Geospatial Analysis of Soil Erosion and Subsequent Geomorphic Hazards in the Eastern Himalayan Region, India

Geo-environmentally, the eastern Himalaya region is highly vulnerable to erosion and associated geomorphic hazard due to heavy annual rainfall (1600–3600 mm), young and highly erodible rock formations (mainly comprised of sandstones, siltstones and shales), fragmented reshaping geomorphology, high erodibility of soils. Despite that, anthropogenic activities have been enhancing this geo-environmental vulnerability to erosion hazard through rapid unplanned urbanization and shifting cultivation practices. Addressing this burning environmental problem, a geospatial technology-based case study of the Kohima district, Nagaland state (India) from eastern Himalaya is presented here. Various experiential models are available for computing soil erosion; however, a revised universal soil loss equation (RUSLE) integrated with the GIS framework was applied in the current study due to its robustness and high accuracy level. Six key RUSLE factors such as erosivity of rainfall (RE), erodibility of soil (ES), erodibility of rock (ER), slope length (LS), crop management (CM) and conservation practice (CP) were calculated using required data sets in a GIS environment. RE ranges between 648.12 and 1294.15 MJ mm/ha/h/year, ES varies minimum of 0.10 to a maximum of 0.41 among the existing 15 classes of soils, ER factor values ranges 0.01–0.04, LS factor values range between 0 and 1.22, CM factor values vary from a minimum of 0.0 for dense forest area to maximum 1.80 for buildup areas whereas the CP value varies 0.1–1.0 across the study region to land use/cover pattern. The accumulated impact of these erosion and soil loss factors resulted in a quite higher average rate (about 16 t/ha/year) than the threshold value of soil erosion (< 10 t/ha/year). This value ranges from 1 to 92.18 t/ha/year. Thus, it has been essential to minimize the high rate of erosion through intensifying CP factors at the government level, community level and even individual level by adopting scientific crop patterns, agro forestry and reforestation programs. If these necessary actions were not taken timely, it may lead to other erosion-induced geomorphic hazards such as land degradation, mass movement, landslides, slope failure etc.