Abstract:
Soil erosion is being detected as a risk to humnan survival by diminishing food and water
availability of the planet Earth in the 21st century. Assesment and management of this
resource is becoming extremely important. This study aimed to investigate Soil Erosion Risk
and Prioritize Management Options in Midhagdu Watershed of Western Hararghe Highlands,
Eastern Ethiopia. Satellite data, SRTM DEM, Land sat 8 OLI with 30m resolution, rainfall
and soil data were used to generate all soil erosion risk factor maps and integrated to
generate a composite map of soil loss for the watershed. The RUSLE model in combination
with remote sensing and GIS techniques was used to identify the five thematic maps as an
input to estimate mean annual soil loss. The results of the spatial distribution of soil erosion
risk factors indicated that rainfall erosivity, soil erodibility, slope length and steepness, cover
management and anthropogenic soil erosion control practices values ranged from 41.365 to
43.793MJ mm ha−1
yr
−1
, 0.26 to 0.31t ha−1MJ−1
mm
−1
, 0 to 220.512, 0.21 to 0.87and 0.11 to 1
respectively. And the most powerful factor that influences soil erosion risk is topography
followed by anthropogenic soil erosion control practices. The results of the study showed that
the annual soil loss rate in the watershed ranged from 0 in gentle slopes to 1504 t ha-1yr-1
at
the steepest slope of the watershed with a mean annual soil loss of 48.5 t ha-1
yr
-1
at Midhagdu
watershed level.The soil loss map was categorized into five soil loss numerical ranges and soil
loss risk nominal scales: low, moderate, high, very high and extremely high using Ethiopian
highland maximum soil loss threshold level 18 t ha-1
y
-1
.The model output revealed that
52.24% of Midhagdu watershed fell in low to moderat soil erosion risk levels and 47.76% fell
under high to extremely high soil erosion risk levels.The soil loss risk levels identified at 28
micro watersheds showed that twelve micro watersheds rated as first, eleven micro
watersheds as second and three micro watersheds as third priority for soil erosion risk
management options implementation. Out of 28 micro watersheds 26 fell above Ethiopian
highland maximum soil loss threshold levels. Therefore, the study result indicated that
Midhagdu watershed needs immediate intervention for better soil erosion risk management
options planning and implementations by considering identified soil erosion risk areas and
priority classes to control soil erosion risk below the national threshold level.
