Abstract:
Soil erosion remains a critical environmental issue in tropical highland regions, with significant
implications for agricultural productivity, land erosion and ecological stability. The present
study aims to model the risk of soil erosion in the Nuwara Eliya district of Sri Lanka, which is
affected by hill land use practices, especially tea cultivation. The Revised Universal Soil Loss
Equation (RUSLE) was employed in combination with geographical information system (GIS)
and remote sensing techniques to determine spatial variations in annual soil loss. Key RUSLE
parameters are: rainfall erosivity (R), soil erodibility (K), slope length and steepness (LS), cover
management (C), and conservation support practices (P) were derived using 30-meter
resolution Digital Elevation Models (DEMs), LANDSAT imagery, and localized soil and
meteorological datasets. The model results reveal that the average annual soil loss in the district
is 28.7 tons per hectare per year, with 45% of the land area exceeding the tolerable soil erosion
threshold of 11 tons per hectare. Severe erosion hotspots, surpassing 52 tons per hectare
annually, are predominantly concentrated in steep-sloped tea-growing zones (>30%), notably
in the Ragala Tea Belt, Hakgala Slopes, and Moon Plains. In contrast, forested areas recorded
minimal erosion rates (<5 tons per hectare). The LS-factor and C-factor emerged as the most
influential determinants of soil loss. The study highlights the applicability of the RUSLE-GIS
framework for erosion risk assessment in complex highland landscapes. It recommends site
specific soil conservation interventions such as contour terracing, agroforestry integration, and
regulatory land-use policies. The outcomes contribute to a replicable methodological
framework for regional-scale erosion modelling and sustainable land management planning in
similar agro-ecological contexts.
