Utilisation des systèmes d'information géographiques et des modèles hydrologiques pour l'extraction des caractéristiques physiques du bassin versant d'Assaka (Guelmim, sud du Maroc) [ The use of geographic information system for the extraction of physical characteristics of assaka watershed: sub-basins of sayed and oum laachar wadis (southern Morocco) ]

In order to establish a flood hazard and flood risk maps of Guelmim city (south of Morocco), physical characteristics evaluation of the Assaka watershed proves primordial; mainly the Sayed and Oum Laachar wadis sub-watersheds. In the end of 2014, the Assaka basin with its main affluents Sayed and Oum Laachar wadis were subject to floods causing huge human and material damages. The methodological approach is based on the use of Geographic Information System ArcGIS and spatial hydrological models, HEC-GeoDozer and HEC-GeoHMS, for the treatment of a field digital model (Modèle Numérique de Terrain : MNT) to extract the physical characteristics of both sub-watersheds. The data obtained will provide an important basis for the elaboration of a hydrological model; an easy tool for decision-makers for the management of the Sayed and Oum Laachar wadis and the prevention against their flooding. The final result of the GIS processing is a spatial hydrologic database containing a very dense hydrographic network of the two basins and a variable slope, strong at the edge of the basin and lower in the plain of Guelmim, which favors the rainwater accumulation and the wadis overflow during floods.