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Abstract

The Indian Himalayan ranges are prone to natural hazards, such as cloudbursts, flash floods, and landslides. These events cause significant damage to the environment, economy, and society. Frequent flash-floods cause significant soil erosion, leading to issues such as flooding, water siltation, and pollution in the Himalayan watersheds. The problem is further exacerbated by the undulating topography and inadequate soil and water conservation practices in the region. Thus, prioritizing sub-basins of the Himalayas is crucial for effective water resource management and sustainable development. In this study, a morphometry-based approach using combination method and principal component analysis (PCA) was used to identify the soil erosion-prone sub-basins of the Alaknanda River. These parameters were combined using a weighted linear combination method to generate a composite index for each of the 12 sub-basin. Additionally, PCA was applied to identify the most important morphometric parameters that influence sub-basin prioritization. The results of PCA showed that four morphometric parameters - Drainage density (Dd), Elongation ratio (Re), Relative relief (Rr), and Ruggedness number (Rn) - are highly interrelated, which cumulatively explains 89.7% of total variance. Both techniques yielded the same result with respect to sub-basin ranking, placing WS3 at the top and WS8 at the bottom. The results of the estimation were validated by conducting a field survey of the sub-basins. The study provides a detailed analysis of the Himalayan watershed's geomorphology, which is crucial for effective watershed management. By identifying high-risk sub-basins, stakeholders can implement strategies to reduce flash-flood induced erosion and improve the watershed's health.