GIS-based landslide susceptibility mapping in the Safi region, West Morocco

Abstract

This study aims to establish susceptibility maps for the Moroccan Safi region, which is affected by karstification processes. This process is the predisposing factor for various landslide types such as debris flows and rock falls. In the first phase of this study, a landslide inventory was prepared by geomorphological approach based on visual interpretation of aerial photographs combined with direct observations in the field. The obtained inventory included 234 landslides: 14 rock slides and 75 debris flows in Brown Clay Formation, 74 rock falls in sandstone and 71 rock topples in Dridrat Limestone Formations. The inventory map showed that landslide phenomena occur mainly in the northwest and along the active coastal cliffs in the south of Safi. In the second phase, four landslide susceptibility maps were realized using the bivariate statistical method of Geographical Information System (GIS) matrix method (GMM). The established landslide susceptibility maps were validated by the degree of fit method. Obtained results showed that landslide phenomenon occurs mainly in the northwest and along the coastal cliffs in the south of the study area. Moreover, very high and high susceptibility levels were limited to the area including industrial and touristic activities as well as historical monuments. Overall, landslides were associated to karstification, lithology, karstic rocks and karstic spring presence, which are considered as predisposing and causal factors.