Flash Flood

New technologies promise reduced flash flood losses. However, real-time observations with vast multi-sensor networks, more precise mapping capabilities using remote sensing and GIS, quicker hydrological and meteorological models, and increasing forecast lead times have not reduced losses. In November, 1999, 35 researchers from nine countries met in Ravello, Italy at a NATO sponsored Advanced Study Institute, to discuss these issues and to develop a research agenda that incorporates the various components required to cope with flash floods. The key recommendations from the Institute were: (1) greater emphasis on increasing understanding of the social processes involved in flash flood warning, particularly in the response phases, and (2) the need to reduce vulnerability in sustainable ways compatible with long-term economic and social goals. The relationship between hydrometeorology and social science is seen as critical to advancing our abilities to cope with flash floods.

The infrastructure of the original Guapo river dam project at El Guamito site (Miranda state, Venezuela), built and commissioning during the 1975-1977 period, collapsed in December 1999 as a result of the extraordinary rains observed at that time, which generated maximum discharges with magnitudes higher than the design discharge of the work. Therefore, it is necessary to analyze the relationship between the hydrogeomorphological response of the Guapo river basin generated by this extraordinary rains event, the characteristics of the physical and biological media, and the conditions that these determined for the collapse of the dam. Variables of the physical and biological media, in particular climatic and hydrological aspects, were characterized. Morphometric parameters of the basin and its drainage network were measured and calculated. Topographic and geomorphological features were described with the construction of profiles. The physical and biological elements (geology, relief, geomorphology, topography, soil, vegetation, climate, drainage and hydrology) that coexist in the area of the basin have an important influence on the hydrogeomorphological responses of the system (floods, sediment production and haulage and mass movements). The morphometric characteristics of the basin indicate a high correspondence between these aspects and the collapse of the spillway, since they favoured the high discharges that were estimated at the dam site during the occurrence of this adverse event.

Das, P.J. (2013). Jiadhal River Catchment, Assam, India: Building community capacity for flash flood risk management In: Shrestha, AB; Bajracharya, SR (eds) (2013) Case studies on flash flood risk management in the Himalayas: In support of specific flash flood policies. Kathmandu: ICIMOD, pages 24-30.

Banjir bandang merupakan salah satu bahaya yang mengancam di DAS Juwana; dan
berpotensi menyebabkan kerusakan pada permukiman, jembatan, sawah, serta korban jiwa.
Meskipun demikian, penelitian mengenai banjir bandang di Indonesia terbilang masih minim.
Kebutuhan untuk lebih memahami kejadian banjir bandang sangat diperlukan terutama
dalam upaya manajemen bencana. Tujuan dari penelitian ini adalah untuk mengidentifikasi
tingkat kerawanan banjir bandang di DAS Juwana dengan pendekatan geomorfologi. Metode
yang digunakan adalah stepwise assessment atau penilaian bertahap terhadap kerawanan
banjir bandang. Langkah awal adalah menentukan batas sub-DAS berdasarkan klasifikasi
orde sungai. Tiap Sub-DAS tersebut dianggap mewakili sistem-sistem sungai yang masingmasing
memiliki parameter tertentu. Parameter kuantitatif yang digunakan meliputi
Perbedaan Ketinggian Relatif (Relative Height Differences/RHD), Lereng, dan Kerapatan
Drainase. Parameter tersebut dipilih untuk mewakili komponen geomorfologi berupa
morfografi, morfogenesis, morfometri, dan morfoproses. RHD dihitung dengan membagi tiap
sistem sub-DAS menjadi dua area berdasarkan kerapatan konturnya (up-stream dan downstream),
kemudian dihitung selisih rata-rata elevasi dari dua area tersebut. Lereng dihitung
sebagai rata-rata kemiringan lereng untuk tiap sistem sub-DAS. Kerapatan Aliran dihitung
berdasarkan rumus panjang seluruh sungai dalam suatu sub-DAS dibagi dengan total area
sub-DAS tersebut. Penilaian kerawanan dilakukan dengan menjumlahkan skor tiap
parameter dikalikan bobot tiap parameter yang dibangun berdasarkan asumsi dari studi
literatur. Berdasarkan analisis tersebut, diketahui bahwa 20 sub-DAS di DAS Juwana
memiliki tingkat kerawanan tinggi. Temuan tersebut divalidasi dengan survey lapangan dan
berdasarkan berita kejadian banjir bandang. Sebagai kesimpulan, analisis sidik cepat
dengan pendekatan geomorfologi dapat mengidentifikasi sub-DAS yang rawan banjir
bandang dan menjadi prioritas.

