Use of 3D classified topographic data with FullSWOF for high resolution simulation of a river flood event over a dense urban area

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 standard 2D Shallow Water Equations (SWE) based numerical codes. FullSWOF (Full Shallow Water equations for Overland Flow) is a code based on 2D SWE under conservative form. This code relies on a wellbalanced 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 FullSWOF allows to handle properly flow regime changes, preservation of water depth positivity at wet/dry cells transitions and steady state preservation. FullSWOF has already been tested on analytical solution library (SWASHES) and has been used to simulate runoff and dam-breaks. FullSWOFs 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 FullSWOF code properties for overland flow simulation in urban environment. ∗Polytech Nice Sophia & I-CiTy, University of Nice Sophia Antipolis, France, e-mail : [email protected] †Lab. J.A. Dieudonné & EPU Nice Sophia, University of Nice, France, e-mail : [email protected] ‡Polytech Nice Sophia & I-CiTy, University of Nice Sophia Antipolis, France §Institut for Radioprotection and Nuclear Safety (IRSN), France ¶MAPMO, fédération Denis Poisson, University of Orléans, France, e-mail : [email protected] ‖Institut for Radioprotection and Nuclear Safety (IRSN), France, e-mail : [email protected] ∗∗Polytech Nice Sophia & I-CiTy, University of Nice Sophia Antipolis, France 1 ar X iv :1 60 3. 07 46 3v 1 [ m at h. N A ] 2 4 M ar 2 01 6 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 FullSWOF 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 FullSWOF performances for such a purpose are highlighted.