In the U.S., the Flash Flood Guidance (FFG) estimates the average number of inches of rainfall for given durations required to produce flash flooding in the indicated county. In Europe, flash flood often occurred on small catchments (approximately 100 km2) and it has been shown that the spatial variability of rainfall has a great impact on the catchment response (Le Lay and Saulnier, 2007). Therefore, in this study, based on the Flash flood Guidance method, rainfall spatial variability information is introduced in the threshold estimation. As for FFG, the threshold is the number of millimeters of rainfall required to produce a discharge higher than the discharge corresponding to the first level (yellow) warning of the French flood warning service (SCHAPI: Service Central d'Hydrométéorologie et d'Appui à la Prévision des Inondations). The indexes δ1 and δ2 of Zoccatelli et al. (2010), based on the spatial moments of catchment rainfall, are used to characterize the rainfall spatial distribution. Rainfall spatial variability impacts on warning threshold and on hydrological processes are then studied. The spatially distributed hydrological model MARINE (Roux et al., 2011), dedicated to flash flood prediction is forced with synthetic rainfall patterns of different spatial distributions. This allows the determination of a warning threshold diagram: knowing the spatial distribution of the rainfall forecast and therefore the 2 indexes δ1 and δ2, the threshold value is read on the diagram. A warning threshold diagram is

  2. Improving flash flood frequency analyses by using non-systematic dendrogeomorphic data

    Science.gov (United States)

    Mediero, Luis; María Bodoque, Jose; Garrote, Julio; Ballesteros-Cánovas, Juan Antonio; Aroca-Jimenez, Estefania

    2017-04-01

    Flash floods have a rapid hydrological response in catchments with short lag times, characterized by ''peaky'' hydrographs. The peak flows are reached within a few hours, thus giving little or no advance warning to prevent and mitigate flood damage. As a result, flash floods may result in a high social risk, as shown for instance by the 1997 Biescas disaster in Spain. The analysis and management of flood risk are clearly conditioned by data availability, especially in mountain areas where usually flash-floods occur. Nevertheless, in mountain basins there is often short data series available that are not accurate in terms of statistical significance. In addition, when flow data is ready for use maximum annual values are generally not as reliable as average flow values, since conventional stream gauge stations may not record the extreme floods, leading to gaps in the time series. Dendrogeomorphology has been shown to be especially useful for improving flood frequency analyses in catchments where short flood series limit the use of conventional hydrological methods. This study presents pros and cons of using a given probability distribution function, such as the Generalized Extreme Value (GEV), and Bayesian Markov Chain Monte Carlo (MCMC) methods to account for non-systematic data provided by dendrogeomorphic techniques, in order to asses flood quantile estimates accuracy. To this end, we have considered a set of locations in Central Spain, where systematic flow available at a gauging site can be extended with non-systematic data obtained from implementation of dendrogeomorphic techniques.

  3. Improving the flash flood frequency analysis applying dendrogeomorphological evidences

    Science.gov (United States)

    Ruiz-Villanueva, V.; Ballesteros, J. A.; Bodoque, J. M.; Stoffel, M.; Bollschweiler, M.; Díez-Herrero, A.

    2009-09-01

    Flash floods are one of the natural hazards that cause major damages worldwide. Especially in Mediterranean areas they provoke high economic losses every year. In mountain areas with high stream gradients, floods events are characterized by extremely high flow and debris transport rates. Flash flood analysis in mountain areas presents specific scientific challenges. On one hand, there is a lack of information on precipitation and discharge due to a lack of spatially well distributed gauge stations with long records. On the other hand, gauge stations may not record correctly during extreme events when they are damaged or the discharge exceeds the recordable level. In this case, no systematic data allows improvement of the understanding of the spatial and temporal occurrence of the process. Since historic documentation is normally scarce or even completely missing in mountain areas, tree-ring analysis can provide an alternative approach. Flash floods may influence trees in different ways: (1) tilting of the stem through the unilateral pressure of the flowing mass or individual boulders; (2) root exposure through erosion of the banks; (3) injuries and scars caused by boulders and wood transported in the flow; (4) decapitation of the stem and resulting candelabra growth through the severe impact of boulders; (5) stem burial through deposition of material. The trees react to these disturbances with specific growth changes such as abrupt change of the yearly increment and anatomical changes like reaction wood or callus tissue. In this study, we sampled 90 cross sections and 265 increment cores of trees heavily affected by past flash floods in order to date past events and to reconstruct recurrence intervals in two torrent channels located in the Spanish Central System. The first study site is located along the Pelayo River, a torrent in natural conditions. Based on the external disturbances of trees and their geomorphological position, 114 Pinus pinaster (Ait

  4. Flash floods in the Tatra Mountain streams: frequency and triggers.

    Science.gov (United States)

    Ballesteros-Cánovas, J A; Czajka, B; Janecka, K; Lempa, M; Kaczka, R J; Stoffel, M

    2015-04-01

    Flash floods represent a frequently recurring natural phenomenon in the Tatra Mountains. On the northern slopes of the mountain chain, located in Poland, ongoing and expected future changes in climate are thought to further increase the adverse impacts of flash floods. Despite the repeat occurrence of major floods in the densely populated foothills of the Polish Tatras, the headwaters have been characterized by a surprising lack of data, such that any analysis of process variability or hydrometeorological triggers has been largely hampered so far. In this study, dendrogeomorphic techniques have been employed in four poorly-gauged torrential streams of the northern slope of the Tatra Mountains to reconstruct temporal and spatial patterns of past events. Using more than 1100 increment cores of trees injured by past flash floods, we reconstruct 47 events covering the last 148 years and discuss synoptic situations leading to the triggering of flash floods with the existing meteorological and flow gauge data. Tree-ring analyses have allowed highlighting the seasonality of events, providing new insights about potential hydrometeorological triggers as well as a differentiating flash flood activity between catchments. Results of this study could be useful to design future strategies to deal with flash flood risks at the foothills of the Polish Tatras and in the Vistula River catchment.

  5. Interim report on flash floods, Area 5 - Nevada Test Site

    Energy Technology Data Exchange (ETDEWEB)

    French, R.H.

    1980-09-01

    Examination of the presently available data indicates that consideration must be given to the possibility of flash floods when siting waste management facilities in Area 5 of the Nevada Test Site. 6 figures, 7 tables.

  6. Modeling Flash Floods in Small Ungaged Watersheds using Embedded GIS

    OpenAIRE

    Knocke, Ethan William

    2006-01-01

    Effective prediction of localized flash flood regions for an approaching rainfall event requires an in-depth knowledge of the land surface and stream characteristics of the forecast area. Flash Flood Guidance (FFG) is currently formulated once or twice a day at the county level by River Forecast Centers (RFC) in the U.S. using modeling systems that contain coarse, generalized land and stream characteristics and hydrologic runoff techniques that often are not calibrated for the forecast regio...

  7. Post-event analysis and flash flood hydrology in Slovakia

    Directory of Open Access Journals (Sweden)

    Hlavčová Kamila

    2016-12-01

    Full Text Available This work examines the main features of the flash flood regime in Central Europe as revealed by an analysis of flash floods that have occurred in Slovakia. The work is organized into the following two parts: The first part focuses on estimating the rainfall-runoff relationships for 3 major flash flood events, which were among the most severe events since 1998 and caused a loss of lives and a large amount of damage. The selected flash floods occurred on the 20th of July, 1998, in the Malá Svinka and Dubovický Creek basins; the 24th of July, 2001, at Štrbský Creek; and the 19th of June, 2004, at Turniansky Creek. The analysis aims to assess the flash flood peaks and rainfall-runoff properties by combining post-flood surveys and the application of hydrological and hydraulic post-event analyses. Next, a spatially-distributed hydrological model based on the availability of the raster information of the landscape’s topography, soil and vegetation properties, and rainfall data was used to simulate the runoff. The results from the application of the distributed hydrological model were used to analyse the consistency of the surveyed peak discharges with respect to the estimated rainfall properties and drainage basins. In the second part these data were combined with observations from flash flood events which were observed during the last 100 years and are focused on an analysis of the relationship between the flood peaks and the catchment area. The envelope curve was shown to exhibit a more pronounced decrease with the catchment size with respect to other flash flood relationships found in the Mediterranean region. The differences between the two relationships mainly reflect changes in the coverage of the storm sizes and hydrological characteristics between the two regions.

  8. Upper limits of flash flood stream power in Europe

    Science.gov (United States)

    Marchi, Lorenzo; Cavalli, Marco; Amponsah, William; Borga, Marco; Crema, Stefano

    2016-11-01

    Flash floods are characterized by strong spatial gradients of rainfall inputs that hit different parts of a river basin with different intensity. Stream power values associated with flash floods therefore show spatial variations that depend on geological controls on channel geometry and sediment characteristics, as well as on the variations of flood intensity: this stresses the need for a field approach that takes into account the variability of the controlling factors. Post-flood assessment of peak discharge after major floods makes it possible to analyse stream power in fluvial systems affected by flash floods. This study analyses the stream power of seven intense (return period of rainfall > 100 years at least in some sectors of the river basin) flash floods that occurred in mountainous basins of central and southern Europe from 2007 to 2014. In most of the analysed cross sections, high values of unit stream power were observed; this is consistent with the high severity of the studied floods. The highest values of cross-sectional stream power and unit stream power usually occur in Mediterranean regions. This is mainly ascribed to the larger peak discharges that characterize flash floods in these regions. The variability of unit stream power with catchment area is clearly nonlinear and has been represented by log-quadratic relations. The values of catchment area at which maximum values of unit stream power occur show relevant differences among the studied floods and are linked to the spatial scale of the events. Values of stream power are generally consistent with observed geomorphic changes in the studied cross sections: bedrock channels show the highest values of unit stream power but no visible erosion, whereas major erosion has been observed in alluvial channels. Exceptions to this general pattern, which mostly occur in semi-alluvial cross sections, urge the recognition of local or event-specific conditions that increase the resistance of channel bed and

  9. Study of flash floods over some parts of Brazil using precipitation index

    Science.gov (United States)

    Souza, D.; de Souza, R. L. M.; Araujo, R.

    2016-12-01

    In Brazil, the main phenomena related to natural disasters are derived from the Earth's external dynamics such as floods and flash floods, landslides and storms, where the flash flood phenomenon causes the second highest number of victims, totaling more than 32% of deaths. Floods and flash floods are natural events often triggered by storms or long period of rains, usually associated with rising volume of rainfall on the watershed, leading the river to exceed its maximum. Whereas the occurrence of natural disasters in Brazil is increasing in recent years, the use of more accurate tools to aid in the monitoring of extreme hydrological events it becomes necessary, aiming to decrease the number of human and material losses. In this context, this paper aims to implement an early warning and monitoring system related to extreme precipitation values and hydrological processes. So, initially was studied flood events in the states of São Paulo and Paraná, aimed de determination of the characteristics of rainfall and atmosphere. Later it was used an indicator of precipitation based on the climatology, which indicates warning points on the drainage network related to extreme precipitation, which are obtained by remote sensing sources, for example, radar and satellite, and numerical weather prediction data of short and very short term. The results indicated that most of the flood events over the study area was related to rainfall of deep convection. The use of precipitation indicators also helped the monitoring and the early warning, showing this to be an excellent tool for applications related to flash floods.

  10. A retrospective analysis of the flash flood in Braunsbach on May 29th, 2016

    Science.gov (United States)

    Laudan, Jonas; Öztürk, Ugur; Sieg, Tobias; Wendi, Dadiyorto; Riemer, Adrian; Agarwal, Ankit; Rözer, Viktor; Korup, Oliver; Thieken, Annegret; Vogel, Kristin

    2017-04-01

    At the end of May and early June 2016 several rainstorms caused severe surface water flooding and flash floods, partly accompanied by mud and debris flows, in Central Europe, and especially in southern Germany. On the evening of May 29, 2016, a flood outburst with massive amounts of rubble and muddy sediments hit the town of Braunsbach, Baden-Württemberg, damaging numerous buildings, cars, and town facilities. The DFG Graduate School "Natural hazards and risks in a changing world" (NatRiskChange) at the University of Potsdam investigated the Braunsbach "flash flood" as an exemplary catastrophic event triggered by severe weather. Bringing together scientists from the fields of meteorology, hydrology, geomorphology, flood risk, natural hazards, and mathematics the research team was especially interested in the interplay of causes and triggers leading to the event. Accordingly, the team focused on the entire process chain from heavy precipitation to runoff and flood generation and the geomorphic aftermath. The steep slopes in the catchment area promote the episodic supply of gravel, debris and organic material, which remains stored for decades to millennia, only to be remobilized during rare and extreme runoff events such as in 2016. Field mapping revealed at least 48 landslides as sources of high sediment loads. Nonetheless, numerous scars of river erosion along the tributary creeks into Braunsbach indicate that most of the material carried by the flash flood was due to bank undercutting. The flow also entrained more rubble, trees, cars, and other anthropogenic sediments further downstream. This enhanced solids load increased the physical impact, and hence damage, to buildings. Local effects of flow depth, flow velocity, and exposition of buildings into the advancing non-steady and non-uniform flow caused the damage to exceed that of a clearwater flood with comparable return period. We conclude that, to meaningfully inform the implementation of precautionary

  11. Flash flooding in small urban watersheds: Storm event hydrologic response

    Science.gov (United States)

    Yang, Long; Smith, James A.; Baeck, Mary Lynn; Zhang, Yan

    2016-06-01

    We analyze flash flooding in small urban watersheds, with special focus on the roles of rainfall variability, antecedent soil moisture, and urban storm water management infrastructure in storm event hydrologic response. Our results are based on empirical analyses of high-resolution rainfall and discharge observations over Harry's Brook watershed in Princeton, New Jersey, during 2005-2006, as well as numerical experiments with the Gridded Surface Subsurface Hydrologic Analysis (GSSHA) model. We focus on two subwatersheds of Harry's Brook, a 1.1 km2 subwatershed which was developed prior to modern storm water management regulations, and a 0.5 km2 subwatershed with an extensive network of storm water detention ponds. The watershed developed prior to modern storm water regulations is an "end-member" in urban flood response, exhibiting a frequency of flood peaks (with unit discharge exceeding 1 m3 s-1 km-2) that is comparable to the "flashiest" watersheds in the conterminous U.S. Observational analyses show that variability in storm event water balance is strongly linked to peak rain rates at time intervals of less than 30 min and only weakly linked to antecedent soil moisture conditions. Peak discharge for both the 1.1 and 0.5 km2 subwatersheds are strongly correlated with rainfall rate averaged over 1-30 min. Hydrologic modeling analyses indicate that the sensitivity of storm event hydrologic response to spatial rainfall variability decreases with storm intensity. Temporal rainfall variability is relatively more important than spatial rainfall variability in representing urban flood response, especially for extreme storm events.

  12. MobRISK: a model for assessing the exposure of road users to flash flood events

    Science.gov (United States)

    Shabou, Saif; Ruin, Isabelle; Lutoff, Céline; Debionne, Samuel; Anquetin, Sandrine; Creutin, Jean-Dominique; Beaufils, Xavier

    2017-09-01

    Recent flash flood impact studies highlight that road networks are often disrupted due to adverse weather and flash flood events. Road users are thus particularly exposed to road flooding during their daily mobility. Previous exposure studies, however, do not take into consideration population mobility. Recent advances in transportation research provide an appropriate framework for simulating individual travel-activity patterns using an activity-based approach. These activity-based mobility models enable the prediction of the sequence of activities performed by individuals and locating them with a high spatial-temporal resolution. This paper describes the development of the MobRISK microsimulation system: a model for assessing the exposure of road users to extreme hydrometeorological events. MobRISK aims at providing an accurate spatiotemporal exposure assessment by integrating travel-activity behaviors and mobility adaptation with respect to weather disruptions. The model is applied in a flash-flood-prone area in southern France to assess motorists' exposure to the September 2002 flash flood event. The results show that risk of flooding mainly occurs in principal road links with considerable traffic load. However, a lag time between the timing of the road submersion and persons crossing these roads contributes to reducing the potential vehicle-related fatal accidents. It is also found that sociodemographic variables have a significant effect on individual exposure. Thus, the proposed model demonstrates the benefits of considering spatiotemporal dynamics of population exposure to flash floods and presents an important improvement in exposure assessment methods. Such improved characterization of road user exposures can present valuable information for flood risk management services.

  13. DERIVING FLASH FLOODS IN THE CASE OF SIMULATED PRECIPITATIONS

    Directory of Open Access Journals (Sweden)

    GYŐRI MARIA-MIHAELA

    2013-01-01

    Full Text Available Deriving flash floods in the case of simulated precipitations. The present study sets to determine the historical flash-floods on the Petriș watershed making use of the implemented mathematical models in a Hydrological Modeling System. In order to simulate the 1%, 2% and 10% exceedance probability flash-floods, the Intensity-Frequency-Duration (IDF curves have been built on the basis of 22 years of precipitation records (1988-2009. They serve as input data together with the hydrological parameters identified by the means of a Geographic Information Systems. The results, computed mainly on the basis of the Soil Conservation Service (SCS method, consist of hyetographs and hydrographs at the outlet of the main watershed, as well as to that of the ungauged tributaries of the Petriș River.

  14. Flash floods, hydro-geomorphic response and risk management

    Science.gov (United States)

    Braud, Isabelle; Borga, Marco; Gourley, Jonathan; Hürlimann, Marcel; Zappa, Massimilano; Gallart, Francesc

    2016-10-01

    Each year, natural disasters are responsible for fatalities and economic losses worldwide with 101 billion USD in economic losses and 7000 fatalities reported for 2014 (SwissRE, 2015). Even if earthquakes are responsible for most of these fatalities, flash floods and landslides are recognized as a significant source of threat to human lives (SwissRE, 2015). Jonkman (2005), in a global assessment of flood-related casualties, showed that flash floods lead to the highest mortality (number of fatalities divided by the number of affected people). They are also often associated with shallow landslides and geomorphic processes that can increase threat to human lives. Analysis of a global data set of fatalities from non-seismically triggered landslides (Petley, 2012) shows that 2620 fatal landslides were recorded worldwide in the period 2004-2010, causing a total of 32,322 recorded fatalities. In addition, heavy precipitation events, at the origin of flash floods and shallow landsliding are expected to increase in the future (e.g. Scoccimarro et al., 2016 for a recent study in Europe). Progress in flash floods and landslides understanding, forecasting and warning is therefore still needed to disentangle the complex interactions between hazards, exposure and vulnerability and to increase resilience (Borga et al., 2014).

  15. Flash flood warning based on fully dynamic hydrology modelling

    Science.gov (United States)

    Pejanovic, Goran; Petkovic, Slavko; Cvetkovic, Bojan; Nickovic, Slobodan

    2016-04-01

    Numerical hydrologic modeling has achieved limited success in the past due to, inter alia, lack of adequate input data. Over the last decade, data availability has improved substantially. For modelling purposes, high-resolution data on topography, river routing, and land cover and soil features have meanwhile become available, as well as the observations such as radar precipitation information. In our study, we have implemented the HYPROM model (Hydrology Prognostic Model) to predict a flash flood event at a smaller-scale basin in Southern Serbia. HYPROM is based on the full set of governing equations for surface hydrological dynamics, in which momentum components, along with the equation of mass continuity, are used as full prognostic equations. HYPROM also includes a river routing module serving as a collector for the extra surface water. Such approach permits appropriate representation of different hydrology scales ranging from flash floods to flows of large and slow river basins. The use of full governing equations, if not appropriately parameterized, may lead to numerical instability systems when the surface water in a model is vanishing. To resolve these modelling problems, an unconditionally stable numerical scheme and a method for height redistribution avoiding shortwave height noise have been developed in HYPROM, which achieve numerical convergence of u, v and h when surface water disappears. We have applied HYPROM, driven by radar-estimated precipitation, to predict flash flooding occurred over smaller and medium-size river basins. Two torrential rainfall cases have been simulated to check the accuracy of the model: the exceptional flooding of May 2014 in Western Serbia, and the convective flash flood of January 2015 in Southern Serbia. The second episode has been successfully predicted by HYPROM in terms of timing and intensity six hours before the event occurred. Such flash flood warning system is in preparation to be operationally implemented in the

  16. Representative rainfall thresholds for flash floods in the Cali river watershed, Colombia

    Directory of Open Access Journals (Sweden)

    A. D. Ávila

    2015-06-01

    Full Text Available In the 21st century, societies face a significant increase in the number of extreme hydrometeorological events associated with climate variability (CV and/or climate change (CC. Research has recently focused on establishing adaptation and mitigation measures to counteract the effects of CV and CC, especially those associated with precipitation, such as flash floods and flooding. In this study, 27 floods, listed in the historical database of natural disasters (DesInventar, occurring between 1980 and 2012, were analyzed. Using the daily hydrometeorological data, representative rainfall thresholds were defined to predict flash floods in the hydrographic basin of the Cali River, Colombia. Antecedent rainfall (AR, or short-term rain (1, 3, 5 and 7 days, and accumulated antecedent rainfall (AAR, or long-term rain (5, 7, 10, 15, 20, 25, 30, 60 and 90 days, levels were defined. The analysis showed that the greatest determinant for the occurrence of floods is AAR, with thresholds greater than 73, 95, 124, 170, 218 and 273 mm, for 5, 7, 10, 15, 20 and 25 days, respectively. Additionally, the data showed that, historically, the greatest number of flash floods (81.7 % occurred in the Cali River basin in the months of April, May, and June.

  17. Dynamic Critical Rainfall-Based Flash Flood Early Warning and Forecasting for Medium-Small Rivers

    Science.gov (United States)

    Liu, Z.; Yang, D.; Hu, J.

    2012-04-01

    China is extremely frequent food disasters hit countries, annual flood season flash floods triggered by rainfall, mudslides, landslides have caused heavy casualties and property losses, not only serious threaten the lives of the masses, but the majority of seriously restricting the mountain hill areas of economic and social development and the people become rich, of building a moderately prosperous society goals. In the next few years, China will focus on prevention and control area in the flash flood disasters initially built "for the surveillance, communications, forecasting, early warning and other non-engineering measure based, non-engineering measures and the combinations of engineering measures," the mitigation system. The latest progresses on global torrential flood early warning and forecasting techniques are reviewed in this paper, and then an early warning and forecasting approach is proposed on the basis of a distributed hydrological model according to dynamic critical rainfall index. This approach has been applied in Suichuanjiang River basin in Jiangxi province, which is expected to provide valuable reference for building a national flash flood early warning and forecasting system as well as control of such flooding.

  18. Modelling (flash) floods in a Dutch lowland catchment

    NARCIS (Netherlands)

    Brauer, C.C.; Teuling, A.J.; Overeem, A.; Velde, Y. van der; Hazenberg, P.; Warmerdam, P.M.M.; Kloosterman, P.; Uijlenhoet, R.

    2012-01-01

    On 26 August 2010 the eastern part of The Netherlands and the bordering part of Germany were struck by a series of rainfall events.We investigated the unprecedented flash flood triggered by this exceptionally heavy rainfall event (return period > 1000 years) in the 6.5 km2 Hupsel Brook catchment, wh

  19. Comparative hazard analysis of processes leading to remarkable flash floods (France, 1930-1999)

    Science.gov (United States)

    Boudou, M.; Lang, M.; Vinet, F.; Cœur, D.

    2016-10-01

    Flash flood events are responsible for large economic losses and lead to fatalities every year in France. This is especially the case in the Mediterranean and oversea territories/departments of France, characterized by extreme hydro-climatological features and with a large part of the population exposed to flood risks. The recurrence of remarkable flash flood events, associated with high hazard intensity, significant damage and socio-political consequences, therefore raises several issues for authorities and risk management policies. This study aims to improve our understanding of the hazard analysis process in the case of four remarkable flood events: March 1930, October 1940, January 1980 and November 1999. Firstly, we present the methodology used to define the remarkability score of a flood event. Then, to identify the factors leading to a remarkable flood event, we explore the main parameters of the hazard analysis process, such as the meteorological triggering conditions, the return period of the rainfall and peak discharge, as well as some additional factors (initial catchment state, flood chronology, cascade effects, etc.). The results contribute to understanding the complexity of the processes leading to flood hazard and highlight the importance for risk managers of taking additional factors into account.

  20. Trends in flash flood events versus convective precipitation in the Mediterranean region: The case of Catalonia

    Science.gov (United States)

    Llasat, Maria Carmen; Marcos, Raul; Turco, Marco; Gilabert, Joan; Llasat-Botija, Montserrat

    2016-10-01

    The aim of this paper is to analyse the potential relationship between flash flood events and convective precipitation in Catalonia, as well as any related trends. The paper starts with an overview of flash floods and their trends in the Mediterranean region, along with their associated factors, followed by the definition of, identification of, and trends in convective precipitation. After this introduction the paper focuses on the north-eastern Iberian Peninsula, for which there is a long-term precipitation series (since 1928) of 1-min precipitation from the Fabra Observatory, as well as a shorter (1996-2011) but more extensive precipitation series (43 rain gauges) of 5-min precipitation. Both series have been used to characterise the degree of convective contribution to rainfall, introducing the β parameter as the ratio between convective precipitation versus total precipitation in any period. Information about flood events was obtained from the INUNGAMA database (a flood database created by the GAMA team), with the aim of finding any potential links to convective precipitation. These flood data were gathered using information on damage where flood is treated as a multifactorial risk, and where any trend or anomaly might have been caused by one or more factors affecting hazard, vulnerability or exposure. Trend analysis has shown an increase in flash flood events. The fact that no trends were detected in terms of extreme values of precipitation on a daily scale, nor on the associated ETCCDI (Expert Team on Climate Change Detection and Indices) extreme index, could point to an increase in vulnerability, an increase in exposure, or changes in land use. However, the summer increase in convective precipitation was concentrated in less torrential events, which could partially explain this positive trend in flash flood events. The β parameter has been also used to characterise the type of flood event according to the features of the precipitation. The highest values

  1. Flash flood characterisation of the Haor area of Bangladesh

    Science.gov (United States)

    Bhattacharya, B.; Suman, A.

    2012-04-01

    Haors are large bowl-shaped flood plain depressions located mostly in north-eastern part of Bangladesh covering about 25% of the entire region. During dry season haors are used for agriculture and during rainy season it is used as fisheries. Haors have profound ecological importance. About 8000 migratory wild birds visit the area annually. Some of the haors are declared at Ramsar sites. Haors are frequently affected by the flash floods due to hilly topography and steep slope of the rivers draining the area. These flash floods spill onto low-lying flood plain lands in the region, inundating crops, damaging infrastructure by erosion and often causing loss of lives and properties. Climate change is exacerbating the situation. For appropriate risk mitigation mechanism it is necessary to explore flood characteristics of that region. The area is not at all studied well. Under a current project a numerical 1D2D model based on MIKE Flood is developed to study the flooding characteristics and estimate the climate change impacts on the haor region. Under this study the progression of flood levels at some key haors in relation to the water level data at specified gauges in the region is analysed. As the region is at the border with India so comparing with the gauges at the border with India is carried out. The flooding in the Haor area is associated with the rainfall in the upstream catchment in India (Meghalaya, Barak and Tripura basins in India). The flood propagation in some of the identified haors in relation to meteorological forcing in the three basins in India is analysed as well. Subsequently, a ranking of haors is done based on individual risks. Based on the IPCC recommendation the precipitation scenario in the upstream catchments under climate change is considered. The study provides the fundamental inputs for preparing a flood risk management plan of the region.

  2. Flow ensemble prediction for flash flood warnings at ungauged basins

    Science.gov (United States)

    Demargne, Julie; Javelle, Pierre; Organde, Didier; Caseri, Angelica; Ramos, Maria-Helena; de Saint Aubin, Céline; Jurdy, Nicolas

    2015-04-01

    Flash floods, which are typically triggered by severe rainfall events, are difficult to monitor and predict at the spatial and temporal scales of interest due to large meteorological and hydrologic uncertainties. In particular, uncertainties in quantitative precipitation forecasts (QPF) and quantitative precipitation estimates (QPE) need to be taken into account to provide skillful flash flood warnings with increased warning lead time. In France, the AIGA discharge-threshold flood warning system is currently being enhanced to ingest high-resolution ensemble QPFs from convection-permitting numerical weather prediction (NWP) models, as well as probabilistic QPEs, to improve flash flood warnings for small-to-medium (from 10 to 1000 km²) ungauged basins. The current deterministic AIGA system is operational in the South of France since 2005. It ingests the operational radar-gauge QPE grids from Météo-France to run a simplified hourly distributed hydrologic model at a 1-km² resolution every 15 minutes (Javelle et al. 2014). This produces real-time peak discharge estimates along the river network, which are subsequently compared to regionalized flood frequency estimates of given return periods. Warnings are then provided to the French national hydro-meteorological and flood forecasting centre (SCHAPI) and regional flood forecasting offices, based on the estimated severity of ongoing events. The calibration and regionalization of the hydrologic model has been recently enhanced to implement an operational flash flood warning system for the entire French territory. To quantify the QPF uncertainty, the COSMO-DE-EPS rainfall ensembles from the Deutscher Wetterdienst (20 members at a 2.8-km resolution for a lead time of 21 hours), which are available on the North-eastern part of France, were ingested in the hydrologic model of the AIGA system. Streamflow ensembles were produced and probabilistic flash flood warnings were derived for the Meuse and Moselle river basins and

  3. floodX: urban flash flood experiments monitored with conventional and alternative sensors

    Science.gov (United States)

    Moy de Vitry, Matthew; Dicht, Simon; Leitão, João P.

    2017-09-01

    The data sets described in this paper provide a basis for developing and testing new methods for monitoring and modelling urban pluvial flash floods. Pluvial flash floods are a growing hazard to property and inhabitants' well-being in urban areas. However, the lack of appropriate data collection methods is often cited as an impediment for reliable flood modelling, thereby hindering the improvement of flood risk mapping and early warning systems. The potential of surveillance infrastructure and social media is starting to draw attention for this purpose. In the floodX project, 22 controlled urban flash floods were generated in a flood response training facility and monitored with state-of-the-art sensors as well as standard surveillance cameras. With these data, it is possible to explore the use of video data and computer vision for urban flood monitoring and modelling. The floodX project stands out as the largest documented flood experiment of its kind, providing both conventional measurements and video data in parallel and at high temporal resolution. The data set used in this paper is available at https://doi.org/10.5281/zenodo.830513.

  4. THE FLASH FLOODS ANALYSIS, REPRESENTATIVE FOR NIRAJ RIVER BETWEEN 1970-2008

    Directory of Open Access Journals (Sweden)

    ROŞCA SANDA

    2011-03-01

    Full Text Available The flash floods analysis, representative for Niraj River between 1970-2008. The need to know the characteristics of the flash floods is derived from the number and the intensity of floods occurred in the drainage basin of the Niraj river. Therefore, there were analyzed only the flash floods representatives for the years: 1970, 1995, 1998, 2001, 2008.The classification of the floods was realized according to the genesis and the flash flood hydrograph shape for the period 1970-2008, before and after the completion of the drainage basin planning/management depending on climatic, morphometric and morphological factors.

  5. The development of a flash flood severity index

    Science.gov (United States)

    Schroeder, Amanda J.; Gourley, Jonathan J.; Hardy, Jill; Henderson, Jen J.; Parhi, Pradipta; Rahmani, Vahid; Reed, Kimberly A.; Schumacher, Russ S.; Smith, Brianne K.; Taraldsen, Matthew J.

    2016-10-01

    Flash flooding is a high impact weather event that requires clear communication regarding severity and potential hazards among forecasters, researchers, emergency managers, and the general public. Current standards used to communicate these characteristics include return periods and the United States (U.S.) National Weather Service (NWS) 4-tiered river flooding severity scale. Return periods are largely misunderstood, and the NWS scale is limited to flooding on gauged streams and rivers, often leaving out heavily populated urban corridors. To address these shortcomings, a student-led group of interdisciplinary researchers came together in a collaborative effort to develop an impact-based Flash Flood Severity Index (FFSI). The index was proposed as a damage-based, post-event assessment tool, and preliminary work toward the creation of this index has been completed and presented here. Numerous case studies were analyzed to develop the preliminary outline for the FFSI, and three examples of such cases are included in this paper. The scale includes five impact-based categories ranging from Category 1 very minor flooding to Category 5 catastrophic flooding. Along with the numerous case studies used to develop the initial outline of the scale, empirical data in the form of semi-structured interviews were conducted with multiple NWS forecasters across the country and their responses were analyzed to gain more perspective on the complicated nature of flash flood definitions and which tools were found to be most useful. The feedback from these interviews suggests the potential for acceptance of such an index if it can account for specific challenges.

  6. Characterization of physically based hydrologic model behaviour with temporal sensitivity analysis for flash floods in Mediterranean catchments

    Directory of Open Access Journals (Sweden)

    P. A. Garambois

    2013-01-01

    Full Text Available This paper presents a detailed analysis of 10 flash flood events in the Mediterranean region using the distributed hydrological model MARINE. Characterizing catchment's response during flash flood events may provide a new and valuable insight into the processes involved for extreme flood response and their dependency on catchment properties and flood severity. The main objective of this study is to analyze hydrologic model sensitivity in the case of flash floods with a new approach in hydrology, allowing model outputs variance decomposition for temporal patterns of parameter sensitivity analysis. Such approaches enable ranking of uncertainty sources for non-linear and non-monotonic mappings with a low computational cost. This study uses hydrologic model and sensitivity analysis as learning tools to derive temporal sensitivity analysis with a variance based method in the case of 10 flash floods that occurred in the French Pyrenees and Cévennes foothills. This constitutes a huge dataset given the scarcity of data about flash flood events. With Nash performances above 0.73 on average for this extended set of validation events, the five sensitive parameters of MARINE distributed physically based model are analyzed. This contribution shows that soil depth explains more than 80% of model output variance when most hydrographs are peaking. Moreover the lateral subsurface transfer is responsible for 80% of model variance for some catchment-flood events' hydrographs during slow declining limbs. The unexplained variance of model output representing interactions between parameters reveals to be very low during modeled flood peaks and informs that model parsimonious parameterization is appropriate to tackle the problem of flash floods. Interactions observed after model initialization or rainfall intensity peaks incite to improve water partition representation between flow components and initialization itself. This paper gives a practical framework for

  7. Flash Flooding and Green Stormwater Infrastructure in Philadelphia: Areas for Further Improvement

    OpenAIRE

    DOĞANAY, Ela; MAGAZINER, Jamie

    2017-01-01

    Flash flooding is one of the most dangerous and the most common catastrophes among the other types of floods occure in USA. Flash flooding may occur in any area that may not even be located in floodplain zone. Since the flash flooding can take a few minutes or a few hours with out any warning and has high damaging potential, in this study, it is focused on identifying areas prone to flash flooding in the Philadelphia city, which has many natural streams and high development rates. In this stu...

  8. Advances in flash floods understanding and modelling derived from the FloodScale project in South-East France

    Directory of Open Access Journals (Sweden)

    Braud Isabelle

    2016-01-01

    Full Text Available The Mediterranean area is prone to intense rainfall events triggering flash floods, characterized by very short response times that sometimes lead to dramatic consequences in terms of casualties and damages. These events can affect large territories, but their impact may be very local in catchments that are generally ungauged. These events remain difficult to predict and the processes leading to their generation still need to be clarified. The HyMeX initiative (Hydrological Cycle in the Mediterranean Experiment, 2010-2020 aims at increasing our understanding of the water cycle in the Mediterranean basin, in particular in terms of extreme events. In order to better understand processes leading to flash floods, a four-year experiment (2012-2015 was conducted in the Cévennes region (South-East France as part of the FloodScale project. Both continuous and opportunistic measurements during floods were conducted in two large catchments (Ardèche and Gard rivers with nested instrumentation from the hillslopes to catchments of about 1, 10, 100 to 1000 km2 covering contrasted geology and land use. Continuous measurements include distributed rainfall, stream water level, discharge, water temperature and conductivity and soil moisture measurements. Opportunistic measurements include surface soil moisture and geochemistry sampling during events and gauging of floods using non-contact methods: portable radars to measure surface water velocity or image sequence analysis using LS-PIV (Large Scale Particle Image Velocimetry. During the period 2012-2014, and in particular during autumn 2014, several intense events affected the catchments and provided very rich data sets. Data collection was complemented with modelling activity aiming at simulating observed processes. The modelling strategy was setup through a wide range of scales, in order to test hypotheses about physical processes at the smallest scales, and aggregated functioning hypothesis at the largest

  9. Initial soil moisture effects on flash flood generation - A comparison between basins of contrasting hydro-climatic conditions

    Science.gov (United States)

    Grillakis, M. G.; Koutroulis, A. G.; Komma, J.; Tsanis, I. K.; Wagner, W.; Blöschl, G.

    2016-10-01

    The purpose of this paper is to contribute to the understanding of the importance of the initial soil moisture state for flash flood magnitudes. Four extreme events that occurred in different case study regions were analysed, one winter and one autumn flash flood in the Giofiros and Almirida catchments in Crete, and two summer floods in the Rastenberg catchment in Austria. The hydrological processes were simulated by the spatially distributed flash flood model Kampus. For the Crete cases Kampus model was calibrated against remotely sensed soil moisture while for the Austrian case the model was calibrated against observed runoff. Kampus model was then used to estimate the sensitivity of the stream flow peak to initial soil moisture. The largest of the events analysed (in terms of specific peak discharge) was found to have a sensitivity of less than 0.2% flood peak change per % soil moisture change while the smallest event had a sensitivity of more than 3% flood peak change per % soil moisture change. This suggests that initial soil moisture effects on the flash flood response probably depend on event magnitude rather than on the climate or region. Moreover, the Austrian catchment was found to exhibit a more nonlinear relationship between antecedent soil moisture and the peak discharge than the Cretan catchments which was explained by differences in the soil type.

  10. Flash flood area mapping utilising SENTINEL-1 radar data

    Science.gov (United States)

    Psomiadis, Emmanouil

    2016-10-01

    The new European Observatory radar data of polar orbiting satellite system Sentinel-1 provide a continuous and systematic data acquisition, enabling flood events monitoring and mapping. The study area is the basin of Sperchios River in Fthiotida Prefecture, Central Greece, having an increased ecological, environmental and socio-economic interest. The catchment area and especially the river delta, faces several problems and threats caused by anthropogenic activities and natural processes. The geomorphology of Sperchios catchment area and the drainage network formation provoke the creation of floods. A large flash flood event took place in late January early February 2015 following an intense and heavy rainfall that occurred in the area. Two space born radar images, obtained from Sentinel-1 covering the same area, one before and another one during the flood event, were processed. Two different methods were utilized so as to produce flood hazard maps, which demonstrate the inundated areas. The results of the two methods were similar and the flooded area was detected and delineated ideally.

  11. Integrated flash flood vulnerability assessment: Insights from East Attica, Greece

    Science.gov (United States)

    Karagiorgos, Konstantinos; Thaler, Thomas; Heiser, Micha; Hübl, Johannes; Fuchs, Sven

    2016-10-01

    In the framework of flood risk assessment, vulnerability is a key concept to assess the susceptibility of elements at risk. Besides the increasing amount of studies on flash floods available, in-depth information on vulnerability in Mediterranean countries was missing so far. Moreover, current approaches in vulnerability research are driven by a divide between social scientists who tend to view vulnerability as representing a set of socio-economic factors, and natural scientists who view vulnerability in terms of the degree of loss to an element at risk. Further, vulnerability studies in response to flash flood processes are rarely answered in the literature. In order to close this gap, this paper implemented an integrated vulnerability approach focusing on residential buildings exposed to flash floods in Greece. In general, both physical and social vulnerability was comparable low, which is interpreted as a result from (a) specific building regulations in Greece as well as general design principles leading to less structural susceptibility of elements at risk exposed, and (b) relatively low economic losses leading to less social vulnerability of citizens exposed. The population show high risk awareness and coping capacity to response to natural hazards event and in the same time the impact of the events are quite low, because of the already high use of local protection measures. The low vulnerability score for East Attica can be attributed especially to the low physical vulnerability and the moderate socio-economic well-being of the area. The consequence is to focus risk management strategies mainly in the reduction of the social vulnerability. By analysing both physical and social vulnerability an attempt was made to bridge the gap between scholars from sciences and humanities, and to integrate the results of the analysis into the broader vulnerability context.

  12. Evolution of gravel-bed channels in response to flash floods in dry environments

    Science.gov (United States)

    Salomon, Reut; Morin, Efrat; Enzel, Yehouda; Haviv, Itai

    2016-04-01

    Longitudinal profiles of alluvial channels may be altered rapidly in response to base-level lowering or changes in streamflow regime. Previous models simulating the response to such changes assumed steady and uniform streamflow discharge, or used a calibrated diffusion coefficient as a proxy for stream discharge. Such models do not account for intra and inter annual variance of flash flood volume and peak discharge which is typically high in channels of dry environments. We developed a new model for evolution of longitudinal profiles of gravel-bed channels combining kinematic wave flood routing with sediment transport based on the Meyer-Peter-Muller equation. The model predicts changes in channel longitudinal profile in response to changing streamflow regimes and base-level lowering rates. We have adopted a stochastic approach by formulating a "flash flood generator" which produces a synthetic data series of floods based on the probability distribution of peak discharge and hydrograph properties in a specific basin. The model was applied to the lower reach of Nahal Darga gravel-bed channel which drains into the Dead Sea Lake and is located in a dry climate regime. During the last 40 years, the initial uniform-gradient profile of this reach has changed to a convex profile as a result of a drastic artificial lowering of the Dead Sea level at a rate of 1 m/y. Measured channel profiles at several points in time were used for the model evaluation. The effect of different scenarios of lake level drop and of flash flood regime on the channel profile has been examined. The modeling results indicate a wide range of possible channel profiles due to the natural flow variance under a given flow regime. Extreme flow events play a major role on the channel profile evolution. Nevertheless, the effective discharge at the Darga channel, consists of floods with medium peak discharge and a recurrence interval of ~10 years.

  13. Flooding hazards from sea extremes and subsidence

    DEFF Research Database (Denmark)

    Sørensen, Carlo; Vognsen, Karsten; Broge, Niels

    2015-01-01

    If we do not understand the effects of climate change and sea level rise (SLR) we cannot live in low-lying coastal areas in the future. Permanent inundation may become a prevalent issue but more often floods related to extreme events have the largest damage potential, and the management of flooding...... hazards needs to integrate the water loading from various sources. Furthermore, local subsidence must be accounted for in order to evaluate current and future flooding hazards and management options. We present the methodology (Figure) and preliminary results from the research project “Coastal Flooding...... Hazards due to Storm Surges and Subsidence” (2014-2017) with the objective to develop and test a practice oriented methodology for combining extreme water level statistics and land movement in coastal flooding hazard mapping and in climate change adaptation schemes in Denmark. From extreme value analysis...

  14. Flash floods in Mediterranean ephemeral streams in Valencia Region (Spain)

    Science.gov (United States)

    Camarasa-Belmonte, Ana M.

    2016-10-01

    Ephemeral streams are typical Mediterranean fluvial systems with high risk of flash flooding, and few data are available about these systems in most locales. However, the SAIH network (Automatic Hydrological Information Systems) of the Jucar River Water Authority has been providing detailed information about ephemeral streams in Spain every 5 min since 1988. Using these data, we evaluated the processes of rainfall-runoff conversion and flood generation in five Mediterranean ephemeral streams ranging in size from 25 to 450 km2. To provide a general framework for hydrological analysis, the study included 142 flash flood events registered between 1989 and 2007. A more detailed analysis was conducted for the Carraixet Basin under the dry antecedent moisture condition (AMC I) to evaluate the influence of rainfall on the basin's response. A simple index called Momentum of Maximum Intensity (MMI) was developed to describe the influence of rainfall intensity on hydrograph. Correlations between the main indicators of precipitation and flow also were assessed. Results showed that flash floods were generally generated by average accumulated rainfall of around 100 mm at high intensities that could exceed 300 mm/h. Initial abstractions and average water losses during the rainfall-runoff conversion processes were very important (runoff coefficients of 6% and runoff thresholds of 62 mm). No correlation was found between initial abstractions (Ia) calculated from the basin characteristics and runoff thresholds (P0) empirically obtained, which create some doubts about the validity of Ia method for predicting floods in ephemeral streams. Accumulated rainfall was very important for flood volume, peak flow and water balance indicators, whereas intensity indicators were more related to the response times of the basins. Rainfall intensity variables influenced lag time. Accumulated rainfall, in combination with high reduced mean intensity and low persistence, were a good predictor for

  15. Extreme flooding tolerance in Rorippa

    NARCIS (Netherlands)

    Akman, M.; Bhikharie, A.; Mustroph, A.; Sasidharan, Rashmi

    2014-01-01

    Low oxygen stress imposed by floods creates a strong selection force shaping plant ecosystems in flood-prone areas. Plants inhabiting these environments adopt various adaptations and survival strategies to cope with increasing water depths. Two Rorippa species, R. sylvestris and R. amphibia that gro

  16. Operational flash flood forecasting platform based on grid technology

    Science.gov (United States)

    Thierion, V.; Ayral, P.-A.; Angelini, V.; Sauvagnargues-Lesage, S.; Nativi, S.; Payrastre, O.

    2009-04-01

    Flash flood events of south of France such as the 8th and 9th September 2002 in the Grand Delta territory caused important economic and human damages. Further to this catastrophic hydrological situation, a reform of flood warning services have been initiated (set in 2006). Thus, this political reform has transformed the 52 existing flood warning services (SAC) in 22 flood forecasting services (SPC), in assigning them territories more hydrological consistent and new effective hydrological forecasting mission. Furthermore, national central service (SCHAPI) has been created to ease this transformation and support local services in their new objectives. New functioning requirements have been identified: - SPC and SCHAPI carry the responsibility to clearly disseminate to public organisms, civil protection actors and population, crucial hydrologic information to better anticipate potential dramatic flood event, - a new effective hydrological forecasting mission to these flood forecasting services seems essential particularly for the flash floods phenomenon. Thus, models improvement and optimization was one of the most critical requirements. Initially dedicated to support forecaster in their monitoring mission, thanks to measuring stations and rainfall radar images analysis, hydrological models have to become more efficient in their capacity to anticipate hydrological situation. Understanding natural phenomenon occuring during flash floods mainly leads present hydrological research. Rather than trying to explain such complex processes, the presented research try to manage the well-known need of computational power and data storage capacities of these services. Since few years, Grid technology appears as a technological revolution in high performance computing (HPC) allowing large-scale resource sharing, computational power using and supporting collaboration across networks. Nowadays, EGEE (Enabling Grids for E-science in Europe) project represents the most important

  17. Characterization of process-oriented hydrologic model behavior with temporal sensitivity analysis for flash floods in Mediterranean catchments

    Directory of Open Access Journals (Sweden)

    P. A. Garambois

    2013-06-01

    Full Text Available This paper presents a detailed analysis of 10 flash flood events in the Mediterranean region using the distributed hydrological model MARINE. Characterizing catchment response during flash flood events may provide new and valuable insight into the dynamics involved for extreme catchment response and their dependency on physiographic properties and flood severity. The main objective of this study is to analyze flash-flood-dedicated hydrologic model sensitivity with a new approach in hydrology, allowing model outputs variance decomposition for temporal patterns of parameter sensitivity analysis. Such approaches enable ranking of uncertainty sources for nonlinear and nonmonotonic mappings with a low computational cost. Hydrologic model and sensitivity analysis are used as learning tools on a large flash flood dataset. With Nash performances above 0.73 on average for this extended set of 10 validation events, the five sensitive parameters of MARINE process-oriented distributed model are analyzed. This contribution shows that soil depth explains more than 80% of model output variance when most hydrographs are peaking. Moreover, the lateral subsurface transfer is responsible for 80% of model variance for some catchment-flood events' hydrographs during slow-declining limbs. The unexplained variance of model output representing interactions between parameters reveals to be very low during modeled flood peaks and informs that model-parsimonious parameterization is appropriate to tackle the problem of flash floods. Interactions observed after model initialization or rainfall intensity peaks incite to improve water partition representation between flow components and initialization itself. This paper gives a practical framework for application of this method to other models, landscapes and climatic conditions, potentially helping to improve processes understanding and representation.

  18. Differentiation of debris-flow and flash-flood deposits: implications for paleoflood investigations

    Science.gov (United States)

    Waythomas, Christopher F.; Jarrett, Robert D.; ,

    1993-01-01

    Debris flows and flash floods are common geomorphic processes in the Colorado Rocky Mountain Front Range and foothills. Usually, debris flows and flash floods are associated with excess summer rainfall or snowmelt, in areas were unconsolidated surficial deposits are relatively thick and slopes are steep. In the Front Range and foothills, flash flooding is limited to areas below about 2300m whereas, debris flow activity is common throughout the foothill and alpine zones and is not necessarily elevation limited. Because flash floods and debris flows transport large quantities of bouldery sediment, the resulting deposits appear somewhat similar even though such deposits were produced by different processes. Discharge estimates based on debris-flow deposits interpreted as flash-flood deposits have large errors because techniques for discharge retrodiction were developed for water floods with negligible sediment concentrations. Criteria for differentiating between debris-flow and flash-flood deposits are most useful for deposits that are fresh and well-exposed. However, with the passage of time, both debris-flow and flash-flood deposits become modified by the combined effects of weathering, colluviation, changes in surface morphology, and in some instances removal of interstitial sediment. As a result, some of the physical characteristics of the deposits become more alike. Criteria especially applicable to older deposits are needed. We differentiate flash-flood from debris-flow and other deposits using clast fabric measurements and other morphologic and sedimentologic techniques (e.g., deposit morphology, clast lithology, particle size and shape, geomorphic setting).

  19. Analysis of flash flood-triggering rainfall for a process-oriented hydrological model

    Science.gov (United States)

    Garambois, P. A.; Larnier, K.; Roux, H.; Labat, D.; Dartus, D.

    2014-02-01

    We propose an extended study of recent flood-triggering storms and resulting hydrological responses for catchments in the Pyrenean foothills up to the Aude region. For hydrometeorological sciences, it appears relevant to characterize flash floods and the storm that triggered them over various temporal and spatial scales. There are very few studies of extreme storm-caused floods in the literature covering the Mediterranean and highlighting, for example, the quickness and seasonality of this natural phenomenon. The present analysis is based on statistics that clarify the dependence between the spatial and temporal distributions of rainfall at catchment scale, catchment morphology and runoff response. Given the specific space and time scales of rainfall cell development, we show that the combined use of radar and a rain gauge network appears pertinent. Rainfall depth and intensity are found to be lower for catchments in the Pyrenean foothills than for the nearby Corbières or Montagne Noire regions. We highlight various hydrological behaviours and show that an increase in initial soil saturation tends to foster quicker catchment flood response times, of around 3 to 10 h. The hydrometeorological data set characterized in this paper constitutes a wealth of information to constrain a physics-based distributed model for regionalization purposes in the case of flash floods. Moreover, the use of diagnostic indices for rainfall distribution over catchment drainage networks highlights a unimodal trend in spatial temporal storm distributions for the entire flood dataset. Finally, it appears that floods in mountainous Pyrenean catchments are generally triggered by rainfall near the catchment outlet, where the topography is lower.

  20. Extreme flooding tolerance in Rorippa.

    Science.gov (United States)

    Akman, Melis; Bhikharie, Amit; Mustroph, Angelika; Sasidharan, Rashmi

    2014-01-01

    Low oxygen stress imposed by floods creates a strong selection force shaping plant ecosystems in flood-prone areas. Plants inhabiting these environments adopt various adaptations and survival strategies to cope with increasing water depths. Two Rorippa species, R. sylvestris and R. amphibia that grow in naturally flooded areas, have high submergence tolerance achieved by the so-called quiescence and escape strategies, respectively. In order to dissect the molecular mechanisms involved in these strategies, we investigated submergence-induced changes in gene expression in flooded roots of Rorippa species. There was a higher induction of glycolysis and fermentation genes and faster carbohydrate reduction in R. amphibia, indicating a higher demand for energy potentially leading to faster mortality by starvation. Moreover, R. sylvestris showed induction of genes improving submergence tolerance, potentially enhancing survival in prolonged floods. Additionally, we compared transcript profiles of these 2 tolerant species to relatively intolerant Arabidopsis and found that only Rorippa species induced various inorganic pyrophosphate dependent genes, alternatives to ATP demanding pathways, thereby conserving energy, and potentially explaining the difference in flooding survival between Rorippa and Arabidopsis.

  1. Geomorphically Effective Energy Expenditure for Quantifying Channel Responses to Extreme Floods

    Science.gov (United States)

    Amponsah, William; Righini, Margherita; Wohl, Ellen E.; Borga, Marco; Marchi, Lorenzo; Rathburn, Sara L.; Surian, Nicola; Zoccatelli, Davide

    2016-04-01

    Flash floods are characterized by strong spatio-temporal rainfall variability and therefore show variations in energy expenditure and associated geomorphic impacts that depend on geological controls on channel geometry and sediment characteristics, as well as on variations in flood intensity. Geomorphic modification is expected to occur in river channels when driving forces (i.e., hydraulic and abrasive forces of water and sediment acting on the channel) exceed threshold of resisting forces (i.e., the ability of channel boundaries to remain unchanged by the passage of water and sediments). However, these forces that determine the capacity of floods to modify existing channel configuration are extremely difficult to quantify. Geomorphic impacts or hazards usually take the form of erosional and depositional modification of the pre-flood channel and valley geometry. A central question in hydrogeomorphology relates to why flash floods of similar magnitudes and intensities sometimes produce dissimilar geomorphic results? In fact, some less magnitude floods in terms of discharge per unit of drainage area have been found to produce major geomorphic damage than some high magnitude events. Furthermore, the use of peak instantaneous flow parameters such as discharge, velocity, shear stress and stream power to quantify geomorphic changes have often been non-deterministic and/or inconclusive. Investigations are therefore needed on how factors such as channel geometry, substrate, riparian vegetation, sediment supply, and flood magnitude and duration can interact and influence geomorphic effectiveness of high magnitude floods. The main objective of this study is to assess the coupled influence of flood-flow duration and total energy expenditure on geomorphic response to extreme flash floods, which is aimed at developing an index that combines flow duration, stream power per unit area and threshold for major channel erosion to be evaluated as a predictor of geomorphic adjustment

  2. Mortality from flash floods: a review of national weather service reports, 1969-81.

    Science.gov (United States)

    French, J; Ing, R; Von Allmen, S; Wood, R

    1983-01-01

    Of all weather-related disasters that occur in the United States, floods are the main cause of death, and most flood-related deaths are attributed to flash floods. Whenever a weather-related disaster involves 30 or more deaths or more than $100 million in property damage, the National Weather Service (NWS) forms a survey team to investigate the disaster and write a report of findings. All NWS survey reports on flash floods issued during 1969-81 were reviewed to determine the mortality resulting from such floods, the effect of warnings on mortality, and the circumstances contributing to death. A total of 1,185 deaths were associated with 32 flash floods, an average of 37 deaths per flash flood. The highest average number of deaths per event was associated with the four flash floods in which dams broke after heavy rains. Although there were 18 flash floods in 1977-81 and only 14 in 1969-76, the number of deaths was 2 1/2 times greater during the earlier period. More than twice as many deaths were associated with flash floods for which the survey team considered the warnings inadequate than with those with warnings considered adequate. Ninety-three percent of the deaths were due to drowning and 42 percent of these drownings were car related. The other drownings occurred in homes, at campsites, or when persons were crossing bridges and streams. The need for monitoring dams during periods of heavy rainfall is highlighted.

  3. Implementing the national AIGA flash flood warning system in France

    Science.gov (United States)

    Organde, Didier; Javelle, Pierre; Demargne, Julie; Arnaud, Patrick; Caseri, Angelica; Fine, Jean-Alain; de Saint Aubin, Céline

    2015-04-01

    The French national hydro-meteorological and flood forecasting centre (SCHAPI) aims to implement a national flash flood warning system to improve flood alerts for small-to-medium (up to 1000 km2) ungauged basins. This system is based on the AIGA method, co-developed by IRSTEA these last 10 years. The method, initially set up for the Mediterranean area, is based on a simple event-based hourly hydrologic distributed model run every 15 minutes (Javelle et al. 2014). The hydrologic model ingests operational radar-gauge rainfall grids from Météo-France at a 1-km² resolution to produce discharges for successive outlets along the river network. Discharges are then compared to regionalized flood quantiles of given return periods and warnings (expressed as the range of the return period estimated in real-time) are provided on a river network map. The main interest of the method is to provide forecasters and emergency services with a synthetic view in real time of the ongoing flood situation, information that is especially critical in ungauged flood prone areas. In its enhanced national version, the hourly event-based distributed model is coupled to a continuous daily rainfall-runoff model which provides baseflow and a soil moisture index (for each 1-km² pixel) at the beginning of the hourly simulation. The rainfall-runoff models were calibrated on a selection of 700 French hydrometric stations with Météo-France radar-gauge reanalysis dataset for the 2002-2006 period. To estimate model parameters for ungauged basins, the 2 hydrologic models were regionalised by testing both regressions (using different catchment attributes, such as catchment area, soil type, and climate characteristic) and spatial proximity techniques (transposing parameters from neighbouring donor catchments), as well as different homogeneous hydrological areas. The most valuable regionalisation method was determined for each model through jack-knife cross-validation. The system performance was then

  4. The Ischia island flash flood of November 2009 (Italy): Phenomenon analysis and flood hazard

    Science.gov (United States)

    Santo, A.; Di Crescenzo, G.; Del Prete, S.; Di Iorio, L.

    The island of Ischia is particularly susceptible to landslides and flash floods due to its particular geological and geomorphological context. Urbanization in recent decades coupled with the development of tourism has increased the risk. After the November 10, 2009 event occurring in the northern sector of the island (the town of Casamicciola), a detailed geo-morphological survey was conducted to ascertain the evolution of the phenomenon. In the watersheds upstream of Casamicciola, many landslides were mapped and the volume of material involved during detachment and sliding was estimated. In the lower course area, near the town and towards the sea, flow pathways were reconstructed with the aid of extensive video footage taken during the event. Rainfall data were also analyzed and a relationship was established between the hourly rainfall rate and the flash flood. The phenomenon was found to be quite complex, with many upstream landslides stopping before reaching the urban area. In the lower course the alluvial event occurred as a flood with a very small sediment discharge, which left a very thin layer of sediment. Reconstruction of the flash flood phenomenon suggested possible action for future risk mitigation, early warning and civil protection plans.

  5. Extreme flood events in the Dead Sea basin

    Science.gov (United States)

    Ahlborn, Marieke; Ben Dor, Yoav; Schwab, Markus J.; Neugebauer, Ina; Plessen, Birgit; Tjallingii, Rik; Erel, Yigal; Enzel, Yehouda; Brauer, Achim

    2016-04-01

    The Dead Sea is a hypersaline, terminal lake located within the Dead Sea basin at the lowest continental elevation on Earth (~425 m below mean sea level). Extreme hydro-meteorological events in terms of flash floods occur regularly during the wet season in the Dead Sea basin and adjacent mountain ranges. However, little is known about the impact of these extreme floods on the sedimentary dynamics in the Dead Sea and possible links to long-term climate changes. The trilateral research project PALEX (Paleoclimate in the Eastern Mediterranean Region - Levante: Paleohydrology and Extreme Flood Events) was recently initiated within the framework of the DFG priority program 1006 ICDP (International Continental Scientific Drilling Program) to investigate extreme flood events in the Dead Sea basin during the Late Pleistocene and Holocene. Within the ICDP Dead Sea Deep Drilling Project (DSDDP) the ~455 m long sediment core 5017-1 was recovered from the northern Dead Sea basin. Previously published results (Neugebauer et al., 2014, 2015) have demonstrated the occurrence of extreme flood events represented in the sediments as thick graded detrital layers during Late Holocene dry phases. Based on these results we will apply a comprehensive analytical approach including microfacies analyses, μXRF element scanning, and stable isotope geochemistry to different time intervals of core 5017-1. Particularly, we aim to investigate the structure and composition of detrital layers in order to decipher sediment transport mechanisms and the provenance of the flood-triggered sediments. The overarching goal is to establish a high-resolution extreme flood time series for the Dead Sea basin on the basis of a previously established radiocarbon and U-Th chronology (Torfstein et al., 2015; Neugebauer et al., 2014) and to study a possible link between the frequency and magnitude of extreme flood events and the long-term climate trend. Neugebauer I, Brauer A, Schwab MJ, et al. (2014) Lithology of

  6. An early warning system for flash floods in Egypt

    Science.gov (United States)

    Cools, J.; Abdelkhalek, A.; El Sammany, M.; Fahmi, A. H.; Bauwens, W.; Huygens, M.

    2009-09-01

    This paper describes the development of the Flash Flood Manager, abbreviated as FlaFloM. The Flash Flood Manager is an early warning system for flash floods which is developed under the EU LIFE project FlaFloM. It is applied to Wadi Watier located in the Sinai peninsula (Egypt) and discharges in the Red Sea at the local economic and tourist hub of Nuweiba city. FlaFloM consists of a chain of four modules: 1) Data gathering module, 2) Forecasting module, 3) Decision support module or DSS and 4) Warning module. Each module processes input data and consequently send the output to the following module. In case of a flash flood emergency, the final outcome of FlaFloM is a flood warning which is sent out to decision-makers. The ‘data gathering module’ collects input data from different sources, validates the input, visualise data and exports it to other modules. Input data is provided ideally as water stage (h), discharge (Q) and rainfall (R) through real-time field measurements and external forecasts. This project, however, as occurs in many arid flash flood prone areas, was confronted with a scarcity of data, and insufficient insight in the characteristics that release a flash flood. Hence, discharge and water stage data were not available. Although rainfall measurements are available through classical off line rain gauges, the sparse rain gauges network couldn’t catch the spatial and temporal characteristics of rainfall events. To overcome this bottleneck, we developed rainfall intensity raster maps (mm/hr) with an hourly time step and raster cell of 1*1km. These maps are derived through downscaling from two sources of global instruments: the weather research and forecasting model (WRF) and satellite estimates from the Tropical Rainfall Measuring Mission (TRMM). The ‘forecast module’ comprises three numerical models that, using data from the gathering module performs simulations on command: a rainfall-runoff model, a river flow model, and a flood model. A

  7. Flash Floods Simulation using a Physical-Based Hydrological Model at Different Hydroclimatic Regions

    Science.gov (United States)

    Saber, Mohamed; Kamil Yilmaz, Koray

    2016-04-01

    Currently, flash floods are seriously increasing and affecting many regions over the world. Therefore, this study will focus on two case studies; Wadi Abu Subeira, Egypt as arid environment, and Karpuz basin, Turkey as Mediterranean environment. The main objective of this work is to simulate flash floods at both catchments considering the hydrometeorological differences between them which in turn effect their flash flood behaviors. An integrated methodology incorporating Hydrological River Basin Environmental Assessment Model (Hydro-BEAM) and remote sensing observations was devised. Global Satellite Mapping of Precipitation (GSMAP) were compared with the rain gauge network at the target basins to estimate the bias in an effort to further use it effectively in simulation of flash floods. Based on the preliminary results of flash floods simulation on both basins, we found that runoff behaviors of flash floods are different due to the impacts of climatology, hydrological and topographical conditions. Also, the simulated surface runoff hydrographs are reasonably coincide with the simulated ones. Consequently, some mitigation strategies relying on this study could be introduced to help in reducing the flash floods disasters at different climate regions. This comparison of different climatic basins would be a reasonable implication for the potential impact of climate change on the flash floods frequencies and occurrences.

  8. All-season flash flood forecasting system for real-time operations

    Science.gov (United States)

    Flash floods can cause extensive damage to both life and property, especially because they are difficult to predict. Flash flood prediction requires high-resolution meteorologic observations and predictions, as well as calibrated hydrologic models in addition to extensive data handling. We have de...

