Geospatial Assessment of Landslide Susceptibility Using Geomorphic and Climatic Factors: A Case Study of the Nilgiri Hills, Tamil Nadu, India

Abstract Landslides are among the most frequent and destructive geomorphic hazards in mountainous environments, posing severe threats to human settlements, infrastructure, and ecosystems. The Nilgiri Hills, situated in the southern part of the Western Ghats of India, have witnessed recurrent landslide occurrences due to the interplay of complex topography, intense monsoonal rainfall, and anthropogenic pressure. This study aims to assess landslide susceptibility using a geospatial approach integrating geomorphic and climatic factors. The research utilizes multi-criteria evaluation in a GIS environment, incorporating parameters such as slope, aspect, elevation, lithology, land use/land cover, drainage density, rainfall intensity, temperature variation, and vegetation cover (NDVI). Using the Analytical Hierarchy Process (AHP), weights were assigned to each factor based on their relative importance derived from expert judgment and statistical correlation with past landslide occurrences. A landslide inventory comprising 238 mapped landslide points (from 2000–2024) was used for model validation. The resulting Landslide Susceptibility Map (LSM) classified the area into five susceptibility zones: very low (12.3%), low (19.8%), moderate (27.5%), high (24.1%), and very high (16.3%). Validation using the Receiver Operating Characteristic (ROC) curve showed an area under the curve (AUC) value of 0.89, indicating high model performance and predictive accuracy. The spatial pattern reveals that areas with steep slopes (>35°), high rainfall (>2500 mm/year), and low vegetation index are more prone to landslides. The study emphasizes that the integration of geomorphic and climatic variables through geospatial modeling provides a robust framework for hazard mitigation and sustainable land management in mountainous regions. This approach can be replicated for other landslide-prone regions in India and globally to support proactive disaster risk reduction strategies and infrastructure planning. Keywords Landslide Susceptibility · Geospatial Analysis · GIS · AHP · Geomorphic Factors · Climatic Factors · Nilgiri Hills · Hazard Mapping