Assessing Erosion Vulnerability and Soil Loss Dynamics in the Eastern Himalayas: A USLE-based Approach in the Kiile Watershed, Arunachal Pradesh, India

Abstract

Quantifying erosion vulnerability at the watershed scale is imperative for understanding sediment dynamics and formulating effective soil conservation strategies. In this study, the erosion vulnerability of the Kiile watershed was evaluated using the Universal Soil Loss Equation (USLE) model to quantify soil loss dynamics across ten distinct sub-watersheds. The model integrated multi-source geospatial datasets, including high-resolution Digital Elevation Model (DEM), satellite-derived land use/land cover (LULC) maps, and long- term rainfall records. These datasets were used to compute the standard USLE parameters: rainfall erosivity (R), soil erodibility (K), slope length and steepness (LS), cover management (C), and conservation practice (P). The analysis revealed that the average annual soil loss in the Kiile watershed ranges between 0 and 138 t ha-1 yr-1, with a mean annual loss of 2.4 t ha-1 yr-1. Based on erosion severity, the study area was categorised into five classes: very high, high, moderate, low, and very low. The SW-8 recorded the highest soil loss of 4.52 t ha-1 yr-1, highlighting an urgent need for site-specific conservation strategies. The findings reveal that intense rainfall, erodible sandy clay loam textures and increasing urban development are the principal determinants of soil loss in this sub-watershed. This study highlights the necessity of integrating climatic and anthropogenic drivers into watershed planning to mitigate soil loss in vulnerable sub-watersheds. The study provides a foundation for decision-makers to formulate effective resource management and conservation strategies, ensuring long-term sustainability of the watershed.