  9. Flash Flood Hazard Mapping Using Satellite Images and GIS Tools: A case study of Najran City, Kingdom of Saudi Arabia (KSA

    Directory of Open Access Journals (Sweden)

    Ismail Elkhrachy

    2015-12-01

    Full Text Available Flash flood in the cities led to high levels of water in the streets and roads, causing many problems such as bridge collapse, building damage and traffic problems. It is impossible to avoid risks of floods or prevent their occurrence, however it is plausible to work on the reduction of their effects and to reduce the losses which they may cause. Flash flood mapping to identify sites in high risk flood zones is one of the powerful tools for this purpose. Mapping flash flood will be beneficial to urban and infrastructure planners, risk managers and disaster response or emergency services during extreme and intense rainfall events. The objective of this paper is to generate flash flood map for Najran city, Saudi Arabia, using satellite images and GIS tools. To do so, we use SPOT and SRTM DEMs data for which accuracy assessment is achieved by using check points, obtained by GPS observations. Analytical Hierarchical Process (AHP is used to determine relative impact weight of flood causative factors to get a composite flood hazard index (FHI. The causative factors in this study are runoff, soil type, surface slope, surface roughness, drainage density, distance to main channel and land use. All used data are finally integrated in an ArcMap to prepare a final flood hazard map for study area. The areas in high risk flood zones are obtained by overlaying the flood hazard index map with the zone boundaries layer. The affected population number and land area are determined and compared.

  10. Structure and evolution of flash flood producing storms in a small urban watershed

    Science.gov (United States)

    Yang, Long; Smith, James; Baeck, Mary Lynn; Smith, Brianne; Tian, Fuqiang; Niyogi, Dev

    2016-04-01

    The objective of this study is to examine the structure and evolution of storms that produce flash floods in "small" urban watersheds. The study site is Harry's Brook, a 1.1 km2 urban watershed in Princeton, New Jersey. A catalog of 15 storms is developed for Harry's Brook based on paired observations of streamflow and rainfall. Lagrangian analyses of storm properties are based on storm tracking procedures utilizing 3-D radar reflectivity observations from the KDIX (Fort Dix, New Jersey) Weather Surveillance Radar, 1988 Doppler. Analyses focus on the storm elements that were responsible for the peak rainfall rates over the watershed. The 22 July 2006 storm, which produced the record flood peak in the catalog (a unit discharge of 26.8 m3 s-1 km-2) was characterized by thunderstorm cells that produced more than 50 cloud-to-ground lightning strikes and "collapsed" over Harry's Brook. The 3 June 2006 storm, which produced the third largest flood peak (a unit discharge of 11.1 m3 s-1 km-2), was a "low-echo centroid" storm with no lightning. We use cloud-to-ground flash rate, echo top height, maximum reflectivity, and height of maximum reflectivity as key variables for characterizing convective intensity. Storm motion is examined through a time series of storm speed and direction. The 22 July 2006 and 3 June 2006 storms provide end-members of storm properties, centering on "convective intensity," which are associated with flash flooding in small urban watersheds. Extreme 1-15 min rainfall rates are produced by warm season convective systems at both ends of the convective intensity spectrum.

  11. Empirical rainfall thresholds and copula based IDF curves for shallow landslides and flash floods

    Science.gov (United States)

    Bezak, Nejc; Šraj, Mojca; Brilly, Mitja; Mikoš, Matjaž

    2015-04-01

    Large mass movements, like deep-seated landslides or large debris flows, and flash floods can endanger human lives and cause huge environmental and economic damage in hazard areas. The main objective of the study was to investigate the characteristics of selected extreme rainfall events, which triggered landslides and caused flash floods, in Slovenia in the last 25 years. Seven extreme events, which occurred in Slovenia (Europe) in the last 25 years (1990-2014) and caused 17 casualties and about 500 million Euros of economic loss, were analysed in this study. Post-event analyses showed that rainfall characteristics triggering flash floods and landslides are different where landslides were triggered by longer duration (up to one or few weeks) rainfall events and flash floods by short duration (few hours to one or two days) rainfall events. The sensitivity analysis results indicate that inter-event time variable, which is defined as the minimum duration of the period without rain between two consecutive rainfall events, and sample definition methodology can have significant influence on the position of rainfall events in the intensity-duration space, on the constructed intensity-duration-frequency (IDF) curves and on the relationship between the empirical rainfall threshold curves and IDF curves constructed using copula approach. The empirical rainfall threshold curves (ID curves) were also evaluated for the selected extreme events. The results indicate that a combination of several empirical rainfall thresholds with appropriate high density of rainfall measuring network can be used as part of the early warning system for initiation of landslides and debris flows. However, different rainfall threshold curves should be used for lowland and mountainous areas in Slovenia. Furthermore, the intensity-duration-frequency (IDF) relationship was constructed using the Frank copula functions for 16 pluviographic meteorological stations in Slovenia using the high resolution

  12. Toward a coupled Hazard-Vulnerability Tool for Flash Flood Impacts Prediction

    Science.gov (United States)

    Terti, Galateia; Ruin, Isabelle; Anquetin, Sandrine; Gourley, Jonathan J.

    2015-04-01

    Flash floods (FF) are high-impact, catastrophic events that result from the intersection of hydrometeorological extremes and society at small space-time scales, generally on the order of minutes to hours. Because FF events are generally localized in space and time, they are very difficult to forecast with precision and can subsequently leave people uninformed and subject to surprise in the midst of their daily activities (e.g., commuting to work). In Europe, FFs are the main source of natural hazard fatalities, although they affect smaller areas than riverine flooding. In the US, also, flash flooding is the leading cause of weather-related deaths most years, with some 200 annual fatalities. There were 954 fatalities and approximately 31 billion U.S. dollars of property damage due to floods and flash floods from 1995 to 2012 in the US. For forecasters and emergency managers the prediction of and subsequent response to impacts due to such a sudden onset and localized event remains a challenge. This research is motivated by the hypothesis that the intersection of the spatio-temporal context of the hazard with the distribution of people and their characteristics across space and time reveals different paths of vulnerability. We argue that vulnerability and the dominant impact type varies dynamically throughout the day and week according to the location under concern. Thus, indices are appropriate to develop and provide, for example, vehicle-related impacts on active population being focused on the road network during morning or evening rush hours. This study describes the methodological developments of our approach and applies our hypothesis to the case of the June 14th, 2010 flash flood event in the Oklahoma City area (Oklahoma, US). Social (i.e. population socio-economic profile), exposure (i.e. population distribution, land use), and physical (i.e. built and natural environment) data are used to compose different vulnerability products based on the forecast location

  13. A Novel Dual Traffic/Flash Flood Monitoring System Using Passive Infrared/Ultrasonic Sensors

    KAUST Repository

    Mousa, Mustafa

    2015-10-19

    Floods are the most common type of natural disaster, causing thousands of casualties every year. Among these events, urban flash floods are particularly deadly because of the short timescales on which they occur, and because of the high concentration of population in cities. Since most flash flood casualties are caused by a lack of information, it is critical to generate accurate and detailed warnings of flash floods. However, deploying an infrastructure that solely monitor flash floods makes little economic sense, since the average periodicity of catastrophic flash floods exceeds the lifetime of a typical sensor network. To address this issue, we propose a new sensing device that can simultaneously monitor urban flash floods and another phenomenon of interest (traffic congestion on the present case). This sensing device is based on the combination of an ultrasonic rangefinder with one or multiple remote temperature sensors. We show an implementation of this device, and illustrate its performance in both traffic flow and flash flood sensing. Field data shows that the sensor can detect vehicles with a 99% accuracy, in addition to estimating their speed and classifying them in function of their length. The same sensor can also monitor urban water levels with an accuracy of less than 2 cm. Two of the sensors have been deployed in a flood prone area, where they captured the only (minor) flash flood that occurred over the one-year test period, with no false detection, and an agreement in the estimated water level estimate (during the flash flood event) of about 2 cm.

  14. Anatomy of extraordinary rainfall and flash flood in a Dutch lowland catchment

    Science.gov (United States)

    Brauer, C. C.; Teuling, A. J.; Overeem, A.; van der Velde, Y.; Hazenberg, P.; Warmerdam, P. M. M.; Uijlenhoet, R.

    2011-06-01

    On 26 August 2010 the eastern part of The Netherlands and the bordering part of Germany were struck by a series of rainfall events lasting for more than a day. Over an area of 740 km2 more than 120 mm of rainfall were observed in 24 h. This extreme event resulted in local flooding of city centres, highways and agricultural fields, and considerable financial loss. In this paper we report on the unprecedented flash flood triggered by this exceptionally heavy rainfall event in the 6.5 km2 Hupsel Brook catchment, which has been the experimental watershed employed by Wageningen University since the 1960s. This study aims to improve our understanding of the dynamics of such lowland flash floods. We present a detailed hydrometeorological analysis of this extreme event, focusing on its synoptic meteorological characteristics, its space-time rainfall dynamics as observed with rain gauges, weather radar and a microwave link, as well as the measured soil moisture, groundwater and discharge response of the catchment. At the Hupsel Brook catchment 160 mm of rainfall was observed in 24 h, corresponding to an estimated return period of well over 1000 years. As a result, discharge at the catchment outlet increased from 4.4 × 10-3 to nearly 5 m3 s-1. Within 7 h discharge rose from 5 × 10-2 to 4.5 m3 s-1. The catchment response can be divided into four phases: (1) soil moisture reservoir filling, (2) groundwater response, (3) surface depression filling and surface runoff and (4) backwater feedback. The first 35 mm of rainfall were stored in the soil without a significant increase in discharge. Relatively dry initial conditions (in comparison to those for past discharge extremes) prevented an even faster and more extreme hydrological response.

  15. Local community perception and awareness of flash floods vulnerability at a small catchment scale in the Bend Subcarpathians, Romania

    Science.gov (United States)

    Micu, Dana; Balteanu, Dan; Sima, Mihaela; Dumitrascu, Monica; Chendes, Viorel; Grigorescu, Ines; Dragota, Carmen; Dogaru, Diana; Costache, Andra

    2015-04-01

    The study aims to identify local communities perception and awareness in terms of hydro-meteorological extreme events in order to better understand the local context of vulnerability and communities resilience to flash floods as well as the mitigation measures undertaken by local authorities to cope with these phenomena. The study-area is located in the Bend Subcarpathians, Romania, a region well known for high tectonic mobility and dynamics of hydro-geomorphic processes (e.g. floods and flash floods, landslides). The study was conducted in the framework of VULMIN project (PN-II-PT-PCCA-2011-3.1-1587), funded by the Ministry of National Education for the period 2012-2016 (http://www.igar-vulmin.ro). The previous analyses conducted in the project showed a high exposure to flash floods of small river catchments (generally below 200 km2 ) located in the study-area (Teleajen-Buzau hydrographic area). Some of the most recent events (2005, 2008, 2010 and 2014) had a high impact on local communities in terms of important losses to their assets and psychological effects. Thus, in the summer 2014, a questionnaire-based survey was addressed to over 50 households (from 5 villages), significantly affected by flash floods and structured interviews were held with local authorities (local municipalities, county Civil Protection Inspectorates). The questionnaire was focused on the perception of human vulnerability to environmental change and extreme events, mainly floods, aiming to outline the personal experience, post-disaster rehabilitation, awareness, worrying and opinion on the measures aimed to prevent and mitigate the effects of flooding. The flash flood events are of major concern for local community, due to their high return period (1-5 years) and magnitude in the recent years. This influences also the population response and adaptive capacity to these events, which is limited to individual measures (e.g. buildings consolidations and relocations). The survey showed a

  16. Risk assessment of flash floods in central Pyrenees (Spain) through land use change analysis

    Science.gov (United States)

    Serrano-Notivoli, Roberto; Mora, Daniel; Sánchez-Fabre, Miguel; Ángel Saz, Miguel; Ollero, Alfredo

    2015-04-01

    Nowadays, the main cause of the damages to human areas is the increased risk exposure. The urbanization in touristic areas in Pyrenees has increased enormously in last 25 years, and the most of urban development have been made on land occupied by the stream channel. We present two different case studies in central Pyrenees: one in Aragón river and one in Ésera river. We made a land use analysis from 1956 to 2013 in the headwaters of these two rivers delimiting the channel in different flash floods events, and analysing the amount and distribution of precipitation at the same time. The results show that the risk exposure is one of the main factors of the impact of flash floods. We found that most of the damage on urbanization and human activities was caused by the urban occupation of areas that were located on the floodplain of the river. For both Aragon and Esera headwaters precipitation events were considered extreme in their time series. However, the amount of precipitation of these extreme events does not support the consequences in geomorphological and human environments. The events of high intensity rainfall over the last years could be expected, yet, it had unexpected consequences that could be predictable by land managers through an appropriate regional planning.

  17. Modeling flash floods in southern France for road management purposes

    Science.gov (United States)

    Vincendon, Béatrice; Édouard, Simon; Dewaele, Hélène; Ducrocq, Véronique; Lespinas, Franck; Delrieu, Guy; Anquetin, Sandrine

    2016-10-01

    Flash-floods are among the most devastating hazards in the Mediterranean. A major subset of damage and casualties caused by flooding is related to road submersion. Distributed hydrological nowcasting can be used for road flooding monitoring. This requires rainfall-runoff simulations at a high space and time resolution. Distributed hydrological models, such as the ISBA-TOP coupled system used in this study, are designed to simulate discharges for any cross-section of a river but they are generally calibrated for certain outlets and give deteriorated results for the sub-catchment outlets. The paper first analyses ISBA-TOP discharge simulations in the French Mediterranean region for target points different from the outlets used for calibration. The sensitivity of the model to its governing factors is examined to highlight the validity of results obtained for ungauged river sections compared with those obtained for the main gauged outlets. The use of improved model inputs is found beneficial for sub-catchments simulation. The calibration procedure however provides the parameters' values for the main outlets only and these choices influence the simulations for ungauged catchments or sub-catchments. As a result, a new version of ISBA-TOP system without any parameter to calibrate is used to produce diagnostics relevant for quantifying the risk of road submersion. A first diagnostic is the simulated runoff spatial distribution, it provides a useful information about areas with a high risk of submersion. Then an indicator of the flood severity is given by simulated discharges presented with respect to return periods. The latter has to be used together with information about the vulnerability of road-river cross-sections.

  18. Neural networks-based operational prototype for flash flood forecasting: application to Liane flash floods (France

    Directory of Open Access Journals (Sweden)

    Bertin Dominique

    2016-01-01

    Full Text Available The Liane River is a small costal river, famous for its floods, which can affect the city of Boulogne-sur-Mer. Due to the complexity of land cover and hydrologic processes, a black-box non-linear modelling was chosen using neural networks. The multilayer perceptron model, known for its property of universal approximation is thus chosen. Four models were designed, each one for one forecasting horizon using rainfall forecasts: 24h, 12h, 6h, 3h. The desired output of the model is original: it represents the maximal value of the water level respectively 24h, 12h, 6h, 3h ahead. Working with best forecasts of rain (the observed ones during the event in the past, on the major flood of the database in test set, the model provides excellent forecasts. Nash criteria calculated for the four lead times are 0.98 (3h, 0.97 (6h, 0.91 (12h, 0.89 (24h. Designed models were thus estimated as efficient enough to be implemented in a specific tool devoted to real time operational use. The software tool is described hereafter: designed in Java, it presents a friendly interface allowing applying various scenarios of future rainfalls, and a graphical visualization of the predicted maximum water levels and their associated real time observed values.

  19. The Use of Water Vapor for Detecting Environments that Lead to Convectively Produced Heavy Precipitation and Flash Floods

    Science.gov (United States)

    Scofield, Rod; Vicente, Gilberto; Hodges, Mike

    2000-01-01

    This Tech Report summarizes years of study and experiences on using GOES Water vapor (6.7 micron and precipitable water) and Special Sensor Microwave Imager (SSM/1) from the Defense Meteorological Satellite Program (DMSP) derived Precipitable Water (PNAI) for detecting environments favorable for convectively produced flash floods. An emphasis is on the moisture. upper air flow, and equivalent potential temperature (Theta(sub e)) patterns that lead to devastating flood events. The 15 minute 6.7 micron water vapor imagery is essential for tracking middle to upper tropospheric disturbances that produce upward vertical motion and initiate flash flood producing systems. Water vapor imagery at 6.7 micron is also used to detect surges of upper level moisture (called tropical water vapor plumes) that have been associated with extremely heavy rainfall. Since the water vapor readily depicts lifting mechanisms and upper level moisture, water vapor imagery is often an excellent source of data for recognizing patterns of heavy precipitation and flash floods. In order to analyze the depth of the moisture, the PW aspects of the troposphere must be measured. The collocation (or nearby location) of high values ofP\\V and instability are antecedent conditions prior to the flash flood or heavy rainfall events. Knowledge of PW magnitudes have been used as thresholds for impending flash flood events, PW trends are essential in flash flood prediction. Conceptual models and water vapor products are used to study some of the characteristics of convective systems that occurred over the United States of America (USA) during the summer of 1997 and the 1997-1998 El Nino. P\\V plumes were associated with most of the \\vest coast heavy precipitation events examined during the winter season of 1997 - 1998, In another study, conducted during the summer season of 1997. results showed that the collocation of water vapor (6.7 micron) and P\\N' plumes possessed higher correlations with predicted

  20. Preparatory investigations for a public dialogue on flash flood risk in the Mehlemer Bach catchment, Germany

    Science.gov (United States)

    Seydel, Elena; Turley, Michael; Becht, Michael; Heckmann, Tobias

    2013-04-01

    On July 3rd, 2010, an extreme precipitation event occurred in the municipality of Wachtberg at the southern urban fringe of the Federal City of Bonn. The 30-min intensity of the torrential rain was estimated to represent a 1000 year event according to the KOSTRA dataset (German Meteorological Service, DWD). Rapid overland flow and the exceedance of the design values of the sewerage system caused a flash flood in the Mehlemer Bach catchment. Roughly 400 buildings were affected in its lower, urbanized part, and it took over two weeks to clear the damage. Similar flash flood events have been recorded in the same catchment regularly since the year 1693, three times in the last 80 years alone. The fact that, in case of the 2010 event, the official weather warning was released almost simultaneously to the beginning of the downpour highlights the urgent need for preparative action in the longer term. Flash flood risk mitigation relies, among others, on risk awareness and preparedness of residents. One aim of this study is to analyse the current risk communication in the drainage area of Mehlemer Bach through questionnaires and expert interviews, which will provide a good basis for an open dialogue between residents and the authorities. There is an urgent need for practical and accessible advice, and it must be ensured that the resources and capabilities of the individuals involved are taken into consideration. In addition, we compare a hazard map of the area to mental maps drawn by the local population in order to assess their risk perception.

  1. A study case of Baranca drainage basin flash-floods using the hydrological model of Hec-Ras

    Directory of Open Access Journals (Sweden)

    Aritina HALIUC

    2012-09-01

    Full Text Available In the last decades, the floods which occurred within Romanian territory stand as proof for the increased frequency of the extreme hydrological hazards which have negative effects on the normal pathway of the human-beings activities. The technological progress among with the increased frequency of floods events are the base for the development of informational programs for the analysis, simulation and flood management. The Baranca brook which drains a considerable part of Zamostea village (Romania was used as a pilot drainage basin for the flash-flood simulation using the Hec-Ras program and the Arcgis extension, HecGeo-Ras. The flash-floods that occurred in the summer of 2010 were used to validate the results of the simulation. Between 28.06.2010 – 29.06.2010, two flash-floods occurred in the Baranca drainage basin with a discharge oscillated between 10m3 and 70m3, a water extent which covered an area of 5.14 km2 and a depth ranging between 0.3-3m. The programs are capable to simulate the water flow and to investigate the floodway encroachments in the study area. The damages evaluated in the field along with the program’s results reveal the fact that more than half of the built-up areas of Zamostea village are established along brooks, within the floodplain area. What is more, after the 2010 floods, the expension of the habitable area was not detained by the water danger, many houses are still built on the floodplain. The programs used, taking an acceptable margin of error, may be integrated into any flood management strategy or in any watershed plan and may provide the necessary support for mitigating the risks associated with floods

  2. The challenge of predicting flash floods from thunderstorm rainfall.

    Science.gov (United States)

    Gupta, Hosin; Sorooshian, Soroosh; Gao, Xiaogang; Imam, Bisher; Hsu, Kuo-Lin; Bastidas, Luis; Li, Jailun; Mahani, Shayesteh

    2002-07-15

    A major characteristic of the hydrometeorology of semi-arid regions is the occurrence of intense thunderstorms that develop very rapidly and cause severe flooding. In summer, monsoon air mass is often of subtropical origin and is characterized by convective instability. The existing observational network has major deficiencies for those regions in providing information that is important to run-off generation. Further, because of the complex interactions between the land surface and the atmosphere, mesoscale atmospheric models are currently able to reproduce only general features of the initiation and development of convective systems. In our research, several interrelated components including the use of satellite data to monitor precipitation, data assimilation of a mesoscale regional atmospheric model, modification of the land component of the mesoscale model to better represent the semi-arid region surface processes that control run-off generation, and the use of ensemble forecasting techniques to improve forecasts of precipitation and run-off potential are investigated. This presentation discusses our ongoing research in this area; preliminary results including an investigation related to the unprecedented flash floods that occurred across the Las Vegas valley (Nevada, USA) in July of 1999 are discussed.

  3. Gauging Flash-Floods: Automated Measurement of Flood Events in Mountain Torrents

    Science.gov (United States)

    Liechti, Katharina; Boss, Stefan; Fritschi, Bruno; Zappa, Massimiliano

    2017-04-01

    Rating curves contain uncertainties, especially in their upper range of higher discharge. This is due to more uncertainties in the measurements and also the typically lower number of measurements of high discharge events. However, it is the upper part of a rating curve that is of interest if it comes to dimensioning protection measures against floods and flash floods. For small municipalities who plan mitigation measures like a dam for protection against flash floods of small mountain torrent a rating curve as accurate as possible can be of great interest. It helps to reduce costs that can be caused by both under- and overdimensioning of a protective structure. We therefore invented a mobile discharge measurement station that is set up to construct a rating curve for small turbulent mountain torrents. It operates with salt dilution method and works in its current setup up to about 10 m3/s. The salt is injected automatically to the torrent when an event of desired magnitude takes place. Further downstream a conductivity measuring sensor records the change in salt concentration of the stream water. This mechanism is guided by automatic continuous observation of radar quantitative precipitation estimates (QPE) and a water pressure sensor. Measurements at a first test site gave promising results. The system does event measurements independent of the time of day and day of the week. The measuring equipment at the field site is only activated in case of an event. Therefore it has a low power consumption and can be run by only two solar panels.

  4. A physically-based parsimonious hydrological model for flash floods in Mediterranean catchments

    Directory of Open Access Journals (Sweden)

    H. Roux

    2011-09-01

    Full Text Available A spatially distributed hydrological model, dedicated to flood simulation, is developed on the basis of physical process representation (infiltration, overland flow, channel routing. Estimation of model parameters requires data concerning topography, soil properties, vegetation and land use. Four parameters are calibrated for the entire catchment using one flood event. Model sensitivity to individual parameters is assessed using Monte-Carlo simulations. Results of this sensitivity analysis with a criterion based on the Nash efficiency coefficient and the error of peak time and runoff are used to calibrate the model. This procedure is tested on the Gardon d'Anduze catchment, located in the Mediterranean zone of southern France. A first validation is conducted using three flood events with different hydrometeorological characteristics. This sensitivity analysis along with validation tests illustrates the predictive capability of the model and points out the possible improvements on the model's structure and parameterization for flash flood forecasting, especially in ungauged basins. Concerning the model structure, results show that water transfer through the subsurface zone also contributes to the hydrograph response to an extreme event, especially during the recession period. Maps of soil saturation emphasize the impact of rainfall and soil properties variability on these dynamics. Adding a subsurface flow component in the simulation also greatly impacts the spatial distribution of soil saturation and shows the importance of the drainage network. Measures of such distributed variables would help discriminating between different possible model structures.

  5. Mapping rivers with a potential danger of damage by flash flooding and debris flows

    Science.gov (United States)

    Peereboom, I.; Svegården, J.; Fergus, T.

    2009-04-01

    Landforms associated with past debris flows such as alluvial fans are typical locations for settlements in Norway. Flash floods with associated debris flows in small and steep river catchments cause a great deal of damage to infrastructure and housing located on alluvial fans. The Norwegian Water Resources and Energy Resources Directorate (NVE) is the national authority responsible for flood and landslide hazard management in Norway. Mapping areas with a risk of damage from flooding and landslides coupled with advice on land use planning, results in better land use practices and an increased awareness of the potential hazard among local authorities and citizens. Methods for mapping floodplain inundation for large rivers are well developed. This is not the case for rivers with small and steep catchments with a potential for high rates of erosion and sediment transport. A method for identifying and mapping rivers with a potential danger of flash flooding and associated debris flows is currently being developed at NVE. The resultant maps will assist local authorities in the first step in land use planning where they are required to identify if there is a potential hazard in the area. The method makes use of spatial data available for the whole country and is based on a 25*25 m terrain model. The method is based on two simple assumptions adapted to the available data: i) Under normal hydraulic conditions there is a balance between processes of erosion and sedimentation. A debris flow will first occur when this balance is disturbed. This is quantified by the relative difference between the discharge of an extreme flood and floods that occur more frequently, ie. if the difference is large the probability of a debris flow occurring is greater and vice versa. ii) Steep rivers with a large difference in height between cells have more energy available for erosion and sediment transport and therefore a larger potential for erosion and sediment transport than less steep rivers

  6. Flash floods along the Italian coastal areas: examples from Pozzuoli city, Campania, Italy

    Science.gov (United States)

    Esposito, Giuseppe; Grimaldi, Giuseppe; Matano, Fabio; Mazzola, Salvatore; Sacchi, Marco

    2014-05-01

    The Italian western coastal areas are the most exposed in the country to low-pressure systems coming from the central-western Mediterranean Sea and Atlantic Ocean. In the last years, many Italian coastal villages were struck by floods and flow processes triggered by high-intensity and short-duration rainfall, typical of flash flood events. In the Campania region (SW Italy) a series of events has caused several fatalities and heavy damages in the last decades, i.e. the flash floods of Casamicciola - Ischia Island (10/11/2009 - 1 fatality) and Atrani (9/9/2010 - 1 fatality). In this work we describe the rainfall properties and the ground effects of the 2009, 2010 and 2011 flash floods which involved the city of Pozzuoli, along the Campi Flegrei coast, where a catastrophic flood event (13 fatalities) is reported in 1918 in the AVI Project database. Rainfall data were measured at a sampling rate of 10 minutes by a regional Civil Protection rain gauge located in the city of Pozzuoli near the areas struck by the flash flood effects. In order to analyze the extreme features of the rainstorms and compare them, we have considered the 1-hour maximum rainfall amount and the 10-min peak storm intensity value for each event. The first rainstorm occurred on 14 September 2009; it was characterized by a 1-hour maximum rainfall amount of 34.4 mm and a 10-min peak storm intensity of 57.6 mm/h. The second rainstorm occurred on 30 July 2010; it was characterized by a 1-hour maximum rainfall amount of 40.6 mm and a 10-min peak storm intensity of 126 mm/h. The third rainstorm occurred on 06 November 2011; it was characterized by a 1-hour maximum rainfall amount of 44.2 mm and a 10-min peak storm intensity of 67.2 mm/h. The three described rainstorms all triggered erosional processes and shallow landslides in the upper part of the Pozzuoli drainage basin that supplied sheet flows and hyperconcentrated flows downstream, with severe damage to the human structures built near or inside the

  7. Perturbation of convection-permitting NWP forecasts for flash-flood ensemble forecasting

    National Research Council Canada - National Science Library

    Vincendon, B; Ducrocq, V; Nuissier, O; Vié, B

    2011-01-01

      Mediterranean intense weather events often lead to devastating flash-floods. Extending the forecasting lead times further than the watershed response times, implies the use of numerical weather prediction (NWP...

  8. Analysis of economic vulnerability to flash floods in urban areas of Castilla y León (Spain)

    Science.gov (United States)

    Aroca-Jimenez, Estefanía; Bodoque, Jose Maria; García, Juan Antonio; Diez-Herrero, Andres

    2017-04-01

    The growth of exposed population to floods, the expansion in allocation of economical activities to flood-prone areas and the rise of extraordinary event frequency over the last few decades, have resulted in an increase of flash flood-related casualties and economic losses. The increase in these losses at an even higher rate than the increase of magnitude and frequency of extreme events, underline that the vulnerability of societies exposed is a key aspect to be considered. Vulnerability is defined as the conditions determined by physical, social, economic and environmental factors or processes which increase the susceptibility of a community to the impact of hazards such as floods, being flash floods one of the natural hazards with the greatest capacity to generate risk. In recent years, numerous papers have deal with the assessment of the social dimension of vulnerability. However, economic factors are often a neglected aspect in traditional risk assessments which mainly focus on structural measures and flood damage models. In this context, the aim of this research is to identify those economic characteristics which render people vulnerable to flash flood hazard, and consider whether these characteristics are identifiable as local patterns at regional level. The result of this task is an Economic Vulnerability Index (EVI) based on susceptibility profiles of the population per township. These profiles are obtained by Hierarchical Segmentation and Latent Class Cluster Analysis of economic information provided by different public institutional databases. The methodology proposed here is implemented in the region of Castilla y León (94,230 km2), placed in Central-Northern Spain. Townships included in this study meet two requirements: i) urban areas are potentially affected by flash floods (i.e. villages are crossed by rivers or streams with a longitudinal slope higher than 0.01 m m-1); ii) urban areas are affected by an area with low or exceptional probability of

  9. Spatial extension of the reconstruction of 1874 Santa Tecla's flash floods in Catalonia (NE Iberian Peninsula)

    Science.gov (United States)

    Lluís Ruiz-Bellet, Josep; Carles Balasch, Josep; Tuset, Jordi; Barriendos, Mariano; Mazón, Jordi; Pino, David

    2014-05-01

    In September 23 1874, a sudden and severe rainstorm caused multiple flash floods in many small catchments (up to 200 km2) in the Southern half of Catalonia (NE Iberian Peninsula). These floods resulted in 575 fatalities and in a huge destruction of dwellings, roads, bridges, canals and crops and, thus, rank among the heaviest events in Catalonia since 1500. The damages were so great that the economic effects of the floods lasted several years. Many flood mark plaques scattered across the affected area remember the date and keep a record of the maximum height reached by the water. This information enables the hydraulic calculation of the peak flow of the flood at the site of the flood mark; so far, this reconstructed peak flow has been calculated in seven sites: Mont-roig and Agramunt on the Sió River, Cervera and Tàrrega on the Ondara River, Vallfogona, Ciutadilla and Guimerà on the Corb River. Moreover, it has been possible to estimate the rainfall from the reconstructed hydrographs. The results agree with the destructive force of the floods: a specific flow of 10 m3•s-1•km-2 in Cervera, an approximate return period of 250 years in Tàrrega, and 150 mm of rain in nine hours in the Ondara catchment, for example. There are many other flood marks that have not been used yet: Granyena on the Vallmajor River, Arbeca on the Turull Torrent, Espluga and Montblanc on the Francolí River, and Vendrell on the Bisbal Torrent. The reconstructed peak flows and rainfalls in these sites will give more insight into the big picture, that is, the temporal and spatial distribution of the meteorological and hydrological factors that produced the fatal event. Our final objective is to compare this regional picture with the even bigger one obtained from the analysis of the synoptic meteorological situation in the days immediately prior to the floods. A secondary objective is to compare this flood with a more recent one, such as the one occurred in September 1962 near Barcelona

  10. WRF model performance under flash-flood associated rainfall

    Science.gov (United States)

    Mejia-Estrada, Iskra; Bates, Paul; Ángel Rico-Ramírez, Miguel

    2017-04-01

    Understanding the natural processes that precede the occurrence of flash floods is crucial to improve the future flood projections in a changing climate. Using numerical weather prediction tools allows to determine one of the triggering conditions for these particularly dangerous events, difficult to forecast due to their short lead-time. However, simulating the spatial and temporal evolution of the rainfall that leads to a rapid rise in river levels requires determining the best model configuration without compromising the computational efficiency. The current research involves the results of the first part of a cascade modeling approach, where the Weather Research and Forecasting (WRF) model is used to simulate the heavy rainfall in the east of the UK in June 2012 when stationary thunderstorms caused 2-hour accumulated values to match those expected in the whole month of June over the city of Newcastle. The optimum model set-up was obtained after extensive testing regarding physics parameterizations, spin-up times, datasets used as initial conditions and model resolution and nesting, hence determining its sensitivity to reproduce localised events of short duration. The outputs were qualitatively and quantitatively assessed using information from the national weather radar network as well as interpolated rainfall values from gauges, respectively. Statistical and skill score values show that the model is able to produce reliable accumulated precipitation values while explicitly solving the atmospheric equations in high resolution domains as long as several hydrometeors are considered with a spin-up time that allows the model to assimilate the initial conditions without going too far back in time from the event of interest. The results from the WRF model will serve as input to run a semi-distributed hydrological model to determine the rainfall-runoff relationship within an uncertainty assessment framework that will allow evaluating the implications of assumptions at

  11. The benefit of high-resolution operational weather forecasts for flash flood warning

    Directory of Open Access Journals (Sweden)

    J. Younis

    2008-07-01

    Full Text Available In Mediterranean Europe, flash flooding is one of the most devastating hazards in terms of loss of human life and infrastructures. Over the last two decades, flash floods have caused damage costing a billion Euros in France alone. One of the problems of flash floods is that warning times are very short, leaving typically only a few hours for civil protection services to act. This study investigates if operationally available short-range numerical weather forecasts together with a rainfall-runoff model can be used for early indication of the occurrence of flash floods.

    One of the challenges in flash flood forecasting is that the watersheds are typically small, and good observational networks of both rainfall and discharge are rare. Therefore, hydrological models are difficult to calibrate and the simulated river discharges cannot always be compared with ground measurements. The lack of observations in most flash flood prone basins, therefore, necessitates the development of a method where the excess of the simulated discharge above a critical threshold can provide the forecaster with an indication of potential flood hazard in the area, with lead times of the order of weather forecasts.

    This study is focused on the Cévennes-Vivarais region in the Southeast of the Massif Central in France, a region known for devastating flash floods. This paper describes the main aspects of using numerical weather forecasting for flash flood forecasting, together with a threshold – exceedance. As a case study the severe flash flood event which took place on 8–9 September 2002 has been chosen.

    Short-range weather forecasts, from the Lokalmodell of the German national weather service, are used as input for the LISFLOOD model, a hybrid between a conceptual and physically based rainfall-runoff model. Results of the study indicate that high resolution operational weather forecasting combined with a rainfall-runoff model could be useful to

  12. Coupling Radar Rainfall Estimation and Hydrological Modelling For Flash-flood Hazard Mitigation

    Science.gov (United States)

    Borga, M.; Creutin, J. D.

    Flood risk mitigation is accomplished through managing either or both the hazard and vulnerability. Flood hazard may be reduced through structural measures which alter the frequency of flood levels in the area. The vulnerability of a community to flood loss can be mitigated through changing or regulating land use and through flood warning and effective emergency response. When dealing with flash-flood hazard, it is gener- ally accepted that the most effective way (and in many instances the only affordable in a sustainable perspective) to mitigate the risk is by reducing the vulnerability of the involved communities, in particular by implementing flood warning systems and community self-help programs. However, both the inherent characteristics of the at- mospheric and hydrologic processes involved in flash-flooding and the changing soci- etal needs provide a tremendous challenge to traditional flood forecasting and warning concepts. In fact, the targets of these systems are traditionally localised like urbanised sectors or hydraulic structures. Given the small spatial scale that characterises flash floods and the development of dispersed urbanisation, transportation, green tourism and water sports, human lives and property are exposed to flash flood risk in a scat- tered manner. This must be taken into consideration in flash flood warning strategies and the investigated region should be considered as a whole and every section of the drainage network as a potential target for hydrological warnings. Radar technology offers the potential to provide information describing rain intensities almost contin- uously in time and space. Recent research results indicate that coupling radar infor- mation to distributed hydrologic modelling can provide hydrologic forecasts at all potentially flooded points of a region. Nevertheless, very few flood warning services use radar data more than on a qualitative basis. After a short review of current under- standing in this area, two

  13. A regional distributed hydrological modelling approach for flash-flood understanding and experimental design

    Science.gov (United States)

    Braud, Isabelle; Anquetin, Sandrine; Roux, Hélène; Vannier, Olivier; Maubourguet, Marie-Madeleine; Viallet, Pierre; Boudevillain, Brice; Dartus, Denis; Creutin, Jean-Dominique

    2010-05-01

    Flash floods represent the most destructive natural hazard in the Mediterranean region, causing around one billion Euros worth of damage in France over the last two decades. Flash floods are associated with extreme and rare rainfall events and usually occur in ungauged river basins. Amongst them, small-ungauged catchments are recognized as the most vulnerable to storm driven flash floods. In order to limit the damages to the population, there is a need to improve our understanding and the simulation tools for these events. In order to provide information over a whole region, hydrological models applicable at this scale, and able to take into account the spatial variability of rainfall and catchment characteristics, must be proposed. This paper presents such a regional distributed approach applied to the 8-9 September 2002 extreme event which affected the Gard region in the south-east of France. In order to identify the variables and catchment characteristics which require improved knowledge, two distributed hydrological models were set up on a set of catchments, with sizes ranging from 2.5 to 99 km2. The models differ in terms of spatial discretization and process representation. They were forced using radar data with a 1 km2 spatial resolution and 5 min time step. The model parameters were specified using the available information, namely a digital terrain model and a soil data base. The latter provides information about soil texture, soil porosity and soil depths. Soil hydraulic properties were defined using pedo-transfer functions. Data from a post-flood field survey of maximum peak discharge were used to assess the quality of the simulations. A reasonable agreement between modeled and observed values was obtained. Sensitivity studies were then performed to asses the respective impact of rainfall estimation and soil variability on the simulated discharge. The analysis shows that rainfall remains the first controlling factor of flash flood dynamics and that high

  14. Extreme weather: Subtropical floods and tropical cyclones

    Science.gov (United States)

    Shaevitz, Daniel A.

    Extreme weather events have a large effect on society. As such, it is important to understand these events and to project how they may change in a future, warmer climate. The aim of this thesis is to develop a deeper understanding of two types of extreme weather events: subtropical floods and tropical cyclones (TCs). In the subtropics, the latitude is high enough that quasi-geostrophic dynamics are at least qualitatively relevant, while low enough that moisture may be abundant and convection strong. Extratropical extreme precipitation events are usually associated with large-scale flow disturbances, strong ascent, and large latent heat release. In the first part of this thesis, I examine the possible triggering of convection by the large-scale dynamics and investigate the coupling between the two. Specifically two examples of extreme precipitation events in the subtropics are analyzed, the 2010 and 2014 floods of India and Pakistan and the 2015 flood of Texas and Oklahoma. I invert the quasi-geostrophic omega equation to decompose the large-scale vertical motion profile to components due to synoptic forcing and diabatic heating. Additionally, I present model results from within the Column Quasi-Geostrophic framework. A single column model and cloud-revolving model are forced with the large-scale forcings (other than large-scale vertical motion) computed from the quasi-geostrophic omega equation with input data from a reanalysis data set, and the large-scale vertical motion is diagnosed interactively with the simulated convection. It is found that convection was triggered primarily by mechanically forced orographic ascent over the Himalayas during the India/Pakistan flood and by upper-level Potential Vorticity disturbances during the Texas/Oklahoma flood. Furthermore, a climate attribution analysis was conducted for the Texas/Oklahoma flood and it is found that anthropogenic climate change was responsible for a small amount of rainfall during the event but the

  15. Ensemble hydro-meteorological simulation for flash flood early detection in southern Switzerland

    Science.gov (United States)

    Alfieri, Lorenzo; Thielen, Jutta; Pappenberger, Florian

    2012-03-01

    SummaryOngoing changing climate has raised the attention towards weather driven natural hazards. Local floodings and debris flows following exceptional downpours often come without any adequate warning and cause heavy tolls to the human society. This work proposes a novel flood alert system for small catchments prone to flash flooding, capable of monitoring a large portion of the European domain. Operational streamflow simulations are produced through distributed hydrological modeling of ensemble weather forecasts. A long-term reforecast dataset is run through the same hydrological model to derive coherent warning thresholds. These are compared with operational discharge ensembles in a threshold exceedance analysis to produce early warnings. A case study in the southern Switzerland is tested over a 17-month period and system skills are evaluated by means of different quantitative and qualitative analyses. Results from three different predictors derived from the streamflow ensemble are shown and compared, also by accounting for the persistence of lagged forecasts. Significant improvements in predicting discharge thresholds exceedance are achieved by fitting gamma probability distributions to the raw ensemble. Further discussion underlines the limits of predictability of extreme events in small catchments due to the comparatively coarse space-time resolution of current weather forecasts.

  16. Impact of climate change on extreme rainfall events and flood risk in India

    Indian Academy of Sciences (India)

    P Guhathakurta; O P Sreejith; P A Menon

    2011-06-01

    The occurrence of exceptionally heavy rainfall events and associated flash floods in many areas during recent years motivate us to study long-term changes in extreme rainfall over India. The analysis of the frequency of rainy days, rain days and heavy rainfall days as well as one-day extreme rainfall and return period has been carried out in this study to observe the impact of climate change on extreme rainfall events and flood risk in India. The frequency of heavy rainfall events are decreasing in major parts of central and north India while they are increasing in peninsular, east and north east India. The study tries to bring out some of the interesting findings which are very useful for hydrological planning and disaster managements. Extreme rainfall and flood risk are increasing significantly in the country except some parts of central India.

  17. High Risk Flash Flood Rainstorm Mapping Based on Regional L-moments Approach

    Science.gov (United States)

    Ding, Hui; Liao, Yifan; Lin, Bingzhang

    2017-04-01

    Difficulties and complexities in elaborating flash flood early-warning and forecasting system prompt hydrologists to develop some techniques to substantially reduce the disastrous outcome of a flash flood in advance. An ideal to specify those areas that are subject at high risk to flash flood in terms of rainfall intensity in a relatively large region is proposed in this paper. It is accomplished through design of the High Risk Flash Flood Rainstorm Area (HRFFRA) based on statistical analysis of historical rainfall data, synoptic analysis of prevailing storm rainfalls as well as the field survey of historical flash flood events in the region. A HRFFRA is defined as the area potentially under hitting by higher intense-precipitation for a given duration with certain return period that may cause a flash flood disaster in the area. This paper has presented in detail the development of the HRFFRA through the application of the end-to-end Regional L-moments Approach (RLMA) to precipitation frequency analysis in combination with the technique of spatial interpolation in Jiangxi Province, South China Mainland. Among others, the concept of hydrometeorologically homogenous region, the precision of frequency analysis in terms of parameter estimation, the accuracy of quantiles in terms of uncertainties and the consistency adjustments of quantiles over durations and space, etc., have been addressed. At the end of this paper, the mapping of the HRFFRA and an internet-based visualized user-friendly data-server of the HRFFRA are also introduced. Key words: HRFFRA; Flash Flood; RLMA; rainfall intensity; Hydrometeorological homogenous region.

  18. Ensemble hydro-meteorological simulation for flash flood early detection in southern Switzerland

    OpenAIRE

    Alfieri, Lorenzo; THIELEN DEL POZO Jutta; Pappenberger, Florian

    2012-01-01

    Ongoing changing climate has raised the attention towards weather driven natural hazards. Local floodings and debris flows following exceptional downpours often come without any adequate warning and cause heavy tolls to the human society. This work proposes a novel flood alert system for small catchments prone to flash flooding, capable of monitoring a large portion of the European domain. Operational streamflow simulations are produced through distributed hydrological modeling of ensemble we...

  19. Flash Flood Detection in Urban Cities Using Ultrasonic and Infrared Sensors

    KAUST Repository

    Mousa, Mustafa

    2016-07-19

    Floods are the most common type of natural disaster. Often leading to loss of lives and properties in the thousands yearly. Among these events, urban flash floods are particularly deadly because of the short timescales on which they occur, and because of the population density of cities. Since most flood casualties are caused by a lack of information on the impending flood (type, location, severity), sensing these events is critical to generate accurate and detailed warnings and short term forecasts. However, no dedicated flash flood sensing systems, that could monitor the propagation of flash floods, in real time, currently exist in cities. In the present paper, firstly a new sensing device that can simultaneously monitor urban flash floods and traffic congestion has been presented. This sensing device is based on the combination of ultrasonic range-finding with remote temperature sensing, and can sense both phenomena with a high degree of accuracy, using a combination of L1-regularized reconstruction and artificial neural networks to process measurement data. Secondly, corresponding algorithms have been implemented on a low-power wireless sensor platform, and their performance in water level estimation in a 6 months test involving four different sensors is illustrated. The results demonstrate that urban water levels can be reliably estimated with error less than 2 cm, and that the preprocessing and machine learning schemes can run in real-time on currently available wireless sensor platforms.

  20. Estimation of the relative severity of floods in small ungauged catchments for preliminary observations on flash flood preparedness: a case study in Korea.

    Science.gov (United States)

    Kim, Eung Seok; Choi, Hyun Il

    2012-04-01

    An increase in the occurrence of sudden local flooding of great volume and short duration has caused significant danger and loss of life and property in Korea as well as many other parts of the World. Since such floods usually accompanied by rapid runoff and debris flow rise quite quickly with little or no advance warning to prevent flood damage, this study presents a new flash flood indexing methodology to promptly provide preliminary observations regarding emergency preparedness and response to flash flood disasters in small ungauged catchments. Flood runoff hydrographs are generated from a rainfall-runoff model for the annual maximum rainfall series of long-term observed data in the two selected small ungauged catchments. The relative flood severity factors quantifying characteristics of flood runoff hydrographs are standardized by the highest recorded maximum value, and then averaged to obtain the flash flood index only for flash flood events in each study catchment. It is expected that the regression equations between the proposed flash flood index and rainfall characteristics can provide the basis database of the preliminary information for forecasting the local flood severity in order to facilitate flash flood preparedness in small ungauged catchments.

  1. The Ensemble Framework for Flash Flood Forecasting: Global and CONUS Applications

    Science.gov (United States)

    Flamig, Z.; Vergara, H. J.; Clark, R. A.; Gourley, J. J.; Kirstetter, P. E.; Hong, Y.

    2015-12-01

    The Ensemble Framework for Flash Flood Forecasting (EF5) is a distributed hydrologic modeling framework combining water balance components such as the Variable Infiltration Curve (VIC) and Sacramento Soil Moisture Accounting (SAC-SMA) with kinematic wave channel routing. The Snow-17 snow pack model is included as an optional component in EF5 for basins where snow impacts are important. EF5 also contains the Differential Evolution Adaptive Metropolis (DREAM) parameter estimation scheme for model calibration. EF5 is made to be user friendly and as such training has been developed into a weeklong course. This course has been tested in modeling workshops held in Namibia and Mexico. EF5 has also been applied to specialized applications including the Flooded Locations and Simulated Hydrographs (FLASH) project. FLASH aims to provide flash flood monitoring and forecasting over the CONUS using Multi-Radar Multi-Sensor precipitation forcing. Using the extensive field measurements database from the 10,000 USGS measurement locations across the CONUS, parameters were developed for the kinematic wave routing in FLASH. This presentation will highlight FLASH performance over the CONUS on basins less than 1,000 km2 and discuss the development of simulated streamflow climatology over the CONUS for data mining applications. A global application of EF5 has also been developed using satellite based precipitation measurements combined with numerical weather prediction forecasts to produce flood and impact forecasts. The performance of this global system will be assessed and future plans detailed.

  2. Empirical atmospheric thresholds for debris flows and flash floods in the Southern French Alps

    Directory of Open Access Journals (Sweden)

    T. Turkington

    2014-01-01

    Full Text Available Debris flows and flash floods are often preceded by intense, convective rainfall. The establishment of reliable rainfall thresholds is an important component for quantitative hazard and risk assessment, and for the development of an early warning system. Traditional empirical thresholds based on peak intensity, duration and antecedent rainfall can be difficult to verify due to the localized character of the rainfall and the absence of weather radar or sufficiently dense rain gauge networks in mountainous regions. However, convective rainfall can be strongly linked to regional atmospheric patterns and profiles. There is potential to employ this in empirical threshold analysis. This work develops a methodology to determine robust thresholds for flash floods and debris flows utilizing regional atmospheric conditions derived from ECMWF ERA-Interim reanalysis data, comparing the results with rain gauge derived thresholds. The method includes selecting the appropriate atmospheric indicators, categorizing the potential thresholds, determining and testing the thresholds. The method is tested in the Ubaye Valley in the southern French Alps, which is known to have localized convection triggered debris flows and flash floods. This paper shows that instability of the atmosphere and specific humidity at 850 hPa are the most important atmospheric indicators for debris flows and flash floods in the study area. Furthermore, this paper demonstrates that atmospheric reanalysis data is an important asset, and could replace rainfall measurements in empirical exceedence thresholds for debris flows and flash floods.

  3. Landslide-amplified flash floods—The June 2008 Panay Island flooding, Philippines

    Science.gov (United States)

    Catane, Sandra G.; Abon, Catherine C.; Saturay, Ricarido M.; Mendoza, Edna Patricia P.; Futalan, Krestabelle M.

    2012-10-01

    The role of landslides in generating or enhancing a flash flood event in Aklan, Panay Island, Philippines, resulting from Typhoon Fengshen, was investigated. The flash flood occurred between 1100 h and 1400 h (GMT + 8) of 21 June 2008 and inundated Sitios Agbatan and Abaya in the municipality of Libacao. Peak discharges at Kipot, a channel constriction in Aklan River about 10 km upstream, were independently derived using a hydrologic model (302.6 m3/s) and Manning's equation (7000 m3/s). The modeled flood peak reached Kipot at 0300 h on 21 June 2008 and the communities between 0600 h and 1000 h on June 21, at the earliest. The actual flood peak arrived at Sitios Agbatan and Abaya between 1100 h and 1400 h on June 21, at least 1 h earlier than the modeled arrival. While the flash flood may have been caused by the preceding rainfall alone (234.4 mm from 0600 h June 20 to 0600 h June 21), the discrepancies in peak discharges and the delayed arrival time suggest the possibility of damming and eventual breaching of the dam. Evidence of the damming was found at the channel constriction in Kipot. A landslide at this site was mapped, characterized, and inferred to have completely blocked the channel and caused the damming. Implications to flash flood risk assessment are discussed.

  4. Coupled prediction of flash flood response and debris flow occurrence in an alpine basin

    Science.gov (United States)

    Amponsah, William

    2015-04-01

    Coupled prediction of flash flood response and debris flow occurrence in an alpine basin Author(s): William Amponsah1, E.I. Nikolopoulos2, Lorenzo Marchi1, Roberto Dinale4, Francesco Marra3,Davide Zoccatelli2 , Marco Borga2 Affiliation(s): 1CNR - IRPI, Corso Stati Uniti 4, 35127, Padova, ITALY, 2Department of Land, Environment, Agriculture and Forestry, University of Padova,VialeDell'Università 16, 35020, Legnaro PD, ITALY 3Department of Geography, Hebrew University of Jerusalem, ISRAEL 4Ufficio Idrografico, Provincia Autonoma di Bolzano, Bolzano, Italy This contribution examines the main hydrologic and morphologic metrics responsible for widespread triggering of debris-flows associated with flash flood occurrences in headwater alpine catchments.To achieve this objective, we investigate the precipitation forcing, hydrologic responses and landslides and debris-flow occurrences that prevailed during the August 4-5, 2012 extreme flash flood on the 140 km2 Vizze basin in the Eastern Alps of Italy. An intensive post-event survey was carried out a few days after the flood. This included the surveys of cross-sectional geometry and flood marks for the estimation of the peak discharges at multiple river sections and of the initiation and deposition areas of several debris flows. Rainfall estimates are based on careful analysis of weather radar observations and raingauge data. These data and observations permitted the implementation and calibration of a spatially distributed hydrological model, which was used to derive simulated flood hydrographs in 58 tributaries of the Vizze basin. Of these, 33 generated debris-flows, with area ranging from 0.02 km2 to 10 km2, with an average of 1.5 km2. With 130 mm peak event rainfall and a duration of 4 hours (with a max intensity of 90 mm h-1 for 10 min), model-simulated unit peak discharges range from 4 m3 s-1 km-2for elementary catchments up to 10 km2 to 2 m3 s-1 km-2 for catchments in the range of 50 - 100 km2. These are very high

  5. An early warning system for flash floods in hyper-arid Egypt

    Science.gov (United States)

    Cools, J.; Vanderkimpen, P.; El Afandi, G.; Abdelkhalek, A.; Fockedey, S.; El Sammany, M.; Abdallah, G.; El Bihery, M.; Bauwens, W.; Huygens, M.

    2012-02-01

    An early warning system (EWS) for flash floods has been developed for part of the Sinai peninsula of Egypt, an hyper-arid area confronted with limited availability of field data, limited understanding of the response of the wadi to rainfall, and a lack of correspondence between rainfall data and observed flash flood events. This paper shows that an EWS is not a "mission impossible" when confronted with large technical and scientific uncertainties and limited data availability. Firstly, the EWS has been developed and tested based on the best available information, this being quantitative data (field measurements, simulations and remote sensing images) complemented with qualitative "expert opinion" and local stakeholders' knowledge. Secondly, a set of essential parameters has been identified to be estimated or measured under data-poor conditions. These are: (1) an inventory of past significant rainfall and flash flood events, (2) the spatial and temporal distribution of the rainfall events and (3) transmission and infiltration losses and (4) thresholds for issuing warnings. Over a period of 30 yr (1979-2010), only 20 significant rain events have been measured. Nine of these resulted in a flash flood. Five flash floods were caused by regional storms and four by local convective storms. The results for the 2010 flash flood show that 90% of the total rainfall volume was lost to infiltration and transmission losses. Finally, it is discussed that the effectiveness of an EWS is only partially determined by technological performance. A strong institutional capacity is equally important, especially skilled staff to operate and maintain the system and clear communication pathways and emergency procedures in case of an upcoming disaster.

  6. An early warning system for flash floods in hyper-arid Egypt

    Directory of Open Access Journals (Sweden)

    J. Cools

    2012-02-01

    Full Text Available An early warning system (EWS for flash floods has been developed for part of the Sinai peninsula of Egypt, an hyper-arid area confronted with limited availability of field data, limited understanding of the response of the wadi to rainfall, and a lack of correspondence between rainfall data and observed flash flood events. This paper shows that an EWS is not a "mission impossible" when confronted with large technical and scientific uncertainties and limited data availability. Firstly, the EWS has been developed and tested based on the best available information, this being quantitative data (field measurements, simulations and remote sensing images complemented with qualitative "expert opinion" and local stakeholders' knowledge. Secondly, a set of essential parameters has been identified to be estimated or measured under data-poor conditions. These are: (1 an inventory of past significant rainfall and flash flood events, (2 the spatial and temporal distribution of the rainfall events and (3 transmission and infiltration losses and (4 thresholds for issuing warnings. Over a period of 30 yr (1979–2010, only 20 significant rain events have been measured. Nine of these resulted in a flash flood. Five flash floods were caused by regional storms and four by local convective storms. The results for the 2010 flash flood show that 90% of the total rainfall volume was lost to infiltration and transmission losses. Finally, it is discussed that the effectiveness of an EWS is only partially determined by technological performance. A strong institutional capacity is equally important, especially skilled staff to operate and maintain the system and clear communication pathways and emergency procedures in case of an upcoming disaster.

  7. Flood protection diversification to reduce probabilities of extreme losses.

    Science.gov (United States)

    Zhou, Qian; Lambert, James H; Karvetski, Christopher W; Keisler, Jeffrey M; Linkov, Igor

    2012-11-01

    Recent catastrophic losses because of floods require developing resilient approaches to flood risk protection. This article assesses how diversification of a system of coastal protections might decrease the probabilities of extreme flood losses. The study compares the performance of portfolios each consisting of four types of flood protection assets in a large region of dike rings. A parametric analysis suggests conditions in which diversifications of the types of included flood protection assets decrease extreme flood losses. Increased return periods of extreme losses are associated with portfolios where the asset types have low correlations of economic risk. The effort highlights the importance of understanding correlations across asset types in planning for large-scale flood protection. It allows explicit integration of climate change scenarios in developing flood mitigation strategy.

  8. Assimilation of Satellite Based Soil Moisture Data in the National Weather Service's Flash Flood Guidance System

    Science.gov (United States)

    Seo, D.; Lakhankar, T.; Cosgrove, B.; Khanbilvardi, R.

    2012-12-01

    Climate change and variability increases the probability of frequency, timing, intensity, and duration of flood events. After rainfall, soil moisture is the most important factor dictating flash flooding, since rainfall infiltration and runoff are based on the saturation of the soil. It is difficult to conduct ground-based measurements of soil moisture consistently and regionally. As such, soil moisture is often derived from models and agencies such as the National Oceanic and Atmospheric Administration's National Weather Service (NOAA/NWS) use proxy estimates of soil moisture at the surface in order support operational flood forecasting. In particular, a daily national map of Flash Flood Guidance (FFG) is produced that is based on surface soil moisture deficit and threshold runoff estimates. Flash flood warnings are issued by Weather Forecast Offices (WFOs) and are underpinned by information from the Flash Flood Guidance (FFG) system operated by the River Forecast Centers (RFCs). This study analyzes the accuracy and limitations of the FFG system using reported flash flood cases in 2010 and 2011. The flash flood reports were obtained from the NWS Storm Event database for the Arkansas-Red Basin RFC (ABRFC). The current FFG system at the ABRFC provides gridded flash flood guidance (GFFG) System using the NWS Hydrology Laboratory-Research Distributed Hydrologic Model (HL-RDHM) to translate the upper zone soil moisture to estimates of Soil Conservation Service Curve Numbers. Comparison of the GFFG and real-time Multi-sensor Precipitation Estimator derived Quantitative Precipitation Estimate (QPE) for the same duration and location were used to analyze the success of the system. Improved flash flood forecasting requires accurate and high resolution soil surface information. The remote sensing observations of soil moisture can improve the flood forecasting accuracy. The Soil Moisture Active and Passive (SMAP) and Soil Moisture and Ocean Salinity (SMOS) satellites are two

  9. Floods

    Science.gov (United States)

    Floods are common in the United States. Weather such as heavy rain, thunderstorms, hurricanes, or tsunamis can ... is breached, or when a dam breaks. Flash floods, which can develop quickly, often have a dangerous ...

  10. Operational tools to help stakeholders to protect and alert municipalities facing uncertainties and changes in karst flash floods

    Science.gov (United States)

    Borrell Estupina, V.; Raynaud, F.; Bourgeois, N.; Kong-A-Siou, L.; Collet, L.; Haziza, E.; Servat, E.

    2015-06-01

    Flash floods are often responsible for many deaths and involve many material damages. Regarding Mediterranean karst aquifers, the complexity of connections, between surface and groundwater, as well as weather non-stationarity patterns, increase difficulties in understanding the basins behaviour and thus warning and protecting people. Furthermore, given the recent changes in land use and extreme rainfall events, knowledge of the past floods is no longer sufficient to manage flood risks. Therefore the worst realistic flood that could occur should be considered. Physical and processes-based hydrological models are considered among the best ways to forecast floods under diverse conditions. However, they rarely match with the stakeholders' needs. In fact, the forecasting services, the municipalities, and the civil security have difficulties in running and interpreting data-consuming models in real-time, above all if data are uncertain or non-existent. To face these social and technical difficulties and help stakeholders, this study develops two operational tools derived from these models. These tools aim at planning real-time decisions given little, changing, and uncertain information available, which are: (i) a hydrological graphical tool (abacus) to estimate flood peak discharge from the karst past state and the forecasted but uncertain intense rainfall; (ii) a GIS-based method (MARE) to estimate the potential flooded pathways and areas, accounting for runoff and karst contributions and considering land use changes. Then, outputs of these tools are confronted to past and recent floods and municipalities observations, and the impacts of uncertainties and changes on planning decisions are discussed. The use of these tools on the recent 2014 events demonstrated their reliability and interest for stakeholders. This study was realized on French Mediterranean basins, in close collaboration with the Flood Forecasting Services (SPC Med-Ouest, SCHAPI, municipalities).

  11. Flash flood forecasting in poorly gauged basins using neural networks: case study of the Gardon de Mialet basin (southern France

    Directory of Open Access Journals (Sweden)

    G. Artigue

    2012-11-01

    Full Text Available In southern France, flash flood episodes frequently cause fatalities and severe damage. In order to inform and warn populations, the French flood forecasting service (SCHAPI, Service Central d'Hydrométéorologie et d'Appui à la Prévision des Inondations initiated the BVNE (Bassin Versant Numérique Expérimental, or Experimental Digital Basin project in an effort to enhance flash flood predictability. The target area for this study is the Gardon d'Anduze basin, located in the heart of the Cévennes range. In this Mediterranean mountainous setting, rainfall intensity can be very high, resulting in flash flooding. Discharge and rainfall gauges are often exposed to extreme weather conditions, which undermines measurement accuracy and continuity. Moreover, the processes governing rainfall-discharge relations are not well understood for these steeply-sloped and heterogeneous basins. In this context of inadequate information on both the forcing variables and process knowledge, neural networks are investigated due to their universal approximation and parsimony properties. We demonstrate herein that thanks to a rigorous variable and complexity selection, efficient forecasting of up to two-hour durations, without requiring rainfall forecasting as input, can be derived using the measured discharges available from a feedforward model. In the case of discharge gauge malfunction, in degraded mode, forecasting may result using a recurrent neural network model. We also observe that neural network models exhibit low sensitivity to uncertainty in rainfall measurements since producing ensemble forecasting does not significantly affect forecasting quality. In providing good results, this study suggests close consideration of our main purpose: generating forecasting on ungauged basins.

  12. Peak discharge evaluation of five exceptional winter flash floods of 2004-2008 in Central-East Sardinian karst areas and their geomorphological effectiveness (Italy)

    Science.gov (United States)

    Cossu, Q. A.; de Waele, J.; Bodini, A.; Sanna, L.; Cabras, S.

    2009-04-01

    In five subsequent winters (2004-2008) extreme meteorological events have occurred in karst areas of Central East Sardinia, leading to flash floods in several watersheds. Codula Ilune and Flumineddu experienced the most severe flash flood in December 2004, Codula Fuili in December 2006 and Codula Sisine in December 2008. The scars of these flash floods are still well visible in the river bed morphology, caused by the huge quantities of water that have passed the river reaches during these extreme floods. Since no gauges are present in none of these watersheds, the only possible way of estimating the peak flow is a combination of geomorphological and hydraulic observations. Three different methods for the estimation of peak flow velocity have been applied in several river reaches of 4 karstic watersheds (Codula Ilune, Codula Fuili and Codula Sisine in the Gulf of Orosei and Riu Flumineddu in Supramonte), using the Manning's equation, the similar Jarrett's formula and the Costa's method (1983) that make use of the mean diameter of the biggest by the flood water transported boulders. These estimates allow to quantify the peak flow of the floods in different river reaches, and also to have an idea of where and how much water penetrates into the karst aquifer, thus feeding the underground karst river network. Based on measurements from raingauges close to the study area, a statistical analysis of the rainfalls that have caused these flash floods has been also carried out. Total volume of water has been estimated for these four watersheds in the 5 events.

  13. Rainstorms able to induce flash floods in a Mediterranean-climate region (Calabria, southern Italy

    Directory of Open Access Journals (Sweden)

    O. G. Terranova

    2014-03-01

    Full Text Available Heavy rainstorms often induce flash flooding, one of the natural disasters most responsible for damage to man-made infrastructure and loss of lives, adversely affecting also the opportunities for socio-economic development of Mediterranean Countries. The frequently dramatic damage of flash floods are often detected with sufficient accuracy by post-event surveys, but rainfall causing them are still only roughly characterized. With the aim of improving the understanding of the temporal structure and spatial distribution of heavy rainstorms in the Mediterranean context, a statistical analysis was carried out in Calabria (southern Italy concerning rainstorms that mainly induced flash floods, but also shallow landslides and debris-flows. Thus a method is proposed – based on the overcoming of heuristically predetermined threshold values of cumulated rainfall, maximum intensity, and kinetic energy of the rainfall event – to select and characterize the rainstorms able to induce flash floods in the Mediterranean-climate Countries. Therefore the obtained (heavy rainstorms were automatically classified and studied according to their structure in time, localization and extension. Rainfall-runoff watershed models can consequently benefit from the enhanced identification of design storms, with a realistic time structure integrated with the results of the spatial analysis. A survey of flash flood events recorded in the last decades provides a preliminary validation of the method proposed to identify the heavy rainstorms and synthetically describe their characteristics. The notable size of the employed sample, including data with a very detailed resolution in time, that relate to several rain gauges well-distributed throughout the region, give robustness to the obtained results.

