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Soil erosion assessment in a humid, Eastern Himalayan watershed undergoing rapid land use changes, using RUSLE, GIS and high-resolution satellite imagery

2019; Springer Science+Business Media; Volume: 6; Issue: 1 Linguagem: Inglês

10.1007/s40808-019-00700-0

2363-6211

Nirmalya Chatterjee,

Flood Risk Assessment and Management

The study aims to understand land degradation in the $$\approx 2000\ \hbox {ha}$$, humid and mountainous Papung khola catchment in the Sikkim Sivalik Range using the revised universal soil loss equation on a GIS platform. The catchment drains into the Tista River and is part of the data-sparse Eastern Himalayan ecoregion. Catchment land-use is changing from broadleaf forests to mixed land-use driven by rising population, and livelihood changes from primary production (forestry, agriculture) to service sectors (tourism, trade, construction). The study uses data on soil characteristics, ground and satellite precipitation and aerial land cover to predict potential soil erosion. Results indicate transitions in land cover/land use from forests to agriculture, disturbances due to construction and the potential increase in frequency of extreme climate events posing a unique risk to soils of the steep catchment causing decrease in soil cover and resultant loss of land productivity. The catchment can be currently categorized under a "very low" or "slightly erosive" regime (mean erosion rates 3.53 $$\hbox {t}\,\hbox {ha}^{-1}\, \hbox {year}^{-1}$$, with > 99% under cover of < 5 $$\hbox {t}\,\hbox {ha}^{-1}\, \hbox {year}^{-1}$$) with around three-quarters of the catchment under forest cover. High precipitation, intensification of diurnal and seasonal wetting-drying cycles, human disturbances to the top soil and rapid land use/land cover changes combining with the extreme topography and slow soil development is driving land degradation, which may stymie sustainable development and livelihood diversification in the future. Moderate erosion levels of $$\approx $$ 10 $$\hbox {t}\,\hbox {ha}^{-1}\, \hbox {year}^{-1}$$ can be expected in the future in areas with intact vegetation cover leading to complete top soil loss given the shallow profile depths.