Modelling flash flood propagation in urban areas using a two-dimensional numerical model |
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Authors: | Kamal El Kadi Abderrezzak André Paquier Emmanuel Mignot |
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Affiliation: | (1) Cemagref, UR HHLY, 3bis quai Chauveau-CP220, F-69336 Lyon, France;(2) LEGI, Laboratory of Geophysical and Industrial Fluid Flows, 1025 rue de la Piscine BP 53, 38041 Grenoble Cedex 9, France |
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Abstract: | This paper reports on the numerical modelling of flash flood propagation in urban areas after an excessive rainfall event or dam/dyke break wave. A two-dimensional (2-D) depth-averaged shallow-water model is used, with a refined grid of quadrilaterals and triangles for representing the urban area topography. The 2-D shallow-water equations are solved using the explicit second-order scheme that is adapted from MUSCL approach. Four applications are described to demonstrate the potential benefits and limits of 2-D modelling: (i) laboratory experimental dam-break wave in the presence of an isolated building; (ii) flash flood over a physical model of the urbanized Toce river valley in Italy; (iii) flash flood in October 1988 at the city of Nîmes (France) and (iv) dam-break flood in October 1982 at the town of Sumacárcel (Spain). Computed flow depths and velocities compare well with recorded data, although for the experimental study on dam-break wave some discrepancies are observed around buildings, where the flow is strongly 3-D in character. The numerical simulations show that the flow depths and flood wave celerity are significantly affected by the presence of buildings in comparison with the original floodplain. Further, this study confirms the importance of topography and roughness coefficient for flood propagation simulation. |
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Keywords: | Urban flash flood Shallow-water equations 2-D depth-averaged model Dam-break wave |
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