  14. Regional models for distributed flash-flood nowcasting: towards an estimation of potential impacts and damages

    Directory of Open Access Journals (Sweden)

    Le Bihan Guillaume

    2016-01-01

    Full Text Available Flash floods monitoring systems developed up to now generally enable a real-time assessment of the potential flash-floods magnitudes based on highly distributed hydrological models and weather radar records. The approach presented here aims to go one step ahead by offering a direct assessment of the potential impacts of flash floods on inhabited areas. This approach is based on an a priori analysis of the considered area in order (1 to evaluate based on a semi-automatic hydraulic approach (Cartino method the potentially flooded areas for different discharge levels, and (2 to identify the associated buildings and/or population at risk based on geographic databases. This preliminary analysis enables to build a simplified impact model (discharge-impact curve for each river reach, which can be used to directly estimate the importance of potentially affected assets based on the outputs of a distributed rainfall-runoff model. This article presents a first case study conducted in the Gard region (south eastern France. The first validation results are presented in terms of (1 accuracy of the delineation of the flooded areas estimated based on the Cartino method and using a high resolution DTM, and (2 relevance and usefulness of the impact model obtained. The impacts estimated at the event scale will now be evaluated in a near future based on insurance claim data provided by CCR (Caisse Centrale de Réassurrance.

  15. Geomorphological impacts of an extreme flood in SE Spain

    Science.gov (United States)

    Hooke, J. M.

    2016-06-01

    Long-term field studies in semiarid ephemeral streams are rare. These geomorphic data are essential for understanding the nature of the processes in order to develop modelling for risk assessments and management. An extreme flood event on 28 September 2012 affected the Murcia region of SE Spain, including long-tem monitoring sites on two fluvial systems in the Guadalentín basin, the Nogalte and Torrealvilla. Detailed morphological data were collected before and immediately after the event; and the amount of morphological change, erosion, and deposition have been related to peak flow conditions at the sites. On the Nogalte channel, peak flow reached 2500 m3 s- 1 at the downstream end of the catchment in less than 1 h. The event had a recurrence interval of > 50 years based on rainfall records and damage to old irrigation structures. The major effect in the braided, gravel channel of the Nogalte was net aggradation, with massive deposition in large flat bars. The measured changes in bankfull capacity were highly correlated with most hydraulic variables. Net changes in cut-and-fill in cross sections on the Nogalte were highly related to peak discharge and stream power but much less so to measures of hydraulic force (velocity, shear stress, unit stream power). Relationships of amount of erosion to hydraulic variables were much weaker than for amount of deposition, which was largely scaled to channel size and flow energy. Changes on the Torrealvilla were much less than on the Nogalte, and net erosion occurred at all sites. Sites on the Nogalte channel in schist exhibited higher deposition than those of the Torrealvilla sites on marl for the same hydraulic values. Overall, less morphological change took place in the extreme event on the Nogalte than predicted from some published hydraulic relations, probably reflecting the high sediment supply and the hydrological characteristics of the event. The results demonstrate the high degree of adjustment of these channels to

  16. A Real-Time Web Services Hub to Improve Situation Awareness during Flash Flood Events

    Science.gov (United States)

    Salas, F. R.; Liu, F.; Maidment, D. R.; Hodges, B. R.

    2011-12-01

    The central Texas corridor is one of the most flash flood-prone regions in the United States. Over the years, flash floods have resulted in hundreds of flood fatalities and billions of dollars in property damage. In order to mitigate risk to residents and infrastructure during flood events, both citizens and emergency responders need to exhibit proactive behavior instead of reactive. Real-time and forecasted flood information is fairly limited and hard to come by at varying spatial scales. The University of Texas at Austin has collaborated with IBM Research-Austin and ESRI to build a distributed real-time flood information system through a framework that leverages large scale data management and distribution, Open Geospatial Consortium standardized web services, and smart map applications. Within this paradigm, observed precipitation data encoded in WaterML is ingested into HEC-HMS and then delivered to a high performance hydraulic routing software package developed by IBM that utilizes the latest advancements in VLSI design, numerical linear algebra and numerical integration techniques on contemporary multicore architecture to solve fully dynamic Saint Venant equations at both small and large scales. In this paper we present a real-time flood inundation map application that in conjunction with a web services Hub, seamlessly integrates hydrologic information available through both public and private data services, model services and mapping services. As a case study for this project, we demonstrate how this system has been implemented in the City of Austin, Texas.

  17. The role of climate variability in extreme floods in Europe

    Science.gov (United States)

    Guimarães Nobre, G.; Jongman, B.; Aerts, J.; Ward, P. J.

    2017-08-01

    Climate variability is shown to be an important driver of spatial and temporal changes in hydrometereological variables in Europe. However, the influence of climate variability on flood damage has received little attention. We investigated the El Niño Southern Oscillation (ENSO), the North Atlantic Oscillation (NAO), and the East Atlantic pattern (EA) during their neutral, positive, and negative phases, to understand their relationships with four flood indicators: Occurrence of Extreme Rainfall, Intensity of Extreme Rainfall, Flood Occurrence, and Flood Damage. We found that positive and negative phases of NAO and EA are associated with more (or less) frequent and intense seasonal extreme rainfall over large areas of Europe. The relationship between ENSO and the Occurrence of Extreme Rainfall and Intensity of Extreme Rainfall in Europe is much smaller than the relationship with NAO or EA, but still significant in some regions. We show that Flood Damage and Flood Occurrence have strong links with climate variability, especially in southern and eastern Europe. Therefore, when investigating flooding across Europe, all three indices of climate variability should be considered. Future research should focus on their joint influence on flood risk. The potential inclusion of seasonal forecasts of indices of climate variability could be effective in forecasting flood damage.

  18. Hydrologic ensembles based on convection-permitting precipitation nowcasts for flash flood warnings

    Science.gov (United States)

    Demargne, Julie; Javelle, Pierre; Organde, Didier; de Saint Aubin, Céline; Ramos, Maria-Helena

    2017-04-01

    In order to better anticipate flash flood events and provide timely warnings to communities at risk, the French national service in charge of flood forecasting (SCHAPI) is implementing a national flash flood warning system for small-to-medium ungauged basins. Based on a discharge-threshold flood warning method called AIGA (Javelle et al. 2014), the current version of the system runs a simplified hourly distributed hydrologic model with operational radar-gauge QPE grids from Météo-France at a 1-km2 resolution every 15 minutes. This produces real-time peak discharge estimates along the river network, which are subsequently compared to regionalized flood frequency estimates to provide warnings according to the AIGA-estimated return period of the ongoing event. To further extend the effective warning lead time while accounting for hydrometeorological uncertainties, the flash flood warning system is being enhanced to include Météo-France's AROME-NWC high-resolution precipitation nowcasts as time-lagged ensembles and multiple sets of hydrological regionalized parameters. The operational deterministic precipitation forecasts, from the nowcasting version of the AROME convection-permitting model (Auger et al. 2015), were provided at a 2.5-km resolution for a 6-hr forecast horizon for 9 significant rain events from September 2014 to June 2016. The time-lagged approach is a practical choice of accounting for the atmospheric forecast uncertainty when no extensive forecast archive is available for statistical modelling. The evaluation on 781 French basins showed significant improvements in terms of flash flood event detection and effective warning lead-time, compared to warnings from the current AIGA setup (without any future precipitation). We also discuss how to effectively communicate verification information to help determine decision-relevant warning thresholds for flood magnitude and probability. Javelle, P., Demargne, J., Defrance, D., Arnaud, P., 2014. Evaluating

  19. Comparative estimation and assessment of initial soil moisture conditions for Flash Flood warning in Saxony

    Science.gov (United States)

    Luong, Thanh Thi; Kronenberg, Rico; Bernhofer, Christian; Janabi, Firas Al; Schütze, Niels

    2017-04-01

    Flash Floods are known as highly destructive natural hazards due to their sudden appearance and severe consequences. In Saxony/Germany flash floods occur in small and medium catchments of low mountain ranges which are typically ungauged. Besides rainfall and orography, pre-event moisture is decisive, as it determines the available natural retention in the catchment. The Flash Flood Guidance concept according to WMO and Prof. Marco Borga (University of Padua) will be adapted to incorporate pre-event moisture in real-time flood forecast within the ESF EXTRUSO project (SAB-Nr. 100270097). To arrive at pre-event moisture for the complete area of the low mountain range with flash flood potential, a widely applicable, accurate but yet simple approach is needed. Here, we use radar precipitation as input time series, detailed orographic, land-use and soil information and a lumped parameter model to estimate the overall catchment soil moisture and potential retention. When combined with rainfall forecast and its intrinsic uncertainty, the approach allows to find the point in time when precipitation exceeds the retention potential of the catchment. Then, spatially distributed and complex hydrological modeling and additional measurements can be initiated. Assuming reasonable rainfall forecasts of 24 to 48hrs, this part can start up to two days in advance of the actual event. The lumped-parameter model BROOK90 is used and tested for well observed catchments. First, physical meaningful parameters (like albedo or soil porosity) a set according to standards and second, "free" parameters (like percentage of lateral flow) were calibrated objectively by PEST (Model-Independent Parameter Estimation and Uncertainty Analysis) with the target on evapotranspiration and soil moisture which both have been measured at the study site Anchor Station Tharandt in Saxony/Germany. Finally, first results are presented for the Wernersbach catchment in Tharandt forest for main flood events in the 50

  20. A UAV based system for real time flash flood monitoring in desert environments using Lagrangian microsensors

    KAUST Repository

    Abdelkader, Mohamed

    2013-05-01

    Floods are the most common natural disasters, causing thousands of casualties every year in the world. In particular, flash flood events are particularly deadly because of the short timescales on which they occur. Most casualties could be avoided with advance warning, for which real time monitoring is critical. While satellite-based high resolution weather forecasts can help predict floods to a certain extent, they are not reliable enough, as flood models depend on a large number of parameters that cannot be estimated beforehand. In this article, we present a novel flood sensing architecture to monitor large scale desert hydrological basins surrounding metropolitan areas, based on unmanned air vehicles. The system relies on Lagrangian (mobile) microsensors, that are released by a swarm of UAVs. A preliminary testbed implementing this technology is briefly described, and future research directions and problems are discussed. © 2013 IEEE.

  1. Analysis of a localized flash-flood event over the central Mediterranean

    Science.gov (United States)

    Gascón, E.; Laviola, S.; Merino, A.; Miglietta, M. M.

    2016-12-01

    On 3 July 2006, an exceptionally heavy convective rainfall affected a small area in Calabria, Italy. A rainfall amount of 202 mm was recorded in 2.5 h, producing considerable damage and causing a localized flash flood. The Weather Research and Forecasting (WRF) model was used to analyze the instability present in the event and the related triggering mechanisms. The high-resolution simulation is able to correctly identify the position of the precipitation peak and to clarify the mesoscale processes involved, although it significantly underestimates the total amount of precipitation. Some sensitivity experiments confirm the importance of the choice of planetary boundary layer and microphysics parameterization schemes for a correct simulation of the event, showing a strong sensitivity to these numerical tests. Also, the need for high horizontal resolution emerges clearly: an accurate representation of the orography at small scales, is required to simulate the event in its correct location. Instability indices identified an extremely favorable environment for convection development, with very high values of CAPE and high moisture content at low levels. The low mountains near the rainfall peak play an important role in triggering the release of instability and controlling the location of rainfall; in particular, the peculiar morphology of the orography creates low-level wind convergence and provides the uplift necessary for the air parcels to reach the level of free convection. In this framework, nondimensional parameters, such as the Froude number, have been calculated to better understand the interaction of the flow with the orography.

  2. Anticipating flash-floods: Multi-scale aspects of the social response

    Science.gov (United States)

    Lutoff, Céline; Creutin, Jean-Dominique; Ruin, Isabelle; Borga, Marco

    2016-10-01

    This paper aims at exploring the anticipation phase before a flash flood, corresponding to the time between the first climatic signs and the peak-flow. We focus the analysis on people's behaviors observing how they use this period to organize themselves for facing the event. The analysis is made through the definition of three specific scales: the timeliness scale, an analytical scale of anticipatory actions and the scale of human response network. Using a cross-scale and cross level analysis enables to define different phases in the anticipation period where different kind of environmental precursors are mobilized by the actors in order to make sense of the situation and adapt. Three main points deserve attention at the end: firstly, the concepts of timeliness, anticipatory actions and crisis network scales enable to understand differently what happens both physically and socially during an extreme event; secondly, analyzing the precursors shows that each level of crisis network uses different kinds of signs for estimating the situation, organizing and reacting; thirdly, there is a potential for improvement in observation on both social and physical processes at different scales, for verifying the theory of the anticipatory phases.

  3. A radar-based hydrological model for flash flood prediction in the dry regions of Israel

    Science.gov (United States)

    Ronen, Alon; Peleg, Nadav; Morin, Efrat

    2014-05-01

    Flash floods are floods which follow shortly after rainfall events, and are among the most destructive natural disasters that strike people and infrastructures in humid and arid regions alike. Using a hydrological model for the prediction of flash floods in gauged and ungauged basins can help mitigate the risk and damage they cause. The sparsity of rain gauges in arid regions requires the use of radar measurements in order to get reliable quantitative precipitation estimations (QPE). While many hydrological models use radar data, only a handful do so in dry climate. This research presents a robust radar-based hydro-meteorological model built specifically for dry climate. Using this model we examine the governing factors of flash floods in the arid and semi-arid regions of Israel in particular and in dry regions in general. The hydrological model built is a semi-distributed, physically-based model, which represents the main hydrological processes in the area, namely infiltration, flow routing and transmission losses. Three infiltration functions were examined - Initial & Constant, SCS-CN and Green&Ampt. The parameters for each function were found by calibration based on 53 flood events in three catchments, and validation was performed using 55 flood events in six catchments. QPE were obtained from a C-band weather radar and adjusted using a weighted multiple regression method based on a rain gauge network. Antecedent moisture conditions were calculated using a daily recharge assessment model (DREAM). We found that the SCS-CN infiltration function performed better than the other two, with reasonable agreement between calculated and measured peak discharge. Effects of storm characteristics were studied using synthetic storms from a high resolution weather generator (HiReS-WG), and showed a strong correlation between storm speed, storm direction and rain depth over desert soils to flood volume and peak discharge.

  4. Forecasting Extreme Flooding in South Asia (Invited)

    Science.gov (United States)

    Webster, P. J.

    2010-12-01

    In most years there is extensive flooding across India, Pakistan and Bangladesh. On average, 40 million people are displaced by floods in India and half that many again in Bangladesh. Occasionally, even more extensive and severe flooding occurs across South Asia. In 2007 and 2008 the Brahmaputra flooded three times causing severe disruption of commerce, agriculture and life in general. Systems set up by an international collaboration predicted these Bangladesh floods with an operational system at the 10 and 15-day horizon. These forecasts determined the risk of flooding and allowed the Bangladeshis in peril to prepare, harvesting crops and storing of household and agricultural assets. Savings in increments of annual income resulted form the forecasts. In July and August 2010, severe flooding occurred in Pakistan causing horrendous damage and loss of life. But these floods were also predictable at the 10-day time scale if the same forecasting system developed for Bangladesh had been implemented. Similar systems could be implemented in India but would require local cooperation. We describe the manner in which quantified probabilistic precipitation forecasts, coupled with hydrological models can provide useful and timely extended warnings of flooding.

  5. A high resolution coupled hydrologic-hydraulic model (HiResFlood-UCI) for flash flood modeling

    Science.gov (United States)

    Nguyen, Phu; Thorstensen, Andrea; Sorooshian, Soroosh; Hsu, Kuolin; AghaKouchak, Amir; Sanders, Brett; Koren, Victor; Cui, Zhengtao; Smith, Michael

    2016-10-01

    HiResFlood-UCI was developed by coupling the NWS's hydrologic model (HL-RDHM) with the hydraulic model (BreZo) for flash flood modeling at decameter resolutions. The coupled model uses HL-RDHM as a rainfall-runoff generator and replaces the routing scheme of HL-RDHM with the 2D hydraulic model (BreZo) in order to predict localized flood depths and velocities. A semi-automated technique of unstructured mesh generation was developed to cluster an adequate density of computational cells along river channels such that numerical errors are negligible compared with other sources of error, while ensuring that computational costs of the hydraulic model are kept to a bare minimum. HiResFlood-UCI was implemented for a watershed (ELDO2) in the DMIP2 experiment domain in Oklahoma. Using synthetic precipitation input, the model was tested for various components including HL-RDHM parameters (a priori versus calibrated), channel and floodplain Manning n values, DEM resolution (10 m versus 30 m) and computation mesh resolution (10 m+ versus 30 m+). Simulations with calibrated versus a priori parameters of HL-RDHM show that HiResFlood-UCI produces reasonable results with the a priori parameters from NWS. Sensitivities to hydraulic model resistance parameters, mesh resolution and DEM resolution are also identified, pointing to the importance of model calibration and validation for accurate prediction of localized flood intensities. HiResFlood-UCI performance was examined using 6 measured precipitation events as model input for model calibration and validation of the streamflow at the outlet. The Nash-Sutcliffe Efficiency (NSE) obtained ranges from 0.588 to 0.905. The model was also validated for the flooded map using USGS observed water level at an interior point. The predicted flood stage error is 0.82 m or less, based on a comparison to measured stage. Validation of stage and discharge predictions builds confidence in model predictions of flood extent and localized velocities

  6. Improving the analysis of social component of flash-floods risk assessment: Application to urban areas of Castilla y León (Spain)

    Science.gov (United States)

    Aroca Jimenez, Estefanía; Bodoque del Pozo, Jose Maria; Garcia Martin, Juan Antonio; Diez Herrero, Andres

    2016-04-01

    The increasing evidence of anthropogenic climate change, the respective intensification of extreme events as well as the increase in human exposure to natural hazards and their vulnerability show that the enhancement of strategies on how to reduce disaster risk and promote adaptation to extreme events is critical to increase resilience. Growing economic losses, high numbers of casualties and the disruption of livelihoods in various places of the world, at an even higher rate than the increase of magnitude and frequency of extreme events, underline that the vulnerability of societies exposed is a key aspect to be considered. Social vulnerability characterizes the predisposition of society to be afflicted by hazards such as floods, being flash floods one of the hazards with the greatest capacity to generate risk. Despite its importance, social vulnerability is often a neglected aspect of traditional risk assessments which mainly focus on economic and structural measures. The aim of this research is to identify those social characteristics which render people vulnerable to flash flood hazards, and consider whether these characteristics are identifiable as local patterns at regional level. The result of this task is a Social Susceptibility Index (SSI) based on susceptibility profiles of the population per township. These profiles are obtained by Hierarchical Segmentation and Latent Class Analysis of demographic and socio-economic information provided by different public organisms. By adding exposure information to SSI, a Social and Infraestructure Flood Vulnerability Index (SIFVI) is created. The methodology proposed here is implemented in the region of Castilla y León (94,226 km2). Townships that are included in this study meet two requirements: i) city centres are affected by an area where potential significant flash-flood risk exists (i.e. villages are crossed by rivers with a longitudinal slope higher than 0.01); ii) city centres are affected by an area with low

  7. Reconstruction and numerical modelling of a flash flood event: Atrani 2010

    Science.gov (United States)

    Ciervo, F.; Papa, M. N.; Medina, V.; Bateman, A.

    2012-04-01

    The work intends to reproduce the flash-flood event that occurred in Atrani (Amalfi Coast - Southern Italy) on the 9 September 2010. In the days leading up to the event, intense low pressure system affected the North Europe attracting hot humid air masses from the Mediterranean areas and pushing them to the southern regions of Italy. These conditions contributed to the development of strong convective storm systems, Mesoscale Convective Systems (MCS) type. The development of intense convective rain cells, over an extremely confined areas, leaded to a cumulative daily rainfall of 129.2 mm; the maximum precipitation in 1hr was 19.4mm. The Dragone river is artificially forced to flow underneath the urban estate of Atrani through a culvert until it finally flows out into the sea. In correspondence of the culvert inlet a minor fraction of the water discharge (5.9m^3/s), skimming over the channel cover, flowed on the street and invaded the village. The channelized flow generated overpressure involving the breaking of the cover of culvert slab and caused a new discharge inlet (20 m^3/s) on the street modifying the downstream flood dynamics. Information acquired, soon after the event, through the local people interviews and the field measurements significantly contributed to the rainfall event reconstruction and to the characterization of the induced effects. In absence of hydrometric data, the support of the amateur videos was of crucial importance for the hydraulic model development and calibration. A geomorphology based rainfall-runoff model, WFIUH type (Instantaneous Unit Hydrograph Width Function), is implemented to extract the hydrograph of the hydrological event. All analysis are performed with GIS support basing on a Digital Terrain System (DTM) 5x5m. Two parameters have been used to calibrate the model: the average watershed velocity (Vmean = 0.08m/s) and hydrodynamic diffusivity (D=10E^-6 m^2/s). The model is calibrated basing on the peak discharge assessed value

  8. GIS ANALYSIS OF POPULATION EVACUATION FROM FLASH FLOODS – CASE STUDY, ȚÂȘLA DRAINAGE BASIN, ROMANIA

    Directory of Open Access Journals (Sweden)

    A. SIMA

    2016-03-01

    Full Text Available Țâșla watershed, composing sub-basin of the larger Vișeu basin, is a highly anthropic area, with an extremely packed residential and transportation infrastructure, mainly along the Țâșla watercourse. Mining and tourist activities have always been and still are the outcome of a great natural potential, this fact leading to the area always getting ranked as one of the top economic centers in Maramureș County. The high frequency of flash flooding is jeopardizing the socio-economic progress of the area, causing substantial damage. This paper’s goal is the adaptation of a GIS tool, proposed by researchers from the U.S. Geological Survey – USGS (Jeanne M. Jones, Peter Ng, Nathan J. Wood, 2014, used in the flash flooding population evacuation analysis, etc. This method is based upon the digital elevation model, land cover, hazard zones and safe zones analysis. The results (evacuation time, evacuation corridors, etc can be a relevant contribution to the decision making management of the emergency situations.

  9. Assessing flash flood vulnerability using a multi-vulnerability approach

    Directory of Open Access Journals (Sweden)

    Karagiorgos Konstantinos

    2016-01-01

    Full Text Available In the framework of flood risk assessment, while the understanding of hazard and exposure has significantly improved over the last years, knowledge on vulnerability remains one of the challenges. Current approaches in vulnerability research are characterised by a division between social scientists and natural scientists. In order to close this gap, we present an approach that combines information on physical and social vulnerability in order to merge information on the susceptibility of elements at risk and society. With respect to physical vulnerability, the study is based on local-scale vulnerability models using nonlinear regression approaches. Modified Weibull distributions were fit to the data in order to represent the relationship between process magnitude and degree of loss. With respect to social vulnerability we conducted a door-to-door survey which resulted in particular insights on flood risk awareness and resilience strategies of exposed communities. In general, both physical and social vulnerability were low in comparison with other European studies, which may result from (a specific building regulations in the four Mediterranean test sites as well as general design principles leading to low structural susceptibility of elements at risk, and (b relatively low social vulnerability of citizens exposed. As a result it is shown that a combination of different perspectives of vulnerability will lead to a better understanding of exposure and capacities in flood risk management.

  10. The October 2015 flash - floods in south eastern France: first discharge estimations and comparison with other flash-floods documented in the framework of the Hymex project

    Science.gov (United States)

    Payrastre, Olivier; Lebouc, Laurent; Ayral, Pierre Alain; Brunet, Pascal; Delrieu, Guy; Douvinet, Johnny; Dramais, Guillaume; Javelle, Pierre; Johannet, Anne; Adamovic, Marko; Adnes, Cyriel; Cantet, Philippe; Chapuis, Margot; Coutouis, Adrien; Creutin, Jean-Dominique; Gonzalez-Sosa, Enrique; Ruin, Isabelle; Saint-Martin, Clotilde; Shabou, Saif; Whilhelm, Bruno

    2016-04-01

    On the 3rd of October 2015, an outstanding hydrometeorological event hit the Mediterranean coast in the Alpes-Maritimes region in south-eastern France. Despite this rainstorm event was very short in time (approximatively 2 hours of intense rainfall), it caused a large rainfall accumulation reaching up to 180 mm. Intense flash floods were observed on all rivers of the affected area, including mostly small watersheds of less than 60 km². They caused 21 fatalities and particularly high damages because of the density of urban areas located in the downstream coastal part of the affected area. The towns of Mandelieu, Cannes, and Antibes were particularly affected. On several watersheds, the reported floods seem be the largest observed from human memory, and may therefore become reference events for flood risk prevention. A post event survey was organised in the framework of the Hymex project in order to document the characteristics of the floods which occurred in a large majority on ungauged rivers, and also destroyed some of the existing stream gauges. A total of 36 peak discharge values were estimated, enabling a detailed description of observed hydrological reactions. This dataset confirms the very large peak discharge values, which remain however significantly below the magnitude of other recent floods observed in other regions of France, and below the existing envelope curves. It may also be observed that the magnitude of this new event is relatively close to what was observed in june 2010 in the nearby Var region. These two events, both being among the largest observed locally from human memory, suggest that the position of the envelope curve should be lower in this eastern part of the French Mediterranean coast, if compared to the Cevennes region which fixes up to now the position of the envelope curve for the whole French territory. A rainfall-runoff analysis of this flood is now in progress to confirm that the runoff rates are not particularly high if compared

  11. Hydrodynamic Modeling of Flash Floods in an Andean Stream: Challenges for Assessing Flood Hazards in Mountain Rivers

    Science.gov (United States)

    Contreras, M. T.; Escauriaza, C. R.

    2015-12-01

    Rain-induced flash floods are common events in regions close to the southern Andes, in north and central Chile. Rapid urban development combined to the changing climate and ENSO effects have resulted in an alarming proximity of flood-prone streams to densely populated areas in the Andean foothills, increasing the risk for cities and infrastructure. Simulations of rapid floods in these complex watersheds are particularly challenging, especially if there is insufficient geomorphological and hydrometeorological data. In the Quebrada de Ramón, an Andean stream that passes through a highly populated area in the east part of Santiago, Chile, previous events have demonstrated that sediment concentration, flow resistance, and the characteristic temporal and spatial scales of the hydrograph, are important variables to predict the arrival time of the peak discharge, flow velocities and the extension of inundated areas. The objective of this investigation is to improve our understanding of the dynamics of flash floods in the Quebrada de Ramón, quantifying the effects of these factors on the flood propagation. We implement a two-dimensional model based on the shallow water equations (Guerra et al. 2014) modified to account for hyperconcentrated flows over natural topography. We evaluate events of specific return periods and sediment concentrations, using different methodologies to quantify the flow resistance in the channel and floodplains. Through this work we provide a framework for future studies aimed at improving hazard assessment, urban planning, and early warning systems in urban areas near mountain streams with limited data, and affected by rapid flood events. Work supported by Fondecyt grant 1130940 and CONICYT/FONDAP grant 15110017.

  12. HyMeX-SOP1: The Field Campaign Dedicated to Heavy Precipitation and Flash Flooding in the Northwestern Mediterranean

    National Research Council Canada - National Science Library

    Ducrocq, Véronique; Braud, Isabelle; Davolio, Silvio; Ferretti, Rossella; Flamant, Cyrille; Jansa, Agustin; Kalthoff, Norbert; Richard, Evelyne; Taupier-Letage, Isabelle; Ayral, Pierre-Alain; Belamari, Sophie; Berne, Alexis; Borga, Marco; Boudevillain, Brice; Bock, Olivier; Boichard, Jean-Luc; Bouin, Marie-Noëlle; Bousquet, Olivier; Bouvier, Christophe; Chiggiato, Jacopo; Cimini, Domenico; Corsmeier, Ulrich; Coppola, Laurent; Cocquerez, Philippe; Defer, Eric; Delanoë, Julien; Di Girolamo, Paolo; Doerenbecher, Alexis; Drobinski, Philippe; Dufournet, Yann; Fourrié, Nadia; Gourley, Jonathan J; Labatut, Laurent; Lambert, Dominique; Le Coz, Jérôme; Marzano, Frank S; Molinié, Gilles; Montani, Andrea; Nord, Guillaume; Nuret, Mathieu; Ramage, Karim; Rison, William; Roussot, Odile; Said, Frédérique; Schwarzenboeck, Alfons; Testor, Pierre; Van Baelen, Joël; Vincendon, Béatrice; Aran, Montserrat; Tamayo, Jorge

    2014-01-01

    The Mediterranean region is frequently affected by heavy precipitation events associated with flash floods, landslides, and mudslides that cause hundreds of millions of euros in damages per year and often, casualties...

  13. The character and causes of flash flood occurrence changes in mountainous small basins of Southern California under projected climatic change

    Directory of Open Access Journals (Sweden)

    Theresa M. Modrick

    2015-03-01

    New hydrological insights for the region: Results indicate an increase in flash flood occurrence for the study region. For two distributed hydrologic models employed, the increase in flash flood occurrence frequency is on average between 30% and 40%. Regional flash flood occurrence is characterized by near saturation of the upper soil layer, and wider ranges in lower soil layer saturation and in precipitation. Overall, a decrease in the total number of precipitation events was found, although with increased precipitation intensity, increased event duration, and higher soil saturation conditions for the 21st century. This combination could signify more hazardous conditions, with fewer precipitation events but higher rainfall intensity and over soils with higher initial soil moisture saturation, leading to more frequent occurrence of flash floods.

  14. Flash Flood Prediction by Coupling KINEROS2 and HEC-RAS Models for Tropical Regions of Northern Vietnam

    National Research Council Canada - National Science Library

    Nguyen, Hong; Degener, Jan; Kappas, Martin

    2015-01-01

    .... As the prediction of potential flash floods represents one crucial element in this circumstance, we will present an approach that combines the two models KINEROS2 and HEC-RAS in order to accurately...

  15. Flash Flood Hazard Susceptibility Mapping Using Frequency Ratio and Statistical Index Methods in Coalmine Subsidence Areas

    Directory of Open Access Journals (Sweden)

    Chen Cao

    2016-09-01

    Full Text Available This study focused on producing flash flood hazard susceptibility maps (FFHSM using frequency ratio (FR and statistical index (SI models in the Xiqu Gully (XQG of Beijing, China. First, a total of 85 flash flood hazard locations (n = 85 were surveyed in the field and plotted using geographic information system (GIS software. Based on the flash flood hazard locations, a flood hazard inventory map was built. Seventy percent (n = 60 of the flooding hazard locations were randomly selected for building the models. The remaining 30% (n = 25 of the flooded hazard locations were used for validation. Considering that the XQG used to be a coal mining area, coalmine caves and subsidence caused by coal mining exist in this catchment, as well as many ground fissures. Thus, this study took the subsidence risk level into consideration for FFHSM. The ten conditioning parameters were elevation, slope, curvature, land use, geology, soil texture, subsidence risk area, stream power index (SPI, topographic wetness index (TWI, and short-term heavy rain. This study also tested different classification schemes for the values for each conditional parameter and checked their impacts on the results. The accuracy of the FFHSM was validated using area under the curve (AUC analysis. Classification accuracies were 86.61%, 83.35%, and 78.52% using frequency ratio (FR-natural breaks, statistical index (SI-natural breaks and FR-manual classification schemes, respectively. Associated prediction accuracies were 83.69%, 81.22%, and 74.23%, respectively. It was found that FR modeling using a natural breaks classification method was more appropriate for generating FFHSM for the Xiqu Gully.

  16. Historical flash floods retromodelling in the Ondara River in Tàrrega (NE Iberian Peninsula

    Directory of Open Access Journals (Sweden)

    J. C. Balasch

    2011-12-01

    Full Text Available Flash floods in the Ondara River have caused many fatalities and damages in the town of Tàrrega in the last 400 yr. Unfortunately, no flow records are available.

    However, floods can sometimes be reconstructed thanks to available historical information: limnimarks, written accounts and archaeological surveys. Indeed, from these data and using the retromodelling method on three different scenarios to take into account morphology changes, the peak flows of the seven greatest floods occurred in Tàrrega since the 17th century were estimated.

    The results showed that the heaviest flood's specific peak flow (10.7 m3 s−1 km−2 ranks among the highest ever modelled or measured in similar-sized catchments in the Western Mediterranean region. The results pointed out, as well, that the changes in channel's morphology (mainly, the disappearance of a mediaeval bridge under sediment caused by one of the floods increased the hydraulic capacity of a crucial cross-section. All this resulted in modest floods invading the town less often, but with much faster and, thus, more destructive flows.

    A preliminary estimation of the results' uncertainty was 4% for great floods and 18% for modest floods.

    The reconstructed peak flows will be introduced in a database for a future use in climatic and hydrological studies.

  17. Winter and summer-autumn flash floods as "drivers" of drought and seasonal flood characteristics (case study of European Russia)

    Science.gov (United States)

    Kireeva, Maria; Frolova, Natalia; Rets, Ekaterina; Ezerova, Natalia

    2016-04-01

    The presence of occasional flood periods on rivers is a typical feature of the hydrological regime of European Russia. Despite the fact that the main high-water phase of a hydrological year here is related to spring, flash floods in other seasons play an equally important role. For example, increased water content during autumn determines soil moisture content that determines the loss of runoff during spring flood. Winter floods caused by thaws result in a significant drawdown of a snow pack. And when it is followed by a return of cold weather an ice crust is formed on the surface of snowpack that significantly reduces rates of melt water filtration process.In recent decades, most of the rivers in the European part of Russia have experienced a significant increase of occasional flood flow share in total annual runoff. For example, in the Don basin this parameter has increased by almost 2 times, in the basin of Oka by 1.5. Though less intense, these trends can be traced in the eastern part of the region - in the basins of Kama and Vyatka. The increase here can is approximately 15-20%. In the north of the Eastern Plain (North Dvina, etc.) this tendency isn't observed. The number of flood waves has several times increased. Until 1970s 1-3 occasional floods a year were generally observed on the rivers of Central and Southern Russia. In the past three decades almost every year there are from 4 to 8 or more periods of high water. They are superimposed on each other, as well as the phase of the spring flood and low flow period. The ratio of the maximum discharge of occasional flood to maximum discharge of seasonal flood has increased several times. Now some outstanding floods can be compared with the spring flood wave or even exceed it.Thus, through winter floods an "interception" of spring flood runoff occurs. Spring floods have a lower height and volume and as a result they don't fully recharge a basin. Dry period in this case begins much earlier and though the moisture

  18. HYMEX-SOPI the field campaign dedicated to heavy precipitation and flash flooding in the Northwestern Mediterranean

    OpenAIRE

    Ducrocq, V; Braud, I.; S. Davolio; Ferretti, R.; Flamant, C; Jansa, A.; Kalthoff, N.; Richard, E.; Taupier-Letage, I.; Ayral, P. A.; Belamari, S.; A. Berne; Borga, M; Boudevillain, B.; Bock, O.

    2014-01-01

    The Mediterranean region is frequently affected by heavy precipitation events associated with flash floods, landslides, and mudslides that cause hundreds of millions of euros in damages per year and, often, casualties. A major field campaign was devoted to heavy precipitation and flash floods from 5 September to 6 November 2012 within the framework of the 10-yr international Hydrological Cycle in the Mediterranean Experiment (HyMeX) dedicated to the hydrological cycle and related high-impact ...

  19. Estimation of flash flood using surface water model and GIS technique in Wadi El Azariq, East Sinai, Egypt

    OpenAIRE

    Osta, Maged M.; Sabri, Mohamed Sh.; Masoud, Milad H.

    2016-01-01

    The study of flash flood hazard phenomenon and runoff potentialities are the major task of a hydrologists especially in arid and semi-arid regions. This paper presents a new approach to modeling flash floods in dryland catchments by the integration between physiographic features of the study basin, Geographic Information System (GIS) and Watershed Modelling System (WMS). Advanced Space borne Thermal Emission and Reflection Radiometer (ASTER) data was used to prepare a digit...

  20. Hydroclimatological Aspects of the Extreme 2011 Assiniboine River Basin Flood

    Science.gov (United States)

    Brimelow, J.; Szeto, K.; Bonsal, B. R.; Hanesiak, J.; Kochtubajda, B.; Stewart, R. E.

    2014-12-01

    In the spring and early summer of 2011, the Assiniboine River Basin in Canada experienced an extreme flood that was unprecedented in terms of duration and volume of water. The flood had significant socioeconomic impacts and caused over one billion dollars in damage. Contrary to what one might expect for such an extreme flood, individual precipitation events before and during the 2011 flood were not extreme; instead, it was the cumulative impact and timing of precipitation events going back to the summer of 2010 that played a key role in the 2011 flood. The summer and fall of 2010 were exceptionally wet, resulting in soil moisture levels being much above normal at the time of freeze up. This was followed by above-average precipitation during the winter of 2010-2011, and record-breaking basin-averaged snow-water equivalent values in March and April 2011. Abnormally cold temperatures in March delayed the spring melt by about two weeks, with the result that the above-average seasonal melt freshet occurred close to the onset of abnormally heavy rains in May and June. The large-scale atmospheric flow during May and June 2011 favoured increased cyclone activity over the central and northern U.S., which produced an anomalously large number of heavy rainfall events over the basin. All of these factors combined to generate extreme surface runoff and flooding. We used JRA-55 reanalysis data to quantify the relative importance of snowmelt, soil moisture and spring precipitation in contributing to the unprecedented flood and to demonstrate how the 2011 flood was unique compared to previous floods in the basin. Data and research from this study can be used to validate and improve flood forecasting techniques over this important basin; our findings also raise important questions regarding the impact of climate change on basins that experience pluvial and nival flooding.

  1. Multi-scale hydrometeorological observation and modelling for flash flood understanding

    OpenAIRE

    Braud, I.; Ayral, P.-A.; Bouvier, C.; Branger, F.; Delrieu, G.; Coz, J.; Nord, G.; Vandervaere, J.-P.; Anquetin, S.; Adamovic, M.; Andrieu, J.; Batiot, C.; Boudevillain, B.; Brunet, P; Carreau, J.

    2014-01-01

    This paper presents a coupled observation and modelling strategy aiming at improving the understanding of processes triggering flash floods. This strategy is illustrated for the Mediterranean area using two French catchments (Gard and Ardèche) larger than 2000 km2. The approach is based on the monitoring of nested spatial scales: (1) the hillslope scale, where processes influencing the runoff generation and its concentration can be tackled; (2) the small to medium cat...

  2. Technical Note: Advances in flash flood monitoring using unmanned aerial vehicles (UAVs)

    Science.gov (United States)

    Perks, Matthew T.; Russell, Andrew J.; Large, Andrew R. G.

    2016-10-01

    Unmanned aerial vehicles (UAVs) have the potential to capture information about the earth's surface in dangerous and previously inaccessible locations. Through image acquisition of flash flood events and subsequent object-based analysis, highly dynamic and oft-immeasurable hydraulic phenomena may be quantified at previously unattainable spatial and temporal resolutions. The potential for this approach to provide valuable information about the hydraulic conditions present during dynamic, high-energy flash floods has until now not been explored. In this paper we adopt a novel approach, utilizing the Kande-Lucas-Tomasi (KLT) algorithm to track features present on the water surface which are related to the free-surface velocity. Following the successful tracking of features, a method analogous to the vector correction method has enabled accurate geometric rectification of velocity vectors. Uncertainties associated with the rectification process induced by unsteady camera movements are subsequently explored. Geo-registration errors are relatively stable and occur as a result of persistent residual distortion effects following image correction. The apparent ground movement of immobile control points between measurement intervals ranges from 0.05 to 0.13 m. The application of this approach to assess the hydraulic conditions present in the Alyth Burn, Scotland, during a 1 : 200 year flash flood resulted in the generation of an average 4.2 at a rate of 508 measurements s-1. Analysis of these vectors provides a rare insight into the complexity of channel-overbank interactions during flash floods. The uncertainty attached to the calculated velocities is relatively low, with a spatial average across the area of ±0.15 m s-1. Little difference is observed in the uncertainty attached to out-of-bank velocities (±0.15 m s-1), and within-channel velocities (±0.16 m s-1), illustrating the consistency of the approach.

  3. Perturbation of convection-permitting NWP forecasts for flash-flood ensemble forecasting

    OpenAIRE

    B. Vincendon; V. Ducrocq; Nuissier, O.; B. Vié

    2011-01-01

    Mediterranean intense weather events often lead to devastating flash-floods. Extending the forecasting lead times further than the watershed response times, implies the use of numerical weather prediction (NWP) to drive hydrological models. However, the nature of the precipitating events and the temporal and spatial scales of the watershed response make them difficult to forecast, even using a high-resolution convection-permitting NWP deterministic forecasting. This study proposes a new metho...

  4. Copula-based IDF curves and empirical rainfall thresholds for flash floods and rainfall-induced landslides

    Science.gov (United States)

    Bezak, Nejc; Šraj, Mojca; Mikoš, Matjaž

    2016-10-01

    Floods, landslides and debris flows are natural events that occur all over the world and are often induced by extreme rainfall conditions. Several extreme events occurred in Slovenia (Europe) in the last 25 years that caused 18 casualties and approximately 500 million Euros of economic loss. The intensity-duration-frequency (IDF) relationship was constructed using the Frank copula function for several rainfall stations using high-resolution rainfall data with an average subsample length of 34 years. The empirical rainfall threshold curves were also evaluated for selected extreme events. Post-event analyses showed that rainfall characteristics triggering flash floods and landslides are different. The sensitivity analysis results indicate that the inter-event time definition (IETD) and subsample definition methodology can have a significant influence on the position of rainfall events in the intensity-duration space, the constructed IDF curves and on the relationship between the empirical rainfall threshold curves and the IDF curves constructed using the copula approach. Furthermore, a combination of several empirical rainfall thresholds with an appropriate high-density rainfall measurement network can be used as part of the early warning system of the initiation of landslides and debris flows. However, different rainfall threshold curves should be used for lowland and mountainous areas in Slovenia.

  5. Lessons learnt from past Flash Floods and Debris Flow events to propose future strategies on risk management

    Science.gov (United States)

    Cabello, Angels; Velasco, Marc; Escaler, Isabel

    2010-05-01

    Floods, including flash floods and debris flow events, are one of the most important hazards in Europe regarding both economic and life loss. Moreover, changes in precipitation patterns and intensity are very likely to increase due to the observed and predicted global warming, rising the risk in areas that are already vulnerable to floods. Therefore, it is very important to carry out new strategies to improve flood protection, but it is also crucial to take into account historical data to identify high risk areas. The main objective of this paper is to show a comparative analysis of the flood risk management information compiled in four test-bed basins (Llobregat, Guadalhorce, Gardon d'Anduze and Linth basins) from three different European countries (Spain, France and Switzerland) and to identify which are the lessons learnt from their past experiences in order to propose future strategies on risk management. This work is part of the EU 7th FP project IMPRINTS which aims at reducing loss of life and economic damage through the improvement of the preparedness and the operational risk management of flash flood and debris flow (FF & DF) events. The methodology followed includes the following steps: o Specific survey on the effectivity of the implemented emergency plans and risk management procedures sent to the test-bed basin authorities that participate in the project o Analysis of the answers from the questionnaire and further research on their methodologies for risk evaluation o Compilation of available follow-up studies carried out after major flood events in the four test-bed basins analyzed o Collection of the lessons learnt through a comparative analysis of the previous information o Recommendations for future strategies on risk management based on lessons learnt and management gaps detected through the process As the Floods Directive (FD) already states, the flood risks associated to FF & DF events should be assessed through the elaboration of Flood Risk

  6. How do people perceive, understand, and anticipate responding to flash flood risks and warnings? Results from a public survey in Boulder, Colorado, USA

    Science.gov (United States)

    Morss, Rebecca E.; Mulder, Kelsey J.; Lazo, Jeffrey K.; Demuth, Julie L.

    2016-10-01

    This study investigates flash flood forecast and warning communication, interpretation, and decision making, using data from a survey of 418 members of the public in Boulder, Colorado, USA. Respondents to the public survey varied in their perceptions and understandings of flash flood risks in Boulder, and some had misconceptions about flash flood risks, such as the safety of crossing fast-flowing water. About 6% of respondents indicated consistent reversals of US watch-warning alert terminology. However, more in-depth analysis illustrates the multi-dimensional, situationally dependent meanings of flash flood alerts, as well as the importance of evaluating interpretation and use of warning information along with alert terminology. Some public respondents estimated low likelihoods of flash flooding given a flash flood warning; these were associated with lower anticipated likelihood of taking protective action given a warning. Protective action intentions were also lower among respondents who had less trust in flash flood warnings, those who had not made prior preparations for flash flooding, and those who believed themselves to be safer from flash flooding. Additional analysis, using open-ended survey questions about responses to warnings, elucidates the complex, contextual nature of protective decision making during flash flood threats. These findings suggest that warnings can play an important role not only by notifying people that there is a threat and helping motivate people to take protective action, but also by helping people evaluate what actions to take given their situation.

  7. Monitoring the variability of precipitable water vapor over the Klang Valley, Malaysia during flash flood

    Science.gov (United States)

    Suparta, W.; Rahman, R.; Singh, M. S. J.

    2014-06-01

    Klang Valley is a focal area of Malaysian economic and business activities where the local weather condition is very important to maintain its reputation. Heavy rainfalls for more than an hour were reported up to 40 mm in September 2013 and 35 mm in October 2013. Both events are monitored as the first and second cases of flash flood, respectively. Based on these cases, we investigate the water vapor, rainfall, surface meteorological data (surface pressure, relative humidity, and temperature) and river water level. The precipitable water vapor (PWV) derived from Global Positioning System (GPS) is used to indicate the impact of flash flood on the rainfall. We found that PWV was dropped 4 mm in 2 hours before rainfall reached to 40 mm and dropped 3 mm in 3 hours before 35 mm of rainfall in respective cases. Variation of PWV was higher in September case compared to October case of about 2 mm. We suggest the rainfall phenomena can disturb the GPS propagation and therefore, the impact of PWV before, during and after the flash flood event at three selected GPS stations in Klang Valley is investigated for possible mitigation in the future.

  8. Perturbation of convection-permitting NWP forecasts for flash-flood ensemble forecasting

    Directory of Open Access Journals (Sweden)

    B. Vincendon

    2011-05-01

    Full Text Available Mediterranean intense weather events often lead to devastating flash-floods. Extending the forecasting lead times further than the watershed response times, implies the use of numerical weather prediction (NWP to drive hydrological models. However, the nature of the precipitating events and the temporal and spatial scales of the watershed response make them difficult to forecast, even using a high-resolution convection-permitting NWP deterministic forecasting. This study proposes a new method to sample the uncertainties of high-resolution NWP precipitation forecasts in order to quantify the predictability of the streamflow forecasts. We have developed a perturbation method based on convection-permitting NWP-model error statistics. It produces short-term precipitation ensemble forecasts from single-value meteorological forecasts. These rainfall ensemble forecasts are then fed into a hydrological model dedicated to flash-flood forecasting to produce ensemble streamflow forecasts. The verification on two flash-flood events shows that this forecasting ensemble performs better than the deterministic forecast. The performance of the precipitation perturbation method has also been found to be broadly as good as that obtained using a state-of-the-art research convection-permitting NWP ensemble, while requiring less computing time.

  9. Flash Flood Risk Perception in an Italian Alpine Region. From Research into Adaptive Strategies.

    Science.gov (United States)

    Scolobig, A.; de Marchi, B.; Borga, M.

    2009-04-01

    Flash floods are characterised by short lead times and high levels of uncertainty. Adaptive strategies to face them need to take into account not only the physical characteristics of the hydro-geological phenomena, but also peoples' risk perceptions, attitudes and behaviours in case of an emergency. It is quite obvious that a precondition for an effective adaptation, e.g. in the case of a warning, is the awareness of being endangered. At the same time the perceptions of those at risk and their likely actions inform hazard warning strategies and recovery programmes following such events. Usually low risk awareness or "wrong perceptions" of the residents are considered among the causes of an inadequate preparedness or response to flash floods as well as a symptom of a scarce self-protection culture. In this paper we will focus on flood risk perception and on how research on this topic may contribute to design adaptive strategies and give inputs to flood policy decisions. We will report on a flood risk perception study of the population residing in four villages in an Italian Alpine Region (Trentino Alto-Adige), carried out between October 2005 and January 2006. A total of 400 standardised questionnaires were submitted to local residents by face to face interviews. The surveys were preceded by focus groups with officers from agencies in charge of flood risk management and semi-structured and in-depth interviews with policy, scientific and technical experts. Survey results indicated that people are not so worried about hydro-geological phenomena, and think that their community is more endangered than themselves. The knowledge of the territory and danger sources, the unpredictability of flash floods and the feeling of safety induced by structural devices are the main elements which make the difference in shaping residents' perceptions. The study also demonstrated a widespread lack of adoption of preparatory measures among residents, together with a general low

  10. Flash flood warnings for ungauged basins based on high-resolution precipitation forecasts

    Science.gov (United States)

    Demargne, Julie; Javelle, Pierre; Organde, Didier; de Saint Aubin, Céline; Janet, Bruno

    2016-04-01

    Early detection of flash floods, which are typically triggered by severe rainfall events, is still challenging due to large meteorological and hydrologic uncertainties at the spatial and temporal scales of interest. Also the rapid rising of waters necessarily limits the lead time of warnings to alert communities and activate effective emergency procedures. To better anticipate such events and mitigate their impacts, the French national service in charge of flood forecasting (SCHAPI) is implementing a national flash flood warning system for small-to-medium (up to 1000 km²) ungauged basins based on a discharge-threshold flood warning method called AIGA (Javelle et al. 2014). The current deterministic AIGA system has been run in real-time in the South of France since 2005 and has been tested in the RHYTMME project (rhytmme.irstea.fr/). It ingests the operational radar-gauge QPE grids from Météo-France to run a simplified hourly distributed hydrologic model at a 1-km² resolution every 15 minutes. This produces real-time peak discharge estimates along the river network, which are subsequently compared to regionalized flood frequency estimates to provide warnings according to the AIGA-estimated return period of the ongoing event. The calibration and regionalization of the hydrologic model has been recently enhanced for implementing the national flash flood warning system for the entire French territory by 2016. To further extend the effective warning lead time, the flash flood warning system is being enhanced to ingest Météo-France's AROME-NWC high-resolution precipitation nowcasts. The AROME-NWC system combines the most recent available observations with forecasts from the nowcasting version of the AROME convection-permitting model (Auger et al. 2015). AROME-NWC pre-operational deterministic precipitation forecasts, produced every hour at a 2.5-km resolution for a 6-hr forecast horizon, were provided for 3 significant rain events in September and November 2014 and

  11. Hydrological disposition of flash flood and debris flows events in an Alpine watershed in Austria

    Science.gov (United States)

    Prenner, David; Kaitna, Roland; Mostbauer, Karin; Hrachowitz, Markus

    2017-04-01

    Debris flows and flash floods including intensive bedload transport represent severe hazards in the Alpine environment of Austria. For neither of these processes, explicit rainfall thresholds - even for specific regions - are available. This may be due to insufficient data on the temporal and spatial variation of precipitation, but probably also due to variations of the geomorphic and hydrological disposition of a watershed to produce such processes in the course of a rainfall event. In this contribution we investigate the importance of the hydrological system state for triggering debris flows and flash floods in the Ill/Suggadin watershed (500 km2), Austria, by analyzing the effects of dynamics in system state variables such as soil moisture, snow pack, or ground water level. The analysis is based on a semi-distributed conceptual rainfall-runoff model, spatially discretizing the watershed according to the available precipitation observations, elevation, topographic considerations and land cover. Input data are available from six weather stations on a daily basis ranging back to 1947. A Thiessen polygon decomposition results in six individual precipitation zones with a maximum area of about 130 km2. Elevation specific behavior of the quantities temperature and precipitation is covered through an elevation-resolved computation every 200 m. Spatial heterogeneity is considered by distinct hydrological response units for bare rock, forest, grassland, and riparian zone. To reduce numerical smearing on the hydrological results, the Implicit Euler scheme was used to discretize the balance equations. For model calibration we utilized runoff hydrographs, snow cover data as well as prior parameter and process constraints. The obtained hydrological output variables are linked to documented observed flash flood and debris flow events by means of a multivariate logistic regression. We present a summary about the daily hydrological disposition of experiencing a flash flood or

  12. Flash-floods in Catalonia: the social perception in a context of changing vulnerability

    Directory of Open Access Journals (Sweden)

    M. C. Llasat

    2008-07-01

    Full Text Available In assessing a flood event two risk components need to be considered: the intrinsic hazard of the hydrometeorological event causing the flood and the vulnerability of the area where the precipitation has been registered. In the present study four flood events selected by the FLASH European project have been classified according to the characteristics of the meteorological event (classification according to hazard and according to the physical and economic damages caused (classification according to vulnerability. The social impact of these events is analysed taking into account the growth of the population. An increase in the number of extraordinary flash-floods was detected in the areas with a major growth of the population, as a consequence of an increased vulnerability of these areas, both from a physical perspective (exposure of infrastructures and from an economic perspective (more goods exposed. In addition, the numerous non-native inhabitants of the region are not aware of the meteorological risks characteristic of the area, and this contributes to increased social vulnerability.

  13. What can we learn from the deadly flash floods? Post Event Review Capability (PERC) analysis of the Bavaria and Baden-Wurttemberg flood events in Summer 2016

    Science.gov (United States)

    Szoenyi, Michael

    2017-04-01

    In May/June 2016, stationary low pressure systems brought intense rainfall with record-braking intensities of well above 100 mm rain in few hours locally in the southern states of Baden-Wurttemberg and Bavaria, Germany. In steep terrains, small channels and creeks became devastating torrents impacting, among others, the villages of Simbach/Inn, Schwäbisch-Gmünd and Braunsbach. Just few days prior, France had also seen devastating rainfall and flooding. Damage in Germany alone is estimated at 2.8 M USD, of which less than 50% are insured. The loss of life was significant, with 18 fatalities reported across the events. This new forensic event analysis as part of Zurich's Post Event Review Capability (PERC) investigates the flash flood events following these record rainfalls in Southern Germany and tries to answer the following questions holistically, across the five capitals (5C) and the full disaster risk management (DRM) cycle, which are key to understanding how to become more resilient to such flood events: - Why have these intense rainfall events led to such devastating consequences? The EU Floods directive and its implementation in the various member states, as well as the 2002 and 2013 Germany floods, have focused on larger rivers and the main asset concentration. The pathway and mechanism of the 2016 floods are very different and need to be better understood. Flash floods and surface flooding may need to become the new focus and be much better communicated to people at risk, as the awareness for such perils has been identified as low. - How can the prevalence for such flash floods be better identified and mapped? Research indicated that affected people and decision makers alike attribute the occurrence of such flash floods as arbitrary, but we argue that hotspots can and must be identified based on an overlay of rainfall intensity maps, topography leading to flash flood processes, and vulnerable assets. In Germany, there are currently no comprehensive hazard

  14. OpenLISEM Flash Flood Modelling Application in Logung Sub-Catchment, Central Java

    Directory of Open Access Journals (Sweden)

    Fitrie Atviana Nurritasari

    2016-02-01

    Full Text Available Juwana Catchment and Logung Sub-catchment in particular has been suffering several major past flood events with significant loss. This study conducted an assessment of flood risk by using OpenLISEM as physical soil and hydrological model to generate the single storm flash flood occurrences. The physical input data were collected from remote sensing image interpretation, field observation and measurement and literature review. There are three return periods chosen as scenarios that represent rainfall intensity in Logung Sub-Catchment. Model validation was done by adjusting initial moisture content and saturated hydraulic conductivity values to equate the calculated total discharge with the measured total discharge in several chosen dates. The results show increases in most of modeled hydrological parameter with respect to increasing of rainfall intensity.

  15. Progressive recovery of a tropical deforested stream community after a flash flood

    Directory of Open Access Journals (Sweden)

    Lucas Cerqueira Marques

    2013-06-01

    Full Text Available AIM: In this study, we evaluated and compared community attributes from a tropical deforested stream, located in a pasture area, in a period before (PRED I and three times after (POSD I, II, and III a flash flood, in order to investigate the existence of temporal modifications in community structure that suggests return to conditions previous to the flash flood. METHODS: Biota samples included algae, macrophytes, macroinvertebrates, and fish assemblages. Changes in stream physical structure we also evaluated. Similarity of the aquatic biota between pre and post-disturbance periods was examined by exploratory ordination, known as Non-Metric Multidimensional Scaling associated with Cluster Analysis, using quantitative and presence/absence Bray-Curtis similarity coefficients. Presence and absence data were used for multivariate correlation analysis (Relate Analysis in order to investigate taxonomic composition similarity of biota between pre and post-disturbance periods. RESULTS: Our results evidenced channel simplification and an expressive decrease in richness and abundance of all taxa right after the flood, followed by subsequent increases of these parameters in the next three samples, indicating trends towards stream community recovery. Bray-Curtis similarity coefficients evidenced a greater community structure disparity among the period right after the flood and the subsequent ones. Multivariate correlation analysis evidenced a greater correlation between macroinvertebrates and algae/macrophytes, demonstrating the narrow relation between their recolonization dynamics. CONCLUSIONS: Despite overall community structure tended to return to previous conditions, recolonization after the flood was much slower than that reported in literature. Finally, the remarkably high flood impact along with the slow recolonization could be a result of the historical presence of anthropic impacts in the region, such as siltation, riparian forest complete depletion

  16. Improvement of resilience of urban areas by integrating social perception in flash-flood risk management

    Science.gov (United States)

    Bodoque, J. M.; Amérigo, M.; Díez-Herrero, A.; García, J. A.; Cortés, B.; Ballesteros-Cánovas, J. A.; Olcina, J.

    2016-10-01

    In urban areas prone to flash floods, characterization of social resilience is critical to guarantee the success of emergency management plans. In this study, we present the methodological approach that led to the submission and subsequent approval of the Civil Protection Plan of Navaluenga (Central Spain), in which the first phase was to analyse flood hazard by combining the Hydrological Modelling System (HEC-HMS) and the Iber 2D hydrodynamic model. We then analysed social vulnerability and designed measures to put into practice within the framework of the Civil Protection Plan. At a later phase, we assessed citizens' flash-flood risk perception and level of awareness regarding some key variables of the Civil Protection Plan. To this end, 254 adults representing roughly 12% of the population census were interviewed. Responses were analysed descriptively, comparing awareness regarding preparedness and response actions with the corresponding information and behaviours previously defined in the Civil Protection Plan. In addition, we carried out a latent class cluster analysis aimed at identifying the different groups present among the interviewees. Our results showed that risk perception is low. Specifically, 60.8% of the interviewees showed low risk perception and low awareness (cluster 1); 24.4% had high risk perception and low awareness (cluster 2), while the remaining 14.8% presented high long-term risk perception and high awareness (cluster 3). These findings suggest the need for integrating these key variables of social risk perception and local tailored information in emergency management plans, especially in urban areas prone to flash-floods where response times are limited.

  17. Simulating a Lowland Flash Flood in a Long-term Experimental Watershed with 7 Standard Hydrological Models

    Science.gov (United States)

    Torfs, P.; Brauer, C.; Teuling, R.; Kloosterman, P.; Willems, G.; Verkooijen, B.; Uijlenhoet, R.

    2012-12-01

    On 26 August 2010 the 6.5 km2 Hupsel Brook catchment in The Netherlands, which has been the experimental watershed employed by Wageningen University since the 1960s, was struck by an exceptionally heavy rainfall event (return period > 1000 years). We investigated the unprecedented flash flood triggered by this event and this study improved our understanding of the dynamics of such lowland flash floods (Brauer et al., 2011). During this extreme event some thresholds became apparent that do not play a role during average conditions and are not incorporated in most rainfall-runoff models. This may lead to errors when these models are used to forecast runoff responses to rainfall events that are extreme today, but likely to become less extreme when climate changes. The aim of this research project was to find out to what extent different types of rainfall-runoff models are able to simulate this extreme event, and, if not, which processes, thresholds or parameters are lacking to describe the event accurately. Five of the 7 employed models treat the catchment as a lumped system. This group includes the well-known HBV and Sacramento models. The Wageningen Model, which has been developed in our group, has a structure similar to HBV and the Sacramento Model. The SWAP (Soil, Water, Atmosphere, Plant) Model represents a physically-based model of a single soil column, but has been used here as a representation for the whole catchment. The LGSI (Lowland Groundwater Surface water Interaction) Model uses probability distributions to account for spatial variability in groundwater depth and resulting flow routes in the catchment. We did not only analyze how accurately each model simulated the discharge, but also whether groundwater and soil moisture dynamics and resulting flow processes were captured adequately. The 6th model is a spatially distributed model called SIMGRO. It is based on a MODFLOW groundwater model, extended with an unsaturated zone based on the previously

  18. Development of roughness updating based on artificial neural network in a river hydraulic model for flash flood forecasting

    Indian Academy of Sciences (India)

    J C Fu; M H Hsu; Y Duann

    2016-02-01

    Flood is the worst weather-related hazard in Taiwan because of steep terrain and storm. The tropical storm often results in disastrous flash flood. To provide reliable forecast of water stages in rivers is indispensable for proper actions in the emergency response during flood. The river hydraulic model based on dynamic wave theory using an implicit finite-difference method is developed with river roughness updating for flash flood forecast. The artificial neural network (ANN) is employed to update the roughness of rivers in accordance with the observed river stages at each time-step of the flood routing process. Several typhoon events at Tamsui River are utilized to evaluate the accuracy of flood forecasting. The results present the adaptive n-values of roughness for river hydraulic model that can provide a better flow state for subsequent forecasting at significant locations and longitudinal profiles along rivers.

  19. Documenting historic and recent extreme floods in Kashmir

    Science.gov (United States)

    Ballesteros-Cánovas, Juan Antonio; Koul Tasaduq, Hussain; Alamgir Shabir, Hussain; Shah Mutayib, Bashir; Stoffel, Markus

    2016-04-01

    Kashmir has been frequently subjected to massive floods along its history. The recent extreme flood events which occurred during September 2014, March 2015 and September 2015 have revealed the high vulnerability of its population. Causes of recent extreme flood events have been attributed to the bowl shaped topography, intense land-use changes and unfavorable climatic change conditions at the onset of the monsoon as well as due to the occurrence of westerly disturbances. This reality implies new challenges to authorities and calls for the development of suitable adaptation strategies focusing on a minimization of the expected negative impacts on inhabitants during future extreme floods. In this context, long-term records can improve our understanding about the flood frequency as well as changes in climate - and land-use - linkages. In this communication, we present an extensive flood records from Kashmir by combining historical descriptions with tree-ring records from headwater catchments as well as with the existing flow gauge records. Historical sources include old records from archives of the Irrigation and Flood Control Department of flood events which have taken place at Jhelum River, but also old pictures and other documents about the river system, going back in time to the British period. At the headwater catchment, we additionally perform tree-ring analyses coupled with classical palaeohydraulic techniques to reconstruct the magnitude and occurrence of recent, yet ungauged extreme events. Both sources of data have been compared and merged with the existing flow records in order to provide a clearer picture about flood phenomena in this region. Historical archives corroborate the assumption that that Srinagar (the main city of Kashmir), as well as the surroundings crops land, have been frequently affected by floods. Although the oldest records are from the 19th century, dense annals including information about water levels are available after the 18th

  20. Experimental study of wave impact on the nearshore structures during extreme coastal floods

    Science.gov (United States)

    Sriram, Venkatachalam; Didenkulova, Ira; Pelinovsky, Efim; Rodin, Artem; Didenkulov, Oleg; Sergeeva, Anna; Nair Vishnu, Reghunathan; Sundar, Vallam; Annamalaisamy Sannasiraj, Sannasi

    2016-04-01

    We study the dynamics of strongly nonlinear waves in the coastal zone and their impact on coasts during flash floods and tsunami. For this we use analytical theory of strongly nonlinear wave propagation along the slope and compare it with the data of experiments carried out in shallow water flume of IIT Madras (72 m long, 2 m wide and up to 2 m deep). Different kinds of waves like elongated solitons, N-waves are simulated and its run-up and impact force on the idealized structure on the slope are evaluated. Different numerical models (CLAWPACK, pseudospectral code for solving nonlinear evolutional equations and FNPT model) areused to describe strongly nonlinear waves along the slope. Results of numerical simulations are compared with predictions of analytical theory and with the data of experiments. The results presented here are the preliminary results obtained within DST - RFBR joint project "Impact of waterborne debris on the nearshore structures during extreme coastal floods".

