GIS-based technic for roadside-slope stability assessment: an bivariate approach for A1 East-West highway, North Algeria

This paper presents a GIS-based method for landslide susceptibility (LS) assessment using slope-movement inventory and field data. The study has been carried out along A1-Highway (A1-H) in Hanif region as this road section is threated by several types of mass wasting. This hilly zone is known by their landslides sensitive terrains in the North of Algeria. The terrain data are collected from a Géologic map, satellite imageries, digital elevation model, rainfall data, field suveys and ancillary data. In this paper Frequency Ratios (FR) based on bivariate statistical method are evaluated by comparing the observed landslides to their controlling factors. The product of the linear summation of the FR values was a landslide susceptibility index (LSI) map. It was categorized using the natural breaks classification method. The resultant LS zonation map delineates the area into five hierarchic zones. The results confirms that the angle of the slope, plays the most role in wasting especially in road sides. The LS can be used for preliminary land use planning and hazard mitigation purpose. By means of this map the current route of the A1-H can be improved to cross less susceptibles zones.