Author(s): Abily Morgan; Delestre Olivier; Amosse Laura; Bertrand Nathalie; Laguerre Christian; Duluc Claire-Marie; Gourbesville Philippe
Linked Author(s): Philippe Gourbesville
Keywords: Flood risks; High resolution modeling; FullS WOF; Photogrammetry; Var river
Abstract: High resolution (infra-metric) topographic data, including photogrammetric born 3D classified data, are becoming commonly available at large range of spatial extend, such as municipality or industrial site scale. This category of dataset is promising for high resolution (HR) Digital Surface Model (DSM) generation, allowing inclusion of fine above-ground structures which might influence overland flow hydrodynamic in urban environment. Nonetheless several categories of technical and numerical challenges arise from this type of data use with standard2D Shallow Water Equations (SWE) based numerical codes. Full SWOF (Full Shallow Water equations for Overland Flow) is a code based on 2D SWE under conservative form. This code relies on a well-balanced finite volume method over a regular grid using numerical method based on hydrostatic reconstruction scheme. When compared to existing industrial codes used for urban flooding simulations, numerical approach implemented in Full SWOF allows to handle properly flow regime changes, preservation of water depth positivity at wet/dry cells transitions and steady state preservation. Full SWOF has already been tested on analytical solution library (SWASHES) and has been used to simulate runoff and dam-breaks. Full SWOF’s above mentioned properties are of good interest for urban overland flow. Objectives of this study are (i) to assess the feasibility and added values of using HR 3D classified topographic data to model river overland flow and (ii) to take advantage of Full SWOF code properties for overland flow simulation in urban environment. A large aerial 3D classified topographic data gathering campaign has been conducted by Nice Municipality (France) in 2010. Accuracy of this classified data is 0. 2 m in both planimetry and altimetry. This data set is available for the low Var river valley where an extreme flood event occurred in 1994. 3D classified data is used to generate different categories of DSMs and Full SWOF code has been adapted to be used in a river flood condition context. Results demonstrate the feasibility and the clear added value of HR topographical data use. Methodology and limits for such an approach for engineering perspectives are raised up. The study highlights the need of using HR topographical data set to model flood event in urban areas and Full SWOF performances for such a purpose are highlighted.