Estimation of Water Erosion in Southern Districts of Tamil Nadu using Geo-spatial Technologies

Abstract

Land degradation can be considered as deterioration of the original quality of land and deterioration or total loss of the production capacity of the soil. Land degradation is caused due to changes in climate and human activities. This study was carried out to map land degradation caused by erosion due to water in Tirunelveli, Thoothukudi and Kanyakumari district using Sentinel-2 optical data. Water erosion is mapped by analyzing the data across Kharif, Rabi and Zaid season between 2017 and 2018. Sentinel-2 optical data has 13 bands with spectral resolution ranging from 0.443 µm to 2.190 µm. The water eroded areas are visually interpreted from the FCC image composed of NIR (8), Red (4) and Green (3) bands with spatial resolution of 10 m. It is estimated that 1563.165 sq.km is degraded due to water erosion. Water erosion areas are more clearly visible in Zaid season when the land conditions are dry. Besides, rainfall, soil, land use land cover and slope data has been used as an input to derive the parameters required for spatial modeling of soil erosion using USLE. Depending on the amount of soil loss they are six categorized into six classes viz. very low erosion (0 -5 t ha -1 yr -1 ), low erosion ( 5 -10 t ha -1 yr -1 ) , moderate erosion (10 -20 t ha -1 yr -1 ), moderately severe erosion (20 -40 t ha -1 yr -1 ) and severe erosion (> 40 t ha -1 yr -1 ). In the study area soil loss classes ranges from low (0-5 t ha -1 yr -1 ) to severe (40-873.145 t ha -1 yr -1 ). The rate of annual soil loss ranges from 0 t ha -1 to 873.145 t ha -1 . The visually interpreted water erosion layer is integrated with soil loss map and the accuracy of the erosion layer is found to be 87.3%. High rate of erosion occurred at bare soil and down slope.