scholarly journals Flash Flood Simulations Based on Shallow Water Equations to Investigate Protection Measures for El Gouna, Egypt

10.29007/kh16 ◽  
2018 ◽  
Author(s):  
Ester Marafini ◽  
Franziska Tügel ◽  
Ilhan Özgen ◽  
Reinhard Hinkelmann ◽  
Michele La Rocca
Keyword(s):  
Shallow Water ◽  
Flash Flood ◽  
Flash Floods ◽  
Flood Event ◽  
Water Model ◽  
Protection Measures ◽  
Environmental Disasters ◽  
Whole Process ◽  
Flood Simulations ◽  
The City

Severe and sudden events like flash floods are considered to be one of the most hazardous environmental disasters. Therefore, predicting the whole process of flooding is fundamental to prevent urban damages. In this context, the simulation of flash floods is an important tool to analyse the flow processes in order to find solutions to the problem. In this work, a case study of the flash flood event of 9th March 2014 in the city of El Gouna in Egypt was carried out using the Hydroinformatics Modeling System (hms), a two-dimensional (2D) shallow water model developed at the Chair of Water Resources Management and Modeling of Hydrosystems, Technische Universität Berlin. The flooding processes are simulated in great detail on unstructured grids. The aim of this work is to investigate the flow field around the settlement of the study area, when structures such as storage basins and dams are adopted as protection measures for the city. Different scenarios are analyzed to find out the most suitable one, which is able to minimize the risk during the flash flood event.

scholarly journals Integral porosity shallow water model at district scale - Case study in Nice

2018 ◽  
Vol 40 ◽  
pp. 06018
Author(s):  
Finn Amann ◽  
Ilhan Özgen ◽  
Morgan Abily ◽  
Jiaheng Zhao ◽  
Dongfang Liang ◽  
...  
Keyword(s):  
High Resolution ◽  
Shallow Water ◽  
Flash Flood ◽  
Water Model ◽  
Triangular Meshes ◽  
Shallow Water Model ◽  
Porous Model ◽  
Processing Step ◽  
The City

After three hours of intense rainfall, the city of Nice was flash flooded on October 3, 2015, resulting in casualties and severe damages in property. This study presents a porous shallow water-model based numerical simulation of the flash flood event in a district of Nice, and compares the results with a high-resolution conventional shallow water model. This contribution aims to discuss practical aspects of applying a porous shallow water model to a real world case. The porous shallow water model is an integral porosity-type shallow water model. It uses unstructured triangular meshes. The conventional shallow water model is a distributed memory parallelized high-performance computing code, that uses a uniform Cartesian grid. The study site is an approximately 5 km2 spanning district of the city of Nice, France. Topography information is available in a 1m resolution and in addition, the available digital elevation model includes inframetric structures such as walls and small bridges. In the presentation of the case study, challenges of the pre-processing step of the integral porosity shallow water model are addressed. Notably, a method to semi-automatically generate “good” triangular meshes using the open-source geoinformation system QGIS and the mesh generator Gmsh is presented. During the post-processing step, the results of the porous model are mapped back onto the high-resolution topography to make the results more meaningful. The agreement between the high-resolution reference solution and the porous model results are poor. A speed up of about 10 to 15 was observed for the present case.

scholarly journals Assessment of flash floods taking into account climate change scenarios in the Llobregat River basin

2013 ◽  
Vol 13 (12) ◽  
pp. 3145-3156 ◽  
Author(s):  
M. Velasco ◽  
P. A. Versini ◽  
A. Cabello ◽  
A. Barrera-Escoda
Keyword(s):  
River Basin ◽  
Extreme Events ◽  
Hydrological Model ◽  
Flash Flood ◽  
Flash Floods ◽  
Climate Change Scenarios ◽  
Whole Process ◽  
The Future ◽  
Peak Over Threshold ◽  
Llobregat River