  1. Application of a fully integrated surface-subsurface physically based flow model for evaluating groundwater recharge from a flash flood event

    Science.gov (United States)

    Pino, Cristian; Herrera, Paulo; Therrien, René

    2017-04-01

    In many arid regions around the world groundwater recharge occurs during flash floods. This transient spatially and temporally concentrated flood-recharge process takes place through the variably saturated zone between surface and usually the deep groundwater table. These flood events are characterized by rapid and extreme changes in surface flow depth and velocity and soil moisture conditions. Infiltration rates change over time controlled by the hydraulic gradients and the unsaturated hydraulic conductivity at the surface-subsurface interface. Today is a challenge to assess the spatial and temporal distribution of groundwater recharge from flash flood events under real field conditions at different scales in arid areas. We apply an integrated surface-subsurface variably saturated physically-based flow model at the watershed scale to assess the recharge process during and after a flash flood event registered in an arid fluvial valley in Northern Chile. We are able to reproduce reasonably well observed groundwater levels and surface flow discharges during and after the flood with a calibrated model. We also investigate the magnitude and spatio-temporal distribution of recharge and the response of the system to variations of different surface and subsurface parameters, initial soil moisture content and groundwater table depths and surface flow conditions. We demonstrate how an integrated physically based model allows the exploration of different spatial and temporal system states, and that the analysis of the results of the simulations help us to improve our understanding of the recharge processes in similar type of systems that are common to many arid areas around the world.

  2. Understanding Extreme Spanish Coastal Flood Events

    Science.gov (United States)

    Diez, J. Javier; Esteban, M. Dolores; Silvestre, J. Manuel

    2013-04-01

    The Santa Irene flood event, at the end of October 1982, is one of the most dramatically widely reported flood events in Spain. Its renown is mainly due to the collapse of the Tous dam, but its main message is to be the paradigm of the incidence of the maritime/littoral weather and its temporal sea level rise by storm surge accompanying rain process on the coastal plains inland floods. Looking at damages the presentation analyzes the adapted measures from the point of view of the aims of the FP7 SMARTeST Project related to the Flood Resilience improvement in urban areas through looking for Technologies, Systems and Tools an appropriate "road to de market". The event was due to the meteorological phenomenon known as "gota fría" (cold drop), a relatively frequent and intense rainy phenomenon affecting one or more basins on the Iberian Peninsula, particularly on the Spanish east to southeast inlands and coasts. There are some circumstances that can easily come together to unleash the cold drop there: cold and dry polar air masses coming onto the whole Iberian Peninsula and the north of Africa, high sea water temperatures, and low atmospheric pressure (cyclone) areas in the western Mediterranean basin; these circumstances are quite common during the autumn season there, and, as it happens, in other places around the world (East/Southeast Africa). Their occurrence, however shows a great space-temporal variability (in a similar way to hurricanes, on Caribbean and western North-Atlantic areas, or to typhoons do). As a matter of fact, all of these equivalent though different phenomena may have different magnitude each time. An overview of the very main events since 11th century in the East to Southeast areas in Spain is shown in the presentation, looking for relation with climatic conditions and Climate changes on one hand, and with geomorphologic and geotechnical conditions on the other It also describes the results of a detailed analysis and reflection about this cold

  3. Modelling large floating bodies in urban area flash-floods via a Smoothed Particle Hydrodynamics model

    Science.gov (United States)

    Albano, Raffaele; Sole, Aurelia; Mirauda, Domenica; Adamowski, Jan

    2016-10-01

    Large debris, including vehicles parked along floodplains, can cause severe damage and significant loss of life during urban area flash-floods. In this study, the authors validated and applied the Smoothed Particle Hydrodynamics (SPH) model, developed in Amicarelli et al. (2015), which reproduces in 3D the dynamics of rigid bodies driven by free surface flows, to the design of flood mitigation measures. To validate the model, the authors compared the model's predictions to the results of an experimental setup, involving a dam breach that strikes two fixed obstacles and three transportable floating bodies. Given the accuracy of the results, in terms of water depth over time and the time history of the bodies' movements, the SPH model explored in this study was used to analyse the mitigation efficiency of a proposed structural intervention - the use of small barriers (groynes) to prevent the transport of floating bodies. Different groynes configurations were examined to identify the most appropriate design and layout for urban area flash-flood damage mitigation. The authors found that groynes positioned upstream and downstream of each floating body can be effective as a risk mitigation measure for damage resulting from their movement.

  4. Evaluation of Golestan Province's Early Warning System for flash floods, Iran, 2006-7.

    Science.gov (United States)

    Ardalan, Ali; Holakouie Naieni, Kourosh; Kabir, Mohamad-Javad; Zanganeh, Ali-Mohamad; Keshtkar, Abbas-Ali; Honarvar, Mohamad-Reza; Khodaie, Hanieh; Osooli, Mehdi

    2009-05-01

    Golestan province located in NE Iran is well known for deadly flash floods. This study aimed to evaluate the region's Early Warning System (EWS) for flash floods. We used an adapted version of the questionnaire developed by the United Nations International Strategy for Disaster Reduction. We reviewed documents on the EWS of Golestan, and conducted a qualitative study comprising interviews with experts and affected people in Kalaleh and Minoodasht. Results were discussed by an expert panel. Regarding risk knowledge, there was a hazard map at Provincial Disaster Taskforce (PDT) drawn by the provincial Office for Water Resource Management, but no risk analysis was available. Local people were aware of their exposure to flooding, but not aware of the existence of a hazard map and their vulnerability situation. In terms of monitoring and warning, PDT faced serious limitations in issuing Early Warnings, including (1) an inability to make point predictions of rainfall, and (2) the absence of a warning threshold. Dissemination and communication issued by the Meteorological Office followed a top-to-bottom direction. The contents were neither clearly understood by other institutions nor reached the potential recipients within an appropriate time frame. There was a need for a comprehensive response plan with adequate exercises, and no evaluation framework existed. Golestan EWS is in dire need of improvement. To fill in the gaps ensuring local people receive timely warning, we propose a community-based model called "Village Disaster Taskforce" (VDT) in which individual villages act as operational units, but interlinked with other villages and PDT.

  5. Construction of an integrated social vulnerability index in urban areas prone to flash flooding

    Science.gov (United States)

    Aroca-Jimenez, Estefania; Bodoque, Jose Maria; Garcia, Juan Antonio; Diez-Herrero, Andres

    2017-09-01

    Among the natural hazards, flash flooding is the leading cause of weather-related deaths. Flood risk management (FRM) in this context requires a comprehensive assessment of the social risk component. In this regard, integrated social vulnerability (ISV) can incorporate spatial distribution and contribution and the combined effect of exposure, sensitivity and resilience to total vulnerability, although these components are often disregarded. ISV is defined by the demographic and socio-economic characteristics that condition a population's capacity to cope with, resist and recover from risk and can be expressed as the integrated social vulnerability index (ISVI). This study describes a methodological approach towards constructing the ISVI in urban areas prone to flash flooding in Castilla y León (Castile and León, northern central Spain, 94 223 km2, 2 478 376 inhabitants). A hierarchical segmentation analysis (HSA) was performed prior to the principal components analysis (PCA), which helped to overcome the sample size limitation inherent in PCA. ISVI was obtained from weighting vulnerability factors based on the tolerance statistic. In addition, latent class cluster analysis (LCCA) was carried out to identify spatial patterns of vulnerability within the study area. Our results show that the ISVI has high spatial variability. Moreover, the source of vulnerability in each urban area cluster can be identified from LCCA. These findings make it possible to design tailor-made strategies for FRM, thereby increasing the efficiency of plans and policies and helping to reduce the cost of mitigation measures.

  6. Meteorological analysis of flash floods in Artvin (NE Turkey) on 24 August 2015

    Science.gov (United States)

    Baltaci, Hakki

    2017-07-01

    On 24 August 2015 intense rainfall episodes generated flash floods and landslides on the eastern Black Sea coast of Turkey. As a consequence of the heavy rainstorm activity over Artvin and its surroundings (NE Turkey), 11 people died and economic losses totaled a million dollars. Over the 6 h of the event (from 05:00 to 11:00 UTC), total accumulated rainfall amounts of 136, 64, and 109 mm were measured in the Hopa, Arhavi, and Borçka settlements of Artvin city, respectively. This study comprehensively investigates the meteorological characteristics of those flash floods. In terms of synoptic mechanisms, the cutoff surface low from the summer Asian monsoon settled over the eastern Black Sea. After two days of quasistationary conditions of this cyclone, sea surface temperatures (SSTs) reached 27.5 °C (1.5 °C higher than normal) and low-level moisture convergence developed. In addition, transfer of moisture by warm northerly flows from the Black Sea and relatively cool southerly flows from the land coasts of the Artvin district exacerbated the unstable conditions and thus played a significant role in the development of deep convective cells. Severe rainstorms as well as the slope instability of the region triggered landslides and worsened flood damages in the Artvin area. This study supports conventional weather analysis, satellite images, and forecast model output to alert forecasters to the potential for heavy rainfall.

  7. Fragile Landscape: Impact and Consequences of May 2014 Flash-flood Disaster in the Aqaba Area, Southern Jordan

    Directory of Open Access Journals (Sweden)

    Yahya Farhan

    2014-09-01

    Full Text Available Flash-flood disasters are common in the Aqaba area. It always has a significant impact on the city and causes immense damages to lives and the infrastructure (highways, roads and dwelling areas. Before the 1990s several flash-floods of medium and high magnitudes were recorded (i.e., the 1963 and 1966 floods. However, low and medium magnitude floods (6-7 and 20 year return period have been a recurrent phenomena over the last three decades. The city and the port of Aqaba are considered crucial to the Jordanian economy and cosequently the protection of the city/port from repetitive flooding is important to maintain future urban and economic development. Since the 1960s all formulated development plans for the city and the southern coast have suffered from a remarkable lack of appreciation and awareness regarding environmental hazards, where 90% of the Aqaba area is exposed to flood and sediment hazards. An intensive post-event geomorphic survey was carried out following a flash-flood that struck the Aqaba area on 6-7th May 2014 to identify the damages that occurred and to recognize the main hydrological characteristics of the flash-flood, the terrain favoring flooding, fluvial processes which initiate large gullies and finally to gain experience regarding natural hazards. Hydrological studies related to previous flooding events indicate that the Aqaba area is exposed to recurrent floods of different magnitudes, associated with high peak discharge, gully erosion, slumping and high sediment load. These caused serious damages to the properties and infrastructure, loss of life and hardship for the people of Aqaba. The resultant large gullies are considered an additional cause of instability and a sediment source which threatened the Aqaba area.

  8. Disaster management in flash floods in Leh (Ladakh: A case study

    Directory of Open Access Journals (Sweden)

    Preeti Gupta

    2012-01-01

    Full Text Available Background: On August 6, 2010, in the dark of the midnight, there were flash floods due to cloud burst in Leh in Ladakh region of North India. It rained 14 inches in 2 hours, causing loss of human life and destruction. The civil hospital of Leh was badly damaged and rendered dysfunctional. Search and rescue operations were launched by the Indian Army immediately after the disaster. The injured and the dead were shifted to Army Hospital, Leh, and mass casualty management was started by the army doctors while relief work was mounted by the army and civil administration. Objective: The present study was done to document disaster management strategies and approaches and to assesses the impact of flash floods on human lives, health hazards, and future implications of a natural disaster. Materials and Methods: The approach used was both quantitative as well as qualitative. It included data collection from the primary sources of the district collectorate, interviews with the district civil administration, health officials, and army officials who organized rescue operations, restoration of communication and transport, mass casualty management, and informal discussions with local residents. Results: 234 persons died and over 800 were reported missing. Almost half of the people who died were local residents (49.6% and foreigners (10.2%. Age-wise analysis of the deaths shows that the majority of deaths were reported in the age group of 25-50 years, accounting for 44.4% of deaths, followed by the 11-25-year age group with 22.2% deaths. The gender analysis showed that 61.5% were males and 38.5% were females. A further analysis showed that more females died in the age groups <10 years and ≥50 years. Conclusions: Disaster preparedness is critical, particularly in natural disasters. The Army′s immediate search, rescue, and relief operations and mass casualty management effectively and efficiently mitigated the impact of flash floods, and restored normal

  9. Integration of social perception in flash flood risk management for resilience improvement

    Science.gov (United States)

    Diez-Herrero, Andres; Amerigo, Maria; Bodoque, Jose Maria; Garcia, Juan Antonio; Olcina-Cantos, Jorge

    2015-04-01

    Spain is, behind Switzerland, the second most mountainous country in Europe, which determines that after the occurrence of heavy or intense rainfall events, a fast hydrological response takes place due to steep slopes and strong hydrological connectivity. As a result, flash floods are, among natural hazards, the main social risk in Spain. In fact, they have provoked some of the greatest natural disasters in recent history of the country (e.g. Yebra and Almoguera in 1995, Biescas in 1996 or Badajoz in 1997, which totalized more than 200 deceased in the last decades). This work is focused on the village of Navaluenga (Central Spain), in which we have been studying flash floods, under the consideration of different perspectives and using different approaches, for the past 20 years; and in which the regional government has recently approved the Civil Protection Plan.In this research, we examine social perception of flash floodsthrough surveys and interviews; one turn previous to the communication plan and other one after this dissemination activities to population. To this end, the individual and groupal differences were explored, by taking into account socio-demographic variables. In addition, we have considered psychological and material dimensions of vulnerability associated to flood risk, as well as to the emotional dimension through the consideration of psyco-environmental variables.Thus, this research aims to identify what aspects of the social perception differs from scientific/technical knowledge acquired which, in turn, may decrease the efficiency of a risk mitigation plan or even determine its failure. To minimize this lack of harmony, and at the same time to increase awareness of population, we propose a risk communication plan to improve preparedness of the community. To this end, we propose an approach in which messages reach the population quickly and in an understandable way. In this regard, risk communication is based on the integration of suitable

  10. Assessment of commuters' daily exposure to flash flooding over the roads of the Gard region, France

    Science.gov (United States)

    Debionne, Samuel; Ruin, Isabelle; Shabou, Saif; Lutoff, Céline; Creutin, Jean-Dominique

    2016-10-01

    Flash floods are responsible for a majority of natural disaster fatalities in the USA and Europe and most of them are vehicle-related. If human exposure to flood is generally assessed through the number of inhabitants per buildings located in flood prone zone, it is clear that this number varies dramatically throughout the day as people move from place to place to follow their daily program of activities. Knowing the number of motorists exposed on flood prone road sections or the factors determining their exposure would allow providing a more realistic evaluation of the degree of exposure. In order to bridge this gap and provide emergency managers with methods to assess the risk level for motorists, this paper describes two methods, a simple rough-and-ready estimate and a traffic attribution method, and applies both of them on datasets of the Gard département, an administrative region of Southern France with about 700 000 inhabitants over 5875 km2. The first method to obtain an overall estimation of motorists flood exposure is to combine (i) the regional density of roads and rivers to derive a count of potential road cuts and (ii) the average daily kilometers driven by commuters of the study area to derive the number of people passing these potential cuts. If useful as a first approximation, this method fails to capture the spatial heterogeneities introduced by the geometry of river and road networks and the distribution of commuters' itineraries. To address this point, this paper (i) uses a pre-established detailed identification of road cuts (Naulin et al., 2013) and (ii) applies a well-known traffic attribution method to existing and freely available census datasets. Both methods indicate that commuters' exposure is much larger than the number of commuters itself, illustrating the risk amplification effect of mobility. Comparing the results from both methods shows that (i) the road network geometry plays a significant role in reducing the risk of river

  11. Flash floods in the Sahara: a case study for the 28 January 2013 flood in Qena, Egypt

    Directory of Open Access Journals (Sweden)

    Moawad Badawy Moawad

    2016-01-01

    Full Text Available Understanding the torrential rainfall and its consequent surface runoff in the Sahara is a crucial issue for better flood protection and water management plans. This is often hampered by the lack of appropriate in situ measurements. Even now the satellite-derived rainfall suffers from great uncertainty. Thus, we adjusted the data obtained from real-time satellite rainfall coverage (HYDIS using the in situ observed rainfall (Robs. Hydro-morphological parameters were then integrated with the empirical curve number (CN approach to estimate the surface runoff in Qena, Egypt during the 28 January 2013 flash flood event. We deduced that the study area received a total precipitation (∑Rcum of ∼35.6 × 106 [mm] and a total rain volume (∑Rvol of ∼88.9 × 109 [m3] mainly from wadi Qena (89.8%. The majority of the rainfalls fell at light intensity (<2.5 [mm hr−1]. The estimated total surface runoff (∑Qsur was 26.5 × 106 mm and the total runoff volume (∑Qvol was 66.2 × 106 [m3]. The total surface transmission losses (∑Tlos were calculated as 9.1 × 106 [mm], which represents about 25.6% of the total precipitation (∑Rcum and creates substantial opportunities for alluvial aquifer recharge. The total surface runoff (∑Qsur and flood magnitude were generally low, therefore, flood influences were restricted to the destruction of some roads in Qena but no fatalities were involved, nevertheless. Most of the running water was contained by El Sail Canal and poured into the Nile River. It is expected that the applied method in this study will be helpful for our understanding and quantification of flood hydrology and contribute to better risk management plan in the arid and hyper-arid regions.

  12. Improving the quantification of flash flood hydrographs and reducing their uncertainty using noncontact streamgauging methods

    Science.gov (United States)

    Branger, Flora; Dramais, Guillaume; Horner, Ivan; Le Boursicaud, Raphaël; Le Coz, Jérôme; Renard, Benjamin

    2015-04-01

    Continuous river discharge data are crucial for the study and management of floods. In most river discharge monitoring networks, these data are obtained at gauging stations, where the stage-discharge relation is modelled with a rating curve to derive discharge from the measurement of water level in the river. Rating curves are usually established using individual ratings (or gaugings). However, using traditional gauging methods during flash floods is challenging for many reasons including hazardous flow conditions (for both equipment and people), short duration of the flood events, transient flows during the time needed to perform the gauging, etc. The lack of gaugings implies that the rating curve is often extrapolated well beyond the gauged range for the highest floods, inducing large uncertainties in the computed discharges. We deployed two remote techniques for gauging floods and improving stage-discharge relations for high flow conditions at several hydrometric stations throughout the Ardèche river catchment in France : (1) permanent video-recording stations enabling the implementation of the image analysis LS-PIV technique (Large Scale Particle Image Velocimetry) ; (2) and mobile gaugings using handheld Surface Velocity Radars (SVR). These gaugings were used to estimate the rating curve and its uncertainty using the Bayesian method BaRatin (Le Coz et al., 2014). Importantly, this method explicitly accounts for the uncertainty of individual gaugings, which is especially relevant for remote gaugings since their uncertainty is generally much higher than that of standard intrusive gauging methods. Then, the uncertainty of streamflow records was derived by combining the uncertainty of the rating curve and the uncertainty of stage records. We assessed the impact of these methodological developments for peak flow estimation and for flood descriptors at various time steps. The combination of field measurement innovation and statistical developments allows

  13. Flash Flood Hazard Mapping Using Satellite Images and GIS Tools: A case study of Najran City, Kingdom of Saudi Arabia (KSA)

    OpenAIRE

    Ismail Elkhrachy

    2015-01-01

    Flash flood in the cities led to high levels of water in the streets and roads, causing many problems such as bridge collapse, building damage and traffic problems. It is impossible to avoid risks of floods or prevent their occurrence, however it is plausible to work on the reduction of their effects and to reduce the losses which they may cause. Flash flood mapping to identify sites in high risk flood zones is one of the powerful tools for this purpose. Mapping flash flood will be beneficial...

  14. Extreme Storm Surges and Coastal Flooding: Intangible Flood Losses in Integrated Risk Analysis

    Directory of Open Access Journals (Sweden)

    D.R. Dassanayake

    2012-12-01

    Full Text Available German coasts are often affected by extreme storm surges which have already led to major damages along the coastline in the past. The joint research project “XtremRisK” was initiated with the main objective of enhancing the knowledge with respect to the uncertainties of extreme storm surge predictions as well as quantifying exemplarily the flood risk under current conditions and future climate scenarios for two pilot sites in Germany: Sylt Island representative for an open coast and Hamburg for an estuarine urban area. Flood risk is generally determined by the product of the flooding probability and the possible losses associated with the flood event. Flood losses are categorized as tangible and intangible depending on whether or not the losses can be assessed in monetary values. Up to date, intangible loses are not or only partially incorporated in flood risk analysis due to the lack of appropriate evaluation and integration methodologies. This study focuses on developing methodologies for the evaluation of intangible losses due to flooding and for their integration with tangible losses in flood risk analysis

  15. Rapid-assessing Methods of Loss in Extremely Heavy Rainfall Disaster Chain in Semiarid Region——A Case Study on a Flash Flood Debris Flow in Minxian County, Gansu Province%半干旱区极端强降雨灾害链损失快速评估方法——以甘肃岷县“5·10”特大山洪泥石流灾害为例

    Institute of Scientific and Technical Information of China (English)

    周洪建; 王曦; 袁艺; 王丹丹

    2014-01-01

    通过对半干旱地区极端强降雨灾害链的研究,构建了基于流域单元、综合多源信息的极端强降雨灾害链损失快速评估方法.其中,流域评估单元的选择、遥感解译与灾害信息员实地调查的房屋易损性判定准则、综合损失的灾害链损失评估思路等是该方法的主要特点.甘肃岷县“5·10”特大山洪泥石流灾害房屋损失评估误差小于15%,基本满足应急救助决策的需要.建立多源数据条件下的洪涝灾害实物量毁损快速评估体系,可提升灾害应急救助效率.%Less attention was paid to the extremely heavy rainfall disaster chain in semiarid regions in the previous researches.Under climate change,the frequency and intensity of extremely heavy rainfall in semiarid areas in China was in an obvious increase trend in recent decades.It is important to develop a methodology of rapid assessment of damage and loss (RADL) in an extremely heavy rainfall so as to enhance the capability of preventing the disasters in semiarid areas.In this paper,a method was developed to assess the damage and loss in an extremely heavy rainfall disaster chain,especially in flash flood and debris flow disaster chains based on multi-source data and information,including the real-time precipitation,inundated area derived from remote sensing image interpretation results,social and economic information of the study area,etc.Three points should be emphasized in the framework of this method:① The assessment unit of the RADL was the combination of watershed unit and GRID unit,in which the watershed unit included the second-level watersheds in the study area,and the spatial resolution of GRID unit was decided by the social and economic information (e.g.population density) ; ② The home vulnerability curve was an important factor to implement the RADL.In this paper,a home vulnerability matrix was established based on the real-time filed survey of disaster information collectors at

  16. Damages caused by floods and flash-floods upon critical infrastructures. Case study: Maramureş county (Romania

    Directory of Open Access Journals (Sweden)

    Eugen Nour

    2011-08-01

    Full Text Available Critical infrastructure is defined as a network including telecommunications, informationservices, energy transport (electrical lines, natural gas and oil pipes, water supply, goods and personstransportation, financial, banking and emergency response services. All these are so significant that adisequilibrium or interruption of their operation would have a disturbing effect upon the daily life.Estimating the damage done by natural hazards to certain critical infrastructure sectors is considered animportant interest topic. The main purpose of this research is the estimation of the damages generatedby floods and flash-floods on the critical infrastructure in Maramureş County during 2005-2010. Thedamages analysis is based mainly on observations and quantitative data, obtained after a thoroughanalysis of literature and reports from the Ministry of Environment and Forests and the Inspectorate forEmergency Situation of Maramureş County. The results of the study were alarming. The damages causedby floods during the period subjected to study reach approximately 32 million dollars, highlighting theneed for an integrated management system for critical infrastructure protection.

  17. Optimisation of Lagrangian Flash Flood Microsensors Dropped by Unmanned Aerial Vehicle

    KAUST Repository

    Abdulaal, Mohammed

    2014-05-01

    Abstract Physical Sciences and Engineering Division Mechanical Engineering Department Master of Science Optimisation of Lagrangian Flash Flood Microsensors Dropped by Unmanned Aerial Vehicle by Mohammed Abdulaal Floods are the most common natural disasters, causing thousands of casualties every year in the world. In particular, ash ood events are particularly deadly because of the short timescales on which they occur. Classical sensing solutions such as xed wireless sensor networks or satellite imagery are either too expensive or too inaccurate. Nevertheless, Unmanned Aerial Vehicles equipped with mobile microsensors could be capable of sensing ash oods in real time for a low overall cost, saving lives and greatly improving the e ciency of the emergency response. Using ood simulation data, we show that this system could be used to detect ash oods. We also present an ongoing implementation of this system using 3D printed sensors and sensor delivery systems on a UAV testbed as well as some preliminary results.

  18. Time Sequence on the Flash Flood Disaster in the Tsurugi River, Hofu City, in Japan

    Science.gov (United States)

    Yamakoshi, T.; Nakano, Y.; Ishizuka, T.; Tamura, K.; Hasegawa, Y.

    2012-04-01

    A rainstorm that hit Hofu city in Yamaguchi Prefecture, Japan on July 21st, 2009 caused flash floods or debris flows in many mountain streams around Hofu, claiming many lives and devastating downstream communities and the national highway. The authors investigated high water marks of the flash flood or debris flow after the devastating rainstorm and interviewed the eyewitnesses that were present during the disaster in order to determine the time sequence of the phenomenon that occurred in one mountainous torrent, the Tsurugi River. The results of the survey conducted so far suggest the following; 1) The peak discharge estimated from the high water marks is around 30 to 69 m3/s at the investigated cross section just downstream of the sediment control dam. It was consistent with a peak discharge value obtained by simple runoff analysis. 2) On the other hand, the estimated peak discharge was much larger than that obtained through the runoff analysis. This is probably because of the influence of the debris flow or hyper-concentrated flow from the tributaries downstream of the sediment control dams. 3) The flood discharge from the Tsurugi River to the national highway suddenly increased at the last moment of the rainstorm at 12:30. At the same time, the ponding behind the bridge of the highway seemed to occur. 4) Blocking of the river flow at the bridge hadn't occurred until around 12:00. However, it probably occurred at around 12:30 due to the occurrences of the debris flow or hyper-concentrated flow from the tributaries. These findings infer that the river channel of the Tsurugi River had succeeded in draining flood runoff until nearly the end of the rainstorm. At the last moment, however, occurrences of the debris flow or hyper-concentrated flow from the tributaries might result in the clogging of the bridge and the inundation.

  19. Multi-scale hydrometeorological observation and modelling for flash-flood understanding

    Directory of Open Access Journals (Sweden)

    I. Braud

    2014-02-01

    Full Text Available This paper presents a coupled observation and modelling strategy aiming at improving the understanding of processes triggering flash floods. This strategy is illustrated for the Mediterranean area using two French catchments (Gard and Ardèche larger than 2000 km2. The approach is based on the monitoring of nested spatial scales: (1 the hillslope scale, where processes influencing the runoff generation and its concentration can be tackled; (2 the small to medium catchment scale (1–100 km2 where the impact of the network structure and of the spatial variability of rainfall, landscape and initial soil moisture can be quantified; (3 the larger scale (100–1000 km2 where the river routing and flooding processes become important. These observations are part of the HyMeX (Hydrological Cycle in the Mediterranean Experiment Enhanced Observation Period (EOP and lasts four years (2012–2015. In terms of hydrological modelling the objective is to set up models at the regional scale, while addressing small and generally ungauged catchments, which is the scale of interest for flooding risk assessment. Top-down and bottom-up approaches are combined and the models are used as "hypothesis testing" tools by coupling model development with data analyses, in order to incrementally evaluate the validity of model hypotheses. The paper first presents the rationale behind the experimental set up and the instrumentation itself. Second, we discuss the associated modelling strategy. Results illustrate the potential of the approach in advancing our understanding of flash flood processes at various scales.

  20. Use of geostationary meteorological satellite images in convective rain estimation for flash-flood forecasting

    Science.gov (United States)

    Wardah, T.; Abu Bakar, S. H.; Bardossy, A.; Maznorizan, M.

    2008-07-01

    SummaryFrequent flash-floods causing immense devastation in the Klang River Basin of Malaysia necessitate an improvement in the real-time forecasting systems being used. The use of meteorological satellite images in estimating rainfall has become an attractive option for improving the performance of flood forecasting-and-warning systems. In this study, a rainfall estimation algorithm using the infrared (IR) information from the Geostationary Meteorological Satellite-5 (GMS-5) is developed for potential input in a flood forecasting system. Data from the records of GMS-5 IR images have been retrieved for selected convective cells to be trained with the radar rain rate in a back-propagation neural network. The selected data as inputs to the neural network, are five parameters having a significant correlation with the radar rain rate: namely, the cloud-top brightness-temperature of the pixel of interest, the mean and the standard deviation of the temperatures of the surrounding five by five pixels, the rate of temperature change, and the sobel operator that indicates the temperature gradient. In addition, three numerical weather prediction (NWP) products, namely the precipitable water content, relative humidity, and vertical wind, are also included as inputs. The algorithm is applied for the areal rainfall estimation in the upper Klang River Basin and compared with another technique that uses power-law regression between the cloud-top brightness-temperature and radar rain rate. Results from both techniques are validated against previously recorded Thiessen areal-averaged rainfall values with coefficient correlation values of 0.77 and 0.91 for the power-law regression and the artificial neural network (ANN) technique, respectively. An extra lead time of around 2 h is gained when the satellite-based ANN rainfall estimation is coupled with a rainfall-runoff model to forecast a flash-flood event in the upper Klang River Basin.

  1. Exceptional sequence of severe thunderstorms and related flash floods in May and June 2016 in Germany - Part 1: Meteorological background

    Science.gov (United States)

    Piper, David; Kunz, Michael; Ehmele, Florian; Mohr, Susanna; Mühr, Bernhard; Kron, Andreas; Daniell, James

    2016-12-01

    During a 15-day episode from 26 May to 9 June 2016, Germany was affected by an exceptionally large number of severe thunderstorms. Heavy rainfall, related flash floods and creek flooding, hail, and tornadoes caused substantial losses running into billions of euros (EUR). This paper analyzes the key features of the severe thunderstorm episode using extreme value statistics, an aggregated precipitation severity index, and two different objective weather-type classification schemes. It is shown that the thunderstorm episode was caused by the interaction of high moisture content, low thermal stability, weak wind speed, and large-scale lifting by surface lows, persisting over almost 2 weeks due to atmospheric blocking.For the long-term assessment of the recent thunderstorm episode, we draw comparisons to a 55-year period (1960-2014) regarding clusters of convective days with variable length (2-15 days) based on precipitation severity, convection-favoring weather patterns, and compound events with low stability and weak flow. It is found that clusters with more than 8 consecutive convective days are very rare. For example, a 10-day cluster with convective weather patterns prevailing during the recent thunderstorm episode has a probability of less than 1 %.

  2. An operational flash-flood forecasting chain applied to the test cases of the EU project HYDROPTIMET

    Directory of Open Access Journals (Sweden)

    A. C. Taramasso

    2005-01-01

    Full Text Available The application of a flash-flood prediction chain, developed by CIMA, to some testcases for the Tanaro river basin in the framework of the EU project HYDROPTIMET is presented here. The components of the CIMA chain are: forecast rainfall depths, a stochastic downscaling procedure and a hydrological model. Different meteorological Limited Area Models (LAMs provide the rainfall input to the hydrological component. The flash-flood prediction chain is run both in a deterministic and in a probabilistic configuration. The sensitivity of forecasting chain performances to different LAMs providing rainfall forecasts is discussed. The results of the application show how the probabilistic forecasting system can give, especially in the case of convective events, a valuable contribution in addressing the uncertainty at different spatio-temporal scales involved in the flash flood forecasting problem in small and medium basins with complex orography.

  3. Geomorphological Impacts of an extreme Flood in Karoon River, Iran

    Science.gov (United States)

    Yousefi, Saleh; Mirzaee, Somaya; Keesstra, Saskia; Piegay, Herve; Pourghasemi, Hamid Reza

    2017-04-01

    An extreme flood occurred on 14.04.2016 in Kroon River. Using the OLI Landsat images on 08.04.2016 (before flood) and 24.04.2016 (after flood) the morphological evolution in different land cover types by this flood event were detected. The results show that the event significantly affected the channel width. The main effect was the high mobilization of channel sediments and severe bank erosion in the studied meandering reach. According to field surveys, the flood occupied the whole channel corridor and even some of the flood plain parts, but the channel pattern was not markedly changed. Results show the average of active channel width increased from 192 m to 256 m respectively for before and after flood. Statistical results indicate a significant change for active channel width and sinuosity index at 99% confidence level for both indexes. Findings show that the channel morphological changes (channel widening) varied significantly in different land cover types along the Karoon River banks. Specifically, the channel has widened less in the residential areas than the other land cover types, which is the result of bank protection activities. Keywords: Remote sensing, fluvial geomorphology, floodplain management, river evolution.

  4. Understanding processes that generate flash floods in the arid Judean Desert to the Dead Sea - a measurement network

    Science.gov (United States)

    Hennig, Hanna; Rödiger, Tino; Laronne, Jonathan B.; Geyer, Stefan; Merz, Ralf

    2016-04-01

    Flash floods in (semi-) arid regions are fascinating in their suddenness and can be harmful for humans, infrastructure, industry and tourism. Generated within minutes, an early warning system is essential. A hydrological model is required to quantify flash floods. Current models to predict flash floods are often based on simplified concepts and/or on concepts which were developed for humid regions. To more closely relate such models to local conditions, processes within catchments where flash floods occur require consideration. In this study we present a monitoring approach to decipher different flash flood generating processes in the ephemeral Wadi Arugot on the western side of the Dead Sea. To understand rainfall input a dense rain gauge network was installed. Locations of rain gauges were chosen based on land use, slope and soil cover. The spatiotemporal variation of rain intensity will also be available from radar backscatter. Level pressure sensors located at the outlet of major tributaries have been deployed to analyze in which part of the catchment water is generated. To identify the importance of soil moisture preconditions, two cosmic ray sensors have been deployed. At the outlet of the Arugot water is sampled and level is monitored. To more accurately determine water discharge, water velocity is measured using portable radar velocimetry. A first analysis of flash flood processes will be presented following the FLEX-Topo concept .(Savenije, 2010), where each landscape type is represented using an individual hydrological model according to the processes within the three hydrological response units: plateau, desert and outlet. References: Savenije, H. H. G.: HESS Opinions "Topography driven conceptual modelling (FLEX-Topo)", Hydrol. Earth Syst. Sci., 14, 2681-2692, doi:10.5194/hess-14-2681-2010, 2010.

  5. Armor Development from Decapitated Flash Flood Bores in Supply-Limited Flume Experiments

    Science.gov (United States)

    Goodwin, K.; Rhodes, R.; Johnson, J. P.

    2013-12-01

    In rivers assumed to have quasi-normal flow, three main processes have been used to explain bed surface armoring: i) selective entrainment and transport of smaller grains, ii) limited supply of smaller grain sizes, and iii) equal mobility of grains of different sizes, which develops through natural feedbacks such that larger, less mobile grains are enriched on the surface relative to smaller grains. Flash flood-dominated river channels in arid environments often completely lack surface armoring, yet it is unclear whether increased sediment supply or transport of all grain sizes prevents armor development. In order to examine armor development in an end-member case of non-normal flow, we conducted a series of laboratory experiments using flash flood bores. The flume is 33.5 m long, 0.5 m wide, 0.8 m tall, and capable of creating reproducible flood bores by raising a high-speed computerized lift gate and releasing impounded water. For each experiment, the gate was quickly lowered as soon as the flood bore traveled the length of the flume, 'decapitating' the bore from subsequent flow, to better isolate the effects of the bore alone on entrainment and transport. Sediment was not fed into the upstream end of the flume and only sourced from the gravel bed (2 mm to 40 mm), resulting in supply-limited experimental conditions. In response to repeated flood bores, the surface grain size distribution rapidly coarsened. We interpret that kinetic sieving was the dominant cause of surface armoring in these experiments. LiDAR scans of the bed topography from before and after each bore show increased surface roughness due to grain size changes, but small surface elevation changes due to relatively limited erosion. Digital gravelometry from photographs taken after each bore show increased armoring, while sediment transported out the downstream end of the flume tended to be as coarse or coarser than the bed surface. Travel distances of three sizes of RFID-tagged tracer clasts show

  6. Simulation of rainfall-runoff for major flash flood events in Karachi

    Science.gov (United States)

    Zafar, Sumaira

    2016-07-01

    Metropolitan city Karachi has strategic importance for Pakistan. With the each passing decade the city is facing urban sprawl and rapid population growth. These rapid changes directly affecting the natural resources of city including its drainage pattern. Karachi has three major cities Malir River with the catchment area of 2252 sqkm and Lyari River has catchment area about 470.4 sqkm. These are non-perennial rivers and active only during storms. Change of natural surfaces into hard pavement causing an increase in rainfall-runoff response. Curve Number is increased which is now causing flash floods in the urban locality of Karachi. There is only one gauge installed on the upstream of the river but there no record for the discharge. Only one gauge located at the upstream is not sufficient for discharge measurements. To simulate the maximum discharge of Malir River rainfall (1985 to 2014) data were collected from Pakistan meteorological department. Major rainfall events use to simulate the rainfall runoff. Maximum rainfall-runoff response was recorded in during 1994, 2007 and 2013. This runoff causes damages and inundation in floodplain areas of Karachi. These flash flooding events not only damage the property but also cause losses of lives

  7. An observational and numerical study of a flash flood event in Eastern Marmara Region.

    Science.gov (United States)

    Kahraman, A.

    2010-09-01

    Warm season cut-off cyclones over North-western Anatolia frequently triggers storms with heavy precipitation over Marmara and Western Black Sea Region. Since the area is highly urbanized with a deficiency in substructure, an important percentage of these storms result in flash floods, producing severe damage and fatalities. A heavy precipitation case from 5th to 9th of June, 2010 is studied. With the large scale circulation of the cut-off low, the storm system over Northern Anatolia moved Black Sea, and after getting richer in moisture, turned back to land over Eastern Marmara Region resulting more than 100 mm of precipitation in 24 hours. A peak of 77 mm in 6 hours is observed at Istanbul Sabiha Gokcen Airport on 7th of June, 2010. Damage in some buildings and one death occured related with the flash flood. In addition to synoptic charts, satellite data, surface and upper air observations, numerical simulation with WRF-ARW is used to make a mesoscale analysis of the meteorological conditions. Heavy rain ingredients such as conditionally unstability, low level jet and high moisture exist over the region according to the model output. Precipitable water and storm relative helicity values are mature and CAPE is moderate.

  8. Uncertainty assessment of climate change adaptation options in urban flash floods

    DEFF Research Database (Denmark)

    Zhou, Qianqian; Arnbjerg-Nielsen, Karsten

    Adaptation is necessary to cope with the increasing flood risk in cities due to anthropogenic climate change in many regions of the world. The choice of adaptation strategies can and should be based on a comprehensive risk-based economic analysis to indicate the net benefits of proposed options...... presented is based on a flood risk framework that is in accordance with the EU flood directive, but adapted and extended to incorporate anticipated future changes due to city development and hydrologic extremes. The framework is used to study the importance of inherent uncertainties in order to find robust...... are calculated using Monte Carlo simulations and thus the resulting uncertainties are described by probability density functions. Two different adaptation options are studied to reduce the increase in risk of flooding, namely increasing the pipe capacity and the use of local infiltration measures to hold water...

  9. A Flash Flood Study on the Small Montaneous River Catchments in Western Romania

    Science.gov (United States)

    Győri, Maria-Mihaela; Haidu, Ionel; Humbert, Joël

    2013-04-01

    The present study focuses on flash flood modeling on several mountaneous catchments situated in Western Romania by the use of two methodologies, when rainfall and catchment characteristics are known. Hence, the Soil Conservation Service (SCS) Method and the Rational Method will be employed for the generation of the 1%, 2% and 10% historical flash flood hydrographs on the basis of data spanning from 1989-2009. The SCS Method has been applied on the three gauged catchments in the study area: Petris, Troas and Monorostia making use of the existing interconnection between GIS and the rainfall-runoff models. The DEM, soil data and land use preprocessing in GIS allowed a determination of the hydrologic parameters needed for the rainfall-runoff model, with special emphasis on determining the time of concentration, Lag time and the weighted Curve Number according to Antecedent Moisture Conditions II, adapted for the Romanian territory. HEC-HMS rainfall-runoff model (Hydrologic Engineering Center- Hydrologic Modeling System) facilitates the historical 1%, 2% and 10% flash flood hydrograph generation for the three afore mentioned watersheds. The model is calibrated against measured streamflow data from the three existing gauging stations. The results show a good match between the resulted hydrographs and the observed hydrographs under the form of the Peak Weighted Error RMS values. The hydrographs generated by surface runoff on the ungauged catchments in the area is based on an automation of a workflow in GIS, built with ArcGIS Model Builder graphical interface, as a large part of the functions needed were available as ArcGIS tools. The several components of this model calculate: the runoff depth in mm, the runoff coefficient, the travel time and finally the discharge module which is an application of the rational method, allowing the discharge computation for every cell within the catchment. The result consists of discharges for each isochrones that will be subsequently

  10. Soil buffer limits flash flood response to extraordinary rainfall in a Dutch lowland catchment

    NARCIS (Netherlands)

    Brauer, C.C.; Teuling, R.; Overeem, A.J.; Velde, van der Y.; Hazenberg, P.; Warmerdam, P.M.M.; Uijlenhoet, R.

    2011-01-01

    On 26 August 2010 the eastern part of The Netherlands and the bordering part of Germany were struck by a series of very heavy rainfall events lasting for more than a day. Over an area of 740 km2 more than 120 mm of rainfall was observed in 24 hours. This extreme event resulted in local flooding of c

  11. Anatomy of extraordinary rainfall and flash flood in a Dutch lowland catchment

    NARCIS (Netherlands)

    Brauer, C.C.; Teuling, R.; Overeem, A.; Velde, van der Y.; Hazenberg, P.; Warmerdam, P.M.M.; Uijlenhoet, R.

    2011-01-01

    On 26 August 2010 the eastern part of The Netherlands and the bordering part of Germany were struck by a series of rainfall events lasting for more than a day. Over an area of 740 km2 more than 120 mm of rainfall were observed in 24 h. This extreme event resulted in local flooding of city centres, h

  12. (Flash) Floods on 27 Augustus 2010 in lowland catchments in The Netherlands and Germany

    NARCIS (Netherlands)

    Brauer, C.C.; Teuling, A.J.; Overeem, A.; Velde, van der Y.; Hazenberg, P.; Warmerdam, P.M.M.; Uijlenhoet, R.; Hobbelt, L.G.

    2011-01-01

    On 26 August 2010 the eastern part of The Netherlands and the bordering part of Germany were struck by a series of rainfall events. Over an area of 740 km2 more than 120 mm of rainfall were observed in 24 h. This extreme event resulted in local flooding of city centres, highways and agricultural fie

  13. Natural and human causes of a flash flood in a small catchment (Rhodes Island, Greece) based on atmospheric forcing and runoff modeling techniques

    Science.gov (United States)

    Karalis, Sotirios; Katsafados, Petros; Karymbalis, Efthimios; Tsanakas, Konstantinos; Valkanou, Kanella

    2014-05-01

    This study investigates the natural (hydro-meteorological and geomorphological) and human induced factors responsible for a flash flood event that occurred on November 22nd, 2013 in a small ungauged catchment (covering an area of about 24km2) of Rhodes Island, Greece. The flash flooding killed four people and caused over â¬10 million worth of damages located mainly around the Kremasti village. In this study the reconstruction of this extreme hydro-meteorological event is attempted by using detailed spatiotemporal rainfall information, a physically based hydrological model (LISEM) and the 1D hydraulic model HEC-RAS. Furthermore, the human impacts, which are responsible for extreme flood discharge within the drainage basin, are recorded and mapped. The major meteorological feature of this event is associated with the passage of a cold front over SE Aegean Sea. The destructive flash flood was triggered by the extreme precipitation (almost 100 mm in 4 hours was recorded at the meteorological stations closest to the flooded area). An advanced nowcasting method is applied in order to provide high spatiotemporal distribution of the precipitation over the catchment area. OpenLisem (Limbourg Soil Erosion Model) is used as a runoff model for exploring the response of the catchment. It is a freeware raster model (based on PCRaster) that simulates the surface water and sediment balance for every gridcell. It is event based and has fine spatial and temporal resolution. The model is designed to simulate the effects of detailed land use changes or conservation measures on runoff, flooding and erosion during heavy rainstorms. Since OpenLISEM provides a detailed simulation of runoff processes, it is very demanding on input data (it requires a minimum of 24 maps depending on the input options). The PCRaster GIS functionality was used to derive the necessary data from the basic maps (DEM, land unit map and map of impermeable areas). The sources for the basic maps include geological

  14. Changes of extreme drought and flood events in Iran

    Science.gov (United States)

    Modarres, Reza; Sarhadi, Ali; Burn, Donald H.

    2016-09-01

    Located in an arid and semi-arid region of the world, Iran has experienced many extreme flood and drought events in the last and current century. The present study aims to assess the changes in Iran's flood magnitude and drought severity for 1950-2010, with some time span variation in some stations. The Mann-Kendall test for monotonic trend was first applied to assess changes in flood and drought severity data. In addition, to consider the effect of serial correlation, two Pre-Whitening Trend (PWT) tests were also applied. It was observed that the number of stations with statistically significant trends has increased after applying PWT tests. Both increasing and decreasing trends were observed for drought severity and flood magnitude in different climate regions and major basins of Iran using these tests. The increase in flood magnitude and drought severity can be attributed partly to land use changes, an annual rainfall negative trend, a maximum rainfall increasing trend, and inappropriate water resources management policies. The paper indicates a critical situation related to extreme climate change in Iran and the increasing risk of environmental changes in the 21st century.

  15. Simplification approach to detect urban areas vulnerable to flash floods using GIS: a case study Warsaw

    Science.gov (United States)

    Wicht, Marzena; Osińska-Skotak, Katarzyna

    2016-04-01

    The aim of this study is to develop a consistent methodology to determine urban areas that are particularly vulnerable to the effects of torrential rains. They are, as a result of climate change, more and more prevalent in the temperate climate, usually spring - summer from mid-May to late August - and involve the risk of flash floods. In recent years, the increase in the incidence of such phenomena is noticeable throughout the whole Europe. It is assumed that through the analysis of environmental and infrastructural conditions, using the developed methodology, it is possible to determine areas vulnerable to flooding due to torrential rains. This may lead to a better management, quicker response in case of a phenomenon, and even to take measures to prevent the occurrence of adverse effects of torrential rains (for instance modernization of the urban drainage system and development of methods to get rid of rapidly collected water). Designation of areas particularly vulnerable to the effects of heavy rains can be achieved by adapting hydrological models, but they require an appropriate adjustment and highly accurate input data: (based on spot or radar measurements of precipitation, land cover, soil type, humidity, wind speed, vegetation species in a given area, growing season, the roughness and porosity of the cover and soil moisture) but such detailed data are generally hard to obtain or not available for less developed areas. It could also be achieved by performing spatial analysis in GIS, which is a more simplified form of modelling, but it gives results more quickly and the methodology can be adapted to the commonly available data. A case study of Warsaw's district Powiśle has been undertaken for three epochs - from 2008 to 2010 and areas, that are particularly vulnerable to the effects of flash floods and heavy rains, have been designated.

  16. Flash-flood forecasting by means of neural networks and nearest neighbour approach – a comparative study

    Directory of Open Access Journals (Sweden)

    A. Piotrowski

    2006-01-01

    Full Text Available In this paper, Multi-Layer Perceptron and Radial-Basis Function Neural Networks, along with the Nearest Neighbour approach and linear regression are utilized for flash-flood forecasting in the mountainous Nysa Klodzka river catchment. It turned out that the Radial-Basis Function Neural Network is the best model for 3- and 6-h lead time prediction and the only reliable one for 9-h lead time forecasting for the largest flood used as a test case.

  17. THE ASSESSMENT OF ECONOMICAL LOSS CAUSED BY FLOODS AND FLASH-FLOODS BY USING COMPUTER TECHNIQUES. CASE STUDY: LOPĂTARI VILLAGE, SLĂNIC RIVER

    Directory of Open Access Journals (Sweden)

    COSTACHE R.

    2015-03-01

    Full Text Available The present study aims to provide an example of the assessment of economical loss caused by floods and flash-floods, by integrating GIS techniques of hydraulic and hydrological modelling. The case study was performed in Lopătari village, which is located in the upper area of Slănic River, one of the most affected areas by floods and flash-floods. The flood event produced on 29.V.2012 was considered in order to perform this study. Thus, a flood hydrograph was simulated by using software HEC-HMS 3.5, based on hourly precipitation data from Bisoca meteorological station from 29.V.2012. The peak discharge resulting from the hydrological modelling software was used in HEC-RAS 4.1 hydraulic modelling software in order to determine the extent of flooding band, the number of the affected elements and the local economical loss. Finally, 21 flooded buildings were identified and 550 m of affected road, the estimated economical damage being about 800,000 RON.

  18. Results of the post flash-flood disaster investigations in the Transylvanian Depression (Romania during the last decade (2001–2010

    Directory of Open Access Journals (Sweden)

    V. Arghiuş

    2013-11-01

    Full Text Available Flash flood disasters are very rare in the Transylvanian Depression. In the last decades just three events were signalled in the study area, all of them during the last 10 yr. The flash floods occurring in the study area during the last decade had a significant impact on several localities situated at the Transylvanian Depression border. Based on the post flash flood investigation, the present study intends to find out the main characteristics of the flash-floods and the causes that have led to disasters in a region rarely affected by such kind of events. Analyzing the hydrological data, has been seen that the maximum intensity of the flash floods was observed in the upper and middle basins. By comparing the unit peak discharges from the studied region with other specific peak discharges related to the significant flash floods from Romania, it was noticed that the events from the Transylvanian Depression have moderate to low intensity. On the other hand, the results showed that beside high stream power and unexpected character common to flash floods, the inappropriate flood risk management measures increased the dimension of negative effects, leading to tens of life losses and economical damages of tens million dollars.

  19. Optimizing Satellite-Based Precipitation Estimation for Nowcasting of Rainfall and Flash Flood Events over the South African Domain

    OpenAIRE

    Estelle de Coning

    2013-01-01

    The South African Weather Service is mandated to issue warnings of hazardous weather events, including those related to heavy precipitation, in order to safeguard life and property. Flooding and flash flood events are common in South Africa. Frequent updates and real-time availability of precipitation data are crucial to support hydrometeorological warning services. Satellite rainfall estimation provides a very important data source for flash flood guidance systems as well as nowcasting of pr...

  20. Assessment of floodplain vulnerability during extreme Mississippi River flood 2011

    Science.gov (United States)

    Goodwell, Allison E.; Zhu, Zhenduo; Dutta, Debsunder; Greenberg, Jonathan A.; Kumar, Praveen; Garcia, Marcelo H.; Rhoads, Bruce L.; Holmes, Jr., Robert R.; Parker, Gary; Berretta, David P.; Jacobson, Robert B.

    2014-01-01

    Regional change in the variability and magnitude of flooding could be a major consequence of future global climate change. Extreme floods have the capacity to rapidly transform landscapes and expose landscape vulnerabilities through highly variable spatial patterns of inundation, erosion, and deposition. We use the historic activation of the Birds Point-New Madrid Floodway during the Mississippi and Ohio River Flooding of 2011 as a scientifically unique stress experiment to analyze indicators of floodplain vulnerability. We use pre- and postflood airborne Light Detection and Ranging data sets to locate erosional and depositional hotspots over the 540 km2 agricultural Floodway. While riparian vegetation between the river and the main levee breach likely prevented widespread deposition, localized scour and deposition occurred near the levee breaches. Eroded gullies nearly 1 km in length were observed at a low ridge of a relict meander scar of the Mississippi River. Our flow modeling and spatial mapping analysis attributes this vulnerability to a combination of erodible soils, flow acceleration associated with legacy fluvial landforms, and a lack of woody vegetation to anchor soil and enhance flow resistance. Results from this study could guide future mitigation and adaptation measures in cases of extreme flooding.

  1. Assessment of floodplain vulnerability during extreme Mississippi River flood 2011.

    Science.gov (United States)

    Goodwell, Allison E; Zhu, Zhenduo; Dutta, Debsunder; Greenberg, Jonathan A; Kumar, Praveen; Garcia, Marcelo H; Rhoads, Bruce L; Holmes, Robert R; Parker, Gary; Berretta, David P; Jacobson, Robert B

    2014-01-01

    Regional change in the variability and magnitude of flooding could be a major consequence of future global climate change. Extreme floods have the capacity to rapidly transform landscapes and expose landscape vulnerabilities through highly variable spatial patterns of inundation, erosion, and deposition. We use the historic activation of the Birds Point-New Madrid Floodway during the Mississippi and Ohio River Flooding of 2011 as a scientifically unique stress experiment to analyze indicators of floodplain vulnerability. We use pre- and postflood airborne Light Detection and Ranging data sets to locate erosional and depositional hotspots over the 540 km(2) agricultural Floodway. While riparian vegetation between the river and the main levee breach likely prevented widespread deposition, localized scour and deposition occurred near the levee breaches. Eroded gullies nearly 1 km in length were observed at a low ridge of a relict meander scar of the Mississippi River. Our flow modeling and spatial mapping analysis attributes this vulnerability to a combination of erodible soils, flow acceleration associated with legacy fluvial landforms, and a lack of woody vegetation to anchor soil and enhance flow resistance. Results from this study could guide future mitigation and adaptation measures in cases of extreme flooding.

  2. Flood risk assessment in France: comparison of extreme flood estimation methods (EXTRAFLO project, Task 7)

    Science.gov (United States)

    Garavaglia, F.; Paquet, E.; Lang, M.; Renard, B.; Arnaud, P.; Aubert, Y.; Carre, J.

    2013-12-01

    In flood risk assessment the methods can be divided in two families: deterministic methods and probabilistic methods. In the French hydrologic community the probabilistic methods are historically preferred to the deterministic ones. Presently a French research project named EXTRAFLO (RiskNat Program of the French National Research Agency, https://extraflo.cemagref.fr) deals with the design values for extreme rainfall and floods. The object of this project is to carry out a comparison of the main methods used in France for estimating extreme values of rainfall and floods, to obtain a better grasp of their respective fields of application. In this framework we present the results of Task 7 of EXTRAFLO project. Focusing on French watersheds, we compare the main extreme flood estimation methods used in French background: (i) standard flood frequency analysis (Gumbel and GEV distribution), (ii) regional flood frequency analysis (regional Gumbel and GEV distribution), (iii) local and regional flood frequency analysis improved by historical information (Naulet et al., 2005), (iv) simplify probabilistic method based on rainfall information (i.e. Gradex method (CFGB, 1994), Agregee method (Margoum, 1992) and Speed method (Cayla, 1995)), (v) flood frequency analysis by continuous simulation approach and based on rainfall information (i.e. Schadex method (Paquet et al., 2013, Garavaglia et al., 2010), Shyreg method (Lavabre et al., 2003)) and (vi) multifractal approach. The main result of this comparative study is that probabilistic methods based on additional information (i.e. regional, historical and rainfall information) provide better estimations than the standard flood frequency analysis. Another interesting result is that, the differences between the various extreme flood quantile estimations of compared methods increase with return period, staying relatively moderate up to 100-years return levels. Results and discussions are here illustrated throughout with the example

  3. Flash-flood impacts cause changes in wood anatomy of Alnus glutinosa, Fraxinus angustifolia and Quercus pyrenaica.

    Science.gov (United States)

    Ballesteros, J A; Stoffel, M; Bollschweiler, M; Bodoque, J M; Díez-Herrero, A

    2010-06-01

    Flash floods may influence the development of trees growing on channel bars and floodplains. In this study, we analyze and quantify anatomical reactions to wounding in diffuse-porous (Alnus glutinosa L.) and ring-porous (Fraxinus angustifolia Vahl. and Quercus pyrenaica Willd.) trees in a Mediterranean environment. A total of 54 cross-sections and wedges were collected from trees that had been injured by past flash floods. From each of the samples, micro-sections were prepared at a tangential distance of 1.5 cm from the injury to determine wounding-related changes in radial width, tangential width and lumen of earlywood vessels, and fibers and parenchyma cells (FPC). In diffuse-porous A. glutinosa, the lumen area of vessels shows a significant (non-parametric test, P-value <0.05) decrease by almost 39% after wounding. For ring-porous F. angustifolia and Q. pyrenaica, significant decreases in vessel lumen area are observed as well by 59 and 42%, respectively. Radial width of vessels was generally more sensitive to the decrease than tangential width, but statistically significant values were only observed in F. angustifolia. Changes in the dimensions of earlywood FPC largely differed between species. While in ring-porous F. angustifolia and Q. pyrenaica the lumen of FPC dropped by 22 and 34% after wounding, we observed an increase in FPC lumen area in diffuse-porous A. glutinosa of approximately 35%. Our data clearly show that A. glutinosa represents a valuable species for flash-flood research in vulnerable Mediterranean environments. For this species, it will be possible in the future to gather information on past flash floods with non-destructive sampling based on increment cores. In ring-porous F. angustifolia and Q. pyrenaica, flash floods leave less drastic, yet still recognizable, signatures of flash-flood activity through significant changes in vessel lumen area. In contrast, the use of changes in FPC dimensions appears less feasible for the determination of

  4. Urban RoGeR: Merging process-based high-resolution flash flood model for urban areas with long-term water balance predictions

    Science.gov (United States)

    Weiler, M.

    2016-12-01

    Heavy rain induced flash floods are still a serious hazard and generate high damages in urban areas. In particular in the spatially complex urban areas, the temporal and spatial pattern of runoff generation processes at a wide spatial range during extreme rainfall events need to be predicted including the specific effects of green infrastructure and urban forests. In addition, the initial conditions (soil moisture pattern, water storage of green infrastructure) and the effect of lateral redistribution of water (run-on effects and re-infiltration) have to be included in order realistically predict flash flood generation. We further developed the distributed, process-based model RoGeR (Runoff Generation Research) to include the relevant features and processes in urban areas in order to test the effects of different settings, initial conditions and the lateral redistribution of water on the predicted flood response. The uncalibrated model RoGeR runs at a spatial resolution of 1*1m² (LiDAR, degree of sealing, landuse), soil properties and geology (1:50.000). In addition, different green infrastructures are included into the model as well as the effect of trees on interception and transpiration. A hydraulic model was included into RoGeR to predict surface runoff, water redistribution, and re-infiltration. During rainfall events, RoGeR predicts at 5 min temporal resolution, but the model also simulates evapotranspiration and groundwater recharge during rain-free periods at a longer time step. The model framework was applied to several case studies in Germany where intense rainfall events produced flash floods causing high damage in urban areas and to a long-term research catchment in an urban setting (Vauban, Freiburg), where a variety of green infrastructures dominates the hydrology. Urban-RoGeR allowed us to study the effects of different green infrastructures on reducing the flood peak, but also its effect on the water balance (evapotranspiration and groundwater

  5. A GIS-Based Model for the analysis of an urban flash flood and its hydro-geomorphic response. The Valencia event of 1957

    Science.gov (United States)

    Portugués-Mollá, I.; Bonache-Felici, X.; Mateu-Bellés, J. F.; Marco-Segura, J. B.

    2016-10-01

    Flash floods are recurrent events around the Mediterranean region. Extreme episodes activate hydro-geomorphic high-intensity processes with low frequency. In urban environments, the complexity becomes higher due to the existence of very quick-response runoff. However, immediate recovery works remove the urban marks. After a short time both the significance and magnitude of the hydro-geomorphic event become completely unrecognizable. Nevertheless, these episodes generate extensive documentation which is testimony of the processes in almost real time. It is necessary to exploit this source typology in order to draw flood sketches when events far in time may lack a sufficiently rich database. This is particularly the case for the Valencia flash flood (October 1957), located in the lower Turia River basin (Eastern Spain). It left numerous pieces of hydro-geomorphic evidence, but its tracks were covered a short while after the flood. In any case, it remains part of a non-systematic legacy that has not yet been exploited, consisting of immediate aerial and oblique high resolution photography, pictures at street level, water marks and administrative records. Paradoxically, despite being considered a milestone in metropolitan territorial planning (the river was definitely diverted), an accurate reconstruction of the hydraulic behaviour was required from an integrated point of view. To this aim, the development of a GIS-Based Model enabled the utilisation of the above-mentioned materials. This non-conventional information was treated jointly from a new perspective. It provided database support through a vast amount of organised, structured and georeferenced information about the 1957 event. In a second stage, the GBM made it possible to characterise the Turia urban reach and interpret both the hydro-geomorphic (trenches along barrier beaches, erosion, deposition, etc.) and hydraulic (urban streams along the streets, flow directions, flood extent, levees breaks, overflows

  6. Reproducing an extreme flood with uncertain post-event information

    Science.gov (United States)

    Fuentes-Andino, Diana; Beven, Keith; Halldin, Sven; Xu, Chong-Yu; Reynolds, José Eduardo; Di Baldassarre, Giuliano

    2017-07-01

    Studies for the prevention and mitigation of floods require information on discharge and extent of inundation, commonly unavailable or uncertain, especially during extreme events. This study was initiated by the devastating flood in Tegucigalpa, the capital of Honduras, when Hurricane Mitch struck the city. In this study we hypothesized that it is possible to estimate, in a trustworthy way considering large data uncertainties, this extreme 1998 flood discharge and the extent of the inundations that followed from a combination of models and post-event measured data. Post-event data collected in 2000 and 2001 were used to estimate discharge peaks, times of peak, and high-water marks. These data were used in combination with rain data from two gauges to drive and constrain a combination of well-known modelling tools: TOPMODEL, Muskingum-Cunge-Todini routing, and the LISFLOOD-FP hydraulic model. Simulations were performed within the generalized likelihood uncertainty estimation (GLUE) uncertainty-analysis framework. The model combination predicted peak discharge, times of peaks, and more than 90 % of the observed high-water marks within the uncertainty bounds of the evaluation data. This allowed an inundation likelihood map to be produced. Observed high-water marks could not be reproduced at a few locations on the floodplain. Identifications of these locations are useful to improve model set-up, model structure, or post-event data-estimation methods. Rainfall data were of central importance in simulating the times of peak and results would be improved by a better spatial assessment of rainfall, e.g. from radar data or a denser rain-gauge network. Our study demonstrated that it was possible, considering the uncertainty in the post-event data, to reasonably reproduce the extreme Mitch flood in Tegucigalpa in spite of no hydrometric gauging during the event. The method proposed here can be part of a Bayesian framework in which more events can be added into the analysis as

  7. Assessment of the susceptibility of roads to flooding based on geographical information - test in a flash flood prone area (the Gard region, France)

    Science.gov (United States)

    Versini, P.-A.; Gaume, E.; Andrieu, H.

    2010-04-01

    In flash flood prone areas, roads are often the first assets affected by inundations which make rescue operations difficult and represent a major threat to lives: almost half of the victims are car passengers trapped by floods. In the past years, the Gard region (France) road management services have realized an extensive inventory of the known road submersions that occurred during the last 40 years. This inventory provided an unique opportunity to analyse the causes of road flooding in an area frequently affected by severe flash floods. It will be used to develop a road submersion susceptibility rating method, representing the first element of a road warning system. This paper presents the results of the analysis of this data set. A companion paper will show how the proposed road susceptibility rating method can be combined with distributed rainfall-runoff simulations to provide accurate road submersion risk maps. The very low correlation between the various possible explanatory factors and the susceptibility to flooding measured by the number of past observed submersions implied the use of particular statistical analysis methods based on the general principals of the discriminant analysis. The analysis led to the definition of four susceptibility classes for river crossing road sections. Validation tests confirmed that this classification is robust, at least in the considered area. One major outcome of the analysis is that the susceptibility to flooding is rather linked to the location of the road sections than to the size of the river crossing structure (bridge or culvert).