The Tillabéri region (population 2.7 million, 97,250 km 2) is the hinterland of the Niger's capital city and the second most susceptible region to flooding in the country, with 416 settlements hit from 2008 to 2013. This chapter aims to present the potential benefits of flood risk assessment at the municipal scale, a tool that can help local authorities in disaster risk reduction. Risk (R) is considered a function of Hazard (H), Exposure (E) and Damages (D) according the equation R = H * E * D. Risk is measured using six indicators. The probability of rain causing settlement flooding each year is measured for each municipality using daily rainfall from meteorological stations (1981-2010) and three-hourly Tropical Rainfall Measuring Mission (TRMM), data-sets by NOAA (1998-2011). Settlements flooded (E), people affected, homes destroyed, fields flooded and livestock killed (D) are sourced from Niger's early warning system and disaster prevention unit (EWS DP), all errors corrected and units of measurement standardised. From the results, it emerged that 765 settlements were flooded between 1998 and 2013. Contrary to what one might expect, the floods caused by the swelling of the River Niger hit few settlements. Most of the areas susceptible to flooding were located in the vast Bosso and Maouri dallols, two fossil rivers that run from Mali towards Niger for over 300 km. The right-bank tributaries of the Niger and along the minor hydrographic network were the next most affected areas. Ninety-five settlements were hit more than once and 19 flooded in two or more consecutive years. Seven municipalities out of 41 were at very high or high risk of being flooded. These are crossed by the River Niger or by its main tributaries on the right bank, by the Ouallam intermittent creek or the Bosso dallol. Seven municipalities showed damage in three areas (people, dwellings, fields).

Surma is a mountainous river, originating at Manipur hills of India enters Bangladesh through Sylhet district. Due to its location near the foothills of Himalaya, this region has a large rate of precipitation. As a result, the river causes frequent flash flood during early monsoon causing a significant change in peak flow. Being sudden and violent in nature, flash flood causes massive destruction in the agricultural productions, transports, navigations and valuable properties. This concerns for a better understanding of Surma River and its flash Flood. The selected reach is almost 85km and spans from Surma Transit at u/s to Sunamganj at d/s. Different hydrodynamic characteristics such as variation in water level, velocity, discharge and flash flood analysis due to peak flow change at the Chhatak transit for the year 2000 are assessed. The result output shows, maximum water level and discharge of Surma River is obtained during the monsoon. The velocity is also high during this period. During the winter, discharge and velocity are almost zero. Flash Flood analysis of Surma River shows rapid change in water level and flow during the month of April, 2000 with respect to flood level. Due to its development on a short time, the changes in water level and discharge will show its devastating impact. Overall, Hydrodynamic analysis will help to understand the characteristics and features of Surma River and Flash Flood analysis will shows its development and occurrence period in Surma River along with impacts.

s u m m a r y In many regions of the world flood events in mountain basins are one of the greatest risks to the local population, due to the pressure placed on land use by social and economic development. Conventional hydrologic–hydraulic methodological approaches are not usually feasible in mountainous basins because they are not gauged at all or, in the best-case scenario, are poorly gauged. In this context, palaeohydro-logical research offers a valuable alternative to the above approaches. However, many palaeohydrological data sources and associated methods have been proposed and initially used in large basins with extensive floodplains. As a result, when they are used in mountainous areas they must be adapted to include different techniques, since the problems to be addressed are different and less data is usually available. In this paper, we review classic data sources and different analytical methods and discuss their advantages and shortcomings with particular attention to mountain basins. For this purpose, examples are provided where improvements in the palaeohydrologic methods are proposed by incorporating uncertainties, describing sources of error or putting forward hypotheses for hydraulic calculation to make palaeoflood hydrology more objective and useful in risk assessment.