Abstract. Global change may imply important changes in the future occurrence and intensity of extreme events. Climate scenarios characterizing these plausible changes were previously obtained for the Llobregat River basin (NE Spain). This paper presents the implementation of these scenarios in the HBV (Hydrologiska Byråns Vattenbalansavdelning) hydrological model. Then, the expected changes in terms of flash flood occurrence and intensity are assessed for two different sub-basins: the Alt Llobregat and the Anoia (Llobregat River basin). The assessment of future flash floods has been done in terms of the intensity and occurrence of extreme events, using a peak over threshold (POT) analysis. For these two sub-basins, most of the simulated scenarios present an increase of the intensity of the peak discharge values. On the other hand, the future occurrence follows different trends in the two sub-basins: an increase is observed in Alt Llobregat but a decrease occurs in Anoia. Despite the uncertainties that appear in the whole process, the results obtained can shed some light on how future flash floods events may occur.

scholarly journals Using High-Resolution Satellite Rainfall Products to Simulate a Major Flash Flood Event in Northern Italy

2013 ◽  
Vol 14 (1) ◽  
pp. 171-185 ◽  
Author(s):  
Efthymios I. Nikolopoulos ◽  
Emmanouil N. Anagnostou ◽  
Marco Borga
Keyword(s):  
High Resolution ◽  
Complex Terrain ◽  
Flash Flood ◽  
Flash Floods ◽  
Hydrologic Model ◽  
Flood Event ◽  
Medium Size ◽  
Soil Conditions ◽  
Model Parameters ◽  
Satellite Rainfall

Abstract Effective flash flood warning procedures are usually hampered by observational limitations of precipitation over mountainous basins where flash floods occur. Satellite rainfall estimates are available over complex terrain regions, offering a potentially viable solution to the observational coverage problem. However, satellite estimates of heavy rainfall rates are associated with significant biases and random errors that nonlinearly propagate in hydrologic modeling, imposing severe limitations on the use of these products in flood forecasting. In this study, the use of three quasi-global and near-real-time high-resolution satellite rainfall products for simulating flash floods over complex terrain basins are investigated. The study uses a major flash flood event that occurred during 29 August 2003 on a medium size mountainous basin (623 km2) in the eastern Italian Alps. Comparison of satellite rainfall with rainfall derived from gauge-calibrated weather radar estimates showed that although satellite products suffer from large biases they could represent the temporal variability of basin-averaged precipitation. Propagation of satellite rainfall through a distributed hydrologic model revealed that systematic error in rainfall was severely magnified when transformed to error in runoff under dry initial soil conditions. Simulation hydrographs became meaningful only after recalibrating the model for each satellite rainfall input separately. However, the unrealistic values of model parameters after recalibration show that this approach is erroneous and that model recalibration using satellite rainfall data should be treated with care. Overall, this study highlights the need for improvement of satellite rainfall retrieval algorithms in order to allow a more appropriate use of satellite rainfall products for flash flood applications.

scholarly journals Towards fast large-scale flood simulations using 2D Shallow water modelling with depth-dependant porosity

2020 ◽  
Author(s):  
Vita Ayoub ◽  
Carole Delenne ◽  
Patrick Matgen ◽  
Pascal Finaud-Guyot ◽  
Renaud Hostache
Keyword(s):  
Shallow Water ◽  
Spatial Data ◽  
Large Scale ◽  
Model Performance ◽  
Water Model ◽  
Computational Time ◽  
Small Scale ◽  
Test Case ◽  
Strong Impact ◽  
Flood Simulations

<p><span>In hydrodynamic modelling, the mesh resolution has a strong impact on run time and result accuracy. Coarser meshes allow faster simulations but often at the cost of accuracy. Conversely, finer meshes offer a better description of complex geometries but require much longer computational time, which makes their use at a large scale challenging. In this context, we aim to assess the potential of a two-dimensional shallow water model with depth-dependant porosity (SW2D-DDP) for flood simulations at a large scale. This modelling approach relies on nesting a sub-grid mesh containing high-resolution topographic and bathymetric data within each computational cell via a so-called depth-dependant storage porosity. It enables therefore faster simulations on rather coarse grids while preserving small-scale topography information. The July 2007 flood event in the Severn River basin (UK) is used as a test case, for which hydrometric measurements and spatial data are available for evaluation. A sensitivity analysis is carried out to investigate the porosity influence on the model performance in comparison with other classical parameters such as boundary conditions.</span></p>