  8. Flash flooding: Toward an Interdisciplinary and Integrated Strategy for Disaster Reduction in a Global Environmental Change Perspective

    Science.gov (United States)

    Ruin, Isabelle

    2014-05-01

    How do people answer to heavy precipitation and flood warnings? How do they adapt their daily schedule and activity to the fast evolution of the environmental circumstances? More generally, how do social processes interact with physical ones? Such questions address the dynamical interactions between hydro-meteorological variables, human perception and representation of the environment, and actual individual and social behavioral responses. It also poses the question of scales and hierarchy issues through seamless interactions between smaller and larger scales. These questions are relevant for both social and physical scientists. They are more and more pertinently addressed in the Global Environmental Change perspective through the concepts of Coupled Human And Natural Systems (CHANS), resilience or panarchy developped in the context of interdisciplinary collaborations. Nevertheless those concepts are complex and not easy to handle, specially when facing with operational goals. One of the main difficulty to advance these integrated approaches is the access to empirical data informing the processes at various scales. In fact, if physical and social processes are well studied by distinct disciplines, they are rarely jointly explored within similar spatial and temporal resolutions. Such coupled observation and analysis poses methodological challenges, specially when dealing with responses to short-fuse and extreme weather events. In fact, if such coupled approach is quite common to study large scale phenomenon like global change (for instance using historical data on green house gaz emissions and the evolution of temperatures worldwide), it is rarer for studing smaller nested sets of scales of human-nature systems where finer resolution data are sparse. Another problem arise from the need to produce comparable analysis on different case studies where social, physical and even cultural contexts may be diverse. Generic and robust framework for data collection, modeling

  9. Simulation of Flash-Flood-Producing Storm Events in Saudi Arabia Using the Weather Research and Forecasting Model

    KAUST Repository

    Deng, Liping

    2015-05-01

    The challenges of monitoring and forecasting flash-flood-producing storm events in data-sparse and arid regions are explored using the Weather Research and Forecasting (WRF) Model (version 3.5) in conjunction with a range of available satellite, in situ, and reanalysis data. Here, we focus on characterizing the initial synoptic features and examining the impact of model parameterization and resolution on the reproduction of a number of flood-producing rainfall events that occurred over the western Saudi Arabian city of Jeddah. Analysis from the European Centre for Medium-Range Weather Forecasts (ECMWF) interim reanalysis (ERA-Interim) data suggests that mesoscale convective systems associated with strong moisture convergence ahead of a trough were the major initial features for the occurrence of these intense rain events. The WRF Model was able to simulate the heavy rainfall, with driving convective processes well characterized by a high-resolution cloud-resolving model. The use of higher (1 km vs 5 km) resolution along the Jeddah coastline favors the simulation of local convective systems and adds value to the simulation of heavy rainfall, especially for deep-convection-related extreme values. At the 5-km resolution, corresponding to an intermediate study domain, simulation without a cumulus scheme led to the formation of deeper convective systems and enhanced rainfall around Jeddah, illustrating the need for careful model scheme selection in this transition resolution. In analysis of multiple nested WRF simulations (25, 5, and 1 km), localized volume and intensity of heavy rainfall together with the duration of rainstorms within the Jeddah catchment area were captured reasonably well, although there was evidence of some displacements of rainstorm events.

  10. Evidence of flash floods in Precambrian gravel dominated ephemeral river deposits

    Science.gov (United States)

    Long, Darrel G. F.

    2017-01-01

    Fluvial strata at the base of the Whyte Inlet Formation on Baffin Island, to the west of Sikosak Bay, are predominantly boulder and cobble bearing large pebble conglomerates of braided fluvial origin. Local development of narrow sinuous channels, possibly within the thalwegs of an initially braided bedrock confined system, is indicated by the presence of lateral accretion surfaces, some of which host isolated sub-vertically oriented boulders. These larger boulders were probably emplaced during exceptional flood events involving either hyper-concentrated flows or dilute debris flows, with velocities in the order of 2.2 m/s. Isolated ridges of boulders and cobbles are perched on the upper parts of lateral accretion surfaces in mixed sandy-gravelly fluvial intervals. These boulder berms developed down stream from channel bends or bedrock constrictions in response to flow expansion during flash floods, with estimated peak discharge of about 1.4 m/s. Associated sandstones on lateral accretion surfaces show evidence of deposition under both upper and lower flow conditions. Similar boulder and cobble berms of this type are known from modern ephemeral and highly seasonal fluvial systems in a wide range of climatic settings, and are a clear indication that highly variable to catastrophic discharge events affected the rivers responsible for deposition of these conglomerates.

  11. Formation of fine sediment deposit from a flash flood river in the Mediterranean Sea

    Science.gov (United States)

    Grifoll, Manel; Gracia, Vicenç; Aretxabaleta, Alfredo L.; Guillén, Jorge; Espino, Manuel; Warner, John C.

    2014-01-01

    We identify the mechanisms controlling fine deposits on the inner-shelf in front of the Besòs River, in the northwestern Mediterranean Sea. This river is characterized by a flash flood regime discharging large amounts of water (more than 20 times the mean water discharge) and sediment in very short periods lasting from hours to few days. Numerical model output was compared with bottom sediment observations and used to characterize the multiple spatial and temporal scales involved in offshore sediment deposit formation. A high-resolution (50 m grid size) coupled hydrodynamic-wave-sediment transport model was applied to the initial stages of the sediment dispersal after a storm-related flood event. After the flood, sediment accumulation was predominantly confined to an area near the coastline as a result of preferential deposition during the final stage of the storm. Subsequent reworking occurred due to wave-induced bottom shear stress that resuspended fine materials, with seaward flow exporting them toward the midshelf. Wave characteristics, sediment availability, and shelf circulation determined the transport after the reworking and the final sediment deposition location. One year simulations of the regional area revealed a prevalent southwestward average flow with increased intensity downstream. The circulation pattern was consistent with the observed fine deposit depocenter being shifted southward from the river mouth. At the southern edge, bathymetry controlled the fine deposition by inducing near-bottom flow convergence enhancing bottom shear stress. According to the short-term and long-term analyses, a seasonal pattern in the fine deposit formation is expected.

  12. Self-accelerated development of salt karst during flash floods along the Dead Sea Coast, Israel

    Science.gov (United States)

    Avni, Yoav; Lensky, Nadav; Dente, Elad; Shviro, Maayan; Arav, Reuma; Gavrieli, Ittai; Yechieli, Yoseph; Abelson, Meir; Lutzky, Hallel; Filin, Sagi; Haviv, Itai; Baer, Gidon

    2016-01-01

    We document and analyze the rapid development of a real-time karst system within the subsurface salt layers of the Ze'elim Fan, Dead Sea, Israel by a multidisciplinary study that combines interferometric synthetic aperture radar and light detection and ranging measurements, sinkhole mapping, time-lapse camera monitoring, groundwater level measurements and chemical and isotopic analyses of surface runoff and groundwater. The >1 m/yr drop of Dead Sea water level and the subsequent change in the adjacent groundwater system since the 1960s resulted in flushing of the coastal aquifer by fresh groundwater, subsurface salt dissolution, gradual land subsidence and formation of sinkholes. Since 2010 this process accelerated dramatically as flash floods at the Ze'elim Fan were drained by newly formed sinkholes. During and immediately after these flood events the dissolution rates of the subsurface salt layer increased dramatically, the overlying ground surface subsided, a large number of sinkholes developed over short time periods (hours to days), and salt-saturated water resurged downstream. Groundwater flow velocities increased by more than 2 orders of magnitudes compared to previously measured velocities along the Dead Sea. The process is self-accelerating as salt dissolution enhances subsidence and sinkhole formation, which in turn increase the ponding areas of flood water and generate additional draining conduits to the subsurface. The rapid terrain response is predominantly due to the highly soluble salt. It is enhanced by the shallow depth of the salt layer, the low competence of the newly exposed unconsolidated overburden and the moderate topographic gradients of the Ze'elim Fan.

  13. Natural hazards on alluvial fans: the debris flow and flash flood disaster of December 1999, Vargas state, Venezuela

    Science.gov (United States)

    Larsen, Matthew C.; Wieczorek, Gerald F.; Eaton, L.S.; Torres-Sierra, Heriberto; Sylva, Walter F.

    2001-01-01

    Large populations live on or near alluvial fans in locations such as Los Angeles, California, Salt Lake City, Utah, Denver, Colorado, and lesser known areas such as Sarno, Italy, and Vargas, Venezuela. Debris flows and flash floods occur episodically in these alluvial fan environments, and place many communities at high risk during intense and prolonged rainfall. In December 1999, rainstorms induced thousands of landslides along the Cordillera de la Costa, Vargas, Venezuela. Rainfall accumulation of 293 mm during the first 2 weeks of December was followed by an additional 911 mm of rainfall on December 14 through 16. Debris flows and floods inundated coastal communities resulting in a catastrophic death toll of as many as 30,000 people. Flash floods and debris flows caused severe property destruction on alluvial fans at the mouths of the coastal mountain drainage network. In time scales spanning thousands of years, the alluvial fans along this Caribbean coastline are dynamic zones of high geomorphic activity. Because most of the coastal zone in Vargas consists of steep mountain fronts that rise abruptly from the Caribbean Sea, the alluvial fans provide practically the only flat areas upon which to build. Rebuilding and reoccupation of these areas requires careful determination of hazard zones to avoid future loss of life and property. KEY TERMS: Debris flows, flash floods, alluvial fans, natural hazards, landslides, Venezuela

  14. The use of radar in hydrological modeling in the Czech Republic – case studies of flash floods

    Directory of Open Access Journals (Sweden)

    M. Šálek

    2006-01-01

    Full Text Available Flash flood induced by severe convection is the hydrometeorological phenomenon that is very difficult to forecast. However, the implementation of radar measurements, especially radar-based Quantitative Precipitation Estimate (QPE and/or radar-based quantitative Precipitation Nowcast (QPN can improve this situation. If the radar is able to capture the development of severe convection and can produce reasonably accurate QPE in short time intervals (e.g. 10 min, then it can be used also with hydrological model. A hydrological model named Hydrog was used for investigation of simulation and possible forecasts of two flash floods that took place in the Czech Republic in 2002 and 2003. The precipitation input consisted of mean-field-bias-adjusted or original radar 10-min estimates along with quantitative precipitation nowcasts up to 2 h based on COTREC method (extrapolation. Taking into account all the limited predictability of the severe convection development and the errors of the radar-based precipitation estimates, the aim of the simulations was to find out to what extend the hydrometeorological prediction system, specifically tuned for these events, was able to forecast a the flash floods. As assumed, the hydrometeorological simulations of the streamflow forecasts lagged behind the actual development but there is still some potential for successful warning, especially for areas where the flood hits lately.

  15. Understanding triggers and dynamics of wood-laden flash floods in mountain catchments: examples from the Zulg River (Switzerland)

    Science.gov (United States)

    Ruiz-Villanueva, Virginia; Galatiotto, Niccolo; Bürkli, Livia; Stoffel, Markus

    2017-04-01

    Mountain rivers are prone to flash floods, and in forested basins, large quantities of wood can be moved and transported long distances downstream during such events. Under certain circumstances, congested transport of wood may result in wood-laden flows in which a large number of logs form a mass moving together with the flow and thus alter its dynamics. This process could significantly increase the flood hazard and risk, however, the knowledge about the formation of these wood-laden flows is still very limited. The Zulg River (23 km long and 89 km2 drainage area) is located in the Swiss Prealps in the canton of Bern (Switzerland). In the Zulg catchment, heavy local precipitation usually leads to a fast reaction of the water level downstream and very often flash floods are transporting significant volume of wood. There are several bridges crossing the river at the area of Steffisburg and downstream of this town the Zulg flows into the Aare River that crosses the city of Bern few kilometres downstream. Therefore, a better understanding of these processes will help to improve the flood risk management of the region. In this work we are analysing four recent floods (i.e., 2012, 2013, 2015 and 2016) with significant wood transport and the goal is to decipher the triggering and formation of the wood-laden flash floods. We collected aerial pictures from before and after each flood to map the pre- and post-flood conditions and mapped riverscape units, landslides and the wood logs and jams already deposited along the river channel. The forest stand volumes recruited during the events is analysed based on the land use maps available and provided by the Cantonal Forest Service. We also analysed movies taken by witnesses during these flash flood events, which may potentially provide highly valuable information (i.e., the amount and type of wood in motion or what was roughly the velocity and direction of the water) to quantify wood fluxes. However, the usage of these home

  16. Estimating the flash flood quantitative parameters affecting the oil-fields infrastructures in Ras Sudr, Sinai, Egypt, during the January 2010 event

    Directory of Open Access Journals (Sweden)

    Safwat Gabr

    2015-12-01

    Full Text Available This paper aims to quantify the hydrological parameters for the flash flood event of 17th January 2010 in Sinai using multiple sets of remote sensing data and field work for the nongaged catchments (approximately 2100 sq km of the wadis affecting Ras Sudr area, which is heavily occupied by numerous oil fields and related activities. The affected areas were visited, and several cross sections of the main active channels were surveyed to estimate the peak discharge rates. The Tropical Rainfall Monitoring Mission (TRMM data have been used to estimate rainfall parameters for the catchments due to the absence of in situ data. The digital elevation model (DEM of the Shuttle Radar Topography Mission (SRTM was used to extract the hydrographic data following standard procedures and techniques of the Geographic Information Systems (GIS. Both of the surveyed and extracted parameters for the active channels were integrated into GIS to estimate the runoff parameters using the open-channel flow equation of Manning’s. The simulated hydrographs show that the total discharge exceeded 5.7 million cubic meters and the peak discharge rate was 70 cubic meters per second. The mitigation of extreme flash flood is possible by altering the natural flow dispersion over the alluvial fan, and conveying the resulting flows into one adjusted channel.

  17. THE INFLUENCE OF CLIMATIC FACTORS UPON THE FLASH-FLOODS OCCURING IN THE SUPERIOR BASIN OF THE RIVER MUREŞ

    Directory of Open Access Journals (Sweden)

    NICOLETA DANIELA GORON

    2012-12-01

    Full Text Available The Influence of climatic factors upon the flash-floods occuring in the superior basin of the river Mureş . The floods triggering factors in the upper river basin of the Mures are likely climatic in which case the analysis is based upon a string of data representative for the period 1986-2010, for eight stations and making reference to average rainfall,maximum rainfall within 24 hours, the thickness and duration of snow.The floods in the upper basin of the Mureş do not cause major damage, except in exceptional cases. Most localities that have reported damage caused by floods are located near the Topliţa-Deda gorge, an area that influences flow concentration through a relatively narrow territory compared to the upstream territory where the Mureş river gathers its tributaries.

  18. Impact of floods induced by extreme precipitation events on public health

    Science.gov (United States)

    Mavroulis, Spyridon; Mavrouli, Maria; Lekkas, Efthymios; Tsakris, Athanassios

    2017-04-01

    Hydrometeorological disasters comprise the most reported type of natural disaster, and floods account for the majority of disasters in this category in both developed and developing countries. Flooding can lead to extensive morbidity and mortality and pose multiple risks to public health throughout the world. This study involved an extensive and systematic literature review of 124 research publications related to public health impact of 98 floods that occurred globally (Oceania 4, Africa 9, America 22, Europe 24, Asia 39) from 1942 to 2014. The inclusion criteria were literature type comprising journal articles and official reports, natural disaster type including floods induced after extreme precipitation events (accumulation of rainwater in poorly-drained environments, riverine and flash floods), population type including humans, and outcome measure characterized by infectious diseases (ID) incidence increase. The potential post-flood ID are classified into 13 groups including rodent-borne (reported in 38 of the total 98 events, 38.78%), water-borne (33, 33.67%), vector-borne (25, 25.51%), respiratory (19, 19.39%), fecal-oral (14, 14.29%), skin (9, 9.18%), blood-borne (4, 4.08%), eye (3, 3.06%), soil-related (3, 3.06%), ear (2, 2.04%), fungal (1, 1.02%) and wound-borne (1, 1.02%) ID. Based on available age and genre data, it is concluded that the most vulnerable population groups are predominantly young children (age ≤ 5 years) and male. The most fatal post-flood ID are leptospirosis and diarrhea followed by respiratory tract infections. The detected risk factors include (1) poor economic status and living in flood prone areas, (2) destruction of infrastructures, disruption of public utilities and interruption of basic public health services such as vector control programs, (3) direct physical exposure to sewage-polluted flood water, (4) lack of adequate potable water and water-supply from contaminated ponds and tube wells along with lack of distribution of

  19. The role of Natural Flood Management in managing floods in large scale basins during extreme events

    Science.gov (United States)

    Quinn, Paul; Owen, Gareth; ODonnell, Greg; Nicholson, Alex; Hetherington, David

    2016-04-01

    There is a strong evidence database showing the negative impacts of land use intensification and soil degradation in NW European river basins on hydrological response and to flood impact downstream. However, the ability to target zones of high runoff production and the extent to which we can manage flood risk using nature-based flood management solution are less known. A move to planting more trees and having less intense farmed landscapes is part of natural flood management (NFM) solutions and these methods suggest that flood risk can be managed in alternative and more holistic ways. So what local NFM management methods should be used, where in large scale basin should they be deployed and how does flow is propagate to any point downstream? Generally, how much intervention is needed and will it compromise food production systems? If we are observing record levels of rainfall and flow, for example during Storm Desmond in Dec 2015 in the North West of England, what other flood management options are really needed to complement our traditional defences in large basins for the future? In this paper we will show examples of NFM interventions in the UK that have impacted at local scale sites. We will demonstrate the impact of interventions at local, sub-catchment (meso-scale) and finally at the large scale. These tools include observations, process based models and more generalised Flood Impact Models. Issues of synchronisation and the design level of protection will be debated. By reworking observed rainfall and discharge (runoff) for observed extreme events in the River Eden and River Tyne, during Storm Desmond, we will show how much flood protection is needed in large scale basins. The research will thus pose a number of key questions as to how floods may have to be managed in large scale basins in the future. We will seek to support a method of catchment systems engineering that holds water back across the whole landscape as a major opportunity to management water

  20. HyMeX-SOP1, the field campaign dedicated to heavy precipitation and flash-flooding in the northwestern Mediterranean

    OpenAIRE

    Ducrocq, V; Braud, I.; S. Davolio; Ferretti, R.; Flamant, C; Jansa, A.; Kalthoff, N.; Richard, E.; Taupier Letage, I.; Ayral, P. A.; Belamari, S.; A. Berne; Borga, M; Boudevillain, B.; Bock, O.

    2014-01-01

    The Mediterranean region is frequently affected by heavy precipitation events associated with flash floods, landslides, and mudslides that cause hundreds of millions of euros in damages per year and often, casualties. A major field campaign was devoted to heavy precipitation and flash floods from 5 September to 6 November 2012 within the framework of the 10-year international HyMeX (Hydrological cycle in the Mediterranean Experiment) dedicated to the hydrological cycle and related high-impact...

  1. A radar-based flash flood forecasting for the Llobregat river basin in the Catalonia region (Spain)

    OpenAIRE

    Quintero Duque, Felipe; Versini, Pierre Antonie; Baltas, Evangelos; Berenguer Ferrer, Marc; Sempere Torres, Daniel

    2011-01-01

    In this research paper, a flash flood modeling system implemented in a Mediterranean river basin is presented. Radar precipitation estimation along with hydrological modeling techniques are implemented within the system for simulating the runoff generation and routing processes occurring in the catchment. However, there exists an uncertainty related with the estimation of radar precipitation (Zawadzki, 1984) and from model calibration (Beven, 2006). Such uncertainty is propagated to the...

  2. Methods of Rainfall Indicator for Flash Flood%山洪临界雨量确定方法述评

    Institute of Scientific and Technical Information of China (English)

    李昌志; 郭良

    2013-01-01

    简要介绍了国内外山洪临界雨量确定的典型方法,如欧美地区FFG法,日本线性相关法,我国台湾地区的降雨驱动指标法,以及大陆地区的实测雨量统计法、水位/流量反推法、暴雨临界曲线法和比拟法等;探索了分布式方法确定临界雨量的方法,重点探讨了以降雨强度、时段雨量、有效累积雨量为指标的山洪临界雨量确定方法;分析了分布式水文法确定临界雨量的优缺点,提出了山洪临界雨量确定方法的建议。%This paper initiated with a review of commonly used methods for estimating rainfal indicator in flash flood forecasting, such as the Flash Flood Guidance (FFG) Method in the United States and Europe, the Linear Relation Method in Japan, and the methods of the Rainfal Driven Factor , the Measured Rainfal Statistics, the Stage/Discharge Inversion, the Rainfal Critical Line, as wel as Analogue in China. A detailed description of a distributed hydrologic method was fol owed for the purpose of finding a fundamental, universal and practical outputs to support flash flood managements in China, with an emphasis on analysis on rain intensity, rainfal within specific duration, effective accumulated rainfal , and rain triggering index. Final y, the merits and demerits of the distributed hydrologic method were discussed, and some suggestions were provided for flash flood critical rainfal computation in China.

  3. The potential of radar-based ensemble forecasts for flash-flood early warning in the southern Swiss Alps

    OpenAIRE

    Liechti, K.; L. Panziera; U. Germann; Zappa, M.

    2013-01-01

    This study explores the limits of radar-based forecasting for hydrological runoff prediction. Two novel radar-based ensemble forecasting chains for flash-flood early warning are investigated in three catchments in the southern Swiss Alps and set in relation to deterministic discharge forecasts for the same catchments. The first radar-based ensemble forecasting chain is driven by NORA (Nowcasting of Orographic Rainfall by means of Analogues), an analogue-based heuristic nowca...

  4. Reproducing an extreme flood with uncertain post-event information

    Directory of Open Access Journals (Sweden)

    D. Fuentes-Andino

    2017-07-01

    Full Text Available Studies for the prevention and mitigation of floods require information on discharge and extent of inundation, commonly unavailable or uncertain, especially during extreme events. This study was initiated by the devastating flood in Tegucigalpa, the capital of Honduras, when Hurricane Mitch struck the city. In this study we hypothesized that it is possible to estimate, in a trustworthy way considering large data uncertainties, this extreme 1998 flood discharge and the extent of the inundations that followed from a combination of models and post-event measured data. Post-event data collected in 2000 and 2001 were used to estimate discharge peaks, times of peak, and high-water marks. These data were used in combination with rain data from two gauges to drive and constrain a combination of well-known modelling tools: TOPMODEL, Muskingum–Cunge–Todini routing, and the LISFLOOD-FP hydraulic model. Simulations were performed within the generalized likelihood uncertainty estimation (GLUE uncertainty-analysis framework. The model combination predicted peak discharge, times of peaks, and more than 90 % of the observed high-water marks within the uncertainty bounds of the evaluation data. This allowed an inundation likelihood map to be produced. Observed high-water marks could not be reproduced at a few locations on the floodplain. Identifications of these locations are useful to improve model set-up, model structure, or post-event data-estimation methods. Rainfall data were of central importance in simulating the times of peak and results would be improved by a better spatial assessment of rainfall, e.g. from radar data or a denser rain-gauge network. Our study demonstrated that it was possible, considering the uncertainty in the post-event data, to reasonably reproduce the extreme Mitch flood in Tegucigalpa in spite of no hydrometric gauging during the event. The method proposed here can be part of a Bayesian framework in which more events

  5. Flash Floods in the Guelmim Area/Southwest Morocco–Use of Remote Sensing and GIS-Tools for the Detection of Flooding-Prone Areas

    Directory of Open Access Journals (Sweden)

    Barbara Theilen-Willige

    2015-05-01

    Full Text Available The violent storms of 22–30 November 2014, resulted in flash floods and wadi floods (rivers in large parts of Southern Morocco, at the foot of the Atlas Mountains. The Guelmim area was the most affected part with at least 32 fatalities and damages due to inundations. The flooding hazard in the Guelmim region initiated this study in order to investigate the use of remote sensing and geographic information system (GIS for the detection and identification of areas most likely to be flooded in the future again due to their morphologic properties during similar weather conditions. By combining morphometric analysis and visual interpretation based on Landsat 8 satellite data and derived images such as water index (NDWI images, areas with relatively higher soil moisture and recently deposited sediments were identified. The resulting maps of weighted overlay procedures, aggregating causal, morphometric factors influencing the susceptibility to flooding (lowest height levels, flattest areas, allowed for the distinguishing of areas with higher, medium and lower susceptibility to flooding. Thus, GIS and remote sensing tools contribut to the recognition and mapping of areas and infrastructure prone to flooding in the Guelmim area.

  6. Element Geochemical Analysis of the Contribution of Aeolian Sand to Suspended Sediment in Desert Stream Flash Floods

    Directory of Open Access Journals (Sweden)

    Xiaopeng Jia

    2014-01-01

    Full Text Available The interaction of wind and water in semiarid and arid areas usually leads to low-frequency flash flood events in desert rivers, which have adverse effects on river systems and ecology. In arid zones, many aeolian dune-fields terminate in stream channels and deliver aeolian sand to the channels. Although aeolian processes are common to many desert rivers, whether the aeolian processes contribute to fluvial sediment loss is still unknown. Here, we identified the aeolian-fluvial cycling process responsible for the high rate of suspended sediment transport in the Sudalaer desert stream in the Ordos plateau of China. On the basis of element geochemistry data analysis, we found that aeolian sand was similar to suspended sediment in element composition, which suggests that aeolian sand contributes to suspended sediment in flash floods. Scatter plots of some elements further confirm that aeolian sand is the major source of the suspended sediment. Factor analysis and the relation between some elements and suspended sediment concentration prove that the greater the aeolian process, the higher the suspended sediment concentration and the greater the contribution of aeolian sand to suspended sediment yield. We conclude that aeolian sand is the greatest contributor to flash floods in the Sudalaer desert stream.

  7. Element geochemical analysis of the contribution of aeolian sand to suspended sediment in desert stream flash floods.

    Science.gov (United States)

    Jia, Xiaopeng; Wang, Haibing

    2014-01-01

    The interaction of wind and water in semiarid and arid areas usually leads to low-frequency flash flood events in desert rivers, which have adverse effects on river systems and ecology. In arid zones, many aeolian dune-fields terminate in stream channels and deliver aeolian sand to the channels. Although aeolian processes are common to many desert rivers, whether the aeolian processes contribute to fluvial sediment loss is still unknown. Here, we identified the aeolian-fluvial cycling process responsible for the high rate of suspended sediment transport in the Sudalaer desert stream in the Ordos plateau of China. On the basis of element geochemistry data analysis, we found that aeolian sand was similar to suspended sediment in element composition, which suggests that aeolian sand contributes to suspended sediment in flash floods. Scatter plots of some elements further confirm that aeolian sand is the major source of the suspended sediment. Factor analysis and the relation between some elements and suspended sediment concentration prove that the greater the aeolian process, the higher the suspended sediment concentration and the greater the contribution of aeolian sand to suspended sediment yield. We conclude that aeolian sand is the greatest contributor to flash floods in the Sudalaer desert stream.

  8. Neural network modeling and geochemical water analyses to understand and forecast karst and non-karst part of flash floods (case study on the Lez river, Southern France)

    Science.gov (United States)

    Darras, T.; Raynaud, F.; Borrell Estupina, V.; Kong-A-Siou, L.; Van-Exter, S.; Vayssade, B.; Johannet, A.; Pistre, S.

    2015-06-01

    Flash floods forecasting in the Mediterranean area is a major economic and societal issue. Specifically, considering karst basins, heterogeneous structure and nonlinear behaviour make the flash flood forecasting very difficult. In this context, this work proposes a methodology to estimate the contribution from karst and non-karst components using toolbox including neural networks and various hydrological methods. The chosen case study is the flash flooding of the Lez river, known for his complex behaviour and huge stakes, at the gauge station of Lavallette, upstream of Montpellier (400 000 inhabitants). After application of the proposed methodology, discharge at the station of Lavallette is spited between hydrographs of karst flood and surface runoff, for the two events of 2014. Generalizing the method to future events will allow designing forecasting models specifically for karst and surface flood increasing by this way the reliability of the forecasts.

  9. Rapid proliferation of Vibrio parahaemolyticus, Vibrio vulnificus, and Vibrio cholerae during freshwater flash floods in French Mediterranean coastal lagoons.

    Science.gov (United States)

    Esteves, Kevin; Hervio-Heath, Dominique; Mosser, Thomas; Rodier, Claire; Tournoud, Marie-George; Jumas-Bilak, Estelle; Colwell, Rita R; Monfort, Patrick

    2015-11-01

    Vibrio parahaemolyticus, Vibrio vulnificus, and Vibrio cholerae of the non-O1/non-O139 serotype are present in coastal lagoons of southern France. In these Mediterranean regions, the rivers have long low-flow periods followed by short-duration or flash floods during and after heavy intense rainstorms, particularly at the end of the summer and in autumn. These floods bring large volumes of freshwater into the lagoons, reducing their salinity. Water temperatures recorded during sampling (15 to 24°C) were favorable for the presence and multiplication of vibrios. In autumn 2011, before heavy rainfalls and flash floods, salinities ranged from 31.4 to 36.1‰ and concentrations of V. parahaemolyticus, V. vulnificus, and V. cholerae varied from 0 to 1.5 × 10(3) most probable number (MPN)/liter, 0.7 to 2.1 × 10(3) MPN/liter, and 0 to 93 MPN/liter, respectively. Following heavy rainstorms that generated severe flash flooding and heavy discharge of freshwater, salinity decreased, reaching 2.2 to 16.4‰ within 15 days, depending on the site, with a concomitant increase in Vibrio concentration to ca. 10(4) MPN/liter. The highest concentrations were reached with salinities between 10 and 20‰ for V. parahaemolyticus, 10 and 15‰ for V. vulnificus, and 5 and 12‰ for V. cholerae. Thus, an abrupt decrease in salinity caused by heavy rainfall and major flooding favored growth of human-pathogenic Vibrio spp. and their proliferation in the Languedocian lagoons. Based on these results, it is recommended that temperature and salinity monitoring be done to predict the presence of these Vibrio spp. in shellfish-harvesting areas of the lagoons. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

  10. Moisture Sources and Large-Scale Dynamics Associated with a Flash Flood Event in Portugal

    Science.gov (United States)

    Liberato, Margarida L. R.; Ramos, Alexandre M.; Trigo, Ricardo M.; Trigo, Isabel F.; María Durán-Quesada, Ana; Nieto, Raquel; Gimeno, Luis

    2013-04-01

    On 18-19 November 1983, the region of Lisbon, in Portugal, was affected by a heavy precipitation event, soon followed by flash flooding, urban inundations and a burst of landslides around Lisbon [Zêzere et al., 2005] causing considerable infrastructure damage and human fatalities. With a total of 95.6 mm in 24 h observed at the longest serving station in Portugal (Lisbon's Dom Luiz Observatory), this was the rainiest day during the twentieth century and one of the rainiest registered since 1864. We found that this event was triggered by the transport of tropical and subtropical moisture associated with an extratropical cyclone. The low favored a large stream of (sub) tropical air that extended over more than 10° of latitude and across the North Atlantic Ocean, carrying a large amount of moisture originally from lower latitudes, a so-called atmospheric river. The stationary position of the jet stream along the East Atlantic Ocean through Iberia caused a strong enhancement of the precipitation associated with the moist air. A Lagrangian analysis of the transport of moisture in the Euro-Atlantic sector was performed based on the methodology developed by Stohl and James [2004, 2005], using the FLEXPART model. This Lagrangian methodology was employed to show that the evaporative sources for the precipitation falling over the area of Lisbon were distributed over large sectors of the tropical-subtropical North Atlantic Ocean and included a significant contribution from the (sub) tropics. This study [Liberato et al., 2012] aims to provide an example of the application of distinct Lagrangian techniques to achieve a better understanding of the relation between extratropical cyclones and the occurrence of a heavy precipitation event on the Iberian Peninsula. Acknowledgments: This work was partially supported by FEDER (Fundo Europeu de Desenvolvimento Regional) funds through the COMPETE (Programa Operacional Factores de Competitividade) Programme and by national funds

  11. Use of «MLCM3» software for flash flood forecasting

    Science.gov (United States)

    Sokolova, Daria; Kuzmin, Vadim

    2017-04-01

    Accurate and timely flash floods forecasting, especially, in ungauged and poorly gauged basins, is one of the most important and challenging problems to be solved by the international hydrological community.In changing climate and variable anthropogenic impact on river basins, as well as due to low density of surface hydrometeorological network, flash flood forecasting based on "traditional" physically based, or conceptual, or statistical hydrological models often becomes inefficient. Unfortunately, most of river basins in Russia are poorly gauged or ungauged; besides, lack of hydrogeological data is quite typical, especially, in remote regions of Siberia. However, the developing economy and population safety make us to issue warnings based on reliable forecasts. For this purpose, a new hydrological model, MLCM3 (Multi-Layer Conceptual Model, 3rd generation) has been developed in the Russian State Hydrometeorological University. MLCM3 is a "rainfall-runoff"model with flexible structure and high level of"conceptualization".Model forcing includes precipitation and evaporation data basically coming from NWP model output. Water comes to the outlet through several layers; their number as well as two parameters (thickness and infiltration rate) for each of them, surface flow velocity (when the top layer is full of water) are optimized. The main advantage of the MLCM3, in comparison to the Sacramento Soil Moisture Accounting Model (SAC-SMA), Australian Water Balance Model (AWBM), Soil Moisture Accounting and Routing (SMAR) model and similar models, is that its automatic calibration is very fast and efficient with less volume of information. For instance, in comparison to SAC-SMA, which is calibrated using either Shuffled Complex Evolution algorithm (SCE-UA), or Stepwise Line Search (SLS), automatically calibrated MLCM3 gives better or comparable results without using any "a priori" data or essential processor resources. This advantage allows using the MLCM3 for very fast

  12. Assessment of the susceptibility of roads to flooding based on geographical information – test in a flash flood prone area (the Gard region, France

    Directory of Open Access Journals (Sweden)

    P.-A. Versini

    2010-04-01

    Full Text Available In flash flood prone areas, roads are often the first assets affected by inundations which make rescue operations difficult and represent a major threat to lives: almost half of the victims are car passengers trapped by floods. In the past years, the Gard region (France road management services have realized an extensive inventory of the known road submersions that occurred during the last 40 years. This inventory provided an unique opportunity to analyse the causes of road flooding in an area frequently affected by severe flash floods. It will be used to develop a road submersion susceptibility rating method, representing the first element of a road warning system.

    This paper presents the results of the analysis of this data set. A companion paper will show how the proposed road susceptibility rating method can be combined with distributed rainfall-runoff simulations to provide accurate road submersion risk maps.

    The very low correlation between the various possible explanatory factors and the susceptibility to flooding measured by the number of past observed submersions implied the use of particular statistical analysis methods based on the general principals of the discriminant analysis.

    The analysis led to the definition of four susceptibility classes for river crossing road sections. Validation tests confirmed that this classification is robust, at least in the considered area. One major outcome of the analysis is that the susceptibility to flooding is rather linked to the location of the road sections than to the size of the river crossing structure (bridge or culvert.

  13. The 20 February 2010 Madeira Island flash-floods: VHR satellite imagery processing in support of landslide inventory and sediment budget assessment

    Directory of Open Access Journals (Sweden)

    C. Lira

    2013-03-01

    Full Text Available On 20 February 2010, an extreme rainfall episode occurred on Madeira Island, which caused an exceptionally strong flash flood and several soil slip-debris flows, producing 45 confirmed deaths and 6 persons declared missing, as well as extensive material damages. In order to understand and quantify the importance of landsliding in routing sediment through mountainous drainage, such as Madeira Island's landscape, it was essential to perform extensive landslide analysis. This study describes the methodology used to semi-automatically detect the landslides, produce the landslide inventory maps and estimate the sediment volume produced during this particular event which ranged from 217 000 m3 to 344 000 m3 and 605 000 m3 to 984 000 m3 for the Funchal and Ribeira Brava basins, respectively. These results contributed to the design and implementation of measures to prevent damages caused by landslides in Madeira Island.

  14. Development of a data-driven semi-distributed hydrological model for regional scale catchments prone to Mediterranean flash floods

    Science.gov (United States)

    Adamovic, M.; Branger, F.; Braud, I.; Kralisch, S.

    2016-10-01

    Flash floods represent one of the most destructive natural hazards in the Mediterranean region. These floods result from very intense and spatially heterogeneous rainfall events. Distributed hydrological models are valuable tools to study these phenomena and increase our knowledge on the main processes governing the generation and propagation of floods over large spatial scales. They are generally built using a bottom-up approach that generalizes small-physics representations of processes. However, top-down or data-driven approach is increasingly shown to provide also valuable knowledge. A simplified semi-distributed continuous hydrological model, named SIMPLEFLOOD, was developed, based on the simple dynamical system approach (SDSA) proposed by Kirchner (WRR, 2009, 45, W02429), and applied to the Ardèche catchment in France (2388 km2). This data-driven method assumes that discharge at the outlet of a given catchment can be expressed as a function only of catchment storage. It leads to a 3-parameter nonlinear model according to rainfall and runoff observations. This model was distributed over sub-catchments and coupled with a kinematic wave based flow propagation module. The parameters were estimated by discharge recession analyses at several gauged stations. Parameter regionalization was conducted using a Factorial Analysis of Mixed Data (FAMD) and Hierarchical Classification on Principal Component (HCPC) in order to find relationships between the SDSA approach and catchments characteristics. Geology was found to be the main predictor of hydrological response variability and model parameters were regionalized according to the dominant geology. The SIMPLEFLOOD model was applied for a 12-year continuous simulation over the Ardèche catchment. Four flash flood events were also selected for further analysis. The simulated hydrographs were compared with the observations at 11 gauging stations with catchment size ranging from 17 to 2300 km2. The results show a good

  15. Impacts of extreme flooding on riverbank filtration water quality.

    Science.gov (United States)

    Ascott, M J; Lapworth, D J; Gooddy, D C; Sage, R C; Karapanos, I

    2016-06-01

    Riverbank filtration schemes form a significant component of public water treatment processes on a global level. Understanding the resilience and water quality recovery of these systems following severe flooding is critical for effective water resources management under potential future climate change. This paper assesses the impact of floodplain inundation on the water quality of a shallow aquifer riverbank filtration system and how water quality recovers following an extreme (1 in 17 year, duration >70 days, 7 day inundation) flood event. During the inundation event, riverbank filtrate water quality is dominated by rapid direct recharge and floodwater infiltration (high fraction of surface water, dissolved organic carbon (DOC) >140% baseline values, >1 log increase in micro-organic contaminants, microbial detects and turbidity, low specific electrical conductivity (SEC) 400% baseline). A rapid recovery is observed in water quality with most floodwater impacts only observed for 2-3 weeks after the flooding event and a return to normal groundwater conditions within 6 weeks (lower fraction of surface water, higher SEC, lower DOC, organic and microbial detects, DO). Recovery rates are constrained by the hydrogeological site setting, the abstraction regime and the water quality trends at site boundary conditions. In this case, increased abstraction rates and a high transmissivity aquifer facilitate rapid water quality recoveries, with longer term trends controlled by background river and groundwater qualities. Temporary reductions in abstraction rates appear to slow water quality recoveries. Flexible operating regimes such as the one implemented at this study site are likely to be required if shallow aquifer riverbank filtration systems are to be resilient to future inundation events. Development of a conceptual understanding of hydrochemical boundaries and site hydrogeology through monitoring is required to assess the suitability of a prospective riverbank filtration

  16. Reconstructing a flash flood record from the late Holocene in sediment cores from the Gulf of Aqaba-Eilat (Red Sea)

    Science.gov (United States)

    Kalman, Akos; Katz, Timor; Mathalon, Alysse; Hill, Paul; Goodman, Beverly

    2017-04-01

    Episodic rainfall over the hyperarid desert may cause flash floods in ephemeral rivers surrounding the Gulf of Aqaba-Eilat. These floods constitute an essential factor in the region's ecology but may also damage infrastructure and risk lives. Some floods reach the head of the Gulf of Aqaba and their sediments deposit on the shelf where they play an important role in structuring the ecosystem, such as limiting the distribution of coral reefs. Much of these sediments are later transported further offshore to the deep basin. To date, there is no continuous record of flash floods that may provide a long term perspective of the frequency and magnitude of flash floods in this region and their shifts over time; anticipation of future risks caused by local flash floods (or prolonged droughts) is therefore largely speculative. This ongoing study aims to reconstruct to the best possible resolution a late Holocene flood record in the GOA and trends therein. The methodology includes chemical and physical characterization of the flood deposits and to recognize them in the microstratigraphy (1 cm intervals) of dated cores from the shallow and deep seafloor. Our results show that characteristics of suspended flood sediment, e.g. grain size distribution and elemental composition are distinguishable and recognizable in the stratigraphy of the cores. Flood sediment concentration changes are clearly detectable in 20-40 cm push cores and a 312 cm long pneumatic core from the shelf (at 13 m depth in front of the floods' drainage outlet) as well as in a 80 cm long core from 450 m depth. Flood sediment stratigraphy in a 312 cm long pneumatic core shows recurring fluctuations, but also three more long term environmental shifts that require further explanation. These promising results will be complemented with micropaleontological analysis of the cores as well as additional dating to reconstruct a long term record of floods and related climatic conditions in the area of the GOA making it

  17. Regional hydrological models for distributed flash-floods forecasting: towards an estimation of potential impacts and damages

    Science.gov (United States)

    Le Bihan, Guillaume; Payrastre, Olivier; Gaume, Eric; Pons, Frederic; Moncoulon, David

    2016-04-01

    Hydrometeorological forecasting is an essential component of real-time flood management. The information it provides is of great help for crisis managers to anticipate the inundations and the associated risks. In the particular case of flash-floods, which may affect a large amount of small watersheds spread over the territory (up to 300 000 km of waterways considering a drained area of 5 km² minimum in France), appropriate flood forecasting systems are still under development. In France, highly distributed hydrological models have been implemented, enabling a real-time assessment of the potential intensity of flash-floods from the records of weather radars: AIGA-hydro system (Lavabre et al., 2005; Javelle et al., 2014), PreDiFlood project (Naulin et al., 2013). The approach presented here aims to go one step further by offering a direct assessment of the potential impacts of the simulated floods on inhabited areas. This approach is based on an a priori analysis of the study area in order (1) to evaluate with a simplified hydraulic approach (DTM treatment) the potentially flooded areas for different discharge levels, and (2) to identify the associated buildings and/or population at risk from geographic databases. This preliminary analysis enables to build an impact model (discharge-impact curve) on each river reach, which is then used to directly estimate the potentially affected assets based on a distributed rainfall runoff model. The overall principle of this approach was already presented at the 8th Hymex workshop. Therefore, the presentation will be here focused on the first validation results in terms of (1) accuracy of flooded areas simulated from DTM treatments, and (2) relevance of estimated impacts. The inundated areas simulated were compared to the European Directive cartography results (where available), showing an overall good correspondence in a large majority of cases, but also very significant errors for approximatively 10% of the river reaches

  18. Improving the Flash Flood Frequency Analysis using dendrogeomorphological evidences in the Arenal River crossing Arenas de San Pedro Village (Spanish Central System)

    Science.gov (United States)

    Ruiz-Villanueva, V.; Ballesteros, J. A.; Díez-Herrero, A.; Bodoque, J. M.

    2009-04-01

    The flash flood frequency analysis in mountainous catchments presents specific scientific challenges. One of the challenges is the relevant gradient in precipitation intensity with altitude. Another challenge is the lack of information from rainfall or discharge gauge stations or from documentary sources. Dendrogeomorphology studies the response in the wood growth pattern and the botanical signs on the trees affected by geomorphological processes. With regard to the flood frequency, the dendrogeomorphological evidences bring forward valuable infomation about single past events (with annual or even seasonal precision) and their occurrence periodicity. The main macro-evidence that we can find in the tree trunk is a stem scar originated by a wound in the bark of the tree. When the tree grows, this wound remains reflected in the tree ring sequence. The best way to analyze the tree ring sequence is by using a complete section of the trunk, this couldn't be possible unless the tree is cut down. Due to the unfeasibility of cutting down the trees, in Dendrogeomorphology is enough to obtain an increment core, using a Pressler borer. Nevertheless, this study has been based on complete stem sections analysis facilitated for the felling works in the riverine vegetation in the Arenal River, carried out by the Tagus River Water Authority. These felling works have allowed us to obtain sections and to analyze the stump of the tree in situ. On this way, 100 samples of Alnus glutinosa and Fraxinus angustifolia located by the river along the Arenal River crossing Arenas de San Pedro Village (Ávila, northern slopes of the Gredos Mountain Range in the Spanish Central System) have been analyzed. This village is known for its historical problems of flood during extreme events. A meticulous fieldwork has been carried out. Every sample was analyzed locating its geomorphological position, the distance to the riverbed and the height of the stump in which the evidences were observed. Using a

  19. 谈东干渠地区山洪风险图的编制%Compilation of Flash Flood Risk Map in Area around East Trunk Canal

    Institute of Scientific and Technical Information of China (English)

    郭梁

    2012-01-01

    山洪灾害一直以来是山区最严重的自然灾害,治理山洪灾害是山区防灾的重点.山洪风险图是以图表的形式反映一定频率洪水的分布、淹没范围、水深、流量大小的专题风险图,编制山洪风险图能够为山区制定防洪规划提供科学依据.本文以宁夏河东灌区的东干渠地区为例,论述了在该地区编制山洪风险图的具体步骤以及分析了在编制中存在的难点.%Flash flood has been a most serious natural disasters in mountain areas, governance is the focus of mountain disaster prevention. Flash flood risk maps reflect the distribution, flooded area, water depth, flow size of the flood with certain frequency in the form of charts. Compiling flash flood risk maps can provide the scientific basis for the development of flood control planning in mountain areas.Taking the east trunk canal area in Ningxia east irrigation district for example, this paper discusses the specific steps for preparing flash flood risk maps and analyses the difficulties.

  20. Reducing uncertainty in flood frequency analyses: A comparison of local and regional approaches involving information on extreme historical floods

    Science.gov (United States)

    Halbert, K.; Nguyen, C. C.; Payrastre, O.; Gaume, E.

    2016-10-01

    This paper proposes a detailed comparison of local and regional approaches for flood frequency analyses, with a special emphasis on the effects of (a) the information on extreme floods used in the analysis (historical data or recent extreme floods observed at ungauged sites), and (b) the assumptions associated with regional approaches (statistical homogeneity of considered series, independence of observations). The results presented are based on two case studies: the Ard e ̀ che and Argens rivers regions in south-east of France. Four approaches are compared: 1 - local analysis based on continuous measured series, 2 - local analysis with historical information, 3 - regional index-flood analysis based on continuous series, 4 - regional analysis involving information on extremes (including both historical floods and recent floods observed at ungauged sites). The inference approach used is based on a GEV distribution and a Bayesian Monte Carlo Markov Chain approach for parameters estimation. The comparison relies both on (1) available observed datasets and (2) Monte Carlo simulations in order to evaluate the effects of sampling variability and to analyze the possible influence of regional heterogeneities. The results indicate that a relatively limited level of regional heterogeneity, which may not be detected through homogeneity tests, may significantly affect the performances of regional approaches. These results also illustrate the added value of information on extreme floods, historical floods or recent floods observed at ungauged sites, in both local and regional approaches. As far as possible, gathering such information and incorporating it into flood frequency studies should be promoted. Finally, the presented Monte Carlo simulations appear as an interesting analysis tool for adapting the estimation strategy to the available data for each specific case study.

  1. Lessons from the autumn 2014 flash floods in the city of Nîmes and its neighborhood (France: behavior of several mitigation dams and hydrological analysis

    Directory of Open Access Journals (Sweden)

    Fouchier Catherine

    2016-01-01

    Full Text Available The Languedoc area, in Southern France, is prone to autumnal flash floods which are characteristic of the Mediterranean climate. To cope with this threat, the local authorities have chosen to build several dams on the main dangerous rivers of the area. We have focused on the flood mitigation facilities of two operators: the City of Nîmes and the Gardons Rivers Managing authority. After the catastrophic flash flood of October 1988, the city of Nîmes built flood mitigation dams on many of its high-risk streams. These flood barriers worked several times during the intense rainfalls of autumn 2014. The on-site conclusions drawn from these floods and the computation carried out with hydrological models confirmed how well the dams functioned. In 2010, the Gardons Rivers Managing authority built a flood mitigation dam on the Esquielle River to protect the village of Saint-Geniès-de-Malgoirès. The spillway of this dam worked for the first time in the autumn of 2014. We analyzed one of the major floods monitored on that occasion at its outlet. The goals of this study are: (i to evaluate dams efficiency and (ii to test, on a catchment which was not used for its calibration, the AIGA flash flood warning method, which was developed by IRSTEA.

  2. The flash flood of the Bisagno Creek on 9th October 2014: An "unfortunate" combination of spatial and temporal scales

    Science.gov (United States)

    Silvestro, F.; Rebora, N.; Giannoni, F.; Cavallo, A.; Ferraris, L.

    2016-10-01

    On the 9th October, 2014 a strong event hit the central part of Liguria Region producing disastrous consequences to the city of Genoa where the Bisagno Creek flooded causing one death and lots of damage. The precipitation pattern responsible for the event had peculiar spatial and temporal characteristics that led to an unexpected flash flood. The temporal sequence of rainfall intensities and the particular severity of rainfall showers at small temporal scale, together with the size of the sub-basin hit by the most intense part of the rainfall were the unfortunate concurrent ingredients that led to an "almost perfect" flash flood. The peak flow was estimated to be a 100-200 years order return period. The effects of the spatial and temporal scales of the precipitation pattern were investigated by coupling a rainfall downscaling model with a hydrological model setting up an experiment that follows a probabilistic approach. Supposing that the correct volume of precipitation at different spatial and temporal scales is known, the experiment provided the probability of generating events with similar effects in terms of streamflow. Furthermore, the study gives indications regarding the goodness and reliability of the forecasted rainfall field needed, not only in terms of total rainfall volume, but even in spatial and temporal pattern, to produce the observed ground effects in terms of streamflow.

  3. The October 2015 flash-floods in south eastern France: hydrological analyses, inundation mapping and impact estimations

    Science.gov (United States)

    Payrastre, Olivier; Bourgin, François; Lebouc, Laurent; Le Bihan, Guillaume; Gaume, Eric

    2017-04-01

    The October 2015 flash-floods in south eastern France caused more than twenty fatalities, high damages and large economic losses in high density urban areas of the Mediterranean coast, including the cities of Mandelieu-La Napoule, Cannes and Antibes. Following a post event survey and preliminary analyses conducted within the framework of the Hymex project, we set up an entire simulation chain at the regional scale to better understand this outstanding event. Rainfall-runoff simulations, inundation mapping and a first estimation of the impacts are conducted following the approach developed and successfully applied for two large flash-flood events in two different French regions (Gard in 2002 and Var in 2010) by Le Bihan (2016). A distributed rainfall-runoff model applied at high resolution for the whole area - including numerous small ungauged basins - is used to feed a semi-automatic hydraulic approach (Cartino method) applied along the river network - including small tributaries. Estimation of the impacts is then performed based on the delineation of the flooded areas and geographic databases identifying buildings and population at risk.

  4. Response of Glacier Flash Flood to Climate Warming in the Tarim River Basin%塔里木河流域冰川洪水对气候变暖的响应

    Institute of Scientific and Technical Information of China (English)

    沈永平; 王国亚; 邵春

    2007-01-01

    In past 50 years, the air temperature fluctuation was raising trend in Tarim River Basin. The annual mean temperature has increased by 0.3℃ in the whole Tarim River Basin, and by 0.6℃ in the mountain areas. With global warming, the frequency of unstable and extreme climatic events increased, glaciers retreating accelerated and snow meltwater increased have resulted in the more frequency of snow-ice disasters such as glacier debrisflow and glacier flash flood etc. Since 1980s, in the process of intense climate warming, glaciers melting intensified, ice temperature rose and glaciers flows accelerated, and lead to more glacial lakes and extending water storage capacity and stronger glacial lake outburst floods occurrence. It is proposed that the monitoring and evaluating of the impact of climate change on water resources and floods should be enhanced.

  5. Analysis on causes of flash flood in Jeddah city (Kingdom of Saudi Arabia of 2009 and 2011 using multi-sensor remote sensing data and GIS

    Directory of Open Access Journals (Sweden)

    Ahmed M. Youssef

    2016-05-01

    Full Text Available The Jeddah city is located in a coastal plain area, in the middle of the western side of the Kingdom of Saudi Arabia, bounded by the Red Sea to the west and mountains to the east. Jeddah city receives rainfall runoff from the foothills through different drainage pathways (wadis. During intense rainfall events, runoff flows westward from the hills and mountains towards the Red Sea, causing flash floods in the urban areas along the pathways of these wadis. Two major flash flood events occurred in Jeddah city during 20 November 2009 - January 2011. These events were characterized by rainfall precipitation values of 70 and 111 mm, respectively. Each flash flood event has duration of three hours. The impact of these two flood events have been disastrous causing extensive flooding that killed 113 people in 2009 and damaged infrastructure and property (more than 10,000 homes and 17,000 vehicles. This study deals with the analysis of the different factors that caused these flash flood events. The results indicate that the causes of these floods are related to a number of factors which play as a major contribution to the worsening of the flood disaster. These factors were classified into the following: geomorphological features, anthropogenic activities (urban changes, network and catchment factors, and rainfall and climatic changes factors. The climatic changes have a major impact on the rainfall intensity and will appear more in the future. Other factors related to the wadis tributaries are narrow passes, and high slope of the wadi has additional impacts in the flash floods in the area. The anthropogenic activities include the proliferation of slums and construction in the valleys coupled with the lack of suitable water streams to accommodate the amount of water flowing and the presence of dirt led to the direction of flow.

  6. Epidemiological characteristics of lower extremity cellulitis after a typhoon flood.

    Directory of Open Access Journals (Sweden)

    Pei-Chen Lin

    Full Text Available OBJECTIVE: The flood after a typhoon may lead to increase in patients with cellulitis of lower limbs. However, the microbiological features of these cases are rarely reported. We conducted a study of patients with lower extremity cellulitis after a typhoon followed in southern Taiwan to study the risk factors of cellulitis and the bacteriological features of the patients. METHODS: We reviewed all the medical records of cellulitis at emergency departments of two teaching hospitals in southern Taiwan 30 days before and after the landing of Typhoon Morakot and collected data on the demographic and bacteriological characteristics. In addition, we evaluated the relationship between the daily number of patients and the rainfall in the Tainan area. RESULTS: The number of cellulitis patients increased from 183 to 344 during the 30-day period after the typhoon. The number peaked in the third and fourth days and lasted for 3 weeks. The proportion of patients with water immersion of the affected limb was higher after the typhoon (6% vs. 37%, odds ratio [OR]: 9.0, 95% Confidence interval [CI]: 4.7-17.2. We found cultures from the infected limbs with immersion had more polymicrobial (73% vs. 26%, OR: 7.8, 95% CI: 3.2-19.2 and Gram-negative bacilli infection (86% vs. 34%, OR: 11.8, 95% CI: 4.1-34.5. CONCLUSIONS: Flood arose from Typhoon Morakot caused increases in cellulitis patients, which lasted for 3 weeks. Antibiotic treatment that were effective to both Gram-positive cocci and Gram-negative bacilli are recommended for patients with limbs emerged in the water.

  7. Assessing various approaches for flash flood forecasting in the Yzeron periurban catchment (150 km2) south-east Lyon, France

    Science.gov (United States)

    Braud, Isabelle; Breil, Pascal; Javelle, Pierre; Pejakovic, Nikola; Guérin, Stéphane

    2017-04-01

    The Yzeron periurban catchment (150 km2) is prone to flash floods leading to overflow in the downstream part of the catchment. A prevention and management plan has been approved and the set-up of a flood forecasting system is planned. The present study presents a comparison of several solutions for flood forecasting in the catchment. It is based on an extensive data collection (rain gauges, radar/rain gauge reanalyses, discharge and water level data) from this experimental catchment. A set of rainfall-runoff events leading to floods (problematic and non-problematic floods) was extracted and formed the basis for the definition of a first forecasting method. It is based on data analysis and the identification of explaining factors amongst the following: rainfall amount, intensity, antecedent rainfall, initial discharge. Several statistical methods including Factorial Analysis of Mixed Data and Classification and Regression Tree were used for this purpose. They showed that several classes of problematic floods can be identified. The first one is related to wet conditions characterized with high initial discharge and antecedent rainfall. The second class is driven by rainfall amount, initial discharge and rainfall intensity. Thresholds of these variables can be identified to provide a first warning. The second forecasting method assessed in the study is the system that will be operational in France in 2017, based on the AIGA method (Javelle et al., 2016). For this purpose, 18-year discharge simulation using the hydrological model of the AIGA method, forced using radar/rain gauges reanalysis were available at 44 locations within the catchment. The dates for which quantiles of a given return period were overtopped were identified and compared with the list of problematic events. The AIGA method was found relevant in identifying the most problematic events, but the lead time needs further investigation in order to assess the usefulness for population warning. References

  8. Development of a national Flash flood warning system in France using the AIGA method: first results and main issues

    Science.gov (United States)

    Javelle, Pierre; Organde, Didier; Demargne, Julie; de Saint-Aubin, Céline; Garandeau, Léa; Janet, Bruno; Saint-Martin, Clotilde; Fouchier, Catherine

    2016-04-01

    Developing a national flash flood (FF) warning system is an ambitious and difficult task. On one hand it rises huge expectations from exposed populations and authorities since induced damages are considerable (ie 20 casualties in the recent October 2015 flood at the French Riviera). But on the other hand, many practical and scientific issues have to be addressed and limitations should be clearly stated. The FF warning system to be implemented by 2016 in France by the SCHAPI (French national service in charge of flood forecasting) will be based on a discharge-threshold flood warning method called AIGA (Javelle et al. 2014). The AIGA method has been experimented in real time in the south of France in the RHYTMME project (http://rhytmme.irstea.fr). It consists in comparing discharges generated by a simple conceptual hourly hydrologic model run at a 1-km² resolution to reference flood quantiles of different return periods, at any point along the river network. The hydrologic model ingests operational rainfall radar-gauge products from Météo-France. Model calibration was based on ~700 hydrometric stations over the 2002-2015 period and then hourly discharges were computed at ~76 000 catchment outlets, with areas ranging from 10 to 3 500 km², over the last 19 years. This product makes it possible to calculate reference flood quantiles at each outlet. The on-going evaluation of the FF warnings is currently made at two levels: in a 'classical' way, using discharges available at the hydrometric stations, but also in a more 'exploratory' way, by comparing past flood reports and warnings issued by the system over the 76 000 catchment outlets. The interest of the last method is that it better fit the system objectives since it is designed to monitor small ungauged catchments. Javelle, P., Demargne, J., Defrance, D, .Pansu, J, .Arnaud, P. (2014). Evaluating flash-flood warnings at ungauged locations using post-event surveys: a case study with the AIGA warning system

  9. Calibration of commercial microwave link derived- rainfall and its relevance to flash flood occurrence in the Dead Sea area

    Science.gov (United States)

    Eshel, Adam; Alpert, Pinhas; Raich, Roi; Laronne, Jonathan; Merz, Ralf; Geyer, Stefan; Corsmeier, Ulrich

    2016-04-01

    Flash floods are a common phenomenon in arid and semi-arid areas such as the Dead Sea. These floods are generated due to a combination of short lasting, yet intense rainfall and typical low infiltration rates. The rare flow events in ephemeral rivers have significant importance in the replenishment of groundwater via transmission losses and in sustaining the vivid ecology of drylands. In some cases, flash floods cause severe damage to infrastructure as well as to private property, constituting a threat to human life. The temporal variation of rainfall intensity is the main driver generating the majority of flash floods in the Judean Desert, hence its monitoring is crucial in this area as in other remote arid areas worldwide. Cellular communication towers are profusely located. Commercial Microwave Links (CML) attenuation data obtained by cellular companies can be used for environmental monitoring. Rain is one of the most effective meteorological phenomena to attenuate a CML signal which, unlike radar backscatter, relates to near-surface conditions and is, therefore, suitable for surface hydrology. A 16 km CML crosses the Wadi Ze'elim drainage basin (~250 square kilometers), at the outlet of which the discharge is calculated using the Manning formula. The hydrometric data include accurate longitudinal and cross sectional measurements, water level and importantly mean water surface velocity when present during a flash flood. The latter is first-ever obtained in desert flash floods by portable, radar-based surface velocimetry. Acquisition of water velocity data is essential to avoid assuming a constant roughness coefficient, thereby more accurately calculating water discharge. Calibrating the CML-rain intensity, derived from the International Telecommunication Union (ITU)'s power law, is necessary to correlate the surface hydrologic response to the link. Our calibration approach is as follows: all the Israel Meteorological Service C-band radar cells over the CML

  10. Combining criteria for delineating lahar- and flash-flood-prone hazard and risk zones for the city of Arequipa, Peru

    Directory of Open Access Journals (Sweden)

    J.-C. Thouret

    2013-02-01

    Full Text Available Arequipa, the second largest city in Peru, is exposed to many natural hazards, most notably earthquakes, volcanic eruptions, landslides, lahars (volcanic debris flows, and flash floods. Of these, lahars and flash floods, triggered by occasional torrential rainfall, pose the most frequently occurring hazards that can affect the city and its environs, in particular the areas containing low-income neighbourhoods. This paper presents and discusses criteria for delineating areas prone to flash flood and lahar hazards, which are localized along the usually dry (except for the rainy season ravines and channels of the Río Chili and its tributaries that dissect the city. Our risk-evaluation study is based mostly on field surveys and mapping, but we also took into account quality and structural integrity of buildings, available socio-economic data, and information gained from interviews with risk-managers officials.

    In our evaluation of the vulnerability of various parts of the city, in addition to geological and physical parameters, we also took into account selected socio-economic parameters, such as the educational and poverty level of the population, unemployment figures, and population density. In addition, we utilized a criterion of the "isolation factor", based on distances to access emergency resources (hospitals, shelters or safety areas, and water in each city block. By combining the hazard, vulnerability and exposure criteria, we produced detailed risk-zone maps at the city-block scale, covering the whole city of Arequipa and adjacent suburbs. Not surprisingly, these maps show that the areas at high risk coincide with blocks or districts with populations at low socio-economic levels. Inhabitants at greatest risk are the poor recent immigrants from rural areas who live in unauthorized settlements in the outskirts of the city in the upper parts of the valleys. Such settlements are highly exposed to natural hazards and have little access

  11. Combining criteria for delineating lahar- and flash-flood-prone hazard and risk zones for the city of Arequipa, Peru

    Science.gov (United States)

    Thouret, J.-C.; Enjolras, G.; Martelli, K.; Santoni, O.; Luque, J. A.; Nagata, M.; Arguedas, A.; Macedo, L.

    2013-02-01

    Arequipa, the second largest city in Peru, is exposed to many natural hazards, most notably earthquakes, volcanic eruptions, landslides, lahars (volcanic debris flows), and flash floods. Of these, lahars and flash floods, triggered by occasional torrential rainfall, pose the most frequently occurring hazards that can affect the city and its environs, in particular the areas containing low-income neighbourhoods. This paper presents and discusses criteria for delineating areas prone to flash flood and lahar hazards, which are localized along the usually dry (except for the rainy season) ravines and channels of the Río Chili and its tributaries that dissect the city. Our risk-evaluation study is based mostly on field surveys and mapping, but we also took into account quality and structural integrity of buildings, available socio-economic data, and information gained from interviews with risk-managers officials. In our evaluation of the vulnerability of various parts of the city, in addition to geological and physical parameters, we also took into account selected socio-economic parameters, such as the educational and poverty level of the population, unemployment figures, and population density. In addition, we utilized a criterion of the "isolation factor", based on distances to access emergency resources (hospitals, shelters or safety areas, and water) in each city block. By combining the hazard, vulnerability and exposure criteria, we produced detailed risk-zone maps at the city-block scale, covering the whole city of Arequipa and adjacent suburbs. Not surprisingly, these maps show that the areas at high risk coincide with blocks or districts with populations at low socio-economic levels. Inhabitants at greatest risk are the poor recent immigrants from rural areas who live in unauthorized settlements in the outskirts of the city in the upper parts of the valleys. Such settlements are highly exposed to natural hazards and have little access to vital resources. Our

  12. The management of urban surface water flood risks: SUDS performance in flood reduction from extreme events.

    Science.gov (United States)

    Viavattene, C; Ellis, J B

    2013-01-01

    The need to improve the urban drainage network to meet recent urban growth and the redevelopment of old industrial and commercial areas provides an opportunity for managing urban surface water infrastructure in a more sustainable way. The use of sustainable urban drainage systems (SUDS) can reduce urban surface water flooding as well as the pollution impact of urban discharges on receiving waters. However, these techniques are not yet well known by many stakeholders involved in the decision-making process, or at least the evidence of their performance effectiveness may be doubted compared with more traditional engineering solutions often promoted by existing 1D/2D drainage models. The use of geographic information systems (GIS) in facilitating the inter-related risk analysis of sewer surface water overflows and urban flooding as well as in better communication with stakeholders is demonstrated in this paper. An innovative coupled 1D/2D urban sewer/overland flow model has been developed and tested in conjunction with a SUDS selection and location tool (SUDSLOC) to enable a robust management approach to surface water flood risks and to improve the resilience of the urban drainage infrastructure. The paper demonstrates the numerical and modelling basis of the integrated 1D/2D and SUDSLOC approach and the working assumptions and flexibility of the application together with some limitations and uncertainties. The role of the SUDSLOC modelling component in quantifying flow, and surcharge reduction benefits arising from the strategic selection and location of differing SUDS controls are also demonstrated for an extreme storm event scenario.