Entre otros diversos aspectos, el evento de aludes torrenciales de Diciembre de 1999 evidenció a partir de los volúmenes de sedimentos depositados por éstos y la severidad de los daños causados, con diferencias notorias entre distintos sectores del litoral varguense afectado, que existen elementos del medio físico que controlan las características y magnitudes de las respuestas hidrológicas de las cuencas de drenaje. Es por ello que el propósito de este trabajo se centra en el análisis e interpretación de los parámetros morfométricos (geomorfometría) de las cuencas y redes de drenaje de un sector de la vertiente norte del macizo “El Ávila” (estado Vargas, Venezuela), en términos de sus incidencias e implicaciones en las dinámicas hidrológica y geomorfológica de los sistemas estudiados. La metodología consistió básicamente en estimaciones, mediciones y cálculos de los parámetros morfométricos de las cuencas y sus redes de drenaje sobre la cartografía base digitalizada del sector de estudio seleccionado, con apoyo en la herramienta para SIG software ArcGIS 9.2 y sus módulos Spatial Analysis y ArcHydro y el software Microsoft Excel. Se realizó un análisis descriptivo de los datos de los parámetros morfométricos, cuyos estadísticos fueron estimados con el complemento Xlstat de Microsoft Excel. Estos sistemas hidrogeomorfológicos califican en la categoría de microcuencas debido a sus pequeñas dimensiones, son espacios topográficamente muy accidentados de fuertes pendientes y grandes desniveles altitudinales, y corresponden a sistemas de morfologías planimétricas semi-circulares a semi-alargadas. Las cuencas de drenaje estudiadas albergan redes de desagüe de ramificaciones y densidades considerables con cortas longitudes y canales de escasa sinuosidad (rectilíneos), que se corresponden con sistemas de altas magnitudes y órdenes, así como elevados niveles de torrencialidad. En síntesis, las respuestas morfodinámicas e hidrológicas de las cuencas estudiadas son condicionadas y controladas por sus parámetros morfométricos y los de sus redes de drenaje.

El propósito de este trabajo es evaluar la amenaza hidrogeomorfológica en las microcuencas de las quebradas Catuche, Anauco y Gamboa y del río Cotiza, y en particular la generación de crecidas torrenciales. La metodología comprendió: Interpretación geomorfológica, mediciones y cálculos de parámetros morfométricos de las microcuencas y sus redes de drenaje; estimación de los tiempos de concentración de las microcuencas y velocidad promedio del flujo; caracterización del régimen pluviométrico; análisis de eventos extremos y estimación de caudales picos de crecientes. Las respuestas hidrológicas rápidas y violentas (crecidas torrenciales), así como las características de los hidrogramas resultantes, y las magnitudes de los caudales pico de las crecientes, están controladas y condicionadas por las magnitudes de sus parámetros morfométricos, las dimensiones de las tormentas que afectan el área, y la intensidad y duración de las lluvias, en particular vinculadas a eventos extremos.

Una de las amenazas naturales más relevantes que impactan sobre el margen costero carabobeño, lo constituyen las inundaciones, procesos naturales cuyos episodios importantes son activados por lluvias extraordinarias. Por ello, el presente trabajo tiene como propósito, caracterizar y analizar la distribución espacio-temporal y los eventos extremos de las precipitaciones en la franja costera-montañosa Morón – Puerto Cabello – Patanemo del estado Carabobo, con la finalidad de establecer su vinculación con escenarios de inundaciones. La metodología se basó en el tratamiento de datos de precipitación de las estaciones Puerto Cabello-Base Naval, Morón-Dique, Hacienda El Manglar, Santa Rita, Borburata y El Cambur (período 1973-1990), para los cuales se realizaron cálculos de parámetros estadísticos y de anomalías pluviométricas, y análisis de tendencia. Se estudiaron datos de láminas máximas anuales de precipitación para distintas duraciones de la lluvia, correspondientes a las estaciones Borburata (período 1962-1995) y Santa Rita (período 1974-1995), a los cuales se les realizó análisis de intensidad-duración-frecuencia (IDF) para distintos períodos de retorno. Los resultados muestran promedios anuales que oscilan entre 478,4 mm y 1649,6 mm, cuya distribución espacial está determinada por la orientación de la línea de costa, el relieve montañoso (altitud), y la orientación de los valles fluvio-marinos y de las laderas de los estribos montañosos. La distribución temporal de las lluvias exhibe regímenes unimodales y bimodales. A excepción de la estación Borburata, se observa una ligera tendencia a la disminución de los montos totales anuales en las otras estaciones. Las anomalías por exceso de lluvia alcanzan valores de hasta 1366,63 mm, y por déficit de 710,20 mm. El análisis de IDF indica valores críticos para 1 hora de duración de 91,63 mm/h y 102,94 mm/h en un período de retorno de 50 años, y valores de 102,55 mm/h y 115,11 mm/h para un período de retorno de 100 años.

