Assessing landslide susceptibility of Türkiye at drainage basin scale: a semi-quantitative approach

This study uses the Analytical Hierarchy Process (AHP) integrated with Geographic Information Systems (GIS) to assess landslide susceptibility in Türkiye at a drainage basin scale. Türkiye's mountainous terrain makes it highly prone to landslides, especially due to heavy rainfall from climatic changes. Addressing the need for comprehensive assessments, the study integrates multiple parameters such as slope, lithology, internal relief, land cover, and annual rainfall amount using publicly accessible datasets such as digital elevation models (DEM), geological maps, and rainfall records. The first comprehensive landslide susceptibility map for Türkiye was produced, validated through histogram and ROC curve analyses, resulting in 1:500,000 scale maps for each basin. This assessment offers a detailed understanding of landslide occurrences, identifying that moderate slopes (5–15°) and internal relief (200–250 m/km2) significantly influence landslides. A potential threshold for the Topographic Wetness Index (TWI) at 12–13 was also identified. The study highlights the importance of DEM resolution and strategic area subdivision for detailed analysis. The maps and classification methods provide a valuable framework for future research, enhancing understanding of geological hazards and aiding decision-makers in managing landslide risks. Recommendations include prioritizing open data, evaluating TWI, and refining classification methods for improved accuracy.