10.4122/1.1000001748 Lhomme, J. Bouvier, C. Mignot, E. Paquier, A. One-dimensional GIS-based model compared to two-dimensional model in urban floods simulation DTU Library, Technical University of Denmark (DTU) 2005 Crossroads GIS-based model kinematic wave one dimensional models two dimensional models urban floods Maison des Sciences de l\342\200\231Eau, UMR HydroSciences Montpellier UR Hydrologie-Hydraulique, Cemagref en Conference full text 10.4122/1.1000001747 application/pdf 1 ABSTRACT A GIS-based one-dimensional flood simulation model is presented and applied to the centre of the city of N\303\256mes (Gard, France), for mapping flow depths or velocities in the streets network. The geometry of the one-dimensional elements is derived from the Digital Elevation Model (DEM). The flow is routed from one element to the next using the kinematic wave approximation. At the crossroads, the flows in the downstream branches are computed using a conceptual scheme. This scheme was prior designed to fit Y-shaped pipes junctions, and has been here modified to fit X-shaped crossroads. The results were compared with the results of a two-dimensional hydrodynamic model based on the full shallow water equations. The comparison shows that good agreements can be found in the steepest streets of the study zone, but differences may be important in the other streets. Some reasons that can explain the differences between the two models are given and some research possibilities are proposed.