Flood Modeling And Floodplain Mapping Based On Geographical Information System (Gis) And Hec-Ras In Oued Fez Watershed (Morocco)

Abstract

Maps give a more direct and stronger impression of the spatial distribution of the flood risk than other forms of presentation such as diagrams or verbal description. The urban flood risk appears among the major environmental preoccupations of actors in resources management and land planning; and this issue is exacerbated by the climatic and the global change factors. Flood, considered as one of the worst weather-related natural disaster, cause severe damages to life, properties and environment. For the floodplain mapping, we adopted an approach based on modeling of flows processes using US Army Corps of Engineers Hydrological Engineering Corporation’s River Analysis System (HEC-RAS) model. The main sources of information are maps, hydro-meteorological data, Digital Elevation Model (DEM), satellite images, field observation, etc. This research presents a straightforward approach for processing input and output of the HEC-RAS hydraulic model, to enable two and three dimensional floodplain mapping and analysis in the ArcGIS environment. The hydraulic modeling tool HEC-RAS is used to perform the steady flow simulations and the model input files are developed in the ArcMap environment by using the software extension HEC-GeoRAS. The study area concerns Fez located in Saiss plain. The agglomeration of the city is actually being developed in the area of confluence of all the hydrologic network of Oued Fez watershed. This watershed, which is composed of several sub-basins, receive its water from six essential Oueds. The results of the study indicate furthermore that Geographic Information System is an effective environment for floodplain mapping and analysis. The resulting GIS maps, consisting of flood hazard, floodplain extension and risk maps. This helpful information can guide the local early warning system of flood and identify the areas facing flood risks.