Regional Landslide Inventory Mapping of Bashilo River Watershed, Ethiopia

Abstract

This study tentatively identified large bedrock landslide features across the Bashilo River, a tributary of the upper Blue Nile River of Ethiopia, using a geospatial mapping approach. The study aims to highlight the utilization of low-cost mapping techniques that might be applicable across large tracts of land (between 1000 and 500,000 km 2 ). Topographic maps with 40 m contours were draped onto 30-m-spatial-resolution hillshade digital elevation models generated from the Advanced Space-borne Thermal Emission and Reflection Radiometer (ASTER), which were utilized to produce stitched hillshade topographic maps to allow the delineation of possible bedrock landslide features. The landslide identification process was aided by employing anomalous topographic protocols, including: divergent contours, isolated topographic benches, crenulated contours, and disturbed drainage patterns as key indicators of likely landslide-related features. The mapping exercise identified several hundred landslide features, including some landslide complexes believed to be seismically induced, composite bedrock landslides, rotational slumps, earth flows, and translational block slides generally > 500 m in length. This first-pass regional landslide inventory was based on moderate-resolution data and limited resources. The resulting maps are intended to serve as a general guide for regional hazard assessment, realizing that more detailed site-specific studies should be undertaken where mapped landslide features might pose a hazard to the placement of critical infrastructure, such as highways, railroads, pipelines, electrical transmission corridors, and structures.