Urban flash flood index based on historical rainfall events

Abstract. Recent recurring episodes of heavy flash flood-producing rainfall events on the Veneto coastal area have renewed the interest in documenting the frequency and key dynamical ingredients of such events. A climatological analysis of the precipitation in Veneto reveals that, in comparison with the rest of the region, the coastal area is characterized by fewer rain days, lower rainfall accumulations, yet more days with heavy precipitation. If set in relation to the yearly rainfall, daily accumulation can reach values as high as 40% of the yearly total rainfall, more regularly between 15% and 30%, often in periods of 12 h or less. Four such heavy rainfall events were analyzed and synthetically described to highlight key ingredients which appear instrumental in producing the high rainfall accumulations. These comprise an upper-level trough elongating or cutting off into the Western Mediterranean basin after a period of one to two weeks of anticyclonic fair weather conditions with temperatures above normal. The moisture supply over the Adriatic onto north-eastern Italy is favoured by above normal sea surface temperatures, enhanced advection by a surface low in the Gulf of Genoa, and in three of the four cases, an additional surface low over southern Italy. The air flows associated with the upper-level trough for the cases discussed were of moderate to weak intensity, and convectively conditionally unstable. The flow intensity was such that the lower tropospheric portion was blocked by and forced to flow around the Alpine barrier, i.e. manifesting as a north-easterly, low-level flow over much of the north-eastern Italian plains. This blocked flow seemed to interact with the larger-scale synoptic flow to form a distinct and persistent low-level convergence in the area of the Veneto coast. It is suggested that these low-level convergence patterns are key in releasing the convective instability present in the larger-scale flow just on the Veneto coastal area. Hereby, it is the synoptic rather than the convective setting which dictated the observed timescales of intense rainfall. Therefore, the convective rainfall rates paired with the synoptic durations combine to produce the exceptionally high rainfall accumulations observed. Cases like these are significant contributors to forming the coastal precipitation climatology, which for this area is found to be distinctly different than for the rest of the region in terms of precipitation concentration.

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Heavy Rainfall Simulation over Sinai Peninsula Using the Weather Research and Forecasting Model

International Journal of Atmospheric Sciences ◽

10.1155/2013/241050 ◽

2013 ◽

Vol 2013 ◽

pp. 1-11 ◽

Cited By ~ 14

Author(s):

Gamal El Afandi ◽

Mostafa Morsy ◽

Fathy El Hussieny

Keyword(s):

Heavy Rainfall ◽

Flash Flood ◽

Wrf Model ◽

Rain Gauge ◽

Rainfall Simulation ◽

Weather Research And Forecasting ◽

Sinai Peninsula ◽

Rainfall Events ◽

Heavy Rainfall Events ◽

Weather Research

Heavy rainfall is one of major severe weather over Sinai Peninsula and causes many flash floods over the region. The good forecasting of rainfall is very much necessary for providing early warning before the flash flood events to avoid or minimize disasters. In the present study using the Weather Research and Forecasting (WRF) Model, heavy rainfall events that occurred over Sinai Peninsula and caused flash flood have been investigated. The flash flood that occurred on January 18, 2010, over different parts of Sinai Peninsula has been predicted and analyzed using the Advanced Weather Research and Forecast (WRF-ARW) Model. The predicted rainfall in four dimensions (space and time) has been calibrated with the measurements recorded at rain gauge stations. The results show that the WRF model was able to capture the heavy rainfall events over different regions of Sinai. It is also observed that WRF model was able to predict rainfall in a significant consistency with real measurements. In this study, several synoptic characteristics of the depressions that developed during the course of study have been investigated. Also, several dynamic characteristics during the evolution of the depressions were studied: relative vorticity, thermal advection, and geopotential height.

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Estimation of the Flash Flood Severity using Runoff hydrograph and Flash flood index

Journal of Korea Water Resources Association ◽

10.3741/jkwra.2008.41.2.185 ◽

2008 ◽

Vol 41 (2) ◽

pp. 185-196 ◽

Cited By ~ 10

Author(s):

Byung-Sik Kim ◽

Hung-Soo Kim

Keyword(s):

Flash Flood ◽

Runoff Hydrograph ◽

Flood Index

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Impact of Atmospheric Circulation on Flooding Occurrence and Type in Luxembourg (Central Western Europe)

10.5194/egusphere-egu2020-13953 ◽

2020 ◽

Author(s):

Judith Meyer ◽

Audrey Douinot ◽

Erwin Zehe ◽

Carol Tamez-Meléndez ◽

Olivier Francis ◽

...

