GIS-Based AHP and FR Methods for Landslide Susceptibility Mapping in the Abay Gorge, Dejen–Renaissance Bridge, Central, Ethiopia

The study area is situated in the Abay Gorge near Dejen, in Central Ethiopia. The place is affected by landslides, roadside slides, and further road failures. This study provides a detailed evaluation of causative factors for landslides, characterizes the materials on slopes, and assesses the hydrogeological condition of the study area. GIS techniques were employed to produce a zonation map for a landslide by combining the analytical hierarchy process (AHP) and frequency ratio (FR) methods. The prepared landslide hazard zonation map of the area using AHP and FR approaches is classified further into five susceptibility classifications: extremely low (6 & 20%), low (26 & 20%), moderate (3 & 21%), high (20 & 20%), and very high (12 & 19) of AHP and FR respectively. In this study, the causes of the landslide were identified and included slope, aspect, rainfall, land use/cover, elevation, lithology, distance to streams, and distance to the road were analyzed. The results show that the landslides in the area were triggered by heavy rainfall. The fragile nature of the geological materials and heavy stream discharge aggravates the instability of the area. Accordingly, the following solutions are suggested: (1) constructing slope-retaining structures, (2) designing an adequate drainage system for road corridors (3) Encourage afforestation in the affected areas, and (4) Using stream and drainage management practices to reduce flooding.