RUSLE-based quantitative soil erosion assessment in the monsoon-dominated region of Sikkim Himalaya

Abstract

Soil erosion is a major environmental issue influenced by the local climate, topography, soil characteristics, vegetation types and cover, land-use practices and anthropogenic activities. Soil erosion rates vary considerably in the hilly regions due to their complex diverse terrain. Therefore, estimation of soil erosion is essential for identifying areas that are highly susceptible to soil erosion. The present study aims to ascertain soil erosion rate in the surroundings of Namchi region of Sikkim in India, using the Revised Universal Soil Loss Equation (RUSLE) model. In addition, soil erosion rates were estimated with respect to different land-use types and slope classes. The study also examined six soil erosion related factors and their interrelationship using statistical techniques, particularly the Pearson correlation coefficient. The results revealed that the Namchi surrounding area is less vulnerable to soil erosion as compared with many other regions of the Indian Himalaya. The average annual soil loss rate is estimated at 39.10 t ha⁻1 year⁻1, with erosion rates upto 138.62 t ha⁻1 year⁻1. The soil erosion map shows that 89.52%, 6.52% and 3.96% of the study area falls within low, moderate and high erosion risk zones, respectively. Higher soil erosion rates were observed mainly in the southern part of the study area, where slope angles range from 35° to 50°. Among the land-use classes, agricultural land and open land exhibited the highest soil erosion rates, reaching 138.62 t ha−1 year−1. Pearson Correlation coefficient analysis among six soil erosion affecting factor revealed that elevation had a weak but modest positive correlation with slope, relative relief (RR) and drainage density (DD), whereas it exhibited a weak negative correlation with topographic wetness index (TWI).