Estimating soil erosion risk and evaluating erosion control measures for soil conservation planning at Koga watershed in the highlands of Ethiopia

Abstract

Abstract. Soil erosion is one of the major factors affecting sustainability of agricultural production in Ethiopia. The objective of this paper is to estimate soil erosion using the universal soil loss equation (RUSLE) model and to evaluate soil conservation practices in a data-scarce watershed region. For this purpose, soil data, rainfall, erosion control practices, satellite images and topographic maps were collected to determine the RUSLE factors. In addition, measurements of randomly selected soil and water conservation structures were done at three sub-watersheds (Asanat, Debreyakob and Rim). This study was conducted in Koga watershed at upper part of the Blue Nile basin which is affected by high soil erosion rates. The area is characterized by undulating topography caused by intensive agricultural practices with poor soil conservation practices. The soil loss rates were determined and conservation strategies have been evaluated under different slope classes and land uses. The results showed that the watershed is affected by high soil erosion rates (on average 42 t ha −1 yr −1 ), greater than the maximum tolerable soil loss (18 t ha −1 yr −1 ). The highest soil loss (456 t ha −1 yr −1 ) estimated from the upper watershed occurred on cultivated lands of steep slopes. As a result, soil erosion is mainly aggravated by land-use conflicts and topographic factors and the rugged topographic land forms of the area. The study also demonstrated that the contribution of existing soil conservation structures to erosion control is very small due to incorrect design and poor management. About 35 % out of the existing structures can reduce soil loss significantly since they were constructed correctly. Most of the existing structures were demolished due to the sediment overload, vulnerability to livestock damage and intense rainfall. Therefore, appropriate and standardized soil and water conservation measures for different erosion-prone land uses and land forms need to be implemented in Koga watershed.

Effect of Land Use and Land Cover Change on Soil Erosion in Erer Sub-Basin, Northeast Wabi Shebelle Basin, Ethiopia

“…The model was run to estimate the actual annual rates of soil loss in the study landscape for the years 2000 and 2018. The soil erosion risk within the study area was classified into eight categories, based on previous work by Uddin et al [5], and the estimated mean soil loss rates (t ha −1 y −1 ): very low (< 5), low (5-10), low medium (10)(11)(12)(13)(14)(15), medium (15)(16)(17)(18)(19)(20), high medium (20)(21)(22)(23)(24)(25), high (25)(26)(27)(28)(29)(30)(31)(32)(33)(34)(35), very high (35)(36)(37)(38)(39)(40)(41)(42)(43)(44)(45)(46)(47)(48)(49)(50), and extremely high (>50). Areas with a mean annual soil loss rates lower than low were rated as tolerable soil loss limit [52].…”

“…Land 2020, 9, 111 3 of 25 Over the past decades, numerous hydrological models ranging from relatively simple empirical models to more complex physically based prediction models have been developed for the derivation of spatially variable factors and estimating their combined effect on soil erosion and sediment yield [49][50][51][52][53][54][55][56][57][58][59][60][61][62][63]. As compared with the physical-based models, the empirical models are the widely used prediction tools due to their minimal data required and ease of application to estimate soil loss rates at a regional and global scale [4,44].…”

Impact of Forest Road Construction on Topsoil Erosion and Hydro-Physical Soil Properties in a Semi-Arid Mountainous Ecosystem in Turkey

“…Also, soil properties affecting K value affect the soil loss in cut and fill slope through to the forest road [42]. When our study area (forested and open areas) and slopes are evaluated in terms of soil loss in general, annual soil loss in hectares was calculated as <5.0 ton/yr; and in the less sensitive category of erosion according to the results in a tropical region [43]. But this value could be understood as very high because of the ecological conditions in the subtropical regions of the globe [44].…”

Land use and land cover changes in the Haean Basin of Korea: Impacts on soil erosion

“…Soil erosion is a worldwide environmental problem, causing the reduction of the crop productivity and thus economic profits, deterioration of the downgradient stream and river water qualities and their benthic ecosystems, and the reduction of landscape amenities (Jack et al, 2009;Kettering et al, 2012;Pimentel and Burgess, 2013;Zhao et al, 2013;Jung et al, 2015;Molla and Sisheber, 2017). Soil erosion is a natural phenomenon.…”