Spatial Assessment of Soil Loss in the Eastern Region of Nepal Using RUSLE, Geospatial Tools and Remote Sensing

Abstract

Soil loss and associated changes in eastern Nepal are crucial due to their environmental impact and role in the functioning of regional ecosystem. The eastern region has elevation varying from 50 masl to mountainous terrain above 8000 masl with large basins and rivers originating from the glacier that spans to the southern border with India. Land Use and Land Cover map, precipitation data, soil type map, and DEM were used to estimate the soil loss through erosion in the eastern region of Nepal in 2017. Our analysis indicated that majority of the area (47.92%) have soil loss rate of 0-5 t/ha/year followed by 5-10 t/ha/year (19.65%), 10-20t/ha/year (19.25%) in the eastern region of Nepal. By severity, 2.89% of the area had soil loss belonging in severe and extreme category (> 80 t/ha/year) and needed high attention with sustainable management practices. The mean soil loss rate was 14.48 t/ha/year. With regard to land use and land cover category, the highest average soil loss was observed in Bareland (88.89 t/ha/year), followed by Forest cover (12.10 t/ha/year) and Grass land (7.09 t/ha/year), whereas agricultural land had 0.5 t/ha/year. By physiographic region, the annual soil loss rate was the highest in the Himalayan districts (26.23 t/ha/year), followed by hilly districts (8.96 t/ha/year) and the southern Terai districts (1.006 t/ha/year). The results from the RUSLE model also indicated higher amounts of soil loss (19.40 t/ha/year) in steeper slopes (> 26.8%), relatively low in less steep slopes and the lowest (0.41 t/ha/year) in slopes below < 7%. Remediative land conservation strategies like sustainable land management practices, reforestation, perennial plant cover, cover cropping, and contouring among others might be necessary to address the significant amount of soil loss in the bare areas of the region. Our estimation of the soil loss in the eastern region in Nepal would be helpful for stakeholders in Nepal to prioritize areas with high risk, and formulate soil conservation plans and policies for the prevention and reduction of soil loss in the eastern region of Nepal.