Keyword(s):

Atmospheric Circulation ◽

Large Scale ◽

Western Europe ◽

Flash Flood ◽

Flood Events ◽

Intense Rainfall ◽

European Continent ◽

Rainfall Events ◽

Area Of Interest ◽

Winter Flood

In the second half of the 20th century, hydrological regimes in central Western Europe were largely characterised by large-scale winter floods. This type of event was predominantly triggered by westerly atmospheric fluxes, bringing moist and mild air masses from the Atlantic Ocean to the European continent. Since the late 1990&#8217;s, major flooding events seem to have shifted in time and magnitude. Flash flood events, while being a well-known phenomenon in Mediterranean catchments, are increasingly also reported at higher latitudes. Unlike the large-scale winter flood events, flash floods are of very narrow spatial extension and triggered by rather short, but highly intense rainfall events.Here, we focus on the specific case of rivers in Luxembourg that have experienced several flash flood events in recent years, while only small to moderate winter flood events have been reported since the late 1990&#8217;s. National hydro-meteorological monitoring and flood forecasting systems have been designed for large-scale floods and are not suited for simulating local flash flood events. Therefore, there is a need to increase our understanding of the hydro-meteorological processes underlying flash flood occurrences in our area of interest.While increasing air temperature is known to allow a higher air moisture content that can lead to more intense rainfall events and possible flooding, we moreover hypothesize that the recent increase in flash flood occurrences in Luxembourg is reinforced by a change in atmospheric circulation patterns. To test this hypothesis, we analyse the prevailing atmospheric patterns on rainy days during summer and winter months over the period 1954 - 2019, with a particular focus on rainfall events that lead to moderate and extreme floods. In a next step, we intend to extend our findings for Luxembourg in a larger European context. This analysis should allow to better assess the current situation of hydrological extreme events in central Western Europe in order to take precaution measures and prepare for a diversifying hazard.

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Rainfall and water yield in Macizo del Caroig, Eastern Iberian Peninsula. Event runoff at plot scale during a rare flash flood at the Barranco de Benacancil

Cuadernos de Investigación Geográfica ◽

10.18172/cig.4833 ◽

2021 ◽

Cited By ~ 2

Author(s):

A. Cerdà ◽

A. Novara ◽

P. Dlapa ◽

M. López-Vicente ◽

X. Úbeda ◽

...

Keyword(s):

Iberian Peninsula ◽

Flash Flood ◽

Point Of View ◽

Water Yield ◽

Research Station ◽

Water Delivery ◽

Sediment Delivery ◽

Rainfall Events ◽

Runoff Discharge ◽

The Impact

Floods are a consequence of extreme rainfall events. Although surface runoff generation is the origin of discharge, flood research usually focuses on lowlands where the impact is higher. Runoff and sediment delivery at slope and pedon scale receiving much less attention in the effort to understand flood behaviour in time and space. This is especially relevant in areas where, due to climatic and hydrogeological conditions, streams are ephemeral, so-called dry rivers (“wadis”, "ramblas" or “barrancos”) that are widespread throughout the Mediterranean. This paper researches the relationship between water delivery at pedon and slope scale with dry river floods in Macizo del Caroig, Eastern Iberian Peninsula. Plots of 1x1, 1x2, 1x4, and 2x8 m located in the “El Teularet” Soil Erosion and Degradation Research Station were monitored from 2004 to 2014 to measure soil and water delivery. Rainfall and flow at the dry river Barranco de Benacancil were also monitored. Results show that runoff and sediment discharge were concentrated in few events during the 11 years of research. A single flood event was registered in the channel on September 28, 2009, however, the runoff was registered 160 times at the plots. Runoff discharge was dependent on the size of the plots, with larger plots yielding lower runoff discharge per unit area, suggesting short runoff-travel distance and duration. Three rainfall events contributed with 26% of the whole runoff discharge, and five achieved 56% of the runoff. We conclude that the runoff generated at the plot scale is disconnected from the main channel. From a spatial point of view, there is a decrease in runoff coefficient along the slope. From a temporal point of view, the runoff is concentrated in a few rainfall events. These results show that the runoff generated at plot and slope scale does not contribute to the floods except for rainfall events with more than 100 mm day-1. The disconnection of the runoff and sediment delivery is confirmed by the reduction in the runoff delivery at plot scale due to the control of the length of the plot (slope) on the runoff and sediment delivery.

