Soil Erosion Hazard Assessment Using Usle Model: A Case Study of Legedadi & Dire Reservoir Catchment
No Thumbnail Available
Date
2007-07
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Addis Ababa Universty
Abstract
Siltation due to erosion is the major problem facing many of the lakes and reservoirs in
Ethiopia today. The erosion process in Legedadi and Dire catchment transports a lot of
sediment to the reservoir and is the most important factor for reducing their storage
capacity. The two-reservoir catchments are in a state of physical and biological
deterioration due to over exploitation of lands by the inhabitants. A considerable part of
the sediment load is due to present agricultural and livestock management practices and
lack of soil conservation practices. Therefore, a reservoir catchment needs to be managed
effectively in order to reduce the effect of sedimentation.
This study has integrated the USLE model and GIS techniques to assess erosion hazards
in Legedadi and Dire Catchment. Soil loss estimation was carried out based upon the
principles defined in the USLE, which relates soil erosion process to rainfall Erosivity,
soil erodibility, topographic, land cover and conservation practices. The input parameters
of the model, derived from GIS analysis of primary data, were compiled in GIS database
in raster data model with grid resolution of 30 meters. The spatial thematic map of the
respective factors of USLE was created as following: R factor map was interpolated from
point data of station; K factor map by reclassification of soil map; LS factor, relief
parameters, was derived from DEM; C and P factor map by reclassification of landuse/
land-cover map of Landsat ETM+. The assessment approach involved two aspectsestimation
of potential and actual erosion.
After application of USLE model, the potential and actual mean annual soil loss from the
catchment was found to be 120t/ha/yr and 4.8t/ha/yr, respectively. From the level of soil
tolerance limits set by Hurni (1986), mean annual soil loss estimated by the model is
tolerable. 26km2 or 9.1% of the catchment is prone to high erosion hazards. In terms of
relative comparison of dire and Legedadi catchment the Dire catchment was found to be
more endangered by erosion hazards at various intensity.
Key Words: USLE model; Soil erosion; Legedadi& Dire catchment
Description
Keywords
USLE model, Soil erosion, Legedadi&, Dire catchment