Investigating the impact of change in land use on the rate of river sedimentation.A Case study: River Ngenge.

Abstract

Soil erosion and river sedimentation due to changes in land use is a common land degradation problem because of its environmental impacts. Many computer models have been developed and used to predict erosion and river sedimentation. Geographic Information System (GIS) being a well-known tool available for dealing with the major water resources problems, it was used in this study. The main objective of the study was to investigate the impact of change in land use on the rate of river sedimentation in Ngenge catchment. The soil loss from the study area was estimated using USLE model. Land use, and topographical data for the study area was derived using ArcGIS and rainfall data was obtained from Tororo Meteorological station. The five major input parameters used in the study were rainfall Erosivity factor (R), Length slope factor (LS), soil erodibility factor (K), vegetation cover factor (C) and erosion control factor (P). The rainfall Erosivity factor was determined using annual rainfall data of study area. The Digital Soil Map of the World (DSMW) obtained from FAO was used to extract the soil information of the catchment from ArcMap which was used to estimate the soil erodibility factor and DEM of study area was used to generate topographic factor (LS). The value of cover management factor and support practice factor were obtained from NDVI maps generated from land use land cover map. After generation of input parameters, analysis was performed for estimation of soil erosion using Universal Soil Loss Equation USLE. The quantitative soil loss was estimated in (t/year). To determine the sediment yield from the catchment, a delivery ratio which is based on the catchment slope was applied to the total soil lost so as to determine the portion delivered in the river stream. Calibration and validation of the model was carried study carried out according to a study by Donigian et al., (2003) indicating expected range of soil loss per hectare