Instabilities Susceptibility Assessment of Fractured Rock Masses Using Geographic Information System: Application on the Sector of Mako (South-Eastern Senegal)

Abstract

The Mako area located in the region of Kedougou is characterized by very hilly terrains with hardly accessible zones. This situation makes it difficult to map these terrains and exposes the populations to the permanent risk of a rock slide. The issue of this paper is to evaluate the instabilities susceptibility at the Mako zone located at the hilliest zone of Senegal. It is done using Geographic Information Systems (GIS). The predisposing factors that are slope, lithology, hydrography, fracturing, land use are defined by the GIS and field data then are confirmed by field observations. According to field observations, more possible scenarios are SC1 and SC4 at the dry season and rainy season respectively. The instabilities susceptibility maps are taken from weighted overlay of these factors and they show that hilly areas are the most susceptible to rockslide or landslide when fractures are present with percent of moderate to high susceptibility between 13% and 22%. These percentages increase and can reach more than 40% with an intense water flow during the rainy season. Hazard can reach up to two hundred meters of foothill according to maps.