  13. Analysis of Flash Flood along East Trunk Canal and Countermeasures%东干渠沿线山洪灾害分析与防治对策

    Institute of Scientific and Technical Information of China (English)

    郭梁

    2011-01-01

    In this paper, causes that east trunk canal are subject to the dangers of flash floods easily were analyzed, and from the perspective of flood management, the new flood control system planning was put forward based on the former flood control system of east trunk canal, and engineering measures and non-engineering measures were taken to effectively prevent flash floods.%本文分析了东干渠沿线易遭受山洪危害的原因,从洪水管理的角度出发,在原东干渠防洪系统基础上提出了新的防洪系统规划,并采取工程措施和非工程措施对山洪进行有效防治.

  14. Extreme flood events in the Bolivian Amazon wetlands

    Directory of Open Access Journals (Sweden)

    A. Ovando

    2016-03-01

    New hydrological insights for the region: The results showed that large floods are the result of the superimposition of flood waves from major sub-basins of the region. As a previous study suggested, the dynamics of the floods are controlled by an exogenous process, created by the flood wave originating in the Andes piedmont that travels through the Mamoré River; and by an endogenous process, which is the runoff originating in the Llanos. Our study showed that the first process is evident only at the initial phase of the floods, and although important for attenuating the rising flood wave, it is of lesser importance compared to the endogenous process. We conclude that the endogenous process controls the magnitude and duration of major floods.

  15. Flash Flood Risk Mapping for the Watershed of South Branch of Censhui River%涔水南支小流域山洪风险图编制

    Institute of Scientific and Technical Information of China (English)

    李昌志; 王帆; 黄金池; 何晓燕

    2013-01-01

    山洪风险图是山丘区洪水防治重要的非工程措施之一。以涔水南支小流域山洪风险图编制为例,从编制思路、危险性评估、易损性评估、风险评估以及风险图绘制等方面,对涔水南支小流域山洪风险图编制试点工作的思路、流程及成果进行分析,提出了山洪风险图编制过程中需要明确重点河(沟)段、重要城镇、集镇和村组(社)等居民点及其重要基础设施;需要合理地确定山洪计算标准;分析方法应当根据资料详细程度和编制目标进行选择;山洪风险指标体系及阈值划分需要概化和有针对性;山洪风险图编制可考虑分级分阶段推进等编制要求。%Flash flood risk map is one of the important nonstructural measures for flash flood prevention and control in mountainous areas. Taking the South Censhui River Watershed as an example, this paper systematical y introduces the approaches, procedures and outputs in the pilot trial from the aspects of mapping methodology, hazard analysis, vulnerability assessment, risk estimation, and risk mapping. The conclusions include: (1) flash flood risk map is composed of a series maps and corresponding information should be highlighted in each type of maps; (2) the object of flash flood risk mapping should be focused on the residential areas (important river reaches, towns, vil ages) and fundamental infrastructures in the watershed; (3) reasonable standards for flash flood hydrological analysis are required for flash flood risk mapping; (4) the selection of method for hazard analysis is based on the level of data details and objectives of flash flood risk mapping; (5) the indexes for flash flood risk and their grading need to be simplified and targeted; and (6) it is practical that flood risk mapping is carried out at different levels by stages.

  16. HYDRAULIC SIMULATION OF FLASH FLOOD AS TRIGGERED BY NATURAL DAM BREAK

    Directory of Open Access Journals (Sweden)

    Yanuar Tri Kurniawan

    2015-05-01

    Calibration model result showed that the height of natural dam significantly influence changes of water surface elevation at control point. Tracing of flood result in reconstruction of January 2006 flood showed the conformity with the real event. It was observed from the arrival time of flood at certain location. From obtained results, it can be concluded that simulation modeling gave the acceptable results.

  17. Evaluating the impact and risk of pluvial flash flood on intra-urban road network: A case study in the city center of Shanghai, China

    Science.gov (United States)

    Yin, Jie; Yu, Dapeng; Yin, Zhane; Liu, Min; He, Qing

    2016-06-01

    Urban pluvial flood are attracting growing public concern due to rising intense precipitation and increasing consequences. Accurate risk assessment is critical to an efficient urban pluvial flood management, particularly in transportation sector. This paper describes an integrated methodology, which initially makes use of high resolution 2D inundation modeling and flood depth-dependent measure to evaluate the potential impact and risk of pluvial flash flood on road network in the city center of Shanghai, China. Intensity-Duration-Frequency relationships of Shanghai rainstorm and Chicago Design Storm are combined to generate ensemble rainfall scenarios. A hydrodynamic model (FloodMap-HydroInundation2D) is used to simulate overland flow and flood inundation for each scenario. Furthermore, road impact and risk assessment are respectively conducted by a new proposed algorithm and proxy. Results suggest that the flood response is a function of spatio-temporal distribution of precipitation and local characteristics (i.e. drainage and topography), and pluvial flash flood is found to lead to proportionate but nonlinear impact on intra-urban road inundation risk. The approach tested here would provide more detailed flood information for smart management of urban street network and may be applied to other big cities where road flood risk is evolving in the context of climate change and urbanization.

  18. Performance of Models for Flash Flood Warning and Hazard Assessment: The 2015 Kali Gandaki Landslide Dam Breach in Nepal

    Directory of Open Access Journals (Sweden)

    Jeremy D. Bricker

    2017-02-01

    Full Text Available The 2015 magnitude 7.8 Gorkha earthquake and its aftershocks weakened mountain slopes in Nepal. Co- and postseismic landsliding and the formation of landslide-dammed lakes along steeply dissected valleys were widespread, among them a landslide that dammed the Kali Gandaki River. Overtopping of the landslide dam resulted in a flash flood downstream, though casualties were prevented because of timely evacuation of low-lying areas. We hindcast the flood using the BREACH physically based dam-break model for upstream hydrograph generation, and compared the resulting maximum flow rate with those resulting from various empirical formulas and a simplified hydrograph based on published observations. Subsequent modeling of downstream flood propagation was compromised by a coarse-resolution digital elevation model with several artifacts. Thus, we used a digital-elevation-model preprocessing technique that combined carving and smoothing to derive topographic data. We then applied the 1-dimensional HEC-RAS model for downstream flood routing, and compared it to the 2-dimensional Delft-FLOW model. Simulations were validated using rectified frames of a video recorded by a resident during the flood in the village of Beni, allowing estimation of maximum flow depth and speed. Results show that hydrological smoothing is necessary when using coarse topographic data (such as SRTM or ASTER, as using raw topography underestimates flow depth and speed and overestimates flood wave arrival lag time. Results also show that the 2-dimensional model produces more accurate results than the 1-dimensional model but the 1-dimensional model generates a more conservative result and can be run in a much shorter time. Therefore, a 2-dimensional model is recommended for hazard assessment and planning, whereas a 1-dimensional model would facilitate real-time warning declaration.

  19. A database on flash flood events in Campania, southern Italy, with an evaluation of their spatial and temporal distribution

    Science.gov (United States)

    Vennari, Carmela; Parise, Mario; Santangelo, Nicoletta; Santo, Antonio

    2016-11-01

    This study presents an historical database of flash flood events in the Campania region of southern Italy. The study focuses on small catchments characterized by intermittent flow, generally occurring during and after heavy rainstorms, which can be hydrologically defined as small Mediterranean catchments. As the outlet zones of these catchments (consisting mainly of alluvial fans or fan deltas) are highly urbanized in Campania, the population living in the delivery areas is exposed to high risk. Detailed scrutiny and critical analysis of the existing literature, and of the data inventory available, allowed us to build a robust database consisting of about 500 events from 1540 to 2015, which is continuously updated. Since this study is the first step of a longer project to perform a hazard analysis, information about time and site of occurrence is known for all events. As for the hazard analysis envisaged, collecting information about past events could provide information on future events, in terms of damage and also spatial and temporal occurrence. After introducing the issue of flash floods in Italy we then describe the geological and geomorphological settings of the study area. The database is then presented, illustrating the methodology used in collecting information and its general structure. The collected data are then discussed and the statistical data analysis presented.

  20. Use of radar rainfall data for high-resolution flash flood forecasting in the Dallas-Fort Worth Metroplex area

    Science.gov (United States)

    Seo, D. J.; Habibi, H.; Rafieei Nasab, A.; Norouzi, A.; Nazari, B.; Lee, H. S.; Cosgrove, B.; Cui, Z.

    2015-12-01

    For monitoring and prediction of water-related hazards such as flash flooding in urban areas, high-resolution hydrologic and hydraulic modeling is necessary. Because of large sensitivity and scale dependence of rainfall-runoff models to errors in quantitative precipitation estimates (QPE), it is important that the accuracy of QPE be improved to the greatest extent possible. In this presentation, we describe the ongoing efforts in the Dallas-Fort Worth Metroplex area to provide location- and time-specific flash flooding warnings in real-time. The hydrologic modeling system used is the National Weather Service (NWS) Hydrology Laboratory's Research Distributed Hydrologic Model (HLRDHM) applied at spatiotemporal resolutions ranging from 250 m to 2 km and from 1 min to 1 hour. The high-resolution precipitation input is from the DFW Demonstration Network of the Collaborative Adaptive Sensing of the Atmosphere (CASA) radars, the Next Generation QPE (Q2), and the NWS Multisensor Precipitation Estimator (MPE). Also described are the assessment of sensitivity of streamflow simulation to the spatiotemporal resolution of precipitation input and hydrologic modeling, the needs for high-quality high-resolution precipitation data sets for hydro-meteorological and -climatological applications particularly in large urban areas, and possible approaches to realize them.

  1. Flash Flood Prediction by Coupling KINEROS2 and HEC-RAS Models for Tropical Regions of Northern Vietnam

    Directory of Open Access Journals (Sweden)

    Hong Quang Nguyen

    2015-11-01

    Full Text Available Northern Vietnam is a region prone to heavy flash flooding events. These often have devastating effects on the environment, cause economic damage and, in the worst case scenario, cost human lives. As their frequency and severity are likely to increase in the future, procedures have to be established to cope with this threat. As the prediction of potential flash floods represents one crucial element in this circumstance, we will present an approach that combines the two models KINEROS2 and HEC-RAS in order to accurately predict their occurrence. We used a documented event on 23 June 2011 in the Nam Khat and the larger adjacent Nam Kim watershed to calibrate the coupled model approach. Afterward, we evaluated the performance of the coupled models in predicting flow velocity (FV, water levels (WL, discharge (Q and streamflow power (P during the 3–5 days following the event, using two different precipitation datasets from the global spectral model (GSM and the high resolution model (HRM. Our results show that the estimated Q and WL closely matched observed data with a Nash–Sutcliffe simulation efficiency coefficient (NSE of around 0.93 and a coefficient of determination (R2 at above 0.96. The resulting analyses reveal strong relationships between river geometry and FV, WL and P. Although there were some minor errors in forecast results, the model-predicted Q and WL corresponded well to the gauged data.

  2. Using participatory agent-based models to measure flood managers' decision thresholds in extreme event response

    Science.gov (United States)

    Metzger, A.; Douglass, E.; Gray, S. G.

    2016-12-01

    Extreme flooding impacts to coastal cities are not only a function of storm characteristics, but are heavily influenced by decision-making and preparedness in event-level response. While recent advances in climate and hydrological modeling make it possible to predict the influence of climate change on storm and flooding patterns, flood managers still face a great deal of uncertainty related to adapting organizational responses and decision thresholds to these changing conditions. Some decision thresholds related to mitigation of extreme flood impacts are well-understood and defined by organizational protocol, but others are difficult to quantify due to reliance on contextual expert knowledge, experience, and complexity of information necessary to make certain decisions. Our research attempts to address this issue by demonstrating participatory modeling methods designed to help flood managers (1) better understand and parameterize local decision thresholds in extreme flood management situations, (2) collectively learn about scaling management decision thresholds to future local flooding scenarios and (3) identify effective strategies for adaptating flood mitigation actions and organizational response to climate change-intensified flooding. Our agent-based system dynamic models rely on expert knowledge from local flood managers and sophisticated, climate change-informed hydrological models to simulate current and future flood scenarios. Local flood managers from interact with these models by receiving dynamic information and making management decisions as a flood scenario progresses, allowing parametrization of decision thresholds under different scenarios. Flooding impacts are calculated in each iteration as a means of discussing effectiveness of responses and prioritizing response alternatives. We discuss the findings of this participatory modeling and educational process from a case study of Boston, MA, and discuss transferability of these methods to other types

  3. Quantification of flash flood economic risk using ultra-detailed stage-damage functions and 2-D hydraulic models

    Science.gov (United States)

    Garrote, J.; Alvarenga, F. M.; Díez-Herrero, A.

    2016-10-01

    The village of Pajares de Pedraza (Segovia, Spain) is located in the floodplain of the Cega River, a left bank tributary of the Douro River. Repeated flash flood events occur in this small village because of its upstream catchment area, mountainous character and impermeable lithology, which reduce concentration time to just a few hours. River overbank flow has frequently caused flooding and property damage to homes and rural properties, most notably in 1927, 1991, 1996, 2001, 2013 and 2014. Consequently, a detailed analysis was carried out to quantify the economic risk of flash floods in peri-urban and rural areas. Magnitudes and exceedance probabilities were obtained from a flood frequency analysis of maximum discharges. To determine the extent and characteristics of the flooded area, we performed 2D hydraulic modeling (Iber 2.0 software) based on LIDAR (1 m) topography and considering three different scenarios associated with the initial construction (1997) and subsequent extension (2013) of a linear defense structure (rockfill dike or levee) to protect the population. Specific stage-damage functions were expressly developed using in situ data collection for exposed elements, with special emphasis on urban-type categories. The average number of elements and their unit value were established. The relationship between water depth and the height at which electric outlets, furniture, household goods, etc. were located was analyzed; due to its effect on the form of the function. Other nonspecific magnitude-damage functions were used in order to compare both economic estimates. The results indicate that the use of non-specific magnitude-damage functions leads to a significant overestimation of economic losses, partly linked to the use of general economic cost data. Furthermore, a detailed classification and financial assessment of exposed assets is the most important step to ensure a correct estimate of financial losses. In both cases, this should include a

  4. THE VULNERABILITY OF THE TERRITORIAL-ADMINISTRATIVE UNITS TO THE HYDROLOGICAL PHENOMENA OF RISK (FLASH FLOODS. CASE STUDY: THE SUBCARPATHIAN SECTOR OF BUZĂU CATCHMENT

    Directory of Open Access Journals (Sweden)

    Remus PRĂVĂLIE

    2013-06-01

    Full Text Available The present study aims to analyze, on the one hand, the flash-floods forming potential in the Subcarpathian sector of Buzău catchment, an area with high susceptibility to hydrological hazards such as flash-floods, and, on the other hand, the vulnerability of the territorial-administrative units to these risk phenomena. Thus, in the first stage, the Flash floods Susceptibility Index (FFSI index was defined for the Subcarpathian sector of Buzău catchment, based on environmental factors with a relatively static nature, considered causal factors in the flash-flood phenomena genesis. The next stage of this work was the delimitation of the vulnerability index of the territorial-administrative units, based on the highest FFSI index values which correspond to the built surfaces from the analyzed units. The results showed that more than 80% of the territorial-administrative units are exposed to flood phenomena, while almst 20% is currently under serious risk of damage in case of hydrological risk phenomena occurrence.

  5. 山洪预报决策系统的构建%Construction of Flash Floods Forecast Decision-making System

    Institute of Scientific and Technical Information of China (English)

    钱慧; 周新志

    2011-01-01

    山洪是山丘区中流域由降雨引起的突发性、暴涨暴落的洪水.为减少山洪造成的危害,介绍了山洪预警中山洪预报决策系统的设计.设计由水雨情分析预报子系统、预警信息生成子系统以及维护及管理子系统三部分构成.通过对该系统在崇州地区的应用,证实其基本上能达到设计要求.%Flash flood is a kind of sudden flood which is caused by the sudden rainfall, rises up and down sharply in the basin hilly and mountainous areas. In order to reduce the damage caused by flash flood, the design of the flash flood disaster forecasting decision-making system is introduced in the flash flood disaster early warning system. This design contains three parts including rainfall analysis and prediction subsystem, generation of early warning subsystem and maintenance and management subsystem. Through the application of this system in Chongzhou city, it can meet the design requirements on the whole.

  6. Estimation of extreme floods : At-site flood estimates by application of a hydrological model and long synthetic series of precipitation and temperature

    OpenAIRE

    Barkved, Line Johanne

    2007-01-01

    Estimation of extreme floods, based on statistical analyses of observed values of flood series, is associated with several problems leading to high uncertainty in the flood estimates. In particular is this related to the length of the observation series and the extrapolation outside the range of observed values, when estimating the rare extreme floods. In many cases, short hydrological records are the common rule rather than the exceptions. This thesis targets at-site, single station, fr...

  7. Mercury loads into the sea associated with extreme flood.

    Science.gov (United States)

    Saniewska, Dominika; Bełdowska, Magdalena; Bełdowski, Jacek; Jędruch, Agnieszka; Saniewski, Michał; Falkowska, Lucyna

    2014-08-01

    Floods are an important factor determining riverine pollution loads, including toxic mercury (Hg). The impact of the Vistula River flood in 2010, which was the biggest one recorded in 160 years and its influence on marine environment was studied. Mercury concentration was analyzed in river and sea water, suspended matter, phytoplankton and sea surface sediment. Flood and gulf water contained several times higher concentration of Hg (exceeded reference values safe for aquatic organisms) than before or after the flood. In 2010 the Vistula introduced into the Baltic ca. 1576 kg of Hg, of which 75% can be attributed to the flood water. Increase of water temperature, decrease of oxygen content contended increasing of dissolved mercury concentration, which was transported far into the Baltic. This phenomenon led to an increase of Hg concentration in phytoplankton and during many months in surface sediments. It is a potential threat to marine organisms.

  8. Characterization of extreme flood and drought events in Singapore and investigation of their relationships with ENSO

    Science.gov (United States)

    Li, Xin; Babovic, Vladan

    2016-04-01

    Flood and drought are hydrologic extreme events that have significant impact on human and natural systems. Characterization of flood and drought in terms of their start, duration and strength, and investigation of the impact of natural climate variability (i.e., ENSO) and anthropogenic climate change on them can help decision makers to facilitate adaptions to mitigate potential enormous economic costs. To date, numerous studies in this area have been conducted, however, they are primarily focused on extra-tropical regions. Therefore, this study presented a detailed framework to characterize flood and drought events in a tropical urban city-state (i.e., Singapore), based on daily data from 26 precipitation stations. Flood and drought events are extracted from standardized precipitation anomalies from monthly to seasonal time scales. Frequency, duration and magnitude of flood and drought at all the stations are analyzed based on crossing theory. In addition, spatial variation of flood and drought characteristics in Singapore is investigated using ordinary kriging method. Lastly, the impact of ENSO condition on flood and drought characteristics is analyzed using regional regression method. The results show that Singapore can be prone to extreme flood and drought events at both monthly and seasonal time scales. ENSO has significant influence on flood and drought characteristics in Singapore, but mainly during the South West Monsoon season. During the El Niño phase, drought can become more extreme. The results have implications for water management practices in Singapore.

  9. Bibliography of forest water yields, flooding issues, and the hydrologic modeling of extreme flood events

    Science.gov (United States)

    Mark H. Eisenbies; M.B. Adams; W. Michael Aust; James A. Burger

    2007-01-01

    Floods continue to cause significant damage in the United States and elsewhere, and questions about the causes of flooding continue to be debated. A significant amount of research has been conducted on the relationship between forest management activities and water yield, peak flows, and flooding; somewhat less research has been conducted on the modeling of these...

  10. Clumsy Floodplains and the Law: Towards a Responsive Land Policy for Extreme Floods

    NARCIS (Netherlands)

    Hartmann, T.

    2009-01-01

    Almost every year, extreme floods cause enormous damage in floodplains. However, urban development still takes place in these areas. As levees are built up, space for the rivers shrinks. The same patterns of human activity can often be observed in floodplains: values are accumulated there, floods th

  11. Combination of different types of ensembles for the adaptive simulation of probabilistic flood forecasts: hindcasts for the Mulde 2002 extreme event

    Directory of Open Access Journals (Sweden)

    J. Dietrich

    2008-03-01

    Full Text Available Flood forecasts are essential to issue reliable flood warnings and to initiate flood control measures on time. The accuracy and the lead time of the predictions for head waters primarily depend on the meteorological forecasts. Ensemble forecasts are a means of framing the uncertainty of the potential future development of the hydro-meteorological situation.

    This contribution presents a flood management strategy based on probabilistic hydrological forecasts driven by operational meteorological ensemble prediction systems. The meteorological ensemble forecasts are transformed into discharge ensemble forecasts by a rainfall-runoff model. Exceedance probabilities for critical discharge values and probabilistic maps of inundation areas can be computed and presented to decision makers. These results can support decision makers in issuing flood alerts. The flood management system integrates ensemble forecasts with different spatial resolution and different lead times. The hydrological models are controlled in an adaptive way, mainly depending on the lead time of the forecast, the expected magnitude of the flood event and the availability of measured data.

    The aforementioned flood forecast techniques have been applied to a case study. The Mulde River Basin (South-Eastern Germany, Czech Republic has often been affected by severe flood events including local flash floods. Hindcasts for the large scale extreme flood in August 2002 have been computed using meteorological predictions from both the COSMO-LEPS ensemble prediction system and the deterministic COSMO-DE local model. The temporal evolution of a the meteorological forecast uncertainty and b the probability of exceeding flood alert levels is discussed. Results from the hindcast simulations demonstrate, that the systems would have predicted a high probability of an extreme flood event, if they would already have been operational in 2002. COSMO-LEPS showed a reasonably good

  12. Identification of spatial and temporal contributions of rainfalls to flash floods using neural network modelling: case study on the Lez Basin (Southern France

    Directory of Open Access Journals (Sweden)

    T. Darras

    2015-04-01

    Full Text Available Flash floods pose significant hazards in urbanised zones and have important human and financial implications in both the present and future due to the likelihood that global climate change will exacerbate their consequences. It is thus of crucial importance to better model these phenomena especially when they occur in heterogeneous and karst basins where they are difficult to describe physically. Toward this goal, this paper applies a recent methodology (KnoX methodology dedicated to extracting knowledge from a neural network model to better determine the contributions and time responses of several well-identified geographic zones of an aquifer. To assess the interest of this methodology, a case study was conducted in Southern France: the Lez hydrosystem whose river crosses the conurbation of Montpellier (400 000 inhabitants. Rainfall contributions and time transfers were estimated and analysed in four geologically-delimited zones to estimate the sensitivity of flash floods to water coming from the surface or karst. The Causse de Viol-le-Fort is shown to be the main contributor to flash floods and the delay between surface and underground flooding is estimated to be three hours. This study will thus help operational flood warning services to better characterise critical rainfall and develop measurements to design efficient flood forecasting models. This generic method can be applied to any basin with sufficient rainfall–runoff measurements.

  13. Impact of flash flood events on the distribution of organic pollutants in surface sediments from a Mediterranean coastal lagoon (Mar Menor, SE Spain).

    Science.gov (United States)

    León, V M; Moreno-González, R; García, V; Campillo, J A

    2017-02-01

    The influence of flash flood events on the input and distribution of polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and organochlorinated pesticides (OCPs) in surface sediments from the Mar Menor lagoon were characterized in this study. These contaminants were analyzed in surface water samples collected during two flash flood events in the main surface watercourse which flow into the Mar Menor lagoon. Surface sediments were sampled semiannually before and after flash flood events. The total input of PAHs, OCPs, and PCBs (sorbed + dissolved) during two flash flood events was estimated at 0.98, 1.32, and 0.34 kg, respectively, the main input corresponding to p,p'-DDE (1.00 kg). The distribution of organic contaminants in surface sediments was not homogeneous as a consequence of the presence of many simultaneous sources and different meteorological, hydrodynamic, and physicochemical conditions. As a consequence of flash flood events, p,p'-DDE concentrations in surface sediments increased significantly in the central and south zones of the lagoon. However, in the case of PCBs, a dilution effect was observed in the south zone after such events, reducing the environmental risk. These changes in the pollutant distribution persisted at least 1 year later (autumn 2010), showing that the impact of flood events in the distribution of persistent organic contaminants in Mediterranean coastal lagoons is of relevance according to the ecological risk assessment carried out. The impact of these events should be also considered in other coastal systems, especially in semiarid and semiconfined areas.

  14. Driving into danger: Perception and communication of flash flood risk from a cultural perspective

    Science.gov (United States)

    Coles, A.; Hirschboeck, K. K.; Fryberg, S.

    2009-04-01

    Flood risk managers educate the public on the dangers of driving through flooded roadways, yet losses to life and property continue to occur. This study integrates cultural psychology and risk perception theory to explore how culture, psychological processes, and behavior influence one another. Flood risk managers in Tucson, Arizona collaborated in the development of a questionnaire mailed to local residents. Questions regarding levels of trust, self-efficacy, social autonomy, social incorporation, time perspective, and situational factors were analyzed with respect to whether respondents stated that they have or have not driven through a flooded roadway. Respondents' decisions are influenced by the presence of signs and barricades, passengers, risk of personal injury or damage to the vehicle, and the availability of flood-related information. The most influential factor is the prior successful crossing of other vehicles. The results illuminate complex interrelations among the cultural factors and provide considerations for future risk perception research.

  15. Stochastic semi-continuous simulation for extreme flood estimation in catchments with combined rainfall-snowmelt flood regimes

    Science.gov (United States)

    Lawrence, D.; Paquet, E.; Gailhard, J.; Fleig, A. K.

    2014-05-01

    Simulation methods for extreme flood estimation represent an important complement to statistical flood frequency analysis because a spectrum of catchment conditions potentially leading to extreme flows can be assessed. In this paper, stochastic, semi-continuous simulation is used to estimate extreme floods in three catchments located in Norway, all of which are characterised by flood regimes in which snowmelt often has a significant role. The simulations are based on SCHADEX, which couples a precipitation probabilistic model with a hydrological simulation such that an exhaustive set of catchment conditions and responses is simulated. The precipitation probabilistic model is conditioned by regional weather patterns, and a bottom-up classification procedure was used to define a set of weather patterns producing extreme precipitation in Norway. SCHADEX estimates for the 1000-year (Q1000) discharge are compared with those of several standard methods, including event-based and long-term simulations which use a single extreme precipitation sequence as input to a hydrological model, statistical flood frequency analysis based on the annual maximum series, and the GRADEX method. The comparison suggests that the combination of a precipitation probabilistic model with a long-term simulation of catchment conditions, including snowmelt, produces estimates for given return periods which are more in line with those based on statistical flood frequency analysis, as compared with the standard simulation methods, in two of the catchments. In the third case, the SCHADEX method gives higher estimates than statistical flood frequency analysis and further suggests that the seasonality of the most likely Q1000 events differs from that of the annual maximum flows. The semi-continuous stochastic simulation method highlights the importance of considering the joint probability of extreme precipitation, snowmelt rates and catchment saturation states when assigning return periods to floods

  16. Knowledge Discovery, Integration and Communication for Extreme Weather and Flood Resilience Using Artificial Intelligence: Flood AI Alpha

    Science.gov (United States)

    Demir, I.; Sermet, M. Y.

    2016-12-01

    Nobody is immune from extreme events or natural hazards that can lead to large-scale consequences for the nation and public. One of the solutions to reduce the impacts of extreme events is to invest in improving resilience with the ability to better prepare, plan, recover, and adapt to disasters. The National Research Council (NRC) report discusses the topic of how to increase resilience to extreme events through a vision of resilient nation in the year 2030. The report highlights the importance of data, information, gaps and knowledge challenges that needs to be addressed, and suggests every individual to access the risk and vulnerability information to make their communities more resilient. This abstracts presents our project on developing a resilience framework for flooding to improve societal preparedness with objectives; (a) develop a generalized ontology for extreme events with primary focus on flooding; (b) develop a knowledge engine with voice recognition, artificial intelligence, natural language processing, and inference engine. The knowledge engine will utilize the flood ontology and concepts to connect user input to relevant knowledge discovery outputs on flooding; (c) develop a data acquisition and processing framework from existing environmental observations, forecast models, and social networks. The system will utilize the framework, capabilities and user base of the Iowa Flood Information System (IFIS) to populate and test the system; (d) develop a communication framework to support user interaction and delivery of information to users. The interaction and delivery channels will include voice and text input via web-based system (e.g. IFIS), agent-based bots (e.g. Microsoft Skype, Facebook Messenger), smartphone and augmented reality applications (e.g. smart assistant), and automated web workflows (e.g. IFTTT, CloudWork) to open the knowledge discovery for flooding to thousands of community extensible web workflows.

  17. Flash flood occurrences since the 17th century in steep drainage basins in southern Italy.

    Science.gov (United States)

    Petrucci, Olga; Pasqua, A Aurora; Polemio, Maurizio

    2012-11-01

    The historical floods that have occurred since the seventeenth century were collected for a study area in southern Italy. Damages caused by floods, rainfall and the main anthropogenic modifications are discussed all together. The aim was to assess whether the frequency of floods is changing and, if so, whether these changes can be attributed to either rainfall and/or anthropogenic modifications. In 4 % of cases, mainly occurred in past centuries, floods damaged people. Hydraulic works, roads and private buildings were the more frequently damaged elements (25, 18 and 14 % of the cases, respectively). The annual variability of rainfall was discussed using an annual index. Short duration-high intensity rainfalls were characterized considering time series of annual maxima of 1, 3, 6, 12, and 24 h and daily rainfall. The rainfall shows a decreasing trend, in terms of both the annual maximum of short duration and the annual amount. The population has been progressively increasing since the sixteenth century, except during the years following the catastrophic 1908 earthquake. The rate of population growth has been very high since the second half of the twentieth century; the urbanized areas greatly increased, especially following the second half of the twentieth century. At the same time, the trend of damaging floods has been increasing, especially since the seventies. The analysis indicates that, despite a rainfall trend favourable towards a reduction in flood occurrence, floods damage has not decreased. This seems to be mainly the effect of mismanagement of land use modifications.

  18. Operational flood management under large-scale extreme conditions, using the example of the Middle Elbe

    Directory of Open Access Journals (Sweden)

    A. Kron

    2010-06-01

    Full Text Available In addition to precautionary or technical flood protection measures, short-term strategies of the operational management, i.e. the initiation and co-ordination of preventive measures during and/or before a flood event are crucially for the reduction of the flood damages. This applies especially for extreme flood events. These events are rare, but may cause a protection measure to be overtopped or even to fail and be destroyed. In such extreme cases, reliable decisions must be made and emergency measures need to be carried out to prevent even larger damages from occurring.

    Based on improved methods for meteorological and hydrological modelling a range of (physically based extreme flood scenarios can be derived from historical events by modification of air temperature and humidity, shifting of weather fields and recombination of flood relevant event characteristics. By coupling the large scale models with hydraulic and geotechnical models, the whole flood-process-chain can be analysed right down to the local scale. With the developed GIS-based tools for hydraulic modelling FlowGIS and the Dike-Information-System, (IS-dikes it is possible to quantify the endangering shortly before or even during a flood event, so the decision makers can evaluate possible options for action in operational mode.

  19. How Unique was Hurricane Sandy? Sedimentary Reconstructions of Extreme Flooding from New York Harbor

    Science.gov (United States)

    Brandon, Christine M.; Woodruff, Jonathan D.; Donnelly, Jeffrey P.; Sullivan, Richard M.

    2014-12-01

    The magnitude of flooding in New York City by Hurricane Sandy is commonly believed to be extremely rare, with estimated return periods near or greater than 1000 years. However, the brevity of tide gauge records result in significant uncertainties when estimating the uniqueness of such an event. Here we compare resultant deposition by Hurricane Sandy to earlier storm-induced flood layers in order to extend records of flooding to the city beyond the instrumental dataset. Inversely modeled storm conditions from grain size trends show that a more compact yet more intense hurricane in 1821 CE probably resulted in a similar storm tide and a significantly larger storm surge. Our results indicate the occurrence of additional flood events like Hurricane Sandy in recent centuries, and highlight the inadequacies of the instrumental record in estimating current flood risk by such extreme events.

  20. The impacts of '05.6' extreme flood event on riverine carbon fluxes in Xijiang River

    Institute of Scientific and Technical Information of China (English)

    SUN HuiGuo; HAN JingTai; ZHANG ShuRong; LU XiXi

    2007-01-01

    An extreme flood event with a frequency of nearly 200 year occurred in June of 2005 in the Xijiang River,the main trunk stream of the Zhujiang River. Samples were systematically collected during the flood event, and water quality parameters, including total suspended sediment (TSS), dissolved inorganic carbon (DIC), dissolved organic carbon (DOC), and particulate organic carbon (POC) were analyzed,and riverine carbon concentrations associated with its changing pattern through the flood process were discussed. These parameters reflect the changes in basin surface flow and subsurface flow during the flood. This flood event influenced annual flux estimations of POC, DOC, and DIC to great extents.Based on carbon flux estimations for the year 2005 and the flood event (June 21-28) in the Xijiang River, it was found that DIC, DOC, and POC fluxes during '05.6' flood event are 1.52x106 g.km-2.a-1,0.24x106 g.km-2.a-1, and 0.54x106 g.km-2.a-1, and account for 14.87%, 24.75% and 44.89% of the annual fluxes in 2005, respectively. The results suggested that carbon exports during extreme flood events had great contributions to the total carbon fluxes and composition of various carbon components, being important for accurate estimates of annual carbon fluxes in rivers with frequent floods.

  1. THE INFLUENCE OF ATMOSPHERIC CIRCULATION, SHAPE AND CATCHMENT AREA POSITION ON THE AMPLITUDE AND EFFECTS OF THE AUGUST 2005 FLASH-FLOOD (OZANA AND CRACĂU RIVERS

    Directory of Open Access Journals (Sweden)

    A. NIŢOAIA

    2016-03-01

    Full Text Available This paper have as object of study the influence of the Cracău and Ozana watersheds shape and position (relation to the range of Stânişoara Mountains, on the amplitude and effects of the August 2005 flash-flood. Another important aspect is the influence and particularities of the atmospheric circulation on the rainfall quantities in the two basins, in the 17th to 20th of August period. Moreover, this study takes into consideration the characteristics of the flood-related elements and it also quantifies the damages produced by the flood itself.

  2. Automated Detection Of Small And Shallow Landslides After The 2010 Madeira Island Flash-Floods In VHR Imagery

    Science.gov (United States)

    Heleno, Sandra; Lousada, Maura; Pereira, Maria Joao; Pina, Pedro

    2013-12-01

    In this paper we use very high spatial resolution images (GeoEye-1, 0.5m/pixel and orthophotos with 0.4m/pixel) acquired before and after the February 20, 2010 flash-floods in Madeira Island, to test several automated detection methods, seeking for a robust approach able to produce a detailed and complete identification of landslides. We perform an accurate segmentation (delineation of contours) of all the structures (objects) resolved in the remotely sensed images, aiming at landslides scars about tens of squared-metres in area. The best classification performance of segmented objects into landslides/non- landslides is obtained through the combined use of watershed transform for segmentation and support vector machine for classification. We present our preliminary findings, supported and validated by in-situ measurements in different locations of Funchal basin.

  3. Rural livelihoods and household adaptation to extreme flooding in the Okavango Delta, Botswana

    Science.gov (United States)

    Motsholapheko, M. R.; Kgathi, D. L.; Vanderpost, C.

    Adaptation to flooding is now widely adopted as an appropriate policy option since flood mitigation measures largely exceed the capability of most developing countries. In wetlands, such as the Okavango Delta, adaptation is more appropriate as these systems serve as natural flood control mechanisms. The Okavango Delta system is subject to annual variability in flooding with extreme floods resulting in adverse impacts on rural livelihoods. This study therefore seeks to improve the general understanding of rural household livelihood adaptation to extreme flooding in the Okavango Delta. Specific objectives are: (1) to assess household access to forms of capital necessary for enhanced capacity to adapt, (2) to assess the impacts of extreme flooding on household livelihoods, and (3) to identify and assess household livelihood responses to extreme flooding. The study uses the sustainable livelihood and the socio-ecological frameworks to analyse the livelihood patterns and resilience to extreme flooding. Results from a survey of 623 households in five villages, key informant interviews, focus group discussions and review of literature, indicate that access to natural capital was generally high, but low for financial, physical, human and social capital. Households mainly relied on farm-based livelihood activities, some non-farm activities, limited rural trade and public transfers. In 2004 and 2009, extreme flooding resulted in livelihood disruptions in the study areas. The main impacts included crop damage, household displacement, destruction of household property, livestock drowning and mud-trapping, the destruction of public infrastructure and disruption of services. The main household coping strategies were labour switching to other livelihood activities, temporary relocation to less affected areas, use of canoes for early harvesting or evacuation and government assistance, particularly for the most vulnerable households. Household adaptive strategies included

  4. Rapid attribution of the August 2016 flood-inducing extreme precipitation in south Louisiana to climate change

    Science.gov (United States)

    van der Wiel, Karin; Kapnick, Sarah B.; van Oldenborgh, Geert Jan; Whan, Kirien; Philip, Sjoukje; Vecchi, Gabriel A.; Singh, Roop K.; Arrighi, Julie; Cullen, Heidi

    2017-02-01

    A stationary low pressure system and elevated levels of precipitable water provided a nearly continuous source of precipitation over Louisiana, United States (US), starting around 10 August 2016. Precipitation was heaviest in the region broadly encompassing the city of Baton Rouge, with a 3-day maximum found at a station in Livingston, LA (east of Baton Rouge), from 12 to 14 August 2016 (648.3 mm, 25.5 inches). The intense precipitation was followed by inland flash flooding and river flooding and in subsequent days produced additional backwater flooding. On 16 August, Louisiana officials reported that 30 000 people had been rescued, nearly 10 600 people had slept in shelters on the night of 14 August and at least 60 600 homes had been impacted to varying degrees. As of 17 August, the floods were reported to have killed at least 13 people. As the disaster was unfolding, the Red Cross called the flooding the worst natural disaster in the US since Super Storm Sandy made landfall in New Jersey on 24 October 2012. Before the floodwaters had receded, the media began questioning whether this extreme event was caused by anthropogenic climate change. To provide the necessary analysis to understand the potential role of anthropogenic climate change, a rapid attribution analysis was launched in real time using the best readily available observational data and high-resolution global climate model simulations. The objective of this study is to show the possibility of performing rapid attribution studies when both observational and model data and analysis methods are readily available upon the start. It is the authors' aspiration that the results be used to guide further studies of the devastating precipitation and flooding event. Here, we present a first estimate of how anthropogenic climate change has affected the likelihood of a comparable extreme precipitation event in the central US Gulf Coast. While the flooding event of interest triggering this study occurred in south

  5. Investigating the role of geology in the hydrological response of Mediterranean catchments prone to flash-floods: Regional modelling study and process understanding

    Science.gov (United States)

    Vannier, Olivier; Anquetin, Sandrine; Braud, Isabelle

    2016-10-01

    In this study, a regional distributed hydrological model is used to perform long-term and flash-flood event simulations, over the Cévennes-Vivarais region (south of France). The objective is to improve our understanding on the role played by geology on the hydrological processes of catchments during two past flash-flood events. This modelling work is based on Vannier et al. ("Regional estimation of catchment-scale soil properties by means of streamflow recession analysis for use in distributed hydrological models", Hydrological Processes, 2014), where streamflow recessions are analysed to estimate the thickness and hydraulic conductivity of weathered rock layers, depending on the geological nature of catchments. Weathered rock layers are thus implemented into the hydrological model CVN-p, and the contribution of these layers is assessed during flash-flood events simulations as well as during inter-event periods. The model is used without any calibration, to test hypotheses on the active hydrological processes. The results point out two different hydrological behaviours, depending on the geology: on crystalline rocks (granite and gneiss), the addition of a weathered rock layer considerably improves the simulated discharges, during flash-flood events as well as during recession periods, and makes the model able to remarkably reproduce the observed streamflow dynamics. For other geologies (schists especially), the benefits are real, but not sufficient to properly simulate the observed streamflow dynamics. These results probably underline the existence of poorly known processes (flow paths, non-linear spilling process) associated with the planar structure of schisty rocks. On a methodological point of view, this study proposes a simple way to account for the additional storage associated with each geological entity, through the addition of a weathered porous rock layer situated below the traditionally-considered upper soil horizons, and shows its applicability and

  6. The potential of radar-based ensemble forecasts for flash-flood early warning in the southern Swiss Alps

    Directory of Open Access Journals (Sweden)

    K. Liechti

    2013-10-01

    Full Text Available This study explores the limits of radar-based forecasting for hydrological runoff prediction. Two novel radar-based ensemble forecasting chains for flash-flood early warning are investigated in three catchments in the southern Swiss Alps and set in relation to deterministic discharge forecasts for the same catchments. The first radar-based ensemble forecasting chain is driven by NORA (Nowcasting of Orographic Rainfall by means of Analogues, an analogue-based heuristic nowcasting system to predict orographic rainfall for the following eight hours. The second ensemble forecasting system evaluated is REAL-C2, where the numerical weather prediction COSMO-2 is initialised with 25 different initial conditions derived from a four-day nowcast with the radar ensemble REAL. Additionally, three deterministic forecasting chains were analysed. The performance of these five flash-flood forecasting systems was analysed for 1389 h between June 2007 and December 2010 for which NORA forecasts were issued, due to the presence of orographic forcing. A clear preference was found for the ensemble approach. Discharge forecasts perform better when forced by NORA and REAL-C2 rather then by deterministic weather radar data. Moreover, it was observed that using an ensemble of initial conditions at the forecast initialisation, as in REAL-C2, significantly improved the forecast skill. These forecasts also perform better then forecasts forced by ensemble rainfall forecasts (NORA initialised form a single initial condition of the hydrological model. Thus the best results were obtained with the REAL-C2 forecasting chain. However, for regions where REAL cannot be produced, NORA might be an option for forecasting events triggered by orographic precipitation.

  7. Small-scale (flash) flood early warning in the light of operational requirements: opportunities and limits with regard to user demands, driving data, and hydrologic modeling techniques

    Science.gov (United States)

    Philipp, Andy; Kerl, Florian; Büttner, Uwe; Metzkes, Christine; Singer, Thomas; Wagner, Michael; Schütze, Niels

    2016-05-01

    In recent years, the Free State of Saxony (Eastern Germany) was repeatedly hit by both extensive riverine flooding, as well as flash flood events, emerging foremost from convective heavy rainfall. Especially after a couple of small-scale, yet disastrous events in 2010, preconditions, drivers, and methods for deriving flash flood related early warning products are investigated. This is to clarify the feasibility and the limits of envisaged early warning procedures for small catchments, hit by flashy heavy rain events. Early warning about potentially flash flood prone situations (i.e., with a suitable lead time with regard to required reaction-time needs of the stakeholders involved in flood risk management) needs to take into account not only hydrological, but also meteorological, as well as communication issues. Therefore, we propose a threefold methodology to identify potential benefits and limitations in a real-world warning/reaction context. First, the user demands (with respect to desired/required warning products, preparation times, etc.) are investigated. Second, focusing on small catchments of some hundred square kilometers, two quantitative precipitation forecasts are verified. Third, considering the user needs, as well as the input parameter uncertainty (i.e., foremost emerging from an uncertain QPF), a feasible, yet robust hydrological modeling approach is proposed on the basis of pilot studies, employing deterministic, data-driven, and simple scoring methods.

  8. Hydrological extremes : Improving simulations of flood and drought in large river basins

    NARCIS (Netherlands)

    Wanders, N.

    2015-01-01

    Hydrological extremes regularly occur in all regions of the world and as such have large impacts on society. Floods and drought are the most severe hydrological extremes, in terms of their societal impact and potential economic damage. These events are amongst the most costly natural disasters, due

  9. Review of trend analysis and climate change projections of extreme precipitation and floods in Europe

    Science.gov (United States)

    Madsen, H.; Lawrence, D.; Lang, M.; Martinkova, M.; Kjeldsen, T. R.

    2014-11-01

    This paper presents a review of trend analysis of extreme precipitation and hydrological floods in Europe based on observations and future climate projections. The review summaries methods and methodologies applied and key findings from a large number of studies. Reported analyses of observed extreme precipitation and flood records show that there is some evidence of a general increase in extreme precipitation, whereas there are no clear indications of significant trends at large-scale regional or national level of extreme streamflow. Several studies from regions dominated by snowmelt-induced peak flows report decreases in extreme streamflow and earlier spring snowmelt peak flows, likely caused by increasing temperature. The review of likely future changes based on climate projections indicates a general increase in extreme precipitation under a future climate, which is consistent with the observed trends. Hydrological projections of peak flows show large impacts in many areas with both positive and negative changes. A general decrease in flood magnitude and earlier spring floods are projected for catchments with snowmelt-dominated peak flows, which is consistent with the observed trends. Finally, existing guidelines in Europe on design flood and design rainfall estimation are reviewed. The review shows that only few countries have developed guidelines that incorporate a consideration of climate change impacts.

  10. Extreme ultraviolet fluorescence spectroscopy of pure and core-shell rare gas clusters at FLASH

    Energy Technology Data Exchange (ETDEWEB)

    Schroedter, Lasse

    2013-08-15

    The interaction of rare gas clusters with short-wavelength radiation of free-electron lasers (FELs) has been studied extensively over the last decade by means of electron and ion time-of-flight spectroscopy. This thesis describes the design and construction of a fluorescence spectrometer for the extreme ultraviolet (XUV) spectral range and discusses the cluster experiments performed at FLASH, the Free-electron LAser in Hamburg. Fluorescence of xenon and of argon clusters was studied, both in dependence on the FEL pulse intensity and on the cluster size. The FEL wavelength was set to the giant 4d-resonance of xenon at 13.5 nm and the FEL pulse intensity reached peak values of 2.7.10{sup 15} W/cm{sup 2}. For xenon clusters, charge states of at least 11+ were identified. For argon, charge states up to 7+ were detected. The cluster-size dependent study revealed a decrease of the fluorescence yield per atom with increasing cluster size. This decrease is explained with the help of a geometric model. It assumes that virtually the entire fluorescence yield stems from shells of ions on the cluster surface, whereas ions in the cluster core predominantly recombine non-radiatively with electrons. However, the detailed analysis of fluorescence spectra from clusters consisting of a core of Xe atoms and a surrounding shell of argon atoms shows that, in fact, a small fraction of the fluorescence signal comes from Xe ions in the cluster core. Interestingly, these ions are as highly charged as the ions in the shells of a pure Xe cluster. This result goes beyond the current understanding of charge and energy transfer processes in these systems and points toward the observation of ultrafast charging dynamics in a time window where mass spectrometry is inherently blind. (orig.)

  11. Capturing spatial and temporal patterns of widespread, extreme flooding across Europe

    Science.gov (United States)

    Busby, Kathryn; Raven, Emma; Liu, Ye

    2013-04-01

    Statistical characterisation of physical hazards is an integral part of probabilistic catastrophe models used by the reinsurance industry to estimate losses from large scale events. Extreme flood events are not restricted by country boundaries which poses an issue for reinsurance companies as their exposures often extend beyond them. We discuss challenges and solutions that allow us to appropriately capture the spatial and temporal dependence of extreme hydrological events on a continental-scale, which in turn enables us to generate an industry-standard stochastic event set for estimating financial losses for widespread flooding. By presenting our event set methodology, we focus on explaining how extreme value theory (EVT) and dependence modelling are used to account for short, inconsistent hydrological data from different countries, and how to make appropriate statistical decisions that best characterise the nature of flooding across Europe. The consistency of input data is of vital importance when identifying historical flood patterns. Collating data from numerous sources inherently causes inconsistencies and we demonstrate our robust approach to assessing the data and refining it to compile a single consistent dataset. This dataset is then extrapolated using a parameterised EVT distribution to estimate extremes. Our method then captures the dependence of flood events across countries using an advanced multivariate extreme value model. Throughout, important statistical decisions are explored including: (1) distribution choice; (2) the threshold to apply for extracting extreme data points; (3) a regional analysis; (4) the definition of a flood event, which is often linked with reinsurance industry's hour's clause; and (5) handling of missing values. Finally, having modelled the historical patterns of flooding across Europe, we sample from this model to generate our stochastic event set comprising of thousands of events over thousands of years. We then briefly

  12. Probabilistic mapping of urban flood risk: Application to extreme events in Surat, India

    Science.gov (United States)

    Ramirez, Jorge; Rajasekar, Umamaheshwaran; Coulthard, Tom; Keiler, Margreth

    2016-04-01

    Surat, India is a coastal city that lies on the banks of the river Tapti and is located downstream from the Ukai dam. Given Surat's geographic location, the population of five million people are repeatedly exposed to flooding caused by high tide combined with large emergency dam releases into the Tapti river. In 2006 such a flood event occurred when intense rainfall in the Tapti catchment caused a dam release near 25,000 m3 s-1 and flooded 90% of the city. A first step towards strengthening resilience in Surat requires a robust method for mapping potential flood risk that considers the uncertainty in future dam releases. Here, in this study we develop many combinations of dam release magnitude and duration for the Ukai dam. Afterwards we use these dam releases to drive a two dimensional flood model (CAESAR-Lisflood) of Surat that also considers tidal effects. Our flood model of Surat utilizes fine spatial resolution (30m) topography produced from an extensive differential global positioning system survey and measurements of river cross-sections. Within the city we have modelled scenarios that include extreme conditions with near maximum dam release levels (e.g. 1:250 year flood) and high tides. Results from all scenarios have been summarized into probabilistic flood risk maps for Surat. These maps are currently being integrated within the city disaster management plan for taking both mitigation and adaptation measures for different scenarios of flooding.

  13. Impacts of a flash flood on drinking water quality: case study of areas most affected by the 2012 Beijing flood.

    Science.gov (United States)

    Sun, Rubao; An, Daizhi; Lu, Wei; Shi, Yun; Wang, Lili; Zhang, Can; Zhang, Ping; Qi, Hongjuan; Wang, Qiang

    2016-02-01

    In this study, we present a method for identifying sources of water pollution and their relative contributions in pollution disasters. The method uses a combination of principal component analysis and factor analysis. We carried out a case study in three rural villages close to Beijing after torrential rain on July 21, 2012. Nine water samples were analyzed for eight parameters, namely turbidity, total hardness, total dissolved solids, sulfates, chlorides, nitrates, total bacterial count, and total coliform groups. All of the samples showed different degrees of pollution, and most were unsuitable for drinking water as concentrations of various parameters exceeded recommended thresholds. Principal component analysis and factor analysis showed that two factors, the degree of mineralization and agricultural runoff, and flood entrainment, explained 82.50% of the total variance. The case study demonstrates that this method is useful for evaluating and interpreting large, complex water-quality data sets.

  14. Impacts of a flash flood on drinking water quality: case study of areas most affected by the 2012 Beijing flood

    Directory of Open Access Journals (Sweden)

    Rubao Sun

    2016-02-01

    Full Text Available In this study, we present a method for identifying sources of water pollution and their relative contributions in pollution disasters. The method uses a combination of principal component analysis and factor analysis. We carried out a case study in three rural villages close to Beijing after torrential rain on July 21, 2012. Nine water samples were analyzed for eight parameters, namely turbidity, total hardness, total dissolved solids, sulfates, chlorides, nitrates, total bacterial count, and total coliform groups. All of the samples showed different degrees of pollution, and most were unsuitable for drinking water as concentrations of various parameters exceeded recommended thresholds. Principal component analysis and factor analysis showed that two factors, the degree of mineralization and agricultural runoff, and flood entrainment, explained 82.50% of the total variance. The case study demonstrates that this method is useful for evaluating and interpreting large, complex water-quality data sets.

  15. Uncertainty assessment of climate change adaptation options in urban flash floods

    DEFF Research Database (Denmark)

    Zhou, Qianqian; Arnbjerg-Nielsen, Karsten

    2012-01-01

    Introduction. Adaptation is necessary to cope with the increasing flood risk in cities due to climate change in many regions of the world. Decision marking of adaptation strategies often requires a comprehensive risk-based economic analysis to indicate the net benefits of proposed options. Priority...

  16. Hydrological analysis of high waters and flash floods occurred in September 2007 in Slovenia

    Energy Technology Data Exchange (ETDEWEB)

    Kobold, M; Susnik, M; Robic, M; Ulaga, F; Lalic, B [Environmental Agency of the Republic of Slovenia, Vojkova lb, SI-1000 Ljubljana (Slovenia)], E-mail: mira.kobold@gov.si

    2008-11-01

    Heavy and intense precipitation which fell in just a few hours across the western, north-western and northern Slovenia on 18 September 2007, caused quick rise of river discharges especially in the region of Baska grapa, Davca, the Cerkljansko and Skofja Loka hills. In that area the streams caused huge destruction on infrastructure, homes, business buildings and other property. More than 300 mm of rain was recorded on some precipitation measurement stations. The return period of the highest precipitation was more than 100 years. The amount of precipitation decreased from the west to the east of the country where above 100 mm of precipitation was recorded and torrential streams and rivers flooded in the region of Karavanke and foothills of the Kamnik-Savinja Alps, Kranj and Domzale fields, the Tuhinj valley and extensive Celje region. Observed discharges of streams and rivers on the most affected area exceeded periodical maximum discharges. The simulation of flood hydrograph for Zelezniki was done by HEC-1 model. The return period of floods was more than 100 years. Besides flooding many landslides were triggered. The result of this catastrophe was enormous economic damage and loss of six people's lives.

  17. Uncertainty assessment of climate change adaptation options in urban flash floods

    DEFF Research Database (Denmark)

    Zhou, Qianqian; Arnbjerg-Nielsen, Karsten

    2012-01-01

    Introduction. Adaptation is necessary to cope with the increasing flood risk in cities due to climate change in many regions of the world. Decision marking of adaptation strategies often requires a comprehensive risk-based economic analysis to indicate the net benefits of proposed options. Priority...

  18. On the link between extreme floods and excess monsoon epochs in South Asia

    Energy Technology Data Exchange (ETDEWEB)

    Kale, Vishwas [University of Pune, Department of Geography, Pune (India)

    2012-09-15

    This paper provides a synoptic view of extreme monsoon floods on all the nine large rivers of South Asia and their association with the excess (above-normal) monsoon rainfall periods. Annual maximum flood series for 18 gauging stations spread over four countries (India, Pakistan, Bangladesh and Nepal) and long-term monsoon rainfall data were analyzed to ascertain whether the extreme floods were clustered in time and whether they coincided with multi-decade excess monsoon rainfall epochs at the basin level. Simple techniques, such as the Cramer's t-test, regression and Mann-Kendall (MK) tests and Hurst method were used to evaluate the trends and patterns of the flood and rainfall series. MK test reveals absence of any long-term tendency in all the series. However, the Cramer's t test and Hurst-Mandelbrot rescaled range statistic provide evidence that both rainfall and flood time series are persistent. Using the Cramer's t-test the excess monsoon epochs for each basin were identified. The excess monsoon periods for different basins were found to be highly asynchronous with respect to duration as well as the beginning and end. Three main conclusions readily emerge from the analyses. Extreme floods (>90th percentile) in South Asia show a tendency to cluster in time. About three-fourth of the extreme floods have occurred during the excess monsoon periods between {proportional_to}1840 and 2000 AD, implying a noteworthy link between the two. The frequency of large floods was higher during the post-1940 period in general and during three decades (1940s, 1950s and 1980s) in particular. (orig.)

  19. Flash floods and debris flow in the city area of Messina, north-east part of Sicily, Italy in October 2009: the case of the Giampilieri catchment

    Directory of Open Access Journals (Sweden)

    G. T. Aronica

    2012-05-01

    Full Text Available This paper concerns the analysis of the 1 October 2009 flash flood and debris flow event caused by a very intense rainfall concentrated over the Messina area. The storm caused severe flash floods in many villages around the city of Messina, such as Giampilieri, Scaletta Zanclea, Altolia Superiore and Molino, with 38 casualties and significant damages to property, buildings, roads and bridges estimated close to 550 million Euro. The main focus of this work is to perform a post event analysis, putting together available meteorological and hydrological data in order to get better insight into temporal and spatial variability of the rain storm, the soil moisture conditions and the consequent flash flood in the Giampilieri catchment. The event was investigated using observed data from a raingauge network. Statistical analysis using GEV distribution was performed and rainfall return period (storm severity was estimated. Further, measured rainfall data and rainfall-runoff modelling were used to estimate soil moisture conditions, to analyse the hydrological behaviour and to reconstruct flood hydrograph. With the help of GIS technology and particularly spatial analysis, the volume of debris which has gone down into the Giampilieri village was also calculated. GIS maps with landslide and material deposit areas were produced and analysed.

  20. Variations of Dissolved Iron in the Amur River During an Extreme Flood Event in 2013

    Institute of Scientific and Technical Information of China (English)

    YAN Baixing; GUAN Jiunian; Vladimir SHESTERKIN; ZHU Hui

    2016-01-01

    As a key factor limiting primary productivity in marine ecosystem,dissolved iron (DFe) export from fluvial systems has increased recently.There is particular concern about discharges of DFe during extreme flooding,when they are thought to increase considerably.An extreme flood event that caused inundation of extensive areas of Far Eastern Russia and Northeastern China occurred in the basin of the Amur River during summer and autumn 2013.During this event,water samples were collected in the middle reaches of the Amur River and the lower reaches at Khabarovsk City and analyzed for DFe concentrations and other aquatic parameters.The resuits show that the average DFe concentrations in the middle reaches of the Amur River (right bank) and at Khabarovsk were 1.11 mg/L and 0.32 mg/L,respectively,during the extreme flood in 2013.The total discharge of DFe during the flood event was 6.25 x 104 t.The high discharge of DFe during the flood reflects the elevated discharge of the river,hydrologically connected riparian wetlands,vast quantities of terrestrial runoff,and flood discharges from the Zeya and Bureya reservoirs.These results show that long-term monitoring is needed to identify and assess the impacts of DFe transport on the downstream reaches,estuarine area,and coastal ecosystems of the Amur River.

  1. Brief communication: On-site data collection of damage caused by flash floods: Experiences from Braunsbach, Germany, in May/June 2016

    Science.gov (United States)

    Laudan, Jonas; Rözer, Viktor; Sieg, Tobias; Vogel, Kristin; Thieken, Annegret

    2017-04-01

    At the end of May and beginning of June 2016, several municipalities in Southern Germany suffered from severe flash floods and debris flows which have been triggered by intense rainfall in Central Europe. Overall, the insured losses of these events amounted to EUR 1.2 billion in Germany. Especially the strong and unexpected flash flood on May 29th in Braunsbach (Baden Wurttemberg) - a small village counting about 1,000 residents - attracted media and policymakers due to its devastating character. The understanding of damage caused by flash floods requires ex-post collection of relevant but yet sparsely available information, linking process intensities to damage by using adequate methods of data gathering. Thus, on-site data collection was carried out after the flash flood event in Braunsbach, using open source software as helpful and efficient tool for data acquisition and evaluation. A digital survey was designed and conducted by a team of five researchers who investigated all buildings affected by water and debris flows. The collected data includes an estimation of a particular damage class, the inundation depth, and other relevant information. A post - hoc data analysis was done with R 3.3.1 and QGIS 2.14.3, performing both, a Random Forest Model (RF) and Random Generalized Linear Model (RGLM) as well as preparing a Spearman's rank correlation matrix. For visual interpretation and better overview of the study area and analysis results, a "process intensity" map was created, revealing important links of damage driving factors. We find that not only the water depth, which is often considered as only damage driving factor in riverine flood loss modelling, but also the exposition of a building to the flow direction and susceptible building parts like e.g. shop windows seem to be risk factors in flash-flood prone regions. Although no significant correlations were found, the analyses indicate that also building material (i.e. half-timbered or masonry) and structural

  2. Flash Flood Disasters and Soil Erosion Prevention%山洪灾害防治与水土流失治理浅析

    Institute of Scientific and Technical Information of China (English)

    马美红; 何秉顺; 常凊睿; 杨金鹏; 李明

    2015-01-01

    水土流失是引发山洪灾害、导致生命财产损失和生态环境恶化的重要因素之一,一定程度上会加重山洪灾害的危害程度,结合山洪灾害和水土流失的特点进行综合治理可以起到优化资源配置、减轻山洪灾害损失和促进山洪灾害防治体系建设的作用。基于全国山洪灾害项目以及全国水利普查水土保持情况公报的数据,分析了山洪灾害与水土流失的特点和防治现状,探讨了二者的关系,提出统筹水土保持与山洪灾害防治工作的对策和建议,以期为二者的防御建设工作提供参考。%Soil erosion is one of the most critical factors which causes flash flood disaster, leads to the loss of life and property, and deteriorates the environment. It can increase the damage caused by flash flood disasters to a certain degree. Combining the characteristics of mountain flood disasters and soil erosion can optimize the al ocation of resources, reduce the losses and promote the system construction, which al contribute to improve the flash flood disaster prevention. Based on the data of the flash flood disasters prevention project and the national soil and water conservation census, this paper analyzed the characteristics and current situation of flash flood prevention and water-soil conservation, and further explored their relationship. The strategies and suggestions are proposed which can provide theory and technical reference for the water- soil conservation and mountain flood disaster prevention.

  3. Uncertainty assessment of climate change adaptation options in urban flash floods

    OpenAIRE

    Zhou, Qianqian; Arnbjerg-Nielsen, Karsten

    2011-01-01

    Adaptation is necessary to cope with the increasing flood risk in cities due to anthropogenic climate change in many regions of the world. The choice of adaptation strategies can and should be based on a comprehensive risk-based economic analysis to indicate the net benefits of proposed options. However, the analysis is complicated by irreducible uncertainties about present and future hydrologic conditions as well as the present and future vulnerability of the area in question. Further, model...

  4. The impacts of climatological adjustment of quantitative precipitation estimates on the accuracy of flash flood detection

    Science.gov (United States)

    Zhang, Yu; Reed, Sean; Gourley, Jonathan J.; Cosgrove, Brian; Kitzmiller, David; Seo, Dong-Jun; Cifelli, Robert

    2016-10-01

    The multisensor Quantitative Precipitation Estimates (MQPEs) created by the US National Weather Service (NWS) are subject to a non-stationary bias. This paper quantifies the impacts of climatological adjustment of MQPEs alone, as well as the compound impacts of adjustment and model calibration, on the accuracy of simulated flood peak magnitude and that in detecting flood events. Our investigation is based on 19 watersheds in the mid-Atlantic region of US, which are grouped into small (500 km2) watersheds. NWS archival MQPEs over 1997-2013 for this region are adjusted to match concurrent gauge-based monthly precipitation accumulations. Then raw and adjusted MQPEs serve as inputs to the NWS distributed hydrologic model-threshold frequency framework (DHM-TF). Two experiments via DHM-TF are performed. The first one examines the impacts of adjustment alone through uncalibrated model simulations, whereas the second one focuses on the compound effects of adjustment and calibration on the detection of flood events. Uncalibrated model simulations show broad underestimation of flood peaks for small watersheds and overestimation those for large watersheds. Prior to calibration, adjustment alone tends to reduce the magnitude of simulated flood peaks for small and large basins alike, with 95% of all watersheds experienced decline over 2004-2013. A consequence is that a majority of small watersheds experience no improvement, or deterioration in bias (0% of basins experiencing improvement). By contrast, most (73%) of larger ones exhibit improved bias. Outcomes of the detection experiment show that the role of adjustment is not diminished by calibration for small watersheds, with only 25% of which exhibiting reduced bias after adjustment with calibrated parameters. Furthermore, it is shown that calibration is relatively effective in reducing false alarms (e.g., false alarm rate is down from 0.28 to 0.19 after calibration for small watersheds with calibrated parameters); but its

  5. Weather patterns and hydro-climatological precursors of extreme floods in Switzerland since 1868

    Directory of Open Access Journals (Sweden)

    Peter Stucki

    2012-12-01

    Full Text Available The generation of 24 extreme floods in large catchments of the central Alps is analyzed from instrumental and documentary data, newly digitized observations of precipitation (DigiHom and 20th Century Reanalysis (20CR data. Extreme floods are determined by the 95th percentile of differences between an annual flood and a defined contemporary flood. For a selection of six events between 1868 and 1910, we describe preconditioning elements such as precipitation, temperature, and snow cover anomalies. Specific weather patterns are assessed through a subjective analysis of three-dimensional atmospheric circulation. A focus is placed on synoptic-scale features including mid-tropospheric ascent, low-level moisture transport, propagation of cyclones, and temperature anomalies. We propose a hydro-meteorological classification of all 24 investigated events according to flood-generating weather conditions. Key elements of the upper-level synoptic-scale flow are summarized by five types: (i pivoting cut-off lows, (ii elongated cut-off lows, (iii elongated troughs, (iv waves (with a kink, and (v approximately zonal flow over the Alpine region. We found that the most extreme floods (as above, but ≥ 98th percentile in Switzerland since 1868 were caused by the interaction of severe hydro-climatologic conditions with a flood-inducing weather situation. The 20CR data provide plausible synoptic-scale meteorological patterns leading to heavy precipitation. The proposed catalogue of weather patterns and hydro-climatologic precursors can give direction when anticipating the possibility of severe floods in the Alpine region.

