Impact of land-use change on soil erosion in the Coonoor Watershed, Nilgiris Mountain Range, Tamil Nadu, India

Abstract

The conversion of native forest to the tea plantation and cropland has intensified throughout the Coonoor watershed of the Nilgiris region over the past few decades. The current study investigates the severity of land cover changes including deforestation activities in the Coonoor watershed region as a result of urbanization, along with the establishment of recreational parks, resorts and tea plantations. In order to analyse the changes, a widely used soil erosion model say Revised Universal Soil Loss Equation (RUSLE) is opted to estimate the average soil loss. Therefore, this work marks the impact of land-use changes on land degradation and the consequent vital natural phenomenon like soil erosion. The change detection was carried out for over 14 years period from 2005 to 2018. Landsat images of corresponding years were classified using the supervised classification technique. The C-factor (cover and management factor) for the corresponding periods were also identified. Conversion of forest land into tea plantations, wastelands and settlements significantly decrease the soil organic matter (SOM) and hydraulic conductivity (HC) of the soil, which leads to a difference in the K-factor (soil erodibility factor) throughout the study period, whereas the R-factor (rainfall and runoff factor) and LS-factor (length-slope factor) were considered to be constant throughout the period. Results indicate the annual soil loss during the period from 2000 to 2018 on each land use/cover classes. viz., tea plantations, 223.26 km2; settlement, 163.35 km2; open forest, 799.02 km2; dense forest, 1158.48 km2; and barren land, 27.18 km2. The total sediment yield in the study area was found to have oddly increased due to the land use/cover changes. The significant rise of soil erosion was found evitable in the deforested region which was converted to infrastructure and wasteland.