Prioritization of sub-watersheds for soil erosion management in the Rangit River Basin: A morphometric and multi-criteria decision-making approach

Soil erosion constitutes a critical environmental hazard in the tectonically active and hydrologically volatile Eastern Himalayas. Sub-watersheds must be given high priority to ensure sustainable land resource management and hydrological stability. This study uses a complete morphometric evaluation and an integrated Multi-Criteria Decision-Making (MCDM) framework to analyze the erosion susceptibility of six sub-watersheds (SW1-SW6) in the Rangit River Basin, a major tributary of the Teesta River. Utilizing high-resolution ASTER Global Digital Elevation Models (GDEM), fourteen distinct morphometric parameters encompassing linear, relief, and areal aspects were extracted to quantify the basin's geometric and hydrological characteristics. Criterion weights were determined using Shannon’s entropy method, after which three MCDM models, i.e., Technique for Order Preference by Similarity to Ideal Solution (TOPSIS), Simple Additive Weighting (SAW), and Complex Proportional Assessment (COPRAS), were applied to prioritize sub-watersheds based on erosion susceptibility. The results reveal that SW1 and SW4 exhibit the highest susceptibility for the soil erosion zone and require immediate conservation interventions. SW2, SW3, and SW5 fall within the medium-priority zone and require mitigation, whereas SW6 falls within the low-priority zone and requires monitoring. The developed integrated geospatial and decision-support methodology offers a methodologically robust geospatial decision-support framework for prioritizing soil erosion management in mountain basins. The prioritization framework supports sustainable watershed management and contributes to SDG 15 (Life on Land), SDG 6 (Clean Water and Sanitation), and SDG 13 (Climate Action) by identifying erosion-prone areas and guiding targeted conservation strategies.