Landslide susceptibility mapping and rock slope stability assessment using frequency ratio and kinematic analysis in the mountains of Mgulat area, Northern Ethiopia

Landslides, mainly triggered by rainfall, are one of the most common natural hazards in the northern and central highlands of Ethiopia, resulting in the loss of human life and property. As part of the Ethiopian highlands, Mgulat Mountain (88.6 km(2)) is a typical example for the occurrence of landslides and associated damages. The main aim of this research was to generate landslide susceptibility map (LSM) for the first time by considering various causative factors typical for the Mgulat Mountain area. The methods used include frequency ratio (FR) and kinematic analysis (KA) supported by GIS tools. The research involved conventional fieldwork (e.g., geological mapping, landslides inventory) and analysis and interpretation of images. From the geological mapping, major rock units were identified: quaternary deposit, basalt, red sandstone, tillite, and white sandstone. A total of 220 landslides (15.45 km(2)) were identified in the study area from field survey, Google Earth and aerial photo interpretation. Five causative factors (lithology, slope steepness, distance from drainage, land use-land cover (LULC), and slope aspect) were selected based on their contribution to landslide initiation as the landslide conditioning factors for generation of the LSM. From the five causative factors, lithology and slope steepness were found to be influential as landslide conditioning factors. Specifically, lithology (red sandstone and tillite), distance to stream (0 to 300 m), LULC (bare land and settlement), and slope steepness (> 25 degrees) have FR > 1, indicating a high relationship with landslide occurrence. Based on the generated LSM, five susceptibility classes or zones were identified (very low, low, moderate, high, and very high susceptibility). The area of each class as percentage of total area was found to be 19.53, 24.15, 22.57, 18.74, and 15.01%, for the very low to the very high class, respectively. The results of KA show potentially and marginally planar, topple, and wedge failures. The generated LSM can serve as an important tool or guide for further land-use planning and to prevent and mitigate landslide-related risks. Consequently, to consider cost-effective and technically sound mitigation measures, detailed and site-specific multidisciplinary investigations are recommended.

Automated summary

The study generated a landslide susceptibility map (LSM) for Mgulat Mountain, identifying red sandstone and tillite lithologies, as well as slope steepness, as major conditioning factors for landslides. Five susceptibility classes were identified based on LSM results, providing important guidance for further land-use planning and mitigation of landslide risks. Detailed multidisciplinary investigations are recommended to consider cost-effective and technically sound mitigation measures.