Development of Two-Dimensional Inundation Modelling Process using MIKE21 Model

Abstract

Because river flooding and urban inundation due to extreme rainfall cause the severe damages on the infrastructure, it is necessary to develop an accurate prediction technique and to overcome the disasters. In this study, numerical simulation method was applied to predict urban inundation area with appropriate assumptions and hydrological data in the Lower Var valley region in France. The application site is located in the southeast of France and also geometrically complex with several hydraulic structures, such as weir and bridge piers from the mainstream of a river to the Mediterranean Sea. With complex geometrical consideration, numerical modelling of inundation was conducted separately with two steps. Firstly, the whole area of river reach with the urban area was simulated and analyzed. From the results, the smaller urbanized area was specified with consideration of the capacity of inundation. Two-dimensional hydrodynamic model, MIKE 21 FM (flow model) is applicable to simulations of river hydraulics and flood inundation including the urbanized properties. Upstream discharges for the boundary conditions were set up with based on the Gumbel distribution and SCHADEX method. From the numerical simulation, inundation area and river flow variation were analyzed and compared with respect to the upstream discharge scenarios. Furthermore, the effect of computational mesh resolution was analyzed with the urban model. Calculated flooded areas from the simulation results of the whole area model and urbanized models were compared and verified as a newly proposed and applied procedure of inundation analysis in the riverine area.