Modeling of Flash Floods in Wadi Systems Using a Robust Shallow Water Model—Case Study El Gouna, Egypt

2018 ◽  
pp. 579-593 ◽  
Author(s):  
Franziska Tügel ◽  
Ilhan Özgen ◽  
Reinhard Hinkelmann ◽  
Ahmed Hadidi ◽  
Uwe Tröger
Keyword(s):  
Shallow Water ◽  
Flash Floods ◽  
Water Model ◽  
Shallow Water Model ◽  
Model Case

scholarly journals Features of the Density Stratification Effects Numerical Simulation in the Greater Reservoirs Dynamics

2016 ◽  
pp. 32
Author(s):  
Keyword(s):  
Shallow Water ◽  
Thermal Power ◽  
Water Bodies ◽  
Density Stratification ◽  
Temperature Fields ◽  
Water Model ◽  
Hydrodynamic Models ◽  
Regulatory Guidelines ◽  
Study Case ◽  
The City

Density stratification effects determined by temperature fields and mineralization fields’ distribution heterogeneity can play an essential role in formation of both hydrological and hydro/chemical regime of surface water bodies. At that, they cannot be described within the frameworks of hydrodynamic models in a shallow water statement. Description of these processes within the framework of the combined approach based on the models conjunction in 1D,2D,3D statement with the study cases (water quality formation downstream the Chusvaya and the Sylva rivers confluence in the Kama thermal electro station backwater; features of the Kama reservoir thermal contamination zones formation due to the Kama thermal electro station operation; special features of the high density waste waters diffusion in water bodies) has been made. It has been demonstrated that the proposed calculation scheme will enable to reproduce effectively the processes of the Sylva River more dense water mass dribbling under the Chusovaya waters during winter periods. This has a critical significance for the city of Perm sustainable drinking water supply. It has been shown (with the thermal contamination zones formed by the Perm thermal power station as a study case) that the proposed approach much more reliable in reproduction and assessment of the temperature fields under study than traditional hydro/dynamic shallow water model in 2D statement. Estimation of the potassium industry excessive brines impact on the Kama reservoir has demonstrated higher effectiveness of the proposed method in comparison with those defined by the currently in force regulatory guidelines.

Geomorphic and Sedimentological Impact of the 2017 Flash Flood Event in the City of Comodoro Rivadavia (Central Patagonia, Argentina)

2021 ◽  
pp. 3-29
Author(s):  
José Matildo Paredes ◽  
Silvina Mariela Ocampo ◽  
Nicolás Foix ◽  
Sabrina Ximena Olazábal ◽  
Mauro Nicolás Valle ◽  
...  
Keyword(s):  
Flash Flood ◽  
Flood Event ◽  
The City

scholarly journals 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

2012 ◽  
Vol 12 (5) ◽  
pp. 1295-1309 ◽  
Author(s):  
G. T. Aronica ◽  
G. Brigandí ◽  
N. Morey
Keyword(s):  
Soil Moisture ◽  
Debris Flow ◽  
Flash Flood ◽  
Flash Floods ◽  
Event Analysis ◽  
Gis Technology ◽  
North East ◽  
Temporal And Spatial Variability ◽  
Moisture Conditions ◽  
The City

Abstract. 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.

scholarly journals What if the 25th October 2011 event that stroke Cinque Terre (Liguria) had happened in Genova, Italy? Flooding scenarios, hazard mapping and damages estimation

