Soil erosion assessment by a GIS approach for a wide area of Northwestern Morocco

Morocco constitutes one of the Mediterranean regions where the erosion has reached its paroxysm. This ecological phenomenon is more relevant in the Rif Chain, to which belongs our study area: the Laou river watershed. This part of the Rif is generally characterized by friable formations and systematically exposed to torrential precipitations; moreover, its plant cover has known a substantial degradation during these last decades. The methodology consists to integrate the descriptive data about specific components of the natural habitat into a GIS platform, in order to survey the potential sensitivity of soils to water erosion. This may be achieved from intersecting information layers on soils, land use and topography. Cumulating the effect of these factors, we may assign a spatially distributed qualitative map of potential sensitivity, within one of 5 grades: very weak, weak, average, elevated and very elevated. The map-rendering show that severe erosion affects the Southern and Northern west sectors of the basin, even if they present the least erodible lands of all the basin and have, as well, a relatively dense plant cover. It may be concluded that both high gradient and damaged terrain state represent the main factors of water erosion in the Laou watershed