Soil Loss Estimation within the Nun River Basin using Revised Universal Soil Loss Equation (RUSLE) integrated in Geographic Information Systems (GIS)

Abstract

River bank erosion can cause undesired river bank expansion, distortion of the river course thereby slowing the river velocity and hindering the water carrying capacity of the river. Slow velocity of the river course can result in fast sediment accretion and accumulation at the bottom of the river. If these trends are not checked, the river may wind down and at best begin to become a delta at its middle course. The focus of this study is to apply GIS  and analytical RUSLE equation to estimate soil loss within the Nun Basin. Core sediment samples were collected from relatively undisturbed areas (nine different stations) using Uwitec Triple sediment cutter. The sediment samples were processed in the lab for sediment particle size analysis (PSA) and Pb-210 atmospheric deposition with age using alpha spectrophotometer. Spatial rainfall data of the study location were employed to generate the rainfall erosivity map in order to determine the erosivity factor (R). Particle size distribution analysis was validated using Scanning Electron Micrograph (SEM) and integrated with Geographic Information Systems (GIS) was employed to create the soil erodibility map which was subsequently used to determine the erodibility factor (K). The cover management factor (P) was determined using the land use land cover map and the resulting data were then employed to model the river bank erosion around the study area. Result of the study revealed that the maximum annual average soil loss rate was estimated to be 0.66 tons/ha. /year around the Nun River based on GIS application using the Revised Universal Soil Loss Equation (RUSLE).