  6. Challenges estimating the return period of extreme floods for reinsurance applications

    Science.gov (United States)

    Raven, Emma; Busby, Kathryn; Liu, Ye

    2013-04-01

    Mapping and modelling extreme natural events is fundamental within the insurance and reinsurance industry for assessing risk. For example, insurers might use a 1 in 100-year flood hazard map to set the annual premium of a property, whilst a reinsurer might assess the national scale loss associated with the 1 in 200-year return period for capital and regulatory requirements. Using examples from a range of international flood projects, we focus on exploring how to define what the n-year flood looks like for predictive uses in re/insurance applications, whilst considering challenges posed by short historical flow records and the spatial and temporal complexities of flood. First, we shall explore the use of extreme value theory (EVT) statistics for extrapolating data beyond the range of observations in a marginal analysis. In particular, we discuss how to estimate the return period of historical flood events and explore the impact that a range of statistical decisions have on these estimates. Decisions include: (1) selecting which distribution type to apply (e.g. generalised Pareto distribution (GPD) vs. generalised extreme value distribution (GEV)); (2) if former, the choice of the threshold above which the GPD is fitted to the data; and (3) the necessity to perform a cluster analysis to group flow peaks to temporally represent individual flood events. Second, we summarise a specialised multivariate extreme value model, which combines the marginal analysis above with dependence modelling to generate industry standard event sets containing thousands of simulated, equi-probable floods across a region/country. These events represent the typical range of anticipated flooding across a region and can be used to estimate the largest or most widespread events that are expected to occur. Finally, we summarise how a reinsurance catastrophe model combines the event set with detailed flood hazard maps to estimate the financial cost of floods; both the full event set and also

  7. The Influence of Flash Flood Disasters on the Surface of Water Environment%暴洪灾害对地表水环境的影响

    Institute of Scientific and Technical Information of China (English)

    孔凡彬

    2013-01-01

    根据2010年8月甘肃舟曲特大泥石流灾害应急监测结果,分析了暴洪灾害对地表水环境产生的主要影响.%According to Gansu zhouqu espcially big mud-rock flow disaster emergency monitoring results, the main influence of the flash flood disaster on surface water enviroment is analyzed.

  8. Flash Flood Hazard Assessment in Coalmine Goaf Catchment%煤矿采空塌陷区山洪危险性评价

    Institute of Scientific and Technical Information of China (English)

    曹琛; 陈剑平; 宋盛渊; 郑莲婧

    2016-01-01

    The analytic hierarchy process ( AHP) and the FFHIS ( flash flood hazard index-based system) were applied for producing flash flood hazard zoning map in Xiqu gully by the ArcGIS software. The proposed index-based system processes information of seven parameters, namely, elevation, coalmine goaf risk zoning, waviness, vegetation types, rainfall intensity, soil types and slope angle. The assignment of different levels in the same parameter was based on the different severity. Based on the weight values, the data was superimposed to obtain the flash flood hazard zoning map. The historical flood events were used for validation. The validation showed that the flash flood hazard zoning map was consistent with the actual situations. The proposed index-based system and method were practical and effective for flash flood hazard assessment in Xiqu Gully.%利用层次分析法和山洪危险性指标体系,将ArcGIS空间分析模块运用到西区沟小流域危险性分区制图中.山洪危险性指标体系包括高程、采空危险分区、起伏度、植被类型、降雨强度、岩土类型和坡度7个指标,根据各指标不同等级影响洪水危险性的严重程度进行赋值.结合指标权重值,将指标系统进行数据叠加,获取山洪危险性分区图.最后将分区结果与历史洪水事件记录做验证对比,其结果与实际情况具有较好的一致性,该方法对西区沟的山洪危险性评价实用有效.

  9. Conjunctively optimizing flash flood control and water quality in urban water reservoirs by model predictive control and dynamic emulation

    Science.gov (United States)

    Galelli, Stefano; Goedbloed, Albert; Schmitter, Petra; Castelletti, Andrea

    2014-05-01

    Urban water reservoirs are a viable adaptation option to account for increasing drinking water demand of urbanized areas as they allow storage and re-use of water that is normally lost. In addition, the direct availability of freshwater reduces pumping costs and diversifies the portfolios of drinking water supply. Yet, these benefits have an associated twofold cost. Firstly, the presence of large, impervious areas increases the hydraulic efficiency of urban catchments, with short time of concentration, increased runoff rates, losses of infiltration and baseflow, and higher risk of flash floods. Secondly, the high concentration of nutrients and sediments characterizing urban discharges is likely to cause water quality problems. In this study we propose a new control scheme combining Model Predictive Control (MPC), hydro-meteorological forecasts and dynamic model emulation to design real-time operating policies that conjunctively optimize water quantity and quality targets. The main advantage of this scheme stands in its capability of exploiting real-time hydro-meteorological forecasts, which are crucial in such fast-varying systems. In addition, the reduced computational requests of the MPC scheme allows coupling it with dynamic emulators of water quality processes. The approach is demonstrated on Marina Reservoir, a multi-purpose reservoir located in the heart of Singapore and characterized by a large, highly urbanized catchment with a short (i.e. approximately one hour) time of concentration. Results show that the MPC scheme, coupled with a water quality emulator, provides a good compromise between different operating objectives, namely flood risk reduction, drinking water supply and salinity control. Finally, the scheme is used to assess the effect of source control measures (e.g. green roofs) aimed at restoring the natural hydrological regime of Marina Reservoir catchment.

  10. Estimating a-priori kinematic wave model parameters based on regionalization for flash flood forecasting in the Conterminous United States

    Science.gov (United States)

    Vergara, Humberto; Kirstetter, Pierre-Emmanuel; Gourley, Jonathan J.; Flamig, Zachary L.; Hong, Yang; Arthur, Ami; Kolar, Randall

    2016-10-01

    This study presents a methodology for the estimation of a-priori parameters of the widely used kinematic wave approximation to the unsteady, 1-D Saint-Venant equations for hydrologic flow routing. The approach is based on a multi-dimensional statistical modeling of the macro scale spatial variability of rating curve parameters using a set of geophysical factors including geomorphology, hydro-climatology and land cover/land use over the Conterminous United States. The main goal of this study was to enable prediction at ungauged locations through regionalization of model parameters. The results highlight the importance of regional and local geophysical factors in uniquely defining characteristics of each stream reach conforming to physical theory of fluvial hydraulics. The application of the estimates is demonstrated through a hydrologic modeling evaluation of a deterministic forecasting system performed on 1672 gauged basins and 47,563 events extracted from a 10-year simulation. Considering the mean concentration time of the basins of the study and the target application on flash flood forecasting, the skill of the flow routing simulations is significantly high for peakflow and timing of peakflow estimation, and shows consistency as indicated by the large sample verification. The resulting a-priori estimates can be used in any hydrologic model that employs the kinematic wave model for flow routing. Furthermore, probabilistic estimates of kinematic wave parameters are enabled based on uncertainty information that is generated during the multi-dimensional statistical modeling. More importantly, the methodology presented in this study enables the estimation of the kinematic wave model parameters anywhere over the globe, thus allowing flood modeling in ungauged basins at regional to global scales.

  11. The Synoptic Model of Widespread Extensive Flash-Flood-Producing Rainstorm Processes in Guangxi%广西大范围致洪暴雨天气模型

    Institute of Scientific and Technical Information of China (English)

    黄香杏; 林开平; 赵江洁

    2001-01-01

    Based on the analysis of spatial and temporal distribution on the flash-flood-producing rainstorm and the features of affecting synoptic systems, the synoptic model of widespread extensive flash-flood-producing rainstorm processes was established and divided into three types, as well. The feature of circle situation and favorable conditions that probably caused the flash-flood-producing rainstorm were given in each type. As a result, the synoptic systems will be useful in forecasting the torrential rainfall processes in the future.%通过致洪暴雨时空分布特点和相应影响天气系统特征的分析,将广西大范围致洪暴雨天气模型分为3个类型,提出各类模型的环流特征、入型条件和致洪暴雨产生的有利条件,为今后制作致洪暴雨预报作出新的尝试。

  12. 五莲县山洪灾害现状、成因及对策%Current Situation, Causes and Countermeasures of Flash Flood Disaster in Wulian County

    Institute of Scientific and Technical Information of China (English)

    朱秀红

    2011-01-01

    According to the analysis of the current situation of flash flood disaster in Wulian county of Shandong province, the author pointed out 5 main factors causing the flash flood disaster, including high rainfall intensity, the special high mountains and steep slopes in mountainous area, imperfection of forecasting and early warning systems, weak defense engineering and human factors. It also put forward some feasible countermeasures, such as general investigation of flash flood losses, designating the disaster zone, determining early warning indicators, constructing monitoring system and making pre -arranged plan and so on.%通过分析山东省五莲县山洪灾害现状,找出引起山洪灾害的5种主要原因,包括降水强度大,山区特有的山高坡陡地形地貌,预测、预报、预警系统不完善,防御工程薄弱,人为因素等,并提出了普查山洪灾害损失、划定灾害区划、确定预警指标、建设监测系统、编制预案等可行对策.

  13. Hydrological extremes : Improving simulations of flood and drought in large river basins

    OpenAIRE

    N. Wanders

    2015-01-01

    Hydrological extremes regularly occur in all regions of the world and as such have large impacts on society. Floods and drought are the most severe hydrological extremes, in terms of their societal impact and potential economic damage. These events are amongst the most costly natural disasters, due to their often large spatial extent and high societal impact. The main objective of this thesis is: To reduce uncertainty in simulations, reanalysis, monitoring, forecasting and projections of hydr...

  14. Predicting Sediment and Cesium-137 Transported to Offsite During Extreme Floods

    Energy Technology Data Exchange (ETDEWEB)

    Bao, Y.

    1999-04-12

    This paper presents the methods and results of a research project for predicting contaminated sediment transport from Oak Ridge Reservation to offside under potential extreme flood conditions. A computer model, Hydrologic Simulation Program--FORTRANE (HSPF), was calibrated and validated for White Oak Creek watershed using a five-year data. The model was then used to quantify the effects of a potential 100-year flood event in terms of the sediment transport and {sup 137}Cs movement. Results from computer simulation showed that during a 100-year flood event the watershed and channel bed became the major sources of the {sup 137}Cs. A 100-year flood event may result in 3.2 Ci of the total annual release of {sup 137}Cs which is six times of the averaged annual release observed during a five-year time period.

  15. Sensitivity of quantitative precipitation forecasts to boundary layer parameterization: a flash flood case study in the Western Mediterranean

    Directory of Open Access Journals (Sweden)

    M. Zampieri

    2005-01-01

    Full Text Available The 'Montserrat-2000' severe flash flood event which occurred over Catalonia on 9 and 10 June 2000 is analyzed. Strong precipitation was generated by a mesoscale convective system associated with the development of a cyclone. The location of heavy precipitation depends on the position of the cyclone, which, in turn, is found to be very sensitive to various model characteristics and initial conditions. Numerical simulations of this case study using the hydrostatic BOLAM and the non-hydrostatic MOLOCH models are performed in order to test the effects of different formulations of the boundary layer parameterization: a modified version of the Louis (order 1 model and a custom version of the E-ℓ (order 1.5 model. Both of them require a diagnostic formulation of the mixing length, but the use of the turbulent kinetic energy equation in the E-ℓ model allows to represent turbulence history and non-locality effects and to formulate a more physically based mixing length. The impact of the two schemes is different in the two models. The hydrostatic model, run at 1/5 degree resolution, is less sensitive, but the quantitative precipitation forecast is in any case unsatisfactory in terms of localization and amount. Conversely, the non-hydrostatic model, run at 1/50 degree resolution, is capable of realistically simulate timing, position and amount of precipitation, with the apparently superior results obtained with the E-ℓ parameterization model.

  16. Forest operations, extreme flooding events, and considerations for hydrologic modeling in the Appalachians--A review

    Science.gov (United States)

    M.A. Eisenbies; W.M. Aust; J.A. Burger; M.B. Adams

    2007-01-01

    The connection between forests and water resources is well established, but the relationships among controlling factors are only partly understood. Concern over the effects of forestry operations, particularly harvesting, on extreme flooding events is a recurrent issue in forest and watershed management. Due to the complexity of the system, and the cost of installing...

  17. Flood-risk mapping: contributions towards an enhanced assessment of extreme events and associated risks

    Directory of Open Access Journals (Sweden)

    B. Büchele

    2006-01-01

    Full Text Available Currently, a shift from classical flood protection as engineering task towards integrated flood risk management concepts can be observed. In this context, a more consequent consideration of extreme events which exceed the design event of flood protection structures and failure scenarios such as dike breaches have to be investigated. Therefore, this study aims to enhance existing methods for hazard and risk assessment for extreme events and is divided into three parts. In the first part, a regionalization approach for flood peak discharges was further developed and substantiated, especially regarding recurrence intervals of 200 to 10 000 years and a large number of small ungauged catchments. Model comparisons show that more confidence in such flood estimates for ungauged areas and very long recurrence intervals may be given as implied by statistical analysis alone. The hydraulic simulation in the second part is oriented towards hazard mapping and risk analyses covering the whole spectrum of relevant flood events. As the hydrodynamic simulation is directly coupled with a GIS, the results can be easily processed as local inundation depths for spatial risk analyses. For this, a new GIS-based software tool was developed, being presented in the third part, which enables estimations of the direct flood damage to single buildings or areas based on different established stage-damage functions. Furthermore, a new multifactorial approach for damage estimation is presented, aiming at the improvement of damage estimation on local scale by considering factors like building quality, contamination and precautionary measures. The methods and results from this study form the base for comprehensive risk analyses and flood management strategies.

  18. The role of the sea on the flash floods events over Liguria (northwestern Italy)

    Science.gov (United States)

    Cassola, F.; Ferrari, F.; Mazzino, A.; Miglietta, M. M.

    2016-04-01

    The sensitivity to sea surface temperature (SST) of small-scale, flood-causing convective systems in Mediterranean coastal areas is analyzed by means of mesoscale numerical simulations. Two different SST initializations are considered: a coarse field provided by a global atmospheric model and a high-resolution multisatellite analysis. Quantitative precipitation forecasts are evaluated for a number of recent severe rainfall episodes in Liguria (northwestern Italy). In several cases, using a higher-resolution SST leads to more realistic precipitation estimates in the forecasting range 36-48 h. In the shorter range, the satellite SST has a limited, or even negative, impact, due to the relatively slow adjustment of initial atmospheric fields. In one case, the satellite SST is beneficial for the only run forced with accurate large-scale initial conditions. The results of this work suggest that a potentially significant improvement in severe precipitation forecasting in the Mediterranean could be achieved using realistic small-scale SST fields.

  19. Quantifying Uncertainty in Distributed Flash Flood Forecasting for a Semiarid Region

    Science.gov (United States)

    Samadi, S.; Pourreza Bilondi, M.; Ghahraman, B.; Akhoond-Ali, A. M.

    2015-12-01

    Reliability of semiarid flood forecasting is affected by several factors, including rainfall forcing, the system input-state-output behavior, initial soil moisture conditions and model parameters and structure. This study employed Bayesian frameworks to enable the explicit description and assessment of parameter and predictive uncertainty for convective rainfall-runoff modeling of a semiarid watershed system in Iran. We examined the performance and uncertainty analysis of a mixed conceptual and physical based rainfall-runoff model (AFFDEF) linked with three Markov chain Monte Carlo (MCMC) samplers: the DiffeRential Evolution Adaptive Metropolis (DREAM), the Shuffled Complex Evolution Metropolis (SCEM-UA), and DREAM- ZS, to forecast four potential semiarid convective events with varying rainfall duration (20 mm). Calibration results demonstrated that model predictive uncertainty was heavily dominated by error and bias in the soil water storage capacity which reflect inadequate representation of the upper soil zone processes by hydrological model. Furthermore, parameters associated with infiltration and interception capacity along with contributing area threshold for digital river network were identified the key model parameters and more influential on the modeled flood hydrograph. In addition, parameter inference in the DREAM model showed a consistent behavior with the priori assumption by closely matching the inferred error distribution to the empirical distribution of the model residual, indicating that model parameters are well identified. DREAM result further revealed that the uncertainty associated with rainfall of lower magnitudes was higher than rainfall of higher magnitudes. Uncertainty quantification of semiarid convective events provided significant insights into the mathematical relationship and characteristics of short-term forecast error and may be applicable to other semiarid watershed systems with the similar rainfall-runoff processes.

  20. A new global dataset with extreme sea levels and its application for assessing flood risk

    Science.gov (United States)

    Muis, Sanne; Verlaan, Martin; Winsemius, Hessel; Aerts, Jeroen; Ward, Philip

    2016-04-01

    Extreme sea levels, caused by storm surges and high tides, can have devastating societal impacts. The global coastal population is faced with an increasing trend in flood risk, induced by socio-economic development and climate change. Without action, the increasing trends in flood hazard and exposure will be associated with catastrophic flood losses in the future. The adequate allocation of global investments in adaptation requires an accurate understanding of the current and future coastal flood risk on a global-scale. Here we present the first global reanalysis of storm surges and extreme sea levels (GTSR dataset) based on dynamical modelling. GTSR covers the entire world's coastline and consists of time series of tides and surges and estimates of extreme values for various return periods. The dataset is based on two different hydrodynamic models: FES2012 for modelling tides, and GSTM for modelling storm surges. GSTM is forced by meteorological fields from ERA-Interim to simulate storm surges for the period 1979-2014. Validation showed that there is very good agreement between modelled and observed sea levels. Only in regions prone to tropical cyclones, extreme sea levels are severely underestimated due to the limited resolution of the meteorological forcing. This will be resolved for future updates of GTSR. As a first application of GSTR, we estimate that 99 million people are exposed to a 1 in 100 year flood. This is almost 40% lower than estimates based the DIVA dataset, another global dataset of extreme sea level. We foresee other applications in assessing impacts of climate change and risk management, such as assessing changes in storminess, estimating the impacts of sea level, and providing warning levels to operational models.

  1. The end of trend-estimation for extreme floods under climate change?

    Science.gov (United States)

    Schulz, Karsten; Bernhardt, Matthias

    2016-04-01

    An increased risk of flood events is one of the major threats under future climate change conditions. Therefore, many recent studies have investigated trends in flood extreme occurences using historic long-term river discharge data as well as simulations from combined global/regional climate and hydrological models. Severe floods are relatively rare events and the robust estimation of their probability of occurrence requires long time series of data (6). Following a method outlined by the IPCC research community, trends in extreme floods are calculated based on the difference of discharge values exceeding e.g. a 100-year level (Q100) between two 30-year windows, which represents prevailing conditions in a reference and a future time period, respectively. Following this approach, we analysed multiple, synthetically derived 2,000-year trend-free, yearly maximum runoff data generated using three different extreme value distributions (EDV). The parameters were estimated from long term runoff data of four large European watersheds (Danube, Elbe, Rhine, Thames). Both, Q100-values estimated from 30-year moving windows, as well as the subsequently derived trends showed enormous variations with time: for example, estimating the Extreme Value (Gumbel) - distribution for the Danube data, trends of Q100 in the synthetic time-series range from -4,480 to 4,028 m³/s per 100 years (Q100 =10,071m³/s, for reference). Similar results were found when applying other extreme value distributions (Weibull, and log-Normal) to all of the watersheds considered. This variability or "background noise" of estimating trends in flood extremes makes it almost impossible to significantly distinguish any real trend in observed as well as modelled data when such an approach is applied. These uncertainties, even though known in principle are hardly addressed and discussed by the climate change impact community. Any decision making and flood risk management, including the dimensioning of flood

  2. Erosion during extreme flood events dominates Holocene canyon evolution in northeast Iceland.

    Science.gov (United States)

    Baynes, Edwin R C; Attal, Mikaël; Niedermann, Samuel; Kirstein, Linda A; Dugmore, Andrew J; Naylor, Mark

    2015-02-24

    Extreme flood events have the potential to cause catastrophic landscape change in short periods of time (10(0) to 10(3) h). However, their impacts are rarely considered in studies of long-term landscape evolution (>10(3) y), because the mechanisms of erosion during such floods are poorly constrained. Here we use topographic analysis and cosmogenic (3)He surface exposure dating of fluvially sculpted surfaces to determine the impact of extreme flood events within the Jökulsárgljúfur canyon (northeast Iceland) and to constrain the mechanisms of bedrock erosion during these events. Surface exposure ages allow identification of three periods of intense canyon cutting about 9 ka ago, 5 ka ago, and 2 ka ago during which multiple large knickpoints retreated large distances (>2 km). During these events, a threshold flow depth was exceeded, leading to the toppling and transportation of basalt lava columns. Despite continuing and comparatively large-scale (500 m(3)/s) discharge of sediment-rich glacial meltwater, there is no evidence for a transition to an abrasion-dominated erosion regime since the last erosive event because the vertical knickpoints have not diffused over time. We provide a model for the evolution of the Jökulsárgljúfur canyon through the reconstruction of the river profile and canyon morphology at different stages over the last 9 ka and highlight the dominant role played by extreme flood events in the shaping of this landscape during the Holocene.

  3. The Impact of the Extreme Amazonian Flood Season on the Incidence of Viral Gastroenteritis Cases.

    Science.gov (United States)

    Vieira, Carmen Baur; de Abreu Corrêa, Adriana; de Jesus, Michele Silva; Luz, Sérgio Luiz Bessa; Wyn-Jones, Peter; Kay, David; Rocha, Mônica Simões; Miagostovich, Marize Pereira

    2017-06-01

    During the Amazonian flood season in 2012, the Negro River reached its highest level in 110 years, submerging residential and commercial areas which appeared associated with an elevation in the observed gastroenteritis cases in the city of Manaus. The aim of this study was to evaluate the microbiological water quality of the Negro River basin during this extreme flood to investigate this apparent association between the illness cases and the population exposed to the contaminated waters. Forty water samples were collected and analysed for classic and emerging enteric viruses. Human adenoviruses, group A rotaviruses and genogroup II noroviruses were detected in 100, 77.5 and 27.5% of the samples, respectively, in concentrations of 10(3)-10(6) GC/L. All samples were compliant with local bacteriological standards. HAdV2 and 41 and RVA G2, P[6], and P[8] were characterised. Astroviruses, sapoviruses, genogroup IV noroviruses, klasseviruses, bocaviruses and aichiviruses were not detected. Statistical analyses showed correlations between river stage level and reported gastroenteritis cases and, also, significant differences between virus concentrations during this extreme event when compared with normal dry seasons and previous flood seasons of the Negro River. These findings suggest an association between the extreme flood experienced and gastrointestinal cases in the affected areas providing circumstantial evidence of causality between the elevations in enteric viruses in surface waters and reported illness.

  4. Before and after Tambora: Extreme floods in the mid-1810s in Hungary

    Science.gov (United States)

    Kiss, Andrea

    2015-04-01

    Either considering the eruption among the potential causes or not, the vicissitudinous times around the year of the Tambora eruption, with a great number of extreme weather events and serious socio-economic consequences, gained and gain relatively great attention among historians in Hungary. Even if in 1816 and partly already in 1815, different areas of the country were affected in different ways (and partly in different times), the number of extraordinary weather-related extremes with great damages, harvest failures and the great food shortage/famine in large areas made these years (combined with preceding bad years) exceptionally difficult. In the presentation 3 main subject areas are addressed: Based on scientific literature and contemporary documentary evidence, a country-wise overview of the presently known evidence mentioning unusual atmospheric phenomena (e.g. dry fog), extreme weather and related events (with special emphasis on great floods) as well as their immediate consequences (e.g. casualties, damages, food-shortage) are provided concerning the years of 1815 and 1816. In the second part of the presentation, through local case studies (from West-, Central-, and Southeast Hungary), floods occurred in the period individual extremes as well as their short- and (if available) long-term consequences are discussed. While short-term consequences mainly appear in the form of casualties and material damages in all study areas, some of the extreme events, for example the great flood of the Tisza river at Szeged (7 months constant flooding btw. Dec. 1815-June 1816, and then an extraordinary huge flood in June 1816), clearly had long-term effects in the area (e.g. in terms of flood protection issues). The years of 1815 and 1816 were part of a multi-annual crisis period in Hungary which - with an increased number of weather extremes, bad harvests, food shortage and in some areas even severe famine as a consequence - can be already detected (at least) from the year

  5. The 2010 Pakistan Flood and the Russia Heat Wave: Teleconnection of Extremes

    Science.gov (United States)

    Lau, William K.; Kim, K. M.

    2010-01-01

    The Pakistan flood and the Russia heat wave/Vvild fires of the summer of2010 were two of the most extreme, and catastrophic events in the histories of the two countries occurring at about the same time. To a casual observer, the timing may just be a random coincidence of nature, because the two events were separated by long distances, and represented opposite forces of nature, i.e., flood vs. drought, and water vs. fire. In this paper, using NASA satellite and NOAA reanalysis data, we presented observation evidences that that the two events were indeed physically connected.

  6. Comparison of regional index flood estimation procedures based on the extreme value type I distribution

    DEFF Research Database (Denmark)

    Kjeldsen, Thomas Rodding; Rosbjerg, Dan

    2002-01-01

    A comparison of different methods for estimating T-year events is presented, all based on the Extreme Value Type I distribution. Series of annual maximum flood from ten gauging stations at the New Zealand South island have been used. Different methods of predicting the 100-year event...... considered applying either a log-linear relationship between at-site mean annual flood and catchment characteristics or a direct log-linear relationship between 100-year events and catchment characteristics. Comparison of the results shows that the existence of at-site measurements significantly diminishes...

  7. Effects of extreme floods on macroinvertebrate assemblages in tributaries to the Mohawk River, New York, USA

    Science.gov (United States)

    Calderon, Mirian R.; Baldigo, Barry P.; Smith, Alexander J.; Endreny, Theodore A.

    2017-01-01

    Climate change is forecast to bring more frequent and intense precipitation to New York which has motivated research into the effects of floods on stream ecosystems. Macroinvertebrate assemblages were sampled at 13 sites in the Mohawk River basin during August 2011, and again in October 2011, following historic floods caused by remnants of Hurricane Irene and Tropical Storm Lee. The annual exceedance probabilities of floods at regional flow-monitoring sites ranged from 0.5 to 0.001. Data from the first 2 surveys, and from additional surveys done during July and October 2014, were assessed to characterize the severity of flood impacts, effect of seasonality, and recovery. Indices of total taxa richness; Ephemeroptera, Plecoptera, and Trichoptera (EPT) richness; Hilsenhoff's biotic index; per cent model affinity; and nutrient biotic index-phosphorus were combined to calculate New York State Biological Assessment Profile scores. Analysis of variance tests were used to determine if the Biological Assessment Profile, its component metrics, relative abundance, and diversity differed significantly (p ≤ .05) among the four surveys. Only total taxa richness and Shannon–Wiener diversity increased significantly, and abundance decreased significantly, following the floods. No metrics differed significantly between the July and August 2014 surveys which indicates that the differences denoted between the August and October 2011 surveys were caused by the floods. Changes in taxa richness, EPT richness, and diversity were significantly correlated with flood annual exceedance probabilities. This study increased our understanding of the resistance and resilience of benthic macroinvertebrate communities by showing that their assemblages were relatively impervious to extreme floods across the region.

  8. Sedimentary structures formed under water surface waves: examples from a sediment-laden flash flood observed by remote camer

    Science.gov (United States)

    Froude, Melanie; Alexander, Jan; Cole, Paul; Barclay, Jenni

    2014-05-01

    On 13-14 October 2012, Tropical Storm Rafael triggered sediment-laden flash floods in the Belham Valley on Montserrat, West Indies. Rainfall was continuous for ~38 hours and intensity peaked at 48 mm/hr. Flow was strongly unsteady, turbulent with sediment concentrations varying up to hyperconcentrated. Time-lapse images captured at >1 frame per second by remote camera overlooking a surveyed valley section show the development of trains of water surface waves at multiple channel locations during different flow stages. Waves grew and diminished in height and remained stationary or migrated upstream. Trains of waves persisted for <5 minutes, until a single wave broke, sometimes initiating the breaking of adjacent waves within the train. Channel-wide surges (bores) propagating downstream with distinct turbulent flow fronts, were observed at irregular intervals during and up to 7 hours after peak stage. These bores are mechanically similar to breaking front tidal bores and arid flood bores, and resulted in a sudden increase in flow depth and velocity. When a bore front came into close proximity (within ~10 m) upstream of a train of water surface waves, the waves appeared to break simultaneously generating a localised surge of water upstream, that was covered by the bore travelling downstream. Those trains in which waves did not break during the passage of a bore temporarily reduced in height. In both cases, water surface waves reformed immediately after the surge in the same location. Deposits from the event, were examined in <4 m deep trenches ~0.5 km downstream of the remote camera. These contained laterally extensive lenticular and sheet-like units comprised of varying admixtures of sand and gravel that are attributed to antidunes, and associated transitions from upper-stage-plane-beds. Some of the structures are organised within concave upward sequences which contain downflow shifts between foreset and backset laminae; interpreted as trough fills from chute

  9. Bayesian objective classification of extreme UK daily rainfall for flood risk applications

    Directory of Open Access Journals (Sweden)

    M. A. Little

    2008-11-01

    Full Text Available In this study we describe an objective classification scheme for extreme UK daily precipitation to be used in flood risk analysis applications. We create a simplified representation of the spatial layout of extreme events based on a new digital archive of UK rainfall. This simplification allows a Bayesian clustering algorithm to compress these representations down to eight prototypical patterns of extreme falls. These patterns are then verified against a five-class, manual, subjective typing scheme, produced independently using known meteorological mechanisms, isohyetal maps and additional descriptive text from the archive. Compared against the manual scheme, the new objective scheme can reproduce the known meteorological conditions, both in terms of spatial layout and seasonal timing, and is shown to be of hydrological relevance when matched to several notable flooding events in the past century. Furthermore, it is computationally simple and straightforward to apply in classifying future extreme rainfall events. We discuss the practical use of this new typing scheme in flood simulations and climate change applications.

  10. Channel response to extreme floods: Insights on controlling factors from six mountain rivers in northern Apennines, Italy

    Science.gov (United States)

    Surian, Nicola; Righini, Margherita; Lucía, Ana; Nardi, Laura; Amponsah, William; Benvenuti, Marco; Borga, Marco; Cavalli, Marco; Comiti, Francesco; Marchi, Lorenzo; Rinaldi, Massimo; Viero, Alessia

    2016-11-01

    This work addresses the geomorphic response of mountain rivers to extreme floods, exploring the relationships between morphological changes and controlling factors. The research was conducted on six tributaries of the Magra River (northern Apennines, Italy) whose catchments were affected by an extreme flood (estimated recurrence interval > 100 years in most of the basins) on 25 October 2011. An integrated approach was deployed to study this flood, including (i) analysis of channel width changes by comparing aerial photographs taken before and after the flood, (ii) estimate of peak discharges in ungauged streams, (iii) detailed mapping of landslides and analysis of their connectivity with the channel network. Channel widening occurred in 35 reaches out of 39. In reaches with channel slope hydraulic variables alone are not sufficient to satisfactorily explain the channel response to extreme floods, and inclusion of other factors such as lateral confinement is needed to increase explanatory capability of regression models. Concerning hydraulic variables, this study showed that the degree of channel widening is more strongly related to unit stream power calculated based on pre-flood channel width than to cross-sectional stream power and to unit stream power calculated with post-flood channel width. This could suggest that most width changes occurred after the flood peak. Finally, in terms of hazard, it is crucial to document the type and magnitude of channel changes, to identify controlling factors, and most importantly, to develop tools enabling us to predict where major geomorphic changes occur during an extreme flood.

  11. A GIS-based model for the hydrological and hydraulic reconstruction of historical flash-floods in urban areas. The case of the river Turia in Valencia (1957)

    Science.gov (United States)

    Portugués Mollá, Iván; Felici, Xavier Bonache i.; Mateu Bellés, Joan F.; Segura, Juan B. Marco

    2015-04-01

    Flash-floods are recurrent events in the Mediterranean arch, mostly derived from cold air pool phenomena triggering hydro-geomorphic high-intensity processes, combining high discharge and low frequency. In urban environments the complexity of the processes become higher due to the existence of very fast-response basins and quick-response runoff. However, immediate activities of cleaning up and restoration delete the urban marks. After a short time both significance and dimension of the hydro-geomorphic event become completely unrecognizable. Nevertheless, these episodes generate extensive administrative documentation which is testimony of the processes in almost real time. Exploiting this source typology in order to reconstruct events far in time within urban areas, which may lack database sufficiently rich, is necessary to understand the hydrological and hydraulic derived processes. This is particularly the case of the Valencia flash-flood (1957), located in the lower Turia River basin (6.400 km2). Within a short interval (15 hours) there were registered two flood peaks (estimated at that time at 2.500 and 3.700 m3/s). The double overflowing inundated a large proportion of the urban area. The flash-flood activated fast processes with high energy that left numerous hydro-geomorphic marks. Although those tracks were deleted in a short while after the flood, it remains a legacy that had not yet been exploited, consisting of immediate aerial and oblique high resolution photography, pictures at street level, water level record and administrative records, such as claim files for compensation. Paradoxically, despite the event is considered as a milestone on metropolitan territorial planning and it was decided to divert the river Turia definitely through a major project (12 km of channeling, known as South Solution), being the scenario notably altered, the analysis of the hydrological and hydraulic process has never been reviewed. Undoubtedly, a modern study would ensure

  12. The influence of non-stationarity in extreme hydrological events on flood frequency estimation

    Directory of Open Access Journals (Sweden)

    Šraj Mojca

    2016-12-01

    Full Text Available Substantial evidence shows that the frequency of hydrological extremes has been changing and is likely to continue to change in the near future. Non-stationary models for flood frequency analyses are one method of accounting for these changes in estimating design values. The objective of the present study is to compare four models in terms of goodness of fit, their uncertainties, the parameter estimation methods and the implications for estimating flood quantiles. Stationary and non-stationary models using the GEV distribution were considered, with parameters dependent on time and on annual precipitation. Furthermore, in order to study the influence of the parameter estimation approach on the results, the maximum likelihood (MLE and Bayesian Monte Carlo Markov chain (MCMC methods were compared. The methods were tested for two gauging stations in Slovenia that exhibit significantly increasing trends in annual maximum (AM discharge series. The comparison of the models suggests that the stationary model tends to underestimate flood quantiles relative to the non-stationary models in recent years. The model with annual precipitation as a covariate exhibits the best goodness-of-fit performance. For a 10% increase in annual precipitation, the 10-year flood increases by 8%. Use of the model for design purposes requires scenarios of future annual precipitation. It is argued that these may be obtained more reliably than scenarios of extreme event precipitation which makes the proposed model more practically useful than alternative models.

  13. Scale orientated analysis of river width changes due to extreme flood hazards

    Directory of Open Access Journals (Sweden)

    G. Krapesch

    2011-08-01

    Full Text Available This paper analyses the morphological effects of extreme floods (recurrence interval >100 years and examines which parameters best describe the width changes due to erosion based on 5 affected alpine gravel bed rivers in Austria. The research was based on vertical aerial photos of the rivers before and after extreme floods, hydrodynamic numerical models and cross sectional measurements supported by LiDAR data of the rivers. Average width ratios (width after/before the flood were calculated and correlated with different hydraulic parameters (specific stream power, shear stress, flow area, specific discharge. Depending on the geomorphological boundary conditions of the different rivers, a mean width ratio between 1.12 (Lech River and 3.45 (Trisanna River was determined on the reach scale. The specific stream power (SSP best predicted the mean width ratios of the rivers especially on the reach scale and sub reach scale. On the local scale more parameters have to be considered to define the "minimum morphological spatial demand of rivers", which is a crucial parameter for addressing and managing flood hazards and should be used in hazard zone plans and spatial planning.

  14. A spatial assessment framework for evaluating flood risk under extreme climates.

    Science.gov (United States)

    Chen, Yun; Liu, Rui; Barrett, Damian; Gao, Lei; Zhou, Mingwei; Renzullo, Luigi; Emelyanova, Irina

    2015-12-15

    Australian coal mines have been facing a major challenge of increasing risk of flooding caused by intensive rainfall events in recent years. In light of growing climate change concerns and the predicted escalation of flooding, estimating flood inundation risk becomes essential for understanding sustainable mine water management in the Australian mining sector. This research develops a spatial multi-criteria decision making prototype for the evaluation of flooding risk at a regional scale using the Bowen Basin and its surroundings in Queensland as a case study. Spatial gridded data, including climate, hydrology, topography, vegetation and soils, were collected and processed in ArcGIS. Several indices were derived based on time series of observations and spatial modeling taking account of extreme rainfall, evapotranspiration, stream flow, potential soil water retention, elevation and slope generated from a digital elevation model (DEM), as well as drainage density and proximity extracted from a river network. These spatial indices were weighted using the analytical hierarchy process (AHP) and integrated in an AHP-based suitability assessment (AHP-SA) model under the spatial risk evaluation framework. A regional flooding risk map was delineated to represent likely impacts of criterion indices at different risk levels, which was verified using the maximum inundation extent detectable by a time series of remote sensing imagery. The result provides baseline information to help Bowen Basin coal mines identify and assess flooding risk when making adaptation strategies and implementing mitigation measures in future. The framework and methodology developed in this research offers the Australian mining industry, and social and environmental studies around the world, an effective way to produce reliable assessment on flood risk for managing uncertainty in water availability under climate change.

  15. High-fidelity numerical modeling of the Upper Mississippi River under extreme flood condition

    Science.gov (United States)

    Khosronejad, Ali; Le, Trung; DeWall, Petra; Bartelt, Nicole; Woldeamlak, Solomon; Yang, Xiaolei; Sotiropoulos, Fotis

    2016-12-01

    We present data-driven numerical simulations of extreme flooding in a large-scale river coupling coherent-structure resolving hydrodynamics with bed morphodynamics under live-bed conditions. The study area is a ∼ 3.2 km long and ∼ 300 m wide reach of the Upper Mississippi River, near Minneapolis MN, which contains several natural islands and man-made hydraulic structures. We employ the large-eddy simulation (LES) and bed-morphodynamic modules of the Virtual Flow Simulator (VFS-Rivers) model, a recently developed in-house code, to investigate the flow and bed evolution of the river during a 100-year flood event. The coupling of the two modules is carried out via a fluid-structure interaction approach using a nested domain approach to enhance the resolution of bridge scour predictions. We integrate data from airborne Light Detection and Ranging (LiDAR), sub-aqueous sonar apparatus on-board a boat and in-situ laser scanners to construct a digital elevation model of the river bathymetry and surrounding flood plain, including islands and bridge piers. A field campaign under base-flow condition is also carried out to collect mean flow measurements via Acoustic Doppler Current Profiler (ADCP) to validate the hydrodynamic module of the VFS-Rivers model. Our simulation results for the bed evolution of the river under the 100-year flood reveal complex sediment transport dynamics near the bridge piers consisting of both scour and refilling events due to the continuous passage of sand dunes. We find that the scour depth near the bridge piers can reach to a maximum of ∼ 9 m. The data-driven simulation strategy we present in this work exemplifies a practical simulation-based-engineering-approach to investigate the resilience of infrastructures to extreme flood events in intricate field-scale riverine systems.

  16. Crossing historical and sedimentary archives to reconstruct an extreme flood event calendar in high alpine areas

    Science.gov (United States)

    Wilhelm, B.; Giguet-Covex, C.; Arnaud, F.; Allignol, F.; Legaz, A.; Melo, A.

    2010-09-01

    to reconstruct a high-resolution flood calendar to assess a reliable frequency of extreme flood events which can be compared with precise climatic parameters as the instrumental and reconstructed temperature. Finally it was equally possible to compare the recorded intensity of flood events between the both archives and thus estimate the hazard perception and vulnerability of local people throughout the last three centuries.

  17. Extremely Soft X-ray Flash as the indicator of off-axis orphan GRB afterglow

    CERN Document Server

    Urata, Yuji; Yamazaki, Ryo; Sakamoto, Takanori

    2015-01-01

    We verified the off-axis jet model of X-ray flashes (XRFs) and examined a discovery of off-axis orphan gamma-ray burst (GRBs) afterglows. The XRF sample was selected on the basis of the following three factors: (1) a constraint on the lower peak energy of the prompt spectrum $E^{src}_{obs}$, (2) redshift measurements, and (3) multi-color observations of an earlier (or brightening) phase. XRF020903 was the only sample selected basis of these criteria. A complete optical multi-color afterglow light curve of XRF020903 obtained from archived data and photometric results in literature showed an achromatic brightening around 0.7 days. An off-axis jet model with a large observing angle (0.21 rad, which is twice the jet opening half-angle, $\\theta_{jet}$) can naturally describe the achromatic brightening and the prompt X-ray spectral properties. This result indicates the existence of off-axis orphan GRB afterglow light curves. Events with a larger viewing angle ($>\\sim2\\theta_{jet}$) could be discovered using an 8-m ...

  18. Extreme floods in the Mekong River Delta under climate change: combined impacts of upstream hydrological changes and sea level rise

    Science.gov (United States)

    Hoang, Long; Nguyen Viet, Dung; Kummu, Matti; Lauri, Hannu; Koponen, Jorma; van Vliet, Michelle T. H.; Supit, Iwan; Leemans, Rik; Kabat, Pavel; Ludwig, Fulco

    2016-04-01

    Extreme floods cause huge damages to human lives and infrastructure, and hamper socio-economic development in the Mekong River Delta in Vietnam. Induced by climate change, upstream hydrological changes and sea level rise are expected to further exacerbate future flood hazard and thereby posing critical challenges for securing safety and sustainability. This paper provides a probabilistic quantification of future flood hazard for the Mekong Delta, focusing on extreme events under climate change. We developed a model chain to simulate separate and combined impacts of two drivers, namely upstream hydrological changes and sea level rise on flood magnitude and frequency. Simulation results show that upstream changes and sea level rise substantially increase flood hazard throughout the whole Mekong Delta. Due to differences in their nature, two drivers show different features in their impacts on floods. Impacts of upstream changes are more dominant in floodplains in the upper delta, causing an increase of up to +0.80 m in flood depth. Sea level rise introduces flood hazard to currently safe areas in the middle and coastal delta zones. A 0.6 m rise in relative sea level causes an increase in flood depth between 0.10 and 0.70 m, depending on location by 2050s. Upstream hydrological changes and sea level rise tend to intensify each other's impacts on floods, resulting in stronger combined impacts than linearly summed impacts of each individual driver. Substantial increase of future flood hazard strongly requires better flood protection and more flood resilient development for the Mekong Delta. Findings from this study can be used as quantified physical boundary conditions to develop flood management strategies and strategic delta management plans.

  19. Extreme flooding in the West African cities of Dakar and Ouagadougou - atmospheric dynamics and implications for flood risk assessments

    Science.gov (United States)

    Engel, Thomas; Fink, Andreas; Knippertz, Peter

    2017-04-01

    In this study, two extreme, high-impact events of heavy rainfall and severe floods in West African urban areas (Ouagadougou in 2009, Dakar in 2012) are investigated in terms of their atmospheric causes and statistical return periods. In terms of the synoptic-convective dynamics, the Ouagadougou case is truly exceptional. A succession of two strong and temporarily slow-moving African Easterly Waves (AEWs) caused record-breaking values of tropospheric moisture and low-level relative vorticity, thereby providing the synoptic forcing for the nighttime genesis of Mesoscale Convective Systems (MCSs). Ouagadougou was hit by two successive MCSs, the latter being possible due to the rotation and swift moisture refuelling by the strong convergence in the AEW-related vortex. It is speculated that this case may allow a glimpse of a new type of extreme Sahelian rainstorms. Similarly to the Ouagadougou case, an AEW was instrumental in the overnight development of an MCSs to the east of Dakar, but neither the AEW vortex nor the tropospheric moisture content was as exceptional as in the Ouagadougou case. The Return Value (RV) analysis suggests that TRMM 3B42 data appears to be suitable to estimate centennial RVs using the "peak-over-threshold" approach with a GPD fit, though the good performance might be a result of errors in estimating extreme rainfall over the arid Sahel. On the contrary PERSIANN-CDR is inappropriate for this purpose, despite having a twice as long observational period. The Ouagadougou event also shows that highly unusual dynamical developments can create extreme situations well outside of any RV estimates from century-long daily rainfall observations.

  20. AP1000{sup R} design robustness against extreme external events - Seismic, flooding, and aircraft crash

    Energy Technology Data Exchange (ETDEWEB)

    Pfister, A.; Goossen, C.; Coogler, K.; Gorgemans, J. [Westinghouse Electric Company LLC, 1000 Westinghouse Drive, Cranberry Township, PA 16066 (United States)

    2012-07-01

    Both the International Atomic Energy Agency (IAEA) and the U.S. Nuclear Regulatory Commission (NRC) require existing and new nuclear power plants to conduct plant assessments to demonstrate the unit's ability to withstand external hazards. The events that occurred at the Fukushima-Dai-ichi nuclear power station demonstrated the importance of designing a nuclear power plant with the ability to protect the plant against extreme external hazards. The innovative design of the AP1000{sup R} nuclear power plant provides unparalleled protection against catastrophic external events which can lead to extensive infrastructure damage and place the plant in an extended abnormal situation. The AP1000 plant is an 1100-MWe pressurized water reactor with passive safety features and extensive plant simplifications that enhance construction, operation, maintenance and safety. The plant's compact safety related footprint and protection provided by its robust nuclear island structures prevent significant damage to systems, structures, and components required to safely shutdown the plant and maintain core and spent fuel pool cooling and containment integrity following extreme external events. The AP1000 nuclear power plant has been extensively analyzed and reviewed to demonstrate that it's nuclear island design and plant layout provide protection against both design basis and extreme beyond design basis external hazards such as extreme seismic events, external flooding that exceeds the maximum probable flood limit, and malicious aircraft impact. The AP1000 nuclear power plant uses fail safe passive features to mitigate design basis accidents. The passive safety systems are designed to function without safety-grade support systems (such as AC power, component cooling water, service water, compressed air or HVAC). The plant has been designed to protect systems, structures, and components critical to placing the reactor in a safe shutdown condition within the steel

  1. Extreme seasonal droughts and floods in Amazonia: causes, trends and impacts

    Science.gov (United States)

    Marengo, J. A.

    2015-12-01

    J. A. Marengo * and J. C. Espinoza** * Centro Nacional de Monitoramento e Alerta de Desastres Naturais, Ministério da Ciência, Tecnologia e Inovação, Sao Paulo, Brazil ** Subdirección de Ciencias de la Atmósfera e Hidrósfera (SCAH), Instituto Geofísico del Perú, Lima, Peru This paper reviews recent progress in the study and understanding of extreme seasonal events in the Amazon region, focusing on drought and floods. The review includes a history of droughts and floods in the past, in the present and some discussions on future extremes in the context of climate change and its impacts on the Amazon region. Several extreme hydrological events, some of them characterized as 'once in a century', have been reported in the Amazon region during the last decade. While abundant rainfall in various sectors of the basin has determined extreme floods along the river's main stem in 1953, 1989, 1999, 2009, 2012-2015, deficient rainfall in 1912, 1926, 1963, 1980, 1983, 1995, 1997, 1998, 2005 and 2010 has caused anomalously low river levels, and an increase in the risk and number of fires in the region, with consequences for humans. This is consistent with changes in the variability of the hydrometeorology of the basin and suggests that extreme hydrological events have been more frequent in the last two decades. Some of these intense/reduced rainfalls and subsequent floods/droughts were associated (but not exclusively) with La Niña/El Niño events. In addition, moisture transport anomalies from the tropical Atlantic into Amazonia, and from northern to southern Amazonia alter the water cycle in the region year-to-year. We also assess the impacts of such extremes on natural and human systems in the region, considering ecological, economic and societal impacts in urban and rural areas, particularly during the recent decades. In the context of the future climate change, studies show a large range of uncertainty, but suggest that drought might intensify through the 21st

  2. Assessment of the effects of multiple extreme floods on flow and transport processes under competing flood protection and environmental management strategies.

    Science.gov (United States)

    Tu, Tongbi; Carr, Kara J; Ercan, Ali; Trinh, Toan; Kavvas, M Levent; Nosacka, John

    2017-07-11

    Extreme floods are regarded as one of the most catastrophic natural hazards and can result in significant morphological changes induced by pronounced sediment erosion and deposition processes over the landscape. However, the effects of extreme floods of different return intervals on the floodplain and river channel morphological evolution with the associated sediment transport processes are not well explored. Furthermore, different basin management action plans, such as engineering structure modifications, may also greatly affect the flood inundation, sediment transport, solute transport and morphological processes within extreme flood events. In this study, a coupled two-dimensional hydrodynamic, sediment transport and morphological model is applied to evaluate the impact of different river and basin management strategies on the flood inundation, sediment transport dynamics and morphological changes within extreme flood events of different magnitudes. The 10-year, 50-year, 100-year and 200-year floods are evaluated for the Lower Cache Creek system in California under existing condition and a potential future modification scenario. Modeling results showed that select locations of flood inundation within the study area tend to experience larger inundation depth and more sediment is likely to be trapped in the study area under potential modification scenario. The proposed two dimensional flow and sediment transport modeling approach implemented with a variety of inflow conditions can provide guidance to decision-makers when considering implementation of potential modification plans, especially as they relate to competing management strategies of large water bodies, such as the modeling area in this study. Copyright © 2017 Elsevier B.V. All rights reserved.

  3. Changing precipitation extremes in a warming climate: A basis for design flood estimation

    Science.gov (United States)

    Wasko, Conrad; Sharma, Ashish

    2016-04-01

    The potential for increasing intensity of future rainfall events has significant implications for flooding and the design of infrastructure. However the questions of how precipitation will change in the future, how important these changes are to flooding, and how engineers incorporate these changes into hydrologic design remain as open questions. In the absence of reliable point based estimates of how precipitation will change, many studies investigate the historical relationship between rainfall intensity and temperature as a proxy for what may happen in a warmer climate. Much of the research to date has focussed on changing precipitation intensity, however, temporal and spatial patterns of precipitation are just as important. Here we link higher temperatures to changes in temporal and spatial patterns of extreme precipitation events. We show, using observed high quality precipitation records from Australia covering all major climatic zones, that storms are intensifying in both time and space resulting in a greater potential for flooding especially in urban locales around the world. Given that precipitation and antecedent conditions are changing, and, the impacts to flooding are significant, methods of incorporating these changes in catchment modelling are required. Continuous simulation offers a natural flexibility to incorporate the many correlated changes in precipitation that may occur in a future climate. An argument for such a framework using existing continuous simulation alternatives is articulated in concluding this presentation.

  4. Ecological Responses to Extreme Flooding Events: A Case Study with a Reintroduced Bird.

    Science.gov (United States)

    Soriano-Redondo, Andrea; Bearhop, Stuart; Cleasby, Ian R; Lock, Leigh; Votier, Stephen C; Hilton, Geoff M

    2016-06-27

    In recent years numerous studies have documented the effects of a changing climate on the world's biodiversity. Although extreme weather events are predicted to increase in frequency and intensity and are challenging to organisms, there are few quantitative observations on the survival, behaviour and energy expenditure of animals during such events. We provide the first data on activity and energy expenditure of birds, Eurasian cranes Grus grus, during the winter of 2013-14, which saw the most severe floods in SW England in over 200 years. We fitted 23 cranes with telemetry devices and used remote sensing data to model flood dynamics during three consecutive winters (2012-2015). Our results show that during the acute phase of the 2013-14 floods, potential feeding areas decreased dramatically and cranes restricted their activity to a small partially unflooded area. They also increased energy expenditure (+15%) as they increased their foraging activity and reduced resting time. Survival did not decline in 2013-14, indicating that even though extreme climatic events strongly affected time-energy budgets, behavioural plasticity alleviated any potential impact on fitness. However under climate change scenarios such challenges may not be sustainable over longer periods and potentially could increase species vulnerability.

  5. Impacts of forced and unforced climate variability on extreme floods using a large climate ensemble

    Science.gov (United States)

    Martel, Jean-Luc; Brissette, François; Chen, Jie

    2016-04-01

    Frequency analysis has been widely used for the inference of flood magnitude and rainfall intensity required in engineering design. However, this inference is based on the concept of stationarity. How accurate is it when taking into account climate variability (i.e. both internal- and externally-forced variabilities)? Even in the absence of human-induced climate change, the short temporal horizon of the historical records renders this task extremely difficult to accomplish. To overcome this situation, large ensembles of simulations from a single climate model can be used to assess the impact of climate variability on precipitation and streamflow extremes. Thus, the objective of this project is to determine the reliability of return period estimates using the CanESM2 large ensemble. The spring flood annual maxima metric over snowmelt-dominated watersheds was selected to take into account the limits of global circulation models to properly simulate convective precipitation. The GR4J hydrological model coupled with the CemaNeige snow model was selected and calibrated using gridded observation datasets on snowmelt-dominated watersheds in Quebec, Canada. Using the hydrological model, streamflows were simulated using bias corrected precipitation and temperature data from the 50 members of CanESM2. Flood frequency analyses on the spring flood annual maxima were then computed using the Gumbel distribution with a 90% confidence interval. The 20-year return period estimates were then compared to assess the impact of natural climate variability over the 1971-2000 return period. To assess the impact of global warming, this methodology was then repeated for three time slices: reference period (1971-2000), near future (2036-2065) and far future (2071-2100). Over the reference period results indicate that the relative error between the return period estimates of two members can be up to 25%. Regarding the near future and far future periods, natural climate variability of extreme

  6. MODIS-based multi-parametric platform for mapping of flood affected areas. Case study: 2006 Danube extreme flood in Romania

    Directory of Open Access Journals (Sweden)

    Craciunescu Vasile

    2016-12-01

    Full Text Available Flooding remains the most widely distributed natural hazard in Europe, leading to significant economic and social impact. Earth observation data is presently capable of making fundamental contributions towards reducing the detrimental effects of extreme floods. Technological advance makes development of online services able to process high volumes of satellite data without the need of dedicated desktop software licenses possible. The main objective of the case study is to present and evaluate a methodology for mapping of flooded areas based on MODIS satellite images derived indices and using state-of-the-art geospatial web services. The methodology and the developed platform were tested with data for the historical flood event that affected the Danube floodplain in 2006 in Romania. The results proved that, despite the relative coarse resolution, MODIS data is very useful for mapping the development flooded area in large plain floods. Moreover it was shown, that the possibility to adapt and combine the existing global algorithms for flood detection to fit the local conditions is extremely important to obtain accurate results.

  7. A low-cost method to measure the timing of post-fire flash floods and debris flows relative to rainfall

    Science.gov (United States)

    Kean, Jason W.; Staley, Dennis M.; Leeper, Robert J.; Schmidt, Kevin Michael; Gartner, Joseph E.

    2012-01-01

    Data on the specific timing of post-fire flash floods and debris flows are very limited. We describe a method to measure the response times of small burned watersheds to rainfall using a low-cost pressure transducer, which can be installed quickly after a fire. Although the pressure transducer is not designed for sustained sampling at the fast rates ({less than or equal to}2 sec) used at more advanced debris-flow monitoring sites, comparisons with high-data rate stage data show that measured spikes in pressure sampled at 1-min intervals are sufficient to detect the passage of most debris flows and floods. Post-event site visits are used to measure the peak stage and identify flow type based on deposit characteristics. The basin response timescale (tb) to generate flow at each site was determined from an analysis of the cross correlation between time series of flow pressure and 5-min rainfall intensity. This timescale was found to be less than 30 minutes for 40 post-fire floods and 11 post-fire debris flows recorded in 15 southern California watersheds ({less than or equal to} 1.4 km2). Including data from 24 other debris flows recorded at 5 more instrumentally advanced monitoring stations, we find there is not a substantial difference in the median tb for floods and debris flows (11 and 9 minutes, respectively); however, there are slight, statistically significant differences in the trends of flood and debris-flow tb with basin area, which are presumably related to differences in flow speed between floods and debris flows.

  8. Impacts of a changing climate on a century of extreme flood regime of northwest Australia

    Directory of Open Access Journals (Sweden)

    A. Rouillard

    2014-10-01

    to be most significant. Here, we sought to identify the main hydroclimatic determinants of the strongly episodic flood regime of a large catchment in the semi-arid, subtropical northwest of Australia and to establish the background of hydrologic variability for the region over the last century. We used a monthly sequence of satellite images to quantify surface water expression on the Fortescue Marsh, the largest water feature of inland northwest Australia, from 1988 to 2012. We used this sequence together with instrumental rainfall data to build a multiple linear model and reconstruct monthly history of floods and droughts since 1912. We found that severe and intense regional rainfall events, as well as the sequence of recharge events both within and between years, determine surface water expression on the floodplain (i.e., total rainfall, number of rain days and carried-over inundated area; R2adj = 0.79; p value ERMSP = 56 km2. The most severe inundation (~1000 km2 over the last century was recorded in 2000. The Fortescue Marsh was completely dry for 32% of all years, for periods of up to four consecutive years. Extremely wet years (seven of the 100 years caused the Marsh to remain inundated for up to 12 months; only 25% of years (9% of all months had floods of greater than 300 km2. Duration, severity and frequency of inundations between 1999 and 2006 were above average and unprecedented when compared to the last century. While there is high inter-annual variability in the system, changes to the flooding regime over the last 20 years suggest that the wetland will become more persistent in response to increased frequency and intensity of extreme rainfall events for the region, which in turn will likely impact on the structure and functioning of this highly specialized ecosystem.

  9. Application of a Coupled WRF-Hydro Model for Extreme Flood Events in the Mediterranean Basins

    Science.gov (United States)

    Fredj, Erick; Givati, Amir

    2015-04-01

    More accurate simulation of precipitation and streamflow is a challenge that can be addressed by using the Weather Research and Forecasting Model (WRF) in conjunction with the hydrological model coupling extension package (WRF-Hydro).This is demonstrated for the country of Israel and surrounding regions. Simulations from the coupled WRF/WRF-Hydro system were verified against measurements from rain gauges and hydrometric stations in the domain for the 2012-2013 and 2013-2014 winters (wet seasons). These periods were characterized by many punctuated hydrometeorological and hydroclimatic events, including both severe drought and extreme floods events. The WRF model simulations were initialized with 0.5 degree NOAA/NCEP GFS model data. The model domain was set up with 3 domains, up to 3km grid spacing resolution. The model configuration used here constitutes a fully distributed, 3-dimensional, variably-saturated surface and subsurface flow model. Application of terrain routing and, subsequently, channel and reservoir routing functions, to the uni-dimensional NOAA land surface model was motivated by the need to account for increased complexity in land surface states and fluxes and to provide a more physically-realistic conceptualization of terrestrial hydrologic processes. The simulation results indicated a good agreement with actual peak discharges for extreme flood events and for full hydrographs. Specifically the coupled WRF/WRF-Hydro model as configured in this study shows improvement in simulated precipitation over one way WRF precipitation simulations. The correlation between the observed and the simulated precipitation using the fully coupled WRF/WRF-Hydro system was higher than the standalone WRF model, especially for convective precipitation events that affect arid regions in the domain. The results suggest that the coupled WRF/WRF-Hydro system has potential for flood forecasting and flood warning purposes at 0-72 hour lead times for large cool season storm

  10. Long-term regimes of extreme precipitation and floods across the Alpine-Carpathian Range

    Science.gov (United States)

    Parajka, Juraj

    2010-05-01

    Kohnová, S.(2), Bálint, G. (8), Barbuc, M.(6), Borga, M.(5), Claps, P. (9), Cheval, S.(4), Gaume, E.(3), Hlavčová, K.(2), Merz, R.(1), Pfaundler, M. (7), Stancalie, G.(4), Szolgay, J.(2), Blöschl, G.(1) (2) Slovak University of Technology, Radlinského 11, 813 68 Bratislava, Slovakia, silvia. kohnova@stuba.sk (3) Laboratoire Central des Ponts et Chaussées, BP 4129, 44341 Bouguenais cedex, France (4) National Meteorological Administration 97, Soseaua Bucuresti-Ploiesti, 013686, Bucharest, Romania (5) Department of Land and Agroforest Environments, University of Padova, AGRIPOLIS,via dell'Università 16, Legnaro (PD), IT-35020, Italy (6) Dynamic and Experimental, Hydrology Department, P.C. 013686 P.B. 18, Sos. Bucuresti-Ploiesti 97, Bucharest, Romania (7)Sektion Gewässerbewirtschaftung Abt. Wasser BAFU, Papiermühlestrasse 172, CH-3063 Ittigen, Switzerland (8) VITUKI Environmental Protection and Water Management Institute, Kvassay út 1., H-1095 Budapest, Hungary (9) Dipartimento di Idraulica, Trasporti e Infrastrutture Civili (DITIC), Politecnico di Torino, C.so Duca degli Abruzzi 24, 10129 Torino (Italy) The study of the seasonality of extreme precipitation and floods has recently attracted renewed interest, especially in connection with water resources management, flood and low flow regionalization, and land cover and climate change assessment studies. The aim of this contribution is to present the differences in the long-term regimes of extreme precipitation and floods across the Alpine-Carpathian range. This analysis is based on seasonality indices and a catalogue of atmospheric circulation patterns. The main investigation will focus on the understanding of main flood producing processes and on the identification of regions with similar precipitation forcing and catchment response. The study region covers the South-Eastern part of France, Switzerland, the northern part of Italy, Austria, the southern part of Germany, Slovakia, Romania and a small region

  11. Geomorphic response to an extreme flood in two Mediterranean rivers (northeastern Sardinia, Italy): Analysis of controlling factors

    Science.gov (United States)

    Righini, Margherita; Surian, Nicola; Wohl, Ellen; Marchi, Lorenzo; Comiti, Francesco; Amponsah, William; Borga, Marco

    2017-08-01

    A high-magnitude, low-frequency flash flood affected two ungauged rivers (northeastern Sardinia, Italy) on 18 November 2013. This study investigates the response of channel reaches in a Mediterranean environment featuring different morphological settings (i.e., alluvial, semialluvial, and bedrock boundaries) with the aims of (i) detecting the morphological effects of this large flood and (ii) analyzing a range of morphological and hydraulic variables as potential controlling factors of channel response. Channel widening was the dominant geomorphic response observed, and it occurred at different magnitudes among the study subreaches. Within individual subreaches, channel width increased from 1.1 to 6.2 times the pre-flood width. A significant trend in channel widening is observed, especially in alluvial subreaches where the narrowest channels were prone to enlarge more compared to the widest channels. Considerable erosion of valley sides also occurred in confined and partly confined semialluvial and bedrock subreaches. A range of parameters influenced the geomorphic role of the flood, and a series of selected morphological and hydraulic controlling factors showed robust correlations with changes in channel width, although correlations were stronger in alluvial subreaches. Analysis and documentation of channel response and its variability through different morphological settings is crucial to provide a basis from which to forecast future river sensitivity to geomorphic adjustment to high-magnitude floods and improve flood management strategies.

