Landslide Hazard Zonation and Evaluation around Debre Werk Town, North West Ethiopia

Abstract The present research was conducted in the town of Debre Werk, East Gojjam, North West Ethiopia, with the ultimate aim of conducting a Landslide Hazard Zonation and Evaluation. To reach this aim, the Slope Stability Susceptibility Evaluation Parameter (SSEP) rating system was adopted to zone and evaluate the landslide status of the area. This rating system was done by considering the parameters of intrinsic and external triggering factors that cause landslides. Systematic and detailed fieldwork had been undertaken as a justification. Secondary data, on the other hand, was required to define the general conditions of the area and to gain a thorough understanding of the field of study. Ratings for intrinsic parameters in the SSEP system include slope morphometry, relative relief, slope content, geological structures/discontinuities, land use land cover, groundwater, and external parameters include erosion, seismicity, and manmade activities. Individual facet-wise ratings for intrinsic causative factors and external triggering factors ratings are summarized to evaluate the landslide hazard zonation of an environment. The sum of all causative parameter ratings will give evaluated landslide hazards (ELH). Therefore, the research was carried out by dividing the study area into 70 facets. Then 85 landslide incidents in the study area were investigated. From 85 landslides, 39 districts showed past landslides, 23 showed active landslides and the remaining 23 districts showed signs of landslides. The delineated 70 facets were categorized into 3 landslide hazard zones. There are about 73.3km2 (27.2%) of the study area within the low hazard zone, 140.8km2 (52.1%) within the moderate hazard zone, and the remaining 55.9km2 (20.7%) within the high hazard zone. Based on the findings of SSEP, it can be deduced that the present research area is highly susceptible to landslide and requires special attention during rainy seasons. Finally, the validity of the prepared LHZ map was checked by overlaying the inventory map over the produced LHZ map. The overlap map shows that 17 districts showing active landslides, 2 districts showing signs of landslides, and 5 districts showing past landslide activities fall into high hazard zones. Likewise, 5 districts showing active landslides, 3 districts showing signs of landslides, and 28 districts showing past landslides fall into moderate hazard zones. The remaining 1 district showing active landslides, 18 districts showing signs of landslides, and 6 districts showing past landslide activities fall into moderate hazard zones.