PG Thesis
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Item Soil erosion risk assessment in a sub-watershed of karuvannur river basin, Thrissur Kerala using rusle model(College of Climate Change and Environmental Science, Vellanikkara, 2023-05-09) Akash, P J; Mary Regina, FA study was conducted to assess the soil erosion risk regions of a sub-watershed and to classify the whole area based on the severity of the erosion rate classes. Kurumali watershed in the Karuvannur river basin in Thrissur district of Kerala, India was selected for the study. The RUSLE soil erosion model is used to calculate the annual value o soil loss and the intensity of soil erosion. The ArcGIS software was used to implement the RUSLE factors. Parameters like Rainfall erosivity factor (R ), Soil erodibility factor (K), Slope length steepness factor (LS), Cover management factor ( C), and Practice factor (P ) were used for the estimation of soil erosion or the working of the RULE model. The Digital Elevation Model (DEM) of the sub-watershed was used to estimate the LS factor. The land use data of the sub-watershed, collected from Kerala State Land Use Board, were used for estimating the C factor and P factor. 20-year (2000-2020) daily rainfall data of two stations (Pudukkad and Varandarapilly) were collected from Irrigation Design and Research Board (IDRB) for calculating R factor. Soil samples were collected from various physiographic units in the Kurumali watershed for evaluating soil organic matter, texture, structure, and permeability and these were used to calculate the K factor. The soil erosion risk map was produced in the ArcGIS environment after analysing the RUSLE parameters, R, K, LS, C and P. The maps were converted to raster format using a raster calculator and then combined to produce the soil erosion model. The soil loss values for the Kurmali watershed range from 0 to 70.26 tonnes ha-1y-1 with a standard deviation of 1.24. The average soil erosion rate estimated for the watershed ranges between 0 to 1 tonnes ha-1year-1. It was found that about 82.5% of the area (34969.86 ha) comes under the ‘Very slight’(<1 tonnes ha-1 year-1 ) soil erosion class. 11.1% of areas are classified under ‘Slight’ erosion. The ‘Moderate’ erosion class has an area coverage of 1.97%. About 4.42% of the area is under the ‘Moderately high’ to ‘Very high’ (>10 tonnes ha-1 year-1). Among different land use types barren lands has the highest erosion rate followed by plantations. And dense forest has the least erosion rate, due to its dense canopy cover. Measures must be taken to reduce the soil erosion of the study area. Some practices that can be performed to prevent soil erosion in the study area have been suggested.