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Amro Elfeki, Hatem Ewea and Nassir Al-Amri Dept. of Hydrology and Water Resources Management, Faculty of Meteorology, Environment & Arid Land Agriculture,

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Presentation on theme: "Amro Elfeki, Hatem Ewea and Nassir Al-Amri Dept. of Hydrology and Water Resources Management, Faculty of Meteorology, Environment & Arid Land Agriculture,"— Presentation transcript:

1 Amro Elfeki, Hatem Ewea and Nassir Al-Amri Dept. of Hydrology and Water Resources Management, Faculty of Meteorology, Environment & Arid Land Agriculture, King Abdulaziz University

2 Outline Images of The 25 th Nov. 2009 Storm Event. Objectives. The Proposed Urban Flooding Model Concept. Brief Review of Hydrodynamic Models for Urban Flood Simulations. Integrated Framework with Geomatic Techniques for Modelling Urban Flooding. Simulation of Urban Flooding (Model Results). Conclusions. Elfeki, Ewea & AL-Amri

3 Images of Flood on the 25 th Nov. 2009 at KAU Campus and Surrounding Streets Elfeki, Ewea & AL-Amri

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5 Objectives Developing an integrated framework with geomatics techniques for modelling urban flooding based on a newly proposed hydrodynamic model that has the following features: - Conceptually simple. - Efficient in terms of computer cost (Time and Storage). Using the developed model to simulate the flood event on the 25 th of Nov. 2009 in Jeddah city. Elfeki, Ewea & AL-Amri

6 The Proposed Model Concept The proposed hydrodynamic model is based on a simplified form of St. Venant equations (eliminate local acceleration and inertial terms) and combining the simplified equations with continuity to form a diffusion type partial differential equation (Diffusive wave model). The solution of the model is performed based on the analogy with “Random Walk Theory” used to solve transport equation in groundwater. Elfeki, Ewea & AL-Amri

7 Hydrodynamic Models for Flood Propagation Elfeki, Ewea & AL-Amri Q = discharge u = velocity of flow h = water depth g = acceleration due to gravity S o = bed slope S f = friction slope A = channel cross section

8 Saint Venant Equations in 2D Elfeki, Ewea & AL-Amri u = x-component of the flow velocity v = y-component of the flow velocity x, y = coordinates n = Manning roughness coefficient z b = bed elevation

9 Analogy with 1-D Advection Diffusion Model Elfeki, Ewea & AL-Amri B= channel width c =flood wave celerity D= dispersion coefficient

10 Analogy with 2-D Advection Diffusion Model Elfeki, Ewea & AL-Amri D xx = is the dispersion coefficient in x-direction due to flow in x-direction D yy = is the dispersion coefficient in y-direction due to flow in y-direction D Xy = is the dispersion coefficient in x-direction due to flow in y-direction D yX = is the dispersion coefficient in x-direction due to flow in x-direction ∆z = the difference in bed elevation between two cells ∆x and ∆y = are the cell size in x and y directions k is roughness coefficient given by McCuen (1989) and SCS (1972) provide values of k for several flow situations.

11 Proposed Urban Flooding Model: Random Walk Theory for Solving DWM Elfeki, Ewea & AL-Amri

12 Inundated Depth Elfeki, Ewea & AL-Amri h(t) = the water depth at time t h(t-∆t) = the water depth at time t n = number of particle in the cell V p = the volume of water per particle (volume from the hydrograph divided by the number of particles chosen in the model

13 Integrated Framework with Geomatics for Urban Flooding Modeling Procedure:  Extraction of Wadi Qows Catchment using WMS based on DEM (30 m) form NASA.  Identifying Land Use and Land Cover (from Satellite Images) and Estimation of CN.  Formulating data in a GIS Format (Arc-View).  Rainfall Frequency Analysis (SMADA).  Rainfall-Runoff Modeling (HEC-HMS).  The Proposed Hydrodynamic Model for Urban Flood Modeling.  Superimposing the Inundated Area (model output) on Satellite Images (SURFER). Elfeki, Ewea & AL-Amri

14 Wadi Qows Catchment Elfeki, Ewea & AL-Amri WadiArea (km2) Length (km) Slope (m/m) Mean basin elevation (m) CN Wadi Qows 63.4170.0518143.570 Main parameters of Wadi Qows

15 Spatial Distribution of the 25 th of Nov 2009 Storm Elfeki, Ewea & AL-Amri 25 th of Nov 2009 Storm Recorded by Radar from Global Precipitation Mission (UNESCO, G-WADI and California University)

16 Rainfall Analysis Elfeki, Ewea & AL-Amri Fitting probability distribution functions to the rainfall data at King Abdulaziz Airport Station (Data from General Presidency of Meteorology, KSA) Standard Error Best Probability Distribution King Abdulaziz Airport Station 2 Parameter Log-normal53.72 3 Parameter Log-normal23.09 Pearson Type III17.85 Log-Pearson Type III20.96 Gumbel Type I20.96

17 Synthetic Flood Hydrograph of Wadi Qows for the 25 th Nov. 2009 Storm Elfeki, Ewea & AL-Amri SCS Method has been used to generate synthetic flood hydrograph of Wadi Qows for the 25 th Nov. 2009 storm (HEC-HMS)

18 Urban Flooding: Modeled Area Elfeki, Ewea & AL-Amri

19 Regions and Buildings Representation in the Study Elfeki, Ewea & AL-Amri The area is divided into cells 20 by 20 ms. Buildings and streets are assumed to have the same sizes. The Buildings are of infinite tall. The flow is only allowed to move in the streets and around the buildings. The flow is driven from East to West under ground surface gradients. Not all buildings are represented in the model.

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26 Simulation of the Flooded Area Elfeki, Ewea & AL-Amri

27 Visual Comparison Elfeki, Ewea & AL-Amri

28 Conclusions An integration of geomatics techniques (GIS, Satellite Images, WMS) with hydrological (HEC-HMS) and hydraulic models (DWM) is presented. A model has been proposed for flood simulation in urban areas. The model is based on a simplified version of St. Venant equations )diffusive wave model( in two dimensions and solved by the random walk method. The model is suitable to show the flooding of initially dry areas. The model is in its early stage it cannot reproduce the details of the flow structure. Compared to other numerical schemes it has the advantage that it is efficient in terms of computational costs. Elfeki, Ewea & AL-Amri

29 Outlook Future research will address issues that are not yet resolved to further improve the quality and the reliability of the results for flood hazard assessment. Elfeki, Ewea & AL-Amri


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