Flash flood has become one of the most exposed hazards in Juwana Catchment. It becomes important to know the susceptible area of flash flood. Flash flood occurence is mainly controlled by two main factors, i.e. rough topography and heavy rainfall. Therefore, two methods were used to assess the flash flood: by using geomorphological approach and hydrological model. Geomorphological approach includes the quantitative parameters: Relative Height Differences – Slope – Drainage Density; which are to represent the components of morphographic, morphogenesis, morphometry, and morphoprocess. On the other hand, hydrological model provides detailed flash flood process computing complex parameters such as DEM, land cover, channel, vegetation and house cover as its input.
Main objective of the research is to provide a stepwise assessment of flash flood susceptibility by using geomorphological approach and hydrological model. The specific objectives of this research are: 1) To identify the flash flood susceptible area based on geomorphological approach, 2) To simulate the flash flood by using hydrological model, and 3) To analyze flash flood susceptibility based on the result of geomorphological approach and hydrological model. The geomorphological approach was mainly based on quantitative method by using weighted scoring of Relative Height Differences (RHD), Drainage Density, Slope. Hydrological model was using openLisem model. The main input maps are DEM, channel, road, land cover, and vegetation cover. The advantage of using openLisem in the hydrological model is that it may provides 1D/2D model of flash flood.
The result of geomorphological analysis shows the location of flash flood prone area that highly controlled by the slope and drainage density. Based on the medium scale analysis, it was found that 20 sub-catchments in Juwana Catchment are prone to flash flood. On large scale and field survey, the dominant factors affecting flash flood are slope and the surface morphology. Meanwhile, the hydrological model shows flow dynamic and the effect of catchment properties. The spatial distribution of flash flood is generally accumulate near the meeting of channels and in the flat terrain in the middle of the catchment.
As conclusion, the combination between geomorphological approach and hydrological model in flash flood assessment is quite effective in large scale; although still using many assumption and limitation. The geomorphological approach in the medium scale may provide the prone area of flash flood, and may be used as consideration to determine the location which needs extra attention. Larger scale provides insight analyses of the morphology condition. The hydrological model shows the choke points and flat area where the flash flood accumulate.

This study is an attempt to simulate the tropospheric conditions associated with lightning and thunderstorms, which occurred during 28-30 March 2017 over northeastern Bangladesh using WRF model. At Sylhet, rainfall amounts of 119 mm and 134 mm are found to occur on 29 March and 31 March 2017 respectively. The continuous very heavy rainfall has been responsible for the devastating flash flood in Sunamganj and adjoining areas in 2017. The study shows that forecasting of lightning and flash flood producing thunderstorms is possible by analyzing different meteorological parameters simulated by WRF Model. The simulated parameters are rainfall, sea level pressure, geopotential height (m), Convective Available Potential Energy (CAPE), winds at various tropospheric levels, cloud water mixing ratio and ice water mixing ratio, vorticity and x, y, z wind components. A low pressure area and strong circulations are found to develop over West Bengal and adjoining Bangladesh with extended troughs ...

Pakistan is a flood-prone country and almost every year, it is hit by floods of varying magnitudes. This study was conducted to generate a flash flood map using analytical hierarchy process (AHP) and frequency ratio (FR) models in the ArcGIS 10.6 environment. Eight flash-flood-causing physical parameters were considered for this study. Five parameters were based on the digital elevation model (DEM), Advanced Land Observation Satellite (ALOS), and Sentinel-2 satellite, including distance from the river and drainage density slope, elevation, and land cover, respectively. Two other parameters were geology and soil, consisting of different rock and soil formations, respectively, where both layers were classified based on their resistance against water percolation. One parameter was rainfall. Rainfall observation data obtained from five meteorological stations exist close to the Chitral District, Pakistan. According to its significant importance in the occurrence of a flash flood, each c...

Pakistan is a flood-prone country and almost every year, it is hit by floods of varying magnitudes. This study was conducted to generate a flash flood map using analytical hierarchy process (AHP) and frequency ratio (FR) models in the ArcGIS 10.6 environment. Eight flash-flood-causing physical parameters were considered for this study. Five parameters were based on the digital elevation model (DEM), Advanced Land Observation Satellite (ALOS), and Sentinel-2 satellite, including distance from the river and drainage density slope, elevation, and land cover, respectively. Two other parameters were geology and soil, consisting of different rock and soil formations, respectively, where both layers were classified based on their resistance against water percolation. One parameter was rainfall. Rainfall observation data obtained from five meteorological stations exist close to the Chitral District, Pakistan. According to its significant importance in the occurrence of a flash flood, each c...