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Startegic framework for integrated flood Disaster modelling over Bangalore city of India

10.5194/egusphere-egu21-15002 ◽

2021 ◽

Author(s):

Smrati Purwar ◽

Gyanendranath Mohapatra ◽

Rakesh Vasudevan

Keyword(s):

Urban Landscape ◽

Flash Flood ◽

Warning System ◽

Extreme Rainfall ◽

High Elevation ◽

Extreme Rainfall Events ◽

Rainfall Events ◽

Bangalore City ◽

Societal Relevance ◽

The Impact

Hydro-meteorological disasters, particularly the extreme rainfall events (EREs) and associated flash floods, are very frequent in the major metro cities in India during recent years and in many occasions they cause massive destruction to life and property which in long run make adverse socio-economic impacts over the country. Hence, it makes formost importance and has great societal relevance to modellers working such area to develop an advance prediction system for such disasters in India.A strategic framework combining modelling and data analytics is integral part of developing advanced warning system for preparedness during such disasters. In this study, the role of landuse/landcover like built-up, vegetation, barrenland and waterbodies over the Bangalore city in flash flood occurrence is examined using multispectral spatio-temporal satellite data.The recent LULC map evidences a drastic changes in urban landscape that resulted in loss of natural drainage and waterbeds causing frequent floods. Digital Elevation Map (DEM) is analysed to know the&#160; low-lying and high elevation topography compared with&#160; Mean Sea Level(MSL)to quantify the impact of flooding during Extreme Rainfall Events(ERE) on the different part of the Bangalore city. Using Triangular Irregular Network (TIN), flood simulation is carried out for highland and lowlandarea &#160;to study immediate affected areas during EREs Storm Water Modelling &#160;is carried out for different regions in the city to obtain flood pattern, time and volume during selected EREs. The framework developed and simulation results are very useful in generation of management and mitigation strategy by various user agencies.

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Urban flash flood forecast using support vector machine and numerical simulation

Journal of Hydroinformatics ◽

10.2166/hydro.2017.175 ◽

2017 ◽

Vol 20 (1) ◽

pp. 221-231 ◽

Cited By ~ 12

Author(s):

Jun Yan ◽

Jiaming Jin ◽

Furong Chen ◽

Guo Yu ◽

Hailong Yin ◽

...

Keyword(s):

Support Vector Machine ◽

Numerical Model ◽

Flash Flood ◽

Support Vector ◽

Urban Flood ◽

Rainfall Events ◽

Flood Depth ◽

Svm Model ◽

Flood Alert ◽

Statistical Results

Abstract In order to provide urban flood early warning effectively, two support vector machine (SVM) models, using a numerical model as data producer, were developed to forecast the flood alert and the maximum flood depth, respectively. An application in the urban area of Jinlong River Basin, Hangzhou, China, showed the superiority of the proposed models. Statistical results based on the comparison between the results from SVM models and numerical model, proved that the SVM models could provide accurate forecasts for estimating the urban flood. For all the rainfall events tested with an identical desktop, the SVM models only took 2.1 milliseconds while the numerical model took 25 hours. Therefore, the SVM model demonstrates its potential as a valuable tool to improve emergency responses to alleviate the loss of lives and property due to urban flood.

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Flood hazard in Hungary: a re-assessment

Open Geosciences ◽

10.2478/v10085-010-0029-0 ◽

2010 ◽

Vol 2 (4) ◽

Cited By ~ 3

Author(s):

Dénes Lóczy

Keyword(s):

River Flow ◽

Flash Flood ◽

Flood Hazard ◽

Flood Hazards ◽

Rainfall Events ◽

Groundwater Levels ◽

Excess Water ◽

Water Hazard ◽

Map Series ◽

The 19Th Century

AbstractSome decades ago the concept of flood hazard in the Carpathian Basin was interpreted solely as riverine flood hazard, mostly restricted to the Tisza and Danube Rivers, and was closely associated with the impacts of river flow regulation in the second half of the 19th century. Recent assessments, however, allow us to outline a more diverse picture. Climate change is predicted to bring about both an increase in the frequency of droughts and excessive rainfall events, resulting in irregulaties in the water regimes of rivers in Hungary. Excess water hazard from raised groundwater levels is found to affect much larger areas than previously thought. Recent strongly localized cloudbursts, point to the increasing significance of flash floods.Riverine flooding and excess water hazard are more common in lowlands, whereas flash flood hazards are primarily, but not exclusively, affect the mountainous and hilly regions of the country. This paper intends to assess the relative importance of the three types of inundation hazard analyzed and to illustrate their overall spatial occurrences by microregions on a map series.

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