Abstract
Soil erosion by water has accelerated over recent decades due to non-sustainable land use practices resulting in substantial land degradation processes. Spatially explicit information on soil erosion is critical for the development and implementation of appropriate Soil and Water Conservation (SWC) measures.The objectives of this study were to estimate the magnitude of soil loss rate, assess the change of erosion risk, and elucidate their implication for SWC planning in the Gobele Watershed, East Hararghe Zone, Ethiopia. Applying remote sensing data, the study first derived the Revised Universal Soil Loss Equation (RUSLE) model parameters in an ArcGIS environment and estimated the soil loss rates. The estimated total soil loss in the watershed was 1,390,130.48 tons in 2000 and 1,022,445.09 tons in 2016 with a mean erosion rate of 51.04 t ha−1 y−1 and 34.26 t ha−1 y−1, respectively. The study area was divided into eight erosion risk classes ranging from very low to extremely high. We established a change detection matrix of the soil erosion risk classes between 2000 and 2016. The change analysis results have revealed that about 70.80% of the soil erosion risk areas remained unchanged, 19.67% increased in total area, and 9.53% decreased, showing an overall worsening of the situation. We identified and mapped areas with a higher and increasing erosion risk as SWC priority areas using a Multi-criteria Decision Rules (MCDR) method. The top three priority levels marked for the emergency SWC measures account for about 0.04%, 0.49%, and 0.83%, respectively. These priority levels are situated along the steep slope areas in the north, northwest, south, and southeast of the Gobele Watershed. It is, thus, very critical to undertake proper intervention measures in upslope areas based on the priority levels to establish sustainable watershed management in the study area.
Highlights
Soil erosion is a naturally occurring environmental process by which soil materials are displaced, transported, and deposited in downstream areas by wind, water, or gravitational forces [1,2,3]
Eight erosion risk classes were mapped based on the mean soil loss rates showing that a larger portion of the study area are found under the very low, low and low medium classes and only a small part found within the high, very high and extremely high
The change analysis results showed that overall, about 70.80% of the erosion risk areas covered in 2000 continued under the same erosion risk classes in 2016 but 19.67% increased and 9.53% decreased in the total study area
Summary
Soil erosion is a naturally occurring environmental process by which soil materials are displaced, transported, and deposited in downstream areas by wind, water, or gravitational forces [1,2,3]. In the context of water-caused soil erosion, removal of soil particles is the result of raindrops, while surface runoff carried out the transportation process [4]. Land 2018, 7, 25 irregular terrain and surface topography are the other causes of soil erosion. Nill et al [23] reported that “huge investment in a civil engineering work aiming at renovating the results of erosion is comparatively higher than investments in soil conservation.”
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