Le changement climatique en Afrique tropicale expose de nombreux établissements ruraux à des précipitations intenses. La dégradation des bassins versants transforme ces précipitations en inondations catastrophiques. Mais les impacts des précipitations intenses dépendent également de l'expansion du bati dans les zones inondables, sur laquelle les connaissances sont encore rares. L'objectif de ce chapitre est de réaliser une évaluation détaillée du risque, qui identifie les biens exposés aux inondations pluviales, estime l'impact et l'efficacité des mesures de réduction du risque. L'évaluation est réalisée dans quatre petites villes du Niger rural en plein essor, qui ont été inondées à plusieurs reprises au cours des dernières années. Les zones inondables suite à des pluies avec période de retour de 3 et 20 ans sont identifiées à l'aide d'un modèle hydrologique bidimensionnel selon que le bassin versant reste dans son état actuel ou est traité avec des mesures de réduction du risque. Les biens exposés sont identifiés par photointerprétation visuelle d'images à très haute résolution et leur valeur de remplacement est estimée. Les mesures de réduction des risques sont identifiées par des discussions avec les communautés. Le risque résiduel et le rapport bénéfice/coût du traitement du risque sont estimés. Le résultat est qu'au cours des 10 dernières années, l'expansion des 4 petites villes est plus rapide dans la zone inondable. Il reste peu de zones sûres pour permettre une expansion future. La cartographie des zones et des éléments exposés aux inondations est donc essentielle pour réduire l'exposition future aux inondations. La rétention d'eau, les toits en tôle ondulée, les barrières anti-inondation, les latrines surélevées et les puits sont des mesures efficaces pour réduire le risque, surtout en cas de précipitations intenses et fréquentes.

Una de las amenazas naturales más relevantes que impactan sobre el margen costero carabobeño, lo constituyen las inundaciones, procesos naturales cuyos episodios importantes son activados por lluvias extraordinarias. Por ello, el presente trabajo tiene como propósito, caracterizar y analizar la distribución espacio-temporal y los eventos extremos de las precipitaciones en la franja costera-montañosa Morón – Puerto Cabello – Patanemo del estado Carabobo, con la finalidad de establecer su vinculación con escenarios de inundaciones. La metodología se basó en el tratamiento de datos de precipitación de las estaciones Puerto Cabello-Base Naval, Morón-Dique, Hacienda El Manglar, Santa Rita, Borburata y El Cambur (período 1973-1990), para los cuales se realizaron cálculos de parámetros estadísticos y de anomalías pluviométricas, y análisis de tendencia. Se estudiaron datos de láminas máximas anuales de precipitación para distintas duraciones de la lluvia, correspondientes a las estaciones Borburata (período 1962-1995) y Santa Rita (período 1974-1995), a los cuales se les realizó análisis de intensidad-duración-frecuencia (IDF) para distintos períodos de retorno. Los resultados muestran promedios anuales de precipitación que oscilan entre 478,4 mm y 1649,6 mm, cuya distribución espacial está determinada por la orientación de la línea de costa, el relieve montañoso (altitud), y la orientación de los valles fluvio-marinos y de las laderas de los estribos montañosos. La distribución temporal de las lluvias exhibe regímenes unimodales y bimodales. A excepción de la estación Borburata, se observa una ligera tendencia a la disminución de los montos totales anuales en las otras estaciones. Las anomalías por exceso de lluvia alcanzan valores de hasta 1366,63 mm, y por déficit de 710,20 mm. El análisis de IDF indica valores críticos para 1 hora de duración de 91,63 mm/h y 102,94 mm/h en un período de retorno de 50 años, y valores de 102,55 mm/h y 115,11 mm/h para un período de retorno de 100 años.

In Barranquilla, Colombia, the risk of deaths and property losses is associated with flash floods in the streets, which is very high. Therefore, this paper shows the design of a wireless sensor network to monitor realtime hydrological parameters that influence the detecting of dangerousness level of flash floods familiarly known as “arroyos”, product of sudden and heavy rains in a short time. The design of the network is made through a site survey to obtain the data and results that are used in this work. It has also developed a mobile web application that uses the Unified Modeling Language (UML ®) based on a list of requirements that displays real-time, on a street map of the city the dangerousness level of the stream at different points along its path. The designed system will be useful for preventive decision making by the end user and it is further developed to be replicable and scalable in similar environments. Furthermore, in this work it was tested the platform Waspmote and the XBee-PRO ZB (S2) Modules as a technological tool for the WSN.

Flash floods reported for the forecast area of the National Weather Service Forecast Office at Binghamton, New York (BGM), are compared with similar significant precipitation and flash flood watch events not corresponding to flash flood reports. These event types are characterized by measures of surface hydrological conditions, surface and upper-air variables, thermodynamic properties, and proxies for synoptic-scale features. Flash flood and nonflood events are compared quantitatively via discriminant analysis and cross validation, and qualitatively via scatterplots and composite soundings. Results are presented in the context of a flash flood checklist used at BGM prior to this study. Flash floods and nonfloods are found to differ most significantly in antecedent soil moisture. The wind direction at 850 hPa shows differences between flood and nonflood events, with flooding more common for an easterly to southeasterly direction and nonflooding more common for a northwesterly directi...