  12. 汶川地震后岷江上游山洪发育特征与成因分析%Analysis of Flash Flood Formation Character and Cause in the Upper Reaches of Minjiang River after Wenchuan Earthquake

    Institute of Scientific and Technical Information of China (English)

    丁海容; 李勇; 赵国华; 马超

    2013-01-01

    采用了岷江上游15个水文站的多年径流资料及降雨资料,探析了岷江上游降水量-径流量的相关关系,分析了该流域洪水的变化趋势,在此基础上,分析了该流域2010年“8.13”、“8.18”洪水的发育情况与汶川地震对洪水发育的影响.研究结果表明,汶川地震后,岷江上游震后山洪特征表现为:①岷江上游属于汶川地震带,为该区山洪发育提供了基本条件;②震后植被覆盖率降低是洪水加剧的重要条件;③震后强降水是特大山洪发育的诱发因素;④地震滑坡淤堵河道后溃决,加剧了洪水的突发性、破坏性;⑤震后该流域洪水发生的临界雨量明显降低,洪水量和频率将加大.%"5. 12" Wenchuan earthquake hit the upper reaches zone of Minjiang river, consecutive "8. 13", "8. 18" heavy rainstorm attacked these areas in 2010, which triggered severe post-earthquake flash flood disaster in the earthquake zone. Based on runoff and rainfall data of 15 hydrological stations in the upper reaches zone of the Minjiang river, the rainfall-runoff correlation is analyzed, the flash flood change trend is explored, the formation of "8. 13" , "8. 18" flash flood in 2010 and effect of earthquake on the flash flood is researched. Research results show that, after the Wenchuan earthquake, post-earthquake flash flood in upper reaches of Minjiang river is characterized as following: (1 ) The zone in the upper reaches of Minjiang River belongs to the Wenchuan seismic belt, which provides the essential conditions for the flash flood formation; ( 2) The reduction of vegetation coverage ratio after the earthquake is the important factor to aggravate the flash flood; ( 3 ) Heavy rain is one important factors inducing flash flood; (4) Landslides induced by earthquake block river course and then the dam crevasse, which exacerbated the flash flood emergency and destructivity; ( 5 ) The critical rainfall of flash flood occurrence decreased

  13. International Severe Weather and Flash Flood Hazard Early Warning Systems—Leveraging Coordination, Cooperation, and Partnerships through a Hydrometeorological Project in Southern Africa

    Directory of Open Access Journals (Sweden)

    Robert Jubach

    2016-06-01

    Full Text Available Climate, weather and water hazards do not recognize national boundaries. Transboundary/regional programs and cooperation are essential to reduce the loss of lives and damage to livelihoods when facing these hazards. The development and implementation of systems to provide early warnings for severe weather events such as cyclones and flash floods requires data and information sharing in real time, and coordination among the government agencies at all levels. Within a country, this includes local, municipal, provincial-to-national levels as well as regional and international entities involved in hydrometeorological services and Disaster Risk Reduction (DRR. Of key importance are the National Meteorological and Hydrologic Services (NMHSs. The NMHS is generally the authority solely responsible for issuing warnings for these hazards. However, in many regions of the world, the linkages and interfaces between the NMHS and other agencies are weak or non-existent. Therefore, there is a critical need to assess, strengthen, and formalize collaborations when addressing the concept of reducing risk and impacts from severe weather and floods. The U.S. Agency for International Development/Office of U.S. Foreign Disaster Assistance; the United Nations World Meteorological Organization (WMO; the WMO Southern Africa Regional Specialized Meteorological Center, hosted by the South African Weather Service; the U.S. National Oceanic and Atmospheric Administration/National Weather Service and the Hydrologic Research Center (a non-profit corporation are currently implementing a project working with Southern Africa NMHSs on addressing this gap. The project aims to strengthen coordination and collaboration mechanisms from national to local levels. The project partners are working with the NMHSs to apply and implement appropriate tools and infrastructure to enhance currently operational severe weather and flash flood early warning systems in each country in support of

  14. Impacts of extreme events of drought and flood on local communities of Amazon basin

    Science.gov (United States)

    Borma, L. D.; Roballo, S.; Zauner, M.; Nascimento, V. F.

    2013-05-01

    The analysis of drought events of 1997/98, 2005 and 2010 in terms of discharge anomalies in the Amazon region confirmed previous findings, such as: a) the influence of the El Niño in more than one hydrological year; b) the increase of the influence of the Atlantic Multidecadal Oscillation of 1998, 2005 and 2010 drought events; c) the low levels of discharge observed in the 2010 drought are attributed to the association of discharge anomalies of the northern and southern tributaries of the Amazon river, and d) the 2010 drought lasted around 1 month (August to November) more than the other drought events analized here. The riverine communities located along the river banks of Solimões/Amazonas suit their economic activities to the oscillation of the water level. In general, low water periods favor the access to important sources of food such as fish and livestock, still allowing crop cultivation on fertile agricultural areas of the floodplain. Conversely, periods of drought increases the difficulties of transport and drinking water supply. During the high water, access to the main food supply (described above) are greatly hampered. However, the floods are recognized as an importance process of natural fertilization. Thus, despite the political, social and economic shortcomings, the local community has, since the pre-colonial period, learned to get the best of each season, providing local, regional and national markets with varzea products. During periods of extreme weather, however, the advantages of each season appear to be reduced, and the drawbacks increased. In fact, during flooding extremes, the access to primary sources of food is hampered by a long period of time and families find themselves forced to leave their homes, eventually losing them. Analysis of flow data to the extreme flooding of 2009, indicate a period of about 6 months of positive anomalies discharge (occurring mainly during high water). At the same time, Civil Defense data points to a

  15. Experimental Study of Flash Flood Wave Down a Stepped Channel%山区阶梯河道中洪水波运动特性研究

    Institute of Scientific and Technical Information of China (English)

    杨阳; 曹叔尤; 杨奉广

    2011-01-01

    An experiment was conducted to investigate surging waters down a stepped channel, which was 2.4 m long,0.5 m wide and with a slope of 0.133, for the cases of being roughed and non-roughed.The results showed that at the end of the channel, the dimensionless wave front celerity tends to be constant and its magnitude decreases with the increase of the relative step height h* and the relative roughness height k.In addition, for small bed roughness the increase of the relative step height h* will result in the delay of flash flood propagation and increase of energy dissipation to a certain extend.Large bed roughness will not only severely postpone the flash flood propagation, but also greatly enhance the energy dissipation of the flow.The results of the study may provide some advices on the flash flood defense during the reconstruction in the earthquake-hit area.%为了研究阶梯河道中的山区洪水波运动特性,在阶梯坡面上分别进行了无加糙和用粘贴不同粒径的均匀沙定床加糙的2组系列试验.试验结果表明:阶梯坡面末端无量纲波前速度趋近于常数,其大小不仅随相对阶梯高度h*增加而减小,亦随相对粗糙高度k*增加而减小.此外,床面粗糙程度较小时h*的增大会导致山洪行进时间增加及水流能量消耗的增大;床面大粗糙度不仅对山洪行进具有阻碍作用,而且能很大程度上消耗水流能量.研究结果对山区河道中山洪防治提供了参考.

  16. 厄尔尼诺与广西致洪暴雨的关系%Research on the Relationship Between ENSO Cases and Flash-Flood-Producing Rainstorm in Guangxi

    Institute of Scientific and Technical Information of China (English)

    林开平; 李耀先; 李秀存; 梁隽玫

    2001-01-01

    Based on analyzing the relationship between ENSO cases and the flash-flood-producing rainstorm in Guangxi, the result show that the two of them are close. Most of the flash-flood-producing rainstorms happened during the period of ENSO appearing, or in next year after ENSO cases ended. It was very similar that the variability of occurring frequency during the inter-decade, between ENSO cases and the flash-flood-producing rainstorm in Guangxi. In additional, the causes of the flash-flood-producing rainstorm stimulated by ENSO cases in Guangxi was discussed, as well.%分析了ENSO事件的出现与广西致洪暴雨的关系,结果表明了两者关系密切,广西的致洪暴雨基本上都出现于ENSO事件年或ENSO事件结束后的一年里;ENSO事件的出现频率随年代的变化与广西致洪暴雨出现频率随年代的变化非常吻合。此外,还就厄尔尼诺对广西致洪暴雨形成的可能机制进行探讨。

  17. Geomorphological method in the elaboration of hazard maps for flash-floods in the municipality of Jucuarán (El Salvador

    Directory of Open Access Journals (Sweden)

    C. Fernández-Lavado

    2007-07-01

    Full Text Available This work deals with the elaboration of flood hazard maps. These maps reflect the areas prone to floods based on the effects of Hurricane Mitch in the Municipality of Jucuarán of El Salvador. Stream channels located in the coastal range in the SE of El Salvador flow into the Pacific Ocean and generate alluvial fans. Communities often inhabit these fans can be affected by floods. The geomorphology of these stream basins is associated with small areas, steep slopes, well developed regolite and extensive deforestation. These features play a key role in the generation of flash-floods. This zone lacks comprehensive rainfall data and gauging stations. The most detailed topographic maps are on a scale of 1:25 000. Given that the scale was not sufficiently detailed, we used aerial photographs enlarged to the scale of 1:8000. The effects of Hurricane Mitch mapped on these photographs were regarded as the reference event. Flood maps have a dual purpose (1 community emergency plans, (2 regional land use planning carried out by local authorities. The geomorphological method is based on mapping the geomorphological evidence (alluvial fans, preferential stream channels, erosion and sedimentation, man-made terraces. Following the interpretation of the photographs this information was validated on the field and complemented by eyewitness reports such as the height of water and flow typology. In addition, community workshops were organized to obtain information about the evolution and the impact of the phenomena. The superimposition of this information enables us to obtain a comprehensive geomorphological map. Another aim of the study was the calculation of the peak discharge using the Manning and the paleohydraulic methods and estimates based on geomorphologic criterion. The results were compared with those obtained using the rational method. Significant differences in the order of magnitude of the calculated discharges were noted. The rational method

  18. THE SIGNIFICANT FLASH FLOODS IN VIȘEU RIVER BASIN, ROMANIA. CAUSES AND EFFECTS ON THE FLOODPLAIN

    Directory of Open Access Journals (Sweden)

    SIMA A.

    2015-03-01

    Full Text Available Vișeu’s river basin location and morphometry has offered, over the course of time, favourable conditions to the formation of different types of floods. Their increase over the last time due to climate change and chaotic anthropic activities has led to visible changes of the morphology of the floodplain. The present paper analyses the genetic factors, the significant floods and in particular, the impact of these floods on the floodplain of Vișeu river and its main tributaries, Ruscova, Vaser and Țâșla.

  19. Assessing the impact of climate and land use changes on extreme floods in a large tropical catchment

    Science.gov (United States)

    Jothityangkoon, Chatchai; Hirunteeyakul, Chow; Boonrawd, Kowit; Sivapalan, Murugesu

    2013-05-01

    In the wake of the recent catastrophic floods in Thailand, there is considerable concern about the safety of large dams designed and built some 50 years ago. In this paper a distributed rainfall-runoff model appropriate for extreme flood conditions is used to generate revised estimates of the Probable Maximum Flood (PMF) for the Upper Ping River catchment (area 26,386 km2) in northern Thailand, upstream of location of the large Bhumipol Dam. The model has two components: a continuous water balance model based on a configuration of parameters estimated from climate, soil and vegetation data and a distributed flood routing model based on non-linear storage-discharge relationships of the river network under extreme flood conditions. The model is implemented under several alternative scenarios regarding the Probable Maximum Precipitation (PMP) estimates and is also used to estimate the potential effects of both climate change and land use and land cover changes on the extreme floods. These new estimates are compared against estimates using other hydrological models, including the application of the original prediction methods under current conditions. Model simulations and sensitivity analyses indicate that a reasonable Probable Maximum Flood (PMF) at the dam site is 6311 m3/s, which is only slightly higher than the original design flood of 6000 m3/s. As part of an uncertainty assessment, the estimated PMF is sensitive to the design method, input PMP, land use changes and the floodplain inundation effect. The increase of PMP depth by 5% can cause a 7.5% increase in PMF. Deforestation by 10%, 20%, 30% can result in PMF increases of 3.1%, 6.2%, 9.2%, respectively. The modest increase of the estimated PMF (to just 6311 m3/s) in spite of these changes is due to the factoring of the hydraulic effects of trees and buildings on the floodplain as the flood situation changes from normal floods to extreme floods, when over-bank flows may be the dominant flooding process, leading

  20. Assessing the Impacts of Flooding Caused by Extreme Rainfall Events Through a Combined Geospatial and Numerical Modeling Approach

    Science.gov (United States)

    Santillan, J. R.; Amora, A. M.; Makinano-Santillan, M.; Marqueso, J. T.; Cutamora, L. C.; Serviano, J. L.; Makinano, R. M.

    2016-06-01

    In this paper, we present a combined geospatial and two dimensional (2D) flood modeling approach to assess the impacts of flooding due to extreme rainfall events. We developed and implemented this approach to the Tago River Basin in the province of Surigao del Sur in Mindanao, Philippines, an area which suffered great damage due to flooding caused by Tropical Storms Lingling and Jangmi in the year 2014. The geospatial component of the approach involves extraction of several layers of information such as detailed topography/terrain, man-made features (buildings, roads, bridges) from 1-m spatial resolution LiDAR Digital Surface and Terrain Models (DTM/DSMs), and recent land-cover from Landsat 7 ETM+ and Landsat 8 OLI images. We then used these layers as inputs in developing a Hydrologic Engineering Center Hydrologic Modeling System (HEC HMS)-based hydrologic model, and a hydraulic model based on the 2D module of the latest version of HEC River Analysis System (RAS) to dynamically simulate and map the depth and extent of flooding due to extreme rainfall events. The extreme rainfall events used in the simulation represent 6 hypothetical rainfall events with return periods of 2, 5, 10, 25, 50, and 100 years. For each event, maximum flood depth maps were generated from the simulations, and these maps were further transformed into hazard maps by categorizing the flood depth into low, medium and high hazard levels. Using both the flood hazard maps and the layers of information extracted from remotely-sensed datasets in spatial overlay analysis, we were then able to estimate and assess the impacts of these flooding events to buildings, roads, bridges and landcover. Results of the assessments revealed increase in number of buildings, roads and bridges; and increase in areas of land-cover exposed to various flood hazards as rainfall events become more extreme. The wealth of information generated from the flood impact assessment using the approach can be very useful to the

  1. Prediction of extreme floods in the Central Andes by means of Complex Networks

    Science.gov (United States)

    Boers, Niklas; Bookhagen, Bodo; Barbosa, Henrique; Marwan, Norbert; Kurths, Jürgen; Marengo, Jose

    2014-05-01

    Based on a non-linear synchronisation measure and complex network theory, we present a novel framework for the prediction of extreme events of spatially embedded, interrelated time series. This method is general in the sense that it can be applied to any type of spatially sampled time series with significant interrelations, ranging from climate observables to biological or stock market data. In this presentation, we apply our method to extreme rainfall in South America and show how this leads to the prediction of more than 60% (90% during El Niño conditions) of extreme rainfall events in the eastern Central Andes of Bolivia and northern Argentina, with only 1% false alarms. From paleoclimatic to decadal time scales, the Central Andes continue to be subject to pronounced changes in climatic conditions. In particular, our and past work shows that frequency as well as magnitudes of extreme rainfall events have increased significantly during past decades, calling for a better understanding of the involved climatic mechanisms. Due to their large spatial extend and occurrence at high elevations, these extreme events often lead to severe floods and landslides with disastrous socioeconomic impacts. They regularly affect tens of thousands of people and produce estimated costs of the order of several hundred million USD. Alongside with the societal value of predicting natural hazards, our study provides insights into the responsible climatic features and suggests interactions between Rossby waves in polar regions and large scale (sub-)tropical moisture transport as a driver of subseasonal variability of the South American monsoon system. Predictable extreme events result from the propagation of extreme rainfall from the region of Buenos Aires towards the Central Andes given characteristic atmospheric conditions. Our results indicate that the role of frontal systems originating from Rossby waves in polar latitudes is much more dominant for controlling extreme rainfall in

  2. Hydroclimatology of Extreme Precipitation and Floods Originating from the North Atlantic Ocean

    Science.gov (United States)

    Nakamura, Jennifer

    This study explores seasonal patterns and structures of moisture transport pathways from the North Atlantic Ocean and the Gulf of Mexico that lead to extreme large-scale precipitation and floods over land. Storm tracks, such as the tropical cyclone tracks in the Northern Atlantic Ocean, are an example of moisture transport pathways. In the first part, North Atlantic cyclone tracks are clustered by the moments to identify common traits in genesis locations, track shapes, intensities, life spans, landfalls, seasonal patterns, and trends. The clustering results of part one show the dynamical behavior differences of tropical cyclones born in different parts of the basin. Drawing on these conclusions, in the second part, statistical track segment model is developed for simulation of tracks to improve reliability of tropical cyclone risk probabilities. Moisture transport pathways from the North Atlantic Ocean are also explored though the specific regional flood dynamics of the U.S. Midwest and the United Kingdom in part three of the dissertation. Part I. Classifying North Atlantic Tropical Cyclones Tracks by Mass Moments. A new method for classifying tropical cyclones or similar features is introduced. The cyclone track is considered as an open spatial curve, with the wind speed or power information along the curve considered as a mass attribute. The first and second moments of the resulting object are computed and then used to classify the historical tracks using standard clustering algorithms. Mass moments allow the whole track shape, length and location to be incorporated into the clustering methodology. Tropical cyclones in the North Atlantic basin are clustered with K-means by mass moments producing an optimum of six clusters with differing genesis locations, track shapes, intensities, life spans, landfalls, seasonality, and trends. Even variables that are not directly clustered show distinct separation between clusters. A trend analysis confirms recent conclusions

  3. Taming the Mighty Mississippi: Integrating paleo-flood data and modeling to understand the patterns and causes of extreme floods on a major river system

    Science.gov (United States)

    Munoz, Samuel; Giosan, Liviu; Jeffrey, Donnelly; Dee, Sylvia; Shen, Zhixiong

    2016-04-01

    The Mississippi River is an economic artery of the United States that is heavily managed to provide flood control and maintain a navigable shipping channel. The current system of levees and spillway structures was conceived in the early 20th century, but the ability of this system to withstand the altered hydroclimatic conditions projected for the next century is poorly understood. Here, we present initial results from a project that integrates new sedimentary records from floodplain lakes with analyses of sediment geochemistry and climate model simulations to better understand the causes of extreme floods on the lower Mississippi River. In our sedimentary paleoflood records, flood event beds are characterized by an upward fining sequence from deposition of the bedload and suspended load during overbank floods, identified here using high-resolution laser particle-size analysis and elemental composition (XRF), and dated using radioisotopes (137Cs, 210Pb, 14C) and optically-stimulated luminescence (OSL) on quartz. Grain-size descriptors and elemental ratios of Zr/Fe and Fe/Rb are highly correlated, and are used alongside historical discharge records to develop a statistical model for reconstructing flood magnitude in prehistoric contexts. Geochemical analyses of sediments from the floodplains of major tributaries of the Mississippi are used to assess the systematics of 87Sr/86Sr, 143Nd/144Nd, 206Pb/204Pb, and 208Pb/204Pb across the basin, enabling identification of the synoptic patterns of individual paleo-flood events. We investigate the dynamical drivers of past floods on the lower Mississippi using both reanalysis data and the last millennium simulation from NCAR model CESM1 to find that increased likelihoods of extreme floods on the lower Mississippi River are associated with enhanced moisture flux over midcontinental North America that is controlled by the interaction of seasonally variable soil moisture over major tributaries with inter-annual (e.g., ENSO) and

  4. Poster abstract: Water level estimation in urban ultrasonic/passive infrared flash flood sensor networks using supervised learning

    KAUST Repository

    Mousa, Mustafa

    2014-04-01

    This article describes a machine learning approach to water level estimation in a dual ultrasonic/passive infrared urban flood sensor system. We first show that an ultrasonic rangefinder alone is unable to accurately measure the level of water on a road due to thermal effects. Using additional passive infrared sensors, we show that ground temperature and local sensor temperature measurements are sufficient to correct the rangefinder readings and improve the flood detection performance. Since floods occur very rarely, we use a supervised learning approach to estimate the correction to the ultrasonic rangefinder caused by temperature fluctuations. Preliminary data shows that water level can be estimated with an absolute error of less than 2 cm. © 2014 IEEE.

  5. A climate-based multivariate extreme emulator of met-ocean-hydrological events for coastal flooding

    Science.gov (United States)

    Camus, Paula; Rueda, Ana; Mendez, Fernando J.; Tomas, Antonio; Del Jesus, Manuel; Losada, Iñigo J.

    2015-04-01

    Atmosphere-ocean general circulation models (AOGCMs) are useful to analyze large-scale climate variability (long-term historical periods, future climate projections). However, applications such as coastal flood modeling require climate information at finer scale. Besides, flooding events depend on multiple climate conditions: waves, surge levels from the open-ocean and river discharge caused by precipitation. Therefore, a multivariate statistical downscaling approach is adopted to reproduce relationships between variables and due to its low computational cost. The proposed method can be considered as a hybrid approach which combines a probabilistic weather type downscaling model with a stochastic weather generator component. Predictand distributions are reproduced modeling the relationship with AOGCM predictors based on a physical division in weather types (Camus et al., 2012). The multivariate dependence structure of the predictand (extreme events) is introduced linking the independent marginal distributions of the variables by a probabilistic copula regression (Ben Ayala et al., 2014). This hybrid approach is applied for the downscaling of AOGCM data to daily precipitation and maximum significant wave height and storm-surge in different locations along the Spanish coast. Reanalysis data is used to assess the proposed method. A commonly predictor for the three variables involved is classified using a regression-guided clustering algorithm. The most appropriate statistical model (general extreme value distribution, pareto distribution) for daily conditions is fitted. Stochastic simulation of the present climate is performed obtaining the set of hydraulic boundary conditions needed for high resolution coastal flood modeling. References: Camus, P., Menéndez, M., Méndez, F.J., Izaguirre, C., Espejo, A., Cánovas, V., Pérez, J., Rueda, A., Losada, I.J., Medina, R. (2014b). A weather-type statistical downscaling framework for ocean wave climate. Journal of

  6. Effects of an extreme flood on trace elements in river water—From urban stream to major river basin

    Science.gov (United States)

    Barber, Larry B.; Paschke, Suzanne; Battaglin, William A.; Douville, Chris; Fitzgerald, Kevin C.; Keefe, Steffanie H.; Roth, David A.; Vajda, Alan M.

    2017-01-01

    Major floods adversely affect water quality through surface runoff, groundwater discharge, and damage to municipal water infrastructure. Despite their importance, it can be difficult to assess the effects of floods on streamwater chemistry because of challenges collecting samples and the absence of baseline data. This study documents water quality during the September 2013 extreme flood in the South Platte River, Colorado, USA. Weekly time-series water samples were collected from 3 urban source waters (municipal tap water, streamwater, and wastewater treatment facility effluent) under normal-flow and flood conditions. In addition, water samples were collected during the flood at 5 locations along the South Platte River and from 7 tributaries along the Colorado Front Range. Samples were analyzed for 54 major and trace elements. Specific chemical tracers, representing different natural and anthropogenic sources and geochemical behaviors, were used to compare streamwater composition before and during the flood. The results differentiate hydrological processes that affected water quality: (1) in the upper watershed, runoff diluted most dissolved constituents, (2) in the urban corridor and lower watershed, runoff mobilized soluble constituents accumulated on the landscape and contributed to stream loading, and (3) flood-induced groundwater discharge mobilized soluble constituents stored in the vadose zone.

  7. The December 2008 flood event in Rome: Was it really an extreme event?

    Science.gov (United States)

    Lastoria, B.; Mariani, S.; Casaioli, M.; Bussettini, M.

    2009-04-01

    In mid December 2008, Italy suffered bad weather with heavy snowfall blanketing the north and strong winds and downpours pelting the centre-south. In particular, during the period between 10th and 12th December, intense precipitation struck the Tyrrhenian Sea side of the peninsula, inducing a flood event, which captured the attention of the national and international media, on the Tiber river and on its tributary, the Aniene. The relevance of the event was caused by the actual damages occurred in several zones over Rome area, in particular due to the downpours and to damages which would have occurred if Tiber river had overflowed its banks. The event, which was initially considered as extreme, was indeed severe but not so exceptional as shown by the meteo-hydrological post-event analysis. The peak water level of 12.55 m, recorded on 13th December at 1:30 a.m. (local time) at the Ripetta station, which is situated along the Tiber river in the centre of Rome, was higher than those observed during the last ten years (which to the utmost reached 11.41 m in December 2005). However, it did not reach the historical maximum of 16.90 m observed in 1937. Moreover, on the basis of the Ripetta historical series, such a level is associated to an ordinary flood event. Even if the flood was ordinary, a state of emergency was declared by the Rome's Mayor, since the event caused severe damages by disrupting flight and train services, blocking off major roads leading into Rome, flooding underpasses and sealing off industrial activities sited in the flooded areas, in particular nearby the confluence of the Aniene river with the Tiber river. In addition, hundreds of people were evacuated and a woman died in a her car which was submerged by a wave of water and mud in an underpass. Given these premises, the present work examines the relation between a severe, but not extraordinary, event and the considerable damages that occurred as a consequence. First, the meteorological evolution of

  8. Extreme flood event reconstruction spanning the last century in the El Bibane Lagoon (southeastern Tunisia): a multi-proxy approach

    Science.gov (United States)

    Affouri, Aida; Dezileau, Laurent; Kallel, Nejib

    2017-06-01

    Climate models project that rising atmospheric carbon dioxide concentrations will increase the frequency and the severity of some extreme weather events. The flood events represent a major risk for populations and infrastructures settled on coastal lowlands. Recent studies of lagoon sediments have enhanced our knowledge on extreme hydrological events such as palaeo-storms and on their relation with climate change over the last millennium. However, few studies have been undertaken to reconstruct past flood events from lagoon sediments. Here, the past flood activity was investigated using a multi-proxy approach combining sedimentological and geochemical analysis of surfaces sediments from a southeastern Tunisian catchment in order to trace the origin of sediment deposits in the El Bibane Lagoon. Three sediment sources were identified: marine, fluvial and aeolian. When applying this multi-proxy approach on core BL12-10, recovered from the El Bibane Lagoon, we can see that finer material, a high content of the clay and silt, and a high content of the elemental ratios (Fe / Ca and Ti / Ca) characterise the sedimentological signature of the palaeo-flood levels identified in the lagoonal sequence. For the last century, which is the period covered by the BL12-10 short core, three palaeo-flood events were identified. The age of these flood events have been determined by 210Pb and 137Cs chronology and give ages of AD 1995 ± 6, 1970 ± 9 and 1945 ± 9. These results show a good temporal correlation with historical flood events recorded in southern Tunisia in the last century (AD 1932, 1969, 1979 and 1995). Our finding suggests that reconstruction of the history of the hydrological extreme events during the upper Holocene is possible in this location through the use of the sedimentary archives.

  9. Extreme flood event reconstruction spanning the last century in the El Bibane Lagoon (southeastern Tunisia: a multi-proxy approach

    Directory of Open Access Journals (Sweden)

    A. Affouri

    2017-06-01

    Full Text Available Climate models project that rising atmospheric carbon dioxide concentrations will increase the frequency and the severity of some extreme weather events. The flood events represent a major risk for populations and infrastructures settled on coastal lowlands. Recent studies of lagoon sediments have enhanced our knowledge on extreme hydrological events such as palaeo-storms and on their relation with climate change over the last millennium. However, few studies have been undertaken to reconstruct past flood events from lagoon sediments. Here, the past flood activity was investigated using a multi-proxy approach combining sedimentological and geochemical analysis of surfaces sediments from a southeastern Tunisian catchment in order to trace the origin of sediment deposits in the El Bibane Lagoon. Three sediment sources were identified: marine, fluvial and aeolian. When applying this multi-proxy approach on core BL12-10, recovered from the El Bibane Lagoon, we can see that finer material, a high content of the clay and silt, and a high content of the elemental ratios (Fe ∕ Ca and Ti ∕ Ca characterise the sedimentological signature of the palaeo-flood levels identified in the lagoonal sequence. For the last century, which is the period covered by the BL12-10 short core, three palaeo-flood events were identified. The age of these flood events have been determined by 210Pb and 137Cs chronology and give ages of AD 1995 ± 6, 1970 ± 9 and 1945 ± 9. These results show a good temporal correlation with historical flood events recorded in southern Tunisia in the last century (AD 1932, 1969, 1979 and 1995. Our finding suggests that reconstruction of the history of the hydrological extreme events during the upper Holocene is possible in this location through the use of the sedimentary archives.

  10. NASA Global Flood Mapping System

    Science.gov (United States)

    Policelli, Fritz; Slayback, Dan; Brakenridge, Bob; Nigro, Joe; Hubbard, Alfred

    2017-01-01

    Product utility key factors: Near real time, automated production; Flood spatial extent Cloudiness Pixel resolution: 250m; Flood temporal extent; Flash floods short duration on ground?; Landcover--Water under vegetation cover vs open water

  11. 基于网格流出修正法的山洪演进数值模拟%Numerical simulation of flash flood routing based on grid outflow correction method

    Institute of Scientific and Technical Information of China (English)

    张驰; 张家华; 王浩

    2014-01-01

    As floods often occur in steep terrain and water flow changes rapidly, the calculated values in two-dimensional numerical simulations of flash flood disasters are unstable and even the calculation diverges in the simulation. To solve these problems, we present a grid outflow correction method, which is based on the leap-frog finite difference format. Through circular modification of the outflow rate of the grid, this method ensures mass conservation over the whole process of computation and improves the stability of numerical calculation. While using the local dam bursting model, we conducted mass conservation comparison between the simulated result of the grid outflow correction method and that of the algorithm of the implicit alternating direction. The results show that the grid outflow correction method can ensure simulation accuracy and numerical stability under the conditions of steep terrain and a moving boundary. Based on the proposed method, simulation of the process of the extreme flash flood disaster that occurred in 2010 in Zhouqu County, in Gansu Province was carried out. The comparison of simulation results and the results of remote sensing estimation after the disaster shows that the deviation of the flood evolution time, speed, and impact height were within ±5%, and the evolution path was consistent.%为解决山洪泥石流灾害二维数值模拟中,由地形陡峭、水流量急速变化造成的计算数值不稳定甚至计算发散而得不到结果的问题,提出基于leap-frog有限差分格式的网格流出修正法。该方法通过对网格流出率进行循环修正,确保整个计算过程中的质量守恒,提高数值计算的稳定性。在局部溃坝模型下,将网格流出修正法与隐式交替方向算法进行质量守恒对比,模拟结果表明,网格流出修正法能够确保陡峭地形与动边界条件下的模拟精度与数值计算稳定性。基于网格流出修正法,对2010年发生在甘肃

  12. On the Design of an Intelligent Sensor Network for Flash Flood Monitoring, Diagnosis and Management in Urban Areas

    OpenAIRE

    Anconaa, M; Corradi,N ; Dellacasa, A; Delzanno, G; Dugelay, Jean-Luc; Federici, B; Gourbesville, P; Guerrini, G; La Camera, A; Rosso, P; Stephens, J; Tacchella, A; Zolezzi, H

    2014-01-01

    We propose an intelligent sensor system based on a new sensing methodology, relying also on 3D map reconstruction techniques, for computing with high precision, in real-time and without human intervention the parameters needed for stream-flow computation: water levels, morphology of the streams of all potentially flooded areas by each controlled stream. The collected data will be continuously transmitted, through a communication infrastructure, to software agents designed to compute ...

  13. Human impacts of droughts, floods and other extremes in South Moravia

    Science.gov (United States)

    Dolák, Lukáš; Brázdil, Rudolf; Řezníčková, Ladislava; Valášek, Hubert; Chromá, Kateřina

    2015-04-01

    Chronicles and taxation records related to tax relief for farmers whose livelihoods were affected by droughts, floods and other hydrometeorological extremes (HMEs) in South Moravia (the Czech Republic) in the 17th-20th centuries are used to study the impacts of HMEs on the socio-economic situation of the farmers. The first flood event was reported in 1652 on the River Morava and extraordinary dry years were documented since 1718 - in this year the River Dyje totally dried up. Moreover, downpours, hailstorms, windstorms, late frosts and blizzards caused a great damage during the period studied as well and in many cases had a negative effect to human society. The impacts of HMEs are here classified into three categories: agricultural production, material property and the socio-economic situation of individual farmers. Direct impacts took the form of losses to property, supplies and farming equipment, and further of bad field and fruit yields, depletion of livestock, damage to fields and meadows, lack of water for daily use, watermills and transport and increased threat of wildfires. Simple lack of income, debt, impoverishment, reduction in livestock and deterioration in field fertility were among the longer-term effects. Impacts are discussed with respect to approaches to mitigation of the negative effects of HMEs and to problems associated with obtaining support and in terms of a hierarchy of consequent impacts. A great number of records related to HMEs, preserved in the Moravian Land Archives in Brno and other district South Moravian archives, represents a rich source of data allowing re-discovering of historical natural disasters. The paper embodies a methodological approach that is intended for the analysis of HME impacts in South Moravia from the 17th to the 20th centuries.

  14. Flash-flood potential assessment and mapping by integrating the weights-of-evidence and frequency ratio statistical methods in GIS environment – case study: Bâsca Chiojdului River catchment (Romania)

    Indian Academy of Sciences (India)

    Romulus Costache; Liliana Zaharia

    2017-06-01

    Given the significant worldwide human and economic losses caused due to floods annually, reducing the negative consequences of these hazards is a major concern in development strategies at different spatial scales. A basic step in flood risk management is identifying areas susceptible to flood occurrences. This paper proposes a methodology allowing the identification of areas with high potential of accelerated surface run-off and consequently, of flash-flood occurrences. The methodology involves assessment and mapping in GIS environment of flash flood potential index (FFPI), by integrating two statistical methods: frequency ratio and weights-of-evidence. The methodology was applied for Bâsca Chiojdului River catchment (340 km2), located in the Carpathians Curvature region (Romania). Firstly, the areas with torrential phenomena were identified and the main factors controlling the surface run-off were selected (in this study nine geographical factors were considered). Based on the features of the considered factors, many classes were set for each of them. In the next step, the weights of each class/category of the considered factors were determined, by identifying their spatial relationships with the presence or absence of torrential phenomena. Finally, the weights for each class/category of geographical factors were summarized in GIS, resulting the FFPI values for each of the two statistical methods. These values were divided into five classes of intensity and were mapped. The final results were used to estimate the flash-flood potential and also to identify the most susceptible areas to this phenomenon. Thus, the high and very high values of FFPI characterize more than one-third of the study catchment. The result validation was performed by (i) quantifying the rate of the number of pixels corresponding to the torrential phenomena considered for the study (training area) and for the results’ testing (validating area) and (ii) plotting the ROC (receiver operating

  15. Flash-flood potential assessment and mapping by integrating the weights-of-evidence and frequency ratio statistical methods in GIS environment - case study: Bâsca Chiojdului River catchment (Romania)

    Science.gov (United States)

    Costache, Romulus; Zaharia, Liliana

    2017-06-01

    Given the significant worldwide human and economic losses caused due to floods annually, reducing the negative consequences of these hazards is a major concern in development strategies at different spatial scales. A basic step in flood risk management is identifying areas susceptible to flood occurrences. This paper proposes a methodology allowing the identification of areas with high potential of accelerated surface run-off and consequently, of flash-flood occurrences. The methodology involves assessment and mapping in GIS environment of flash flood potential index (FFPI), by integrating two statistical methods: frequency ratio and weights-of-evidence. The methodology was applied for Bâsca Chiojdului River catchment (340 km2), located in the Carpathians Curvature region (Romania). Firstly, the areas with torrential phenomena were identified and the main factors controlling the surface run-off were selected (in this study nine geographical factors were considered). Based on the features of the considered factors, many classes were set for each of them. In the next step, the weights of each class/category of the considered factors were determined, by identifying their spatial relationships with the presence or absence of torrential phenomena. Finally, the weights for each class/category of geographical factors were summarized in GIS, resulting the FFPI values for each of the two statistical methods. These values were divided into five classes of intensity and were mapped. The final results were used to estimate the flash-flood potential and also to identify the most susceptible areas to this phenomenon. Thus, the high and very high values of FFPI characterize more than one-third of the study catchment. The result validation was performed by (i) quantifying the rate of the number of pixels corresponding to the torrential phenomena considered for the study (training area) and for the results' testing (validating area) and (ii) plotting the ROC (receiver operating

  16. Predicting the flow in the floodplains with evolving land occupations during extreme flood events (FlowRes ANR project

    Directory of Open Access Journals (Sweden)

    Proust Sébastien

    2016-01-01

    Full Text Available Flood hazards (flow depth and velocity must be accurately assessed in high-risk areas during extreme flood events. However, the prediction of the very high flows is not an easy task due to the lack of field data and to the strong link between flow resistance and the land occupation of the floodplain. Confinement and inhomogeneity in lateral and longitudinal directions of hydraulic roughness strongly vary with return period T. The physical processes are complex, some still largely unexplored, and the assumptions linked to numerical modelling cannot be validated without field data. The FlowRes project (2015-2018, funded by the French National Research Agency (ANR, aims at improving the flood hazard assessment in floodplains in: 1 investigating in laboratory the hydrodynamic structure associated with extreme flood flows for various land occupations and flow discharge magnitudes; 2 assessing if the existing numerical modelling practices used for T ~ 100 years are still valid for extreme events with T > 1000 years, relying on the experimental data and on one field case. This paper reports some results obtained during the first year of the project.

  17. Characterising the Geomorphic Response of a Tropical Mega-River to an Extreme, Cyclone Induced, Flood Event.

    Science.gov (United States)

    Hackney, C. R.; Leyland, J.; Darby, S. E.; Parsons, D. R.; Aalto, R. E.; Nicholas, A. P.; Best, J.

    2014-12-01

    Extreme events have the ability to induce extensive geomorphic change in fluvial systems as a result of elevated discharge levels, increased sediment transport capacity and associated changes in sheer stresses along channel boundaries. Understanding how rapid rises in water levels change flow structures and channel boundary roughness is key to understanding the relative significance of large events in terms of driving local and system wide geomorphic change. However, capturing the fluvial process dynamics in operation during such events is technically and logistically difficult, especially in the world's largest rivers. During September 2013, on the peak of the monsoon, a series of tropical cyclones induced a large flood event within the Mekong basin. At the peak of the flood wave, discharge measured ~60000 m3/s; the 11th largest flood on record. Pre and post event high resolution topographic surveys of parts of the bed and bank were captured using a combination of contiguous multibeam echo sounding (MBES) and terrestrial laser scanning (TLS) during the event. Simultaneously detailed measurements of cross sectional and near bank flow structure were acquired using an acoustic Doppler current profiler (aDcp). Together, these unique datasets can be used to characterise and assess the geomorphic impact of a cyclone induced extreme flood event on the Mekong. We show how flow structures in the near bank region evolve with stage during the extreme event and how the associated geomorphic response is modulated by the distinctive process dynamics of a mega-river.

  18. Effects of pool formation and flash flooding on relative abundance of young-of-year flannelmouth suckers in the Paria River, Arizona

    Science.gov (United States)

    Thieme, Michele L.; McIvor, C.C.; Brouder, Mark J.; Hoffnagle, T.L.

    2001-01-01

    Flannelmouth sucker, Catostomus latipinnis, a fish endemic to the Colorado River basin in the western United States, appears to experience poor recruitment to adult size in the Colorado River, downstream of Glen Canyon Dam. Lack or impermanence of rearing areas for young-of-year (YOY) fish is hypothesized to be the problem. Knowing the importance of tributary mouths as rearing areas in other river systems, we studied use of the mouth of the Paria River, a tributary of the Colorado River, by YOY flannelmouth suckers, and the availability of rearing area in the mouth at different flow levels in the Colorado River in 1996 and 1997. We also examined the relationship between flash floods in the Paria River and catch-per-unit-effort (CPUE) of YOY in the Paria River between 1991 and 1996. Maximum mean daily discharge in the Paria River was inversely correlated with CPUE of YOY flannelmouth suckers (Spearman Rho = -0.9856, p = 0.0003) during their critical rearing period (15 March-30 June). Thus, it appears that YOY flannelmouth suckers rear longer in the Paria River in years when flash flooding is minimal. Recruitment of YOY flannelmouth suckers at the Paria River may also be improved by enhancing pool formation during spring and summer rearing seasons. YOY flannelmouth sucker was captured in a pool created by high Colorado River flows (??? 336 m3/s) that inundated the mouth of the Paria River during spring and summer, 1996. In 1997, high flows (about 550-750 m3/s) in the Colorado River during winter and spring initially inundated the Paria River and formed a pool in the mouth. However, these high flows eventually caused 0.5-1.0 m of suspended sediment from the incoming Paria River to deposit in the mouth. Thus, despite higher flows than 1996, the slackwater area formed only occasionally in 1997. Differences in pool formation between 1996 and 1997 demonstrate that pool formation cannot be inferred solely from Colorado River flows. ?? 2001 John Wiley & Sons, Ltd.

  19. Toward high-resolution flash flood prediction in large urban areas - Analysis of sensitivity to spatiotemporal resolution of rainfall input and hydrologic modeling

    Science.gov (United States)

    Rafieeinasab, Arezoo; Norouzi, Amir; Kim, Sunghee; Habibi, Hamideh; Nazari, Behzad; Seo, Dong-Jun; Lee, Haksu; Cosgrove, Brian; Cui, Zhengtao

    2015-12-01

    Urban flash flooding is a serious problem in large, highly populated areas such as the Dallas-Fort Worth Metroplex (DFW). Being able to monitor and predict flash flooding at a high spatiotemporal resolution is critical to providing location-specific early warnings and cost-effective emergency management in such areas. Under the idealized conditions of perfect models and precipitation input, one may expect that spatiotemporal specificity and accuracy of the model output improve as the resolution of the models and precipitation input increases. In reality, however, due to the errors in the precipitation input, and in the structures, parameters and states of the models, there are practical limits to the model resolution. In this work, we assess the sensitivity of streamflow simulation in urban catchments to the spatiotemporal resolution of precipitation input and hydrologic modeling to identify the resolution at which the simulation errors may be at minimum given the quality of the precipitation input and hydrologic models used, and the response time of the catchment. The hydrologic modeling system used in this work is the National Weather Service (NWS) Hydrology Laboratory's Research Distributed Hydrologic Model (HLRDHM) applied at spatiotemporal resolutions ranging from 250 m to 2 km and from 1 min to 1 h applied over the Cities of Fort Worth, Arlington and Grand Prairie in DFW. The high-resolution precipitation input is from the DFW Demonstration Network of the Collaborative Adaptive Sensing of the Atmosphere (CASA) radars. For comparison, the NWS Multisensor Precipitation Estimator (MPE) product, which is available at a 4-km 1-h resolution, was also used. The streamflow simulation results are evaluated for 5 urban catchments ranging in size from 3.4 to 54.6 km2 and from about 45 min to 3 h in time-to-peak in the Cities of Fort Worth, Arlington and Grand Prairie. The streamflow observations used in evaluation were obtained from water level measurements via rating

  20. Risk of the residents, infrastructure and water bodies by flash floods and sediment transport - assessment for scale of the Czech Republic

    Science.gov (United States)

    Dostál, Tomáš; Krása, Josef; Bauer, Miroslav; Strouhal, Luděk; Jáchymová, Barbora; Devátý, Jan; David, Václav; Koudelka, Petr; Dočkal, Martin

    2015-04-01

    Pluvial and flash floods, related to massive sediment transport become phenomenon nowadays, under conditions of climate changes. Storm events, related to material damages appear at unexpected places and their effective control is only possible in form of prevention. To apply preventive measures, there have to be defined localities with reasonable reliability, which are endangered by surface runoff and sediment transport produced in the subcatchments, often at agriculturally used landscape. Classification of such localities, concerning of potential damages and magnitude of sediment transport shall be also included within the analyses, to design control measures effectively. Large scale project for whole territory of the Czech Republic (ca 80.000 km2) has therefore been granted b the Ministry of Interior of the Czech Republic, with the aim to define critical points, where interaction between surface runoff connected to massive sediment transport and infrastructure or vulnerable water bodies can occur and to classify them according to potential risk. Advanced GIS routines, based on analyses of land use, soil conditions and morphology had been used to determine the critical points - points, where significant surface runoff occurs and interacts with infrastructure and vulnerable water bodies, based exclusively on the contributing area - flow accumulation. In total, ca 150.000 critical points were determined within the Czech Republic. For each of critical points, its subcatchment had then been analyzed in detail, concerning of soil loss and sediment transport, using simulation model WATEM/SEDEM. The results were used for classification of potential risk of individual critical points, based on mean soil loss within subcatchment, total sediment transport trough the outlet point and subcatchment area. The classification has been done into 5 classes. The boundaries were determined by calibration survey and statistical analysis, performed at three experimental catchments area

  1. Numerical modeling of water flow spreading out over the land surface due to flash flood/debris by methods of nonlinear fluid dynamics and GIS-technologies - a flood zone distribution in time

    Science.gov (United States)

    Abrakhin, Sergey

    2014-05-01

    1. The problem of forecasting, both in time and space, for the flood zones due to catastrophic flash water events is considered in the frames of dynamic model for the water flow movement on the land surface. The analysis is carried out in analogous with sudden dam destruction on the river channel. 2. To solve the problem, a mathematical apparatus has been used to describe the processes of water flow motion in approximation of one-dimensional equation for kinematic wave. In the case, the change of depth for water flow in time is associated with a change in the water flow discharge along the propagation coordinate. The model takes into account both the slope of the river bottom and the surface roughness coefficient resulting in resistance by friction. Because the proposition is that catastrophic events already occurred, and flow speed is sufficiently high, we do not take into account the precipitation and filtration processes. By setting the initial and boundary conditions in spatial-time domain the solution of the problem gives a complete picture of the water flow spreading dynamics for breakthrough wave. The procedure of explicit difference scheme with the use of an uniform grid and a three-point template has been used to find the solution, for a first order approximation. The condition of stability for the solution was obtained. 3. In the model we introduced some database on the land surface parameters being control parameters for the water flow. Forecasting technology is the following: for prediction of the breakthrough wave spreading over the land surface, the river downstream areas divide on the sections, being perpendicular to the riverbed. To estimate the parameters of breakthrough wave we calculate a maximum flood level in each cross-section of the river channel. Next, a flood zone for each section builds as a surface corresponding to the maximum level of flooding. All operations, i.e. on initial database collection as well as construction of the flood zones

  2. Toward a space-time scale framework for the study of everyday life activity's adaptation to hazardous hydro-meteorological conditions: Learning from the June 15th, 2010 flash flood event in Draguignan (France)

    Science.gov (United States)

    Ruin, Isabelle; Boudevillain, Brice; Creutin, Jean-Dominique; Lutoff, Céline

    2013-04-01

    Western Mediterranean regions are favorable locations for heavy precipitating events. In recent years, many of them resulted in destructive flash floods with extended damage and loss of life: Nîmes 1988, Vaison-la-Romaine 1992, Aude 1999 and Gard 2002 and 2005. Because of the suddenness in the rise of water levels and the limited forecasting predictability, flash floods often surprise people in the midst of their daily activity and force them to react in a very limited amount of time. In such fast evolving events impacts depend not just on such compositional variables as the magnitude of the flood event and the vulnerability of those affected, but also on such contextual factors as its location and timing (night, rush hours, working hours...). Those contextual factors can alter the scale and social distribution of impacts and vulnerability to them. In the case of flooding fatalities, for instance, the elderly are often said to be the most vulnerable, but when fatalities are mapped against basin size and response time, it has been shown that in fact it is young adults who are most likely to be killed in flash flooding of small catchments, whereas the elderly are the most frequent victim of large scale fluvial flooding. Further investigations in the Gard region have shown that such tendency could be explained by a difference of attitude across ages with respect to mobility related to daily life routine and constraints. According to a survey of intentional behavior professionals appear to be less prone to adapting their daily activities and mobility to rapidly changing environmental conditions than non-professionals. Nevertheless, even if this appears as a tendency in both the analysis of limited data on death circumstances and intended behavior surveys, behavioral verification is very much needed. Understanding how many and why people decide to travel in hazardous weather conditions and how they adapt (or not) their activities and schedule in response to

  3. Hydrometeorological multi-model ensemble simulations of the 4 November 2011 flash flood event in Genoa, Italy, in the framework of the DRIHM project

    Directory of Open Access Journals (Sweden)

    A. Hally

    2015-03-01

    Full Text Available The e-Science environment developed in the framework of the EU-funded DRIHM project was used to demonstrate its ability to provide relevant, meaningful hydrometeorological forecasts. This was illustrated for the tragic case of 4 November 2011, when Genoa, Italy, was flooded as the result of heavy, convective precipitation that inundated the Bisagno catchment. The Meteorological Model Bridge (MMB, an innovative software component developed within the DRIHM project for the interoperability of meteorological and hydrological models, is a key component of the DRIHM e-Science environment. The MMB allowed three different rainfall-discharge models (DRiFt, RIBS and HBV to be driven by four mesoscale limited-area atmospheric models (WRF-NMM, WRF-ARW, Meso-NH and AROME and a downscaling algorithm (RainFARM in a seamless fashion. In addition to this multi-model configuration, some of the models were run in probabilistic mode, thus giving a comprehensive account of modelling errors and a very large amount of likely hydrometeorological scenarios (> 1500. The multi-model approach proved to be necessary because, whilst various aspects of the event were successfully simulated by different models, none of the models reproduced all of these aspects correctly. It was shown that the resulting set of simulations helped identify key atmospheric processes responsible for the large rainfall accumulations over the Bisagno basin. The DRIHM e-Science environment facilitated an evaluation of the sensitivity to atmospheric and hydrological modelling errors. This showed that both had a significant impact on predicted discharges, the former being larger than the latter. Finally, the usefulness of the set of hydrometeorological simulations was assessed from a flash flood early-warning perspective.

  4. Hydrometeorological multi-model ensemble simulations of the 4 November 2011 flash-flood event in Genoa, Italy, in the framework of the DRIHM project

    Directory of Open Access Journals (Sweden)

    A. Hally

    2014-11-01

    Full Text Available The e-Science environment developed in the framework of the EU-funded DRIHM project was used to demonstrate its capability to provide relevant, meaningful hydrometeorological forecasts. This was illustrated for the tragic case of 4 November 2011, when Genoa, Italy, was flooded as the result of heavy, convective precipitation that inundated the Bisagno catchment. The Meteorological Model Bridge (MMB, an innovative software component developped within the DRIHM project for the interoperability of meteorological and hydrological models, is a key component of the DRIHM e-Science environment. The MMB allowed three different rainfall-discharge models (DRiFt, RIBS, and HBV to be driven by four mesoscale limited-area atmospheric models (WRF-NMM, WRF-ARW, Meso-NH, and AROME and a downscaling algorithm (RainFARM in a seamless fashion. In addition to this multi-model configuration, some of the models were run in probabilistic mode, thus allowing a comprehensive account of modelling errors and a very large amount of likely hydrometeorological scenarios (>1500. The multi-model approach proved to be necessary because, whilst various aspects of the event were successfully simulated by different models, none of the models reproduced all of these aspects correctly. It was shown that the resulting set of simulations helped identify key atmospheric processes responsible for the large rainfall accumulations over the Bisagno basin. The DRIHM e-Science environment facilitated an evaluation of the sensitivity to atmospheric and hydrological modelling errors. This showed that both had a significant impact on predicted discharges, the former being larger than the latter. Finally, the usefulness of the set of hydrometeorological simulations was assessed from a flash-flood early-warning perspective.

  5. On the Role of Flash Floods for Dust Emission over North Africa: Alluvial Sediments acting as Dust Source

    Science.gov (United States)

    Schepanski, K.; Klueser, L.; Tegen, I.

    2014-12-01

    Studies analyzing satellite dust products show that numerous dust sources are located in the foothills of arid and semi-arid mountain regions. There, alluvial sediments deposited on valley bottoms and flood plains are very susceptible to wind erosion and frequently serve as dust source. This study focuses on the spatio-temporal distribution of dust source activation events over the mountain foothills and flood plains over North Africa. Satellite dust retrievals with sub-daily resolution such as from Meteosat Second Generation (MSG) Spinning Enhanced Visible and InfraRed Imager (SEVIRI) and METOP A/B Infrared Atmospheric Sounding Interferometer (IASI) instruments are used to identify dust source regions. Identified dust source regions are then linked to soil properties and land type classification data sets. Information on the mineralogical composition of transported dust inferred from IASI observation are used (a) to investigate the impact of different source geomorphologies and thus different radiative properties of airborne dust particles, and (b) to estimate the contribution of dust uplift from alluvial sediments compared to dust emission from non-hydrological sources. Ultimately, this study contributes to the understanding of controlling mechanism on the interannual variability of dust source activation and will improve current dust emission modules coupled to atmosphere models.

  6. The Analysis of Synoptic Systems causing Flash-Flood-Producing Rainstorm in Guangxi and Diagnosis of Heavy Rainfall Area%广西致洪暴雨的影响系统及暴雨落区分析

    Institute of Scientific and Technical Information of China (English)

    林开平; 姚才; 赵江洁; 董良淼

    2001-01-01

    以“94.6”、“94.7”和“98.6”这几次引发广西特大洪涝灾害的致洪暴雨过程为研究对象,对其环流形势和影响系统的特征进行分析,研究致洪暴雨与环流形势和影响系统的关系,暴雨落区与影响系统的关系。%According to the Study of “94.6”,“94.7” and “98.6” exceptional flash-flood-producing rainstorm, the feature of circulation situation and the synoptic systems that caused flash-flood-producing rainstorm in Guangxi was systematically analyzed. The relationship between flash-flood-producing rainstorm and the circulation situation, as well as the synoptic systems was also discussed. At the same time the torrential rainfall area were diagnosed.

  7. Study of Regionalization of Flash Flood Prevention Based on GIS Index Model%基于GIS指数模型的山洪灾害防治区划方法研究

    Institute of Scientific and Technical Information of China (English)

    王兴菊; 卢岳; 郝玉伟

    2011-01-01

    为合理划分山洪灾害防治区划,采用加权线性综合法综合考虑降雨、地形地质、经济社会三个因素,建立了基于矢量数据的GIS指教模型,并以山东省蒙阴县山洪灾害防治区划为例,通过指数模型计算各像元区域的指数值,根据指数值生成山洪灾害防治区等级地图,将蒙阴县山洪灾害防治区划分为一级重点防治区、二级重点防治区和一般防治区三个区域.%In order to divide regionalization of flash flood disaster prevention rationally, the weighted linear method is applied to establish G1S index model based vector data by considering rainfall, topography and geology, economic and social factors. Taking Mengyin County in Shandong Province for an example, index value of each region pixel is calculated with index model. Regionalization map of flash flood disaster prevention is plotted according to the index value. The region of Mengyin flash flood prevention is divided into three types regions, which names first-order typical prevention region, second-order typical prevention region and general prevention region.

  8. The 2010 Pakistan Flood and Russian Heat Wave: Teleconnection of Hydrometeorological Extremes

    Science.gov (United States)

    Lau, William K. M.; Kim, Kyu-Myong

    2012-01-01

    In this paper, preliminary results are presented showing that the two record-setting extreme events during 2010 summer (i.e., the Russian heat wave-wildfires and Pakistan flood) were physically connected. It is found that the Russian heat wave was associated with the development of an extraordinarily strong and prolonged extratropical atmospheric blocking event in association with the excitation of a large-scale atmospheric Rossby wave train spanning western Russia, Kazakhstan, and the northwestern China-Tibetan Plateau region. The southward penetration of upper-level vorticity perturbations in the leading trough of the Rossby wave was instrumental in triggering anomalously heavy rain events over northern Pakistan and vicinity in mid- to late July. Also shown are evidences that the Russian heat wave was amplified by a positive feedback through changes in surface energy fluxes between the atmospheric blocking pattern and an underlying extensive land region with below-normal soil moisture. The Pakistan heavy rain events were amplified and sustained by strong anomalous southeasterly flow along the Himalayan foothills and abundant moisture transport from the Bay of Bengal in connection with the northward propagation of the monsoonal intraseasonal oscillation.

  9. A Multiple Criteria Decision Modelling approach to selection of estimation techniques for fitting extreme floods

    Science.gov (United States)

    Duckstein, L.; Bobée, B.; Ashkar, F.

    1991-09-01

    The problem of fitting a probability distribution, here log-Pearson Type III distribution, to extreme floods is considered from the point of view of two numerical and three non-numerical criteria. The six techniques of fitting considered include classical techniques (maximum likelihood, moments of logarithms of flows) and new methods such as mixed moments and the generalized method of moments developed by two of the co-authors. The latter method consists of fitting the distribution using moments of different order, in particular the SAM method (Sundry Averages Method) uses the moments of order 0 (geometric mean), 1 (arithmetic mean), -1 (harmonic mean) and leads to a smaller variance of the parameters. The criteria used to select the method of parameter estimation are: - the two statistical criteria of mean square error and bias; - the two computational criteria of program availability and ease of use; - the user-related criterion of acceptability. These criteria are transformed into value functions or fuzzy set membership functions and then three Multiple Criteria Decision Modelling (MCDM) techniques, namely, composite programming, ELECTRE, and MCQA, are applied to rank the estimation techniques.

  10. Determinants of property damage recovery time amongst households affected by an extreme flood event in Metro Manila, Philippines

    Directory of Open Access Journals (Sweden)

    Jamil Paolo Francisco

    2014-03-01

    Full Text Available This study identified the factors that influence household recovery following an extreme flood event, measured in terms of the length of time to repair, rebuild or replace damaged private property. Data was obtained through a survey of 400 households in Marikina City in Metro Manila, Philippines. Results from the empirical analysis indicated that household income, access to credit (borrowing, the use of a flood alarm system, access to safe shelter, membership in a community organisation, adoption of disaster-specific anticipatory measures and adoption of general preventive measures significantly reduced the time it took for affected households to recover from property damage. Evacuation, relief aid, type of housing, education, household size and frequency of flooding in the area did not have significant effects.

  11. Slope mass movements on SPOT satellite images: A case of the Železniki area (W Slovenia after flash floods in September 2007

    Directory of Open Access Journals (Sweden)

    Mateja Jemec

    2008-12-01

    Full Text Available Flash floods in Slovenia, which was exposed on September 18th 2007, demanded 6 lives, several thousand houses and over one thousand kilometres of roads were damaged and more also than 50 bridges. The highest amount of rain fell at west and north-west parts of Slovenia (northern Primorska region and southern Gorenjska region,from where heavy rain spread eastwards over the central Slovenia and in east part of Slovenia. In the article we focused on area of western and north-western part of Slovenia. The aim of present research was in the first phase to describe methodology to determine landslide occurrences from satellite images before and after natural disaster on Železniki region. Second phase was based on comparison of obtained results with the existing models for prediction of slope mass movements, and finally also to determine identificability of landslide types on a satellite image.Results have shown, that the highest part of obtaining area from supervised and unsupervised classification of satellite images, are comparable with classes of landslide susceptibility, where occurrences of landslide are largest.

  12. Rapid Global River Flood Risk Assessment under Climate and Socioeconomic Scenarios: An Extreme Case of Eurasian region

    Science.gov (United States)

    Kwak, Young-joo; Magome, Jun; Hasegawa, Akira; Iwami, Yoichi

    2017-04-01

    Causing widespread devastation with massive economic damage and loss of human lives, flood disasters hamper economic growth and accelerate poverty particularly in developing countries. Globally, this trend will likely continue due to increase in flood magnitude and lack of preparedness for extreme events. In line with risk reduction efforts since the early 21st century, the monitors and governors of global river floods should pay attention to international scientific and policy communities for support to facilitate evidence-based policy making with a special interest in long-term changes due to climate change and socio-economic effects. Although advanced hydrological inundation models and risk models have been developed to reveal flood risk, hazard, exposure, and vulnerability at a river basin, it is obviously hard to identify the distribution and locations of continent-level flood risk based on national-level data. Therefore, we propose a methodological possibility for rapid global flood risk assessment with the results from its application to the two periods, i.e., Present (from 1980 to 2004) and Future (from 2075 to 2099). The method is particularly designed to effectively simplify complexities of a hazard area by calculating the differential inundation depth using GFID2M (global flood inundation depth 2-dimension model), despite low data availability. In this research, we addressed the question of which parts in the Eurasian region (8E to 180E, 0N to 60N) can be found as high-risk areas in terms of exposed population and economy in case of a 50-year return period flood. Economic losses were estimated according to the Shared Socioeconomic Pathways (SSP) scenario, and the flood scale was defined using the annual maximum daily river discharge under the extreme conditions of climate change simulated with MRI-AGCM3.2S based on the Representative Concentration Pathways (RCP8.5) emissions scenario. As a preliminary result, the total potential economic loss in the

  13. Flooding and Schools

    Science.gov (United States)

    National Clearinghouse for Educational Facilities, 2011

    2011-01-01

    According to the Federal Emergency Management Agency, flooding is the nation's most common natural disaster. Some floods develop slowly during an extended period of rain or in a warming trend following a heavy snow. Flash floods can occur quickly, without any visible sign of rain. Catastrophic floods are associated with burst dams and levees,…

  14. Chronic institutional failure and enhanced vulnerability to flash-floods in the Cuenca Altadel Río Lerma, Mexico.

    Science.gov (United States)

    Güiza, Frida; Simmons, Peter; Burgess, Jacquie; McCall, Michael K

    2016-01-01

    The dominant paradigm in disaster risk reduction (DRR) policies has been seriously contested because of its reliance on interventions based on technocratic expertise. In the Mexican context, the influence of informal practices such as clientelism and cartelisation of the political system produces environmental degradation and vulnerability to disasters within the communities in the study site. This paper contributes to understanding of failed institutional processes and parallel practices that intensify vulnerability to disasters by contrasting the discourses of agents within a peri-urban community in central Mexico. Employing the Situational Analysis Approach as a methodological framework, the study identifies divergent views and practices within the community, leading to different responses to disasters and to different perceptions regarding institutional performance. In addition, it finds that institutional decision-making, based only on scientific and technical expertise, has resulted in unintended consequences that influence ongoing vulnerability to floods in the site under review.

  15. Predictability of Extreme Drought/Flood over China in 2015/16 Monster El Niño

    Science.gov (United States)

    Wang, Shanshan; Yuan, Xing; Li, Yaohui

    2017-04-01

    The past monster El Niño of 2015/16 resulted in widespread droughts and floods across the globe. Particularly, North China suffered extreme drought in the summer of 2015 (where two agricultural provinces (Henan and Liaoning) were hit by the worst drought on record since 1951), and the middle and lower riches of Yangtze river underwent catastrophic flooding in June and July of 2016 (where the damages from China's 2016 floods have already topped more than 22 billion according to the International Disasters Database). Both of these devastating hydrological extremes were well captured by a dynamical seasonal climate forecast model with a good prediction of the 2015/16 big El Niño. Nevertheless, a strong El Niño does not necessarily result in an extreme drought, but depending on whether the El Niño evolves synergistically with Eurasian spring snow cover reduction to trigger a positive summer Eurasian teleconnection (EU) pattern that favors anomalous northerly and air sinking over North China. Added to El Niño is the high-latitude snow cover. The decreasing spring snow cover in Eurasia has been considered as one of possible reasons for the increasing of the positive EU pattern and severe droughts in North China in recent decades. We found that a dynamical-statistical forecasting approach that combines both the low- and high-latitudes precursors is more skillful than the dynamical forecast model at long lead. Therefore, the vanishing cryosphere should be considered as important factors for the extreme summer drought in North China as well in a warming future, and optimally combing them with the low-latitude signals (e.g., El Niño) will enhance the predictability of extreme droughts. In addition, we also found that the water vapor transport is more predictable than the extreme precipitation at short lead based on CFS2 seasonal real-time forecast, which may provide useful information for early warning.

  16. Does global warming favour the occurrence of extreme floods in European Alps? First evidences from a NW Alps proglacial lake sediment record

    OpenAIRE

    Wilhelm, B.; ARNAUD, Fabien; Enters, D.; Allignol, F.; Legaz, Aurelie; Magand, Olivier; Revillon, Sidonie; Giguet-Covex, C.; Malet, E.

    2012-01-01

    Flood hazard is expected to increase in the context of global warming. However, long time-series of climate and gauge data at high-elevation are too sparse to assess reliably the rate of recurrence of such events in mountain areas. Here paleolimnological techniques were used to assess the evolution of frequency and magnitude of flash flood events in the North-western European Alps since the Little Ice Age (LIA). The aim was to document a possible effect of the post-19(th) century global warmi...