Soil Erosion Modeling Using Remote Sensing and Geographic Information System: A Case Study of Awassa Area.
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Date
2005-07
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Addis Ababa University
Abstract
Land degradation has been a major global issue because of its adverse impact on agronomic
productivity, the environment, and its effect on food security and the quality of life. Soil
erosion is the major form of land degradation in Ethiopia. This study is done in Awassa
Catchment, which is the central part of the Main Ethiopian Rift. Assessment of soil erosion
rate in the study area is done using the statistical and relatively simple soil erosion model that
is USLE. All factors used in USLE were derived independently, while in reality the factors
interact in a dynamic system and several assumptions have to be made to adapt the model to a
given set of conditions. Based on the analysis of the data, 97.51 % of the study area is
characterized by low to moderate soil erosion rate (0-10.09 t/ha/yr) and 2.49% of the study
area is characterized by high to extremely high soil erosion rate (10.09-20\ .79 t/ha/yr). Out of
97.51% of the study area that is characterized by low to moderate soil erosion rate, 88 .05% of
it is associated with slope gradient factor less than one. 49.32% of areas with erosion rate
greater than I 0.09t/ha/yr (30.92 km2
) are associated with slope gradient factor greater than or
equal to one. And 6.37% (1.97 km2
) of those areas with erosion rate greater than 10.09t/ha/yr
(30.92 km2
) are related to slope length greater than or equal to 4.5. And areas with high to
extremely high erosion rates are associated either higher slope grad ient factor or with
degraded bare land and grassland and shrub land cover. Out of the whole catchment, 30.24
km2 lies under high to extremely high soil erosion rate and this requires immediate .
conservation measures like planting trees which can hold the soil intact. According to the rates
of soil tolerance limits that are developed for tropical soils (0.2 and 11 t/ha/yr), 97.51% of the
study area is under tolerable soil erosion rate.
But one thing to remember is that the USLE measures only rill and interrill erosion therefore
the overall soil erosion rate especially in the Muleti area where ground cracks are observed
could be much higher than the predicted by the USLE. Thus, estimation of soil loss from the
ground cracks in Muleti area should assessed by other models.
Therefore the analysis of high-resolution remote sensing data combined with furth er spatial
information in a GIS environment provides an integrated and cheap tool for resource
management within the scope of sustainable development.
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Earth Science