2016 ◽  
Author(s):  
Francesco Silvestro ◽  
Nicola Rebora ◽  
Lauro Rossi ◽  
Daniele Dolia ◽  
Simone Gabellani ◽  
...  
Keyword(s):  
Flash Flood ◽  
Flash Floods ◽  
Economic Losses ◽  
Risk Level ◽  
Hazard Mapping ◽  
Rainfall Events ◽  
The People ◽  
Set Up ◽  
The City ◽  
Complete Framework

Abstract. During the autumn of 2011 two catastrophic very intense rainfall events affected two different parts of the Liguria Region of Italy causing various flash floods. The first occurred in October and the second at the beginning of November. They became two "school cases" studied by many scientists around the world and they awaken the interest of the local authorities and of the civil protection actors regarding these type of calamities. Due to the large amount of damages and the numerous victims, they caused a general increase of the sensibleness of the citizens of the stricken areas regarding the natural hazards. Two main considerations were done in order to set up this work. The first consideration is that various studies demonstrated that the two events had a similar genesis and similar triggering elements. The second very evident and coarse concern is that two main elements are needed to have a flash flood: a very intense and localized rainfall event and a catchment (or a group of catchments) to be affected. Starting from these assumptions we did the exercise of mixing the two flash floods ingredients by putting the rainfall field of the first event on the main catchment stroke by the second event that has its mouth in correspondence of the biggest city of the Liguria Region: Genova. A complete framework was set up to quantitatively carry out a "what if" experiment with the aim of evaluating the possible damages associated to this event. The approachcombines a probabilistic rainfall downscaling model, a hydrological model, a 2D hydraulic model and a proper methodology for damages estimation. This leads to the estimation of the potential economic losses and of the risk level for the people that stays in the affected area. The results are interesting, surprising and in such a way worrying: a rare but not impossible event (it occurred about 50 km away from Genoa) would have caused huge damages estimated between 120 and 230 million of euros for the affected part of the city of Genova, Italy and more than 17 000 potentially affected people.

scholarly journals Porous Shallow Water Modeling for Urban Floods in the Zhoushan City, China

2021 ◽  
Vol 9 ◽  
Author(s):  
Wei Li ◽  
Bingrun Liu ◽  
Peng Hu ◽  
Zhiguo He ◽  
Jiyu Zou
Keyword(s):  
Shallow Water ◽  
Computational Cost ◽  
Water Model ◽  
Shallow Water Model ◽  
Complex Flow ◽  
Local Complex ◽  
Building Effects ◽  
Refined Meshes ◽  
Complex Building ◽  
The City

Typhoon-induced intense rainfall and urban flooding have endangered the city of Zhoushan every year, urging efficient and accurate flooding prediction. Here, two models (the classical shallow water model that approximates complex buildings by locally refined meshes, and the porous shallow water model that adopts the concept of porosity) are developed and compared for the city of Zhoushan. Specifically, in the porous shallow water model, the building effects on flow storage and conveyance are modeled by the volumetric and edge porosities for each grid, and those on flow resistance are considered by adding extra drag in the flow momentum. Both models are developed under the framework of finite volume method using unstructured triangular grids, along with the Harten-Lax-van Leer-Contact (HLLC) approximate Riemann solver for flux computation and a flexible dry-wet treatment that guarantee model accuracy in dealing with complex flow regimes and topography. The pluvial flooding is simulated during the Super Typhoon Lekima in a 46 km2 mountain-bounded urban area, where efficient and accurate flooding prediction is challenged by local complex building geometry and mountainous topography. It is shown that the computed water depth and flow velocity of the two models agree with each other quite well. For a 2.8-day prediction, the computational cost is 120 min for the porous model using 12 cores of the Intel(R) Xeon(R) Platinum 8173M CPU @ 2.00 GHz processor, whereas it is as high as 17,154 min for the classical shallow water model. It indicates a speed-up of 143 times and sufficient pre-warning time by using the porous shallow water model, without appreciable loss in the quantitative accuracy.

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