Taye Gebeyehu, Teklesilassie Tesfaye, Teka Daniel, Kassa Henok
Department of Land Resource Management and Environmental Protection, Mekelle University, P. O. Box 231, Mekelle, Ethiopia.
Institutes of Geoinformation and Earth Observation Sciences, Mekelle University, P.O.Box 231, Mekelle, Ethiopia.
Heliyon. 2023 Jul 27;9(8):e18648. doi: 10.1016/j.heliyon.2023.e18648. eCollection 2023 Aug.
Soil erosion by water and wind is among the most crucial land degradation processes in Ethiopia. This is also the case for Alage watershed located in the cental Rift Valley system. This study aimed at assessment of soil erosion hazard and its relation to land use land cover change in the watershed during the period from 1984 to 2016 for a better land management. The study is based on application of Remote Sensing (RS) and Geographical Information System (GIS) to extract inputs factor values for the Revised Universal Soil Loss Equation (RUSLE). Time-series satellite imageries of Landsat TM 1984, ETM+ 2000 and OLI 2016 were used for land use land cover change detection and determination of cover management (C) factor of the RUSLE. Biophysical data such as rainfall, soil properties, land management practices including soil and water conservation measures within the watershed were collected using field survey and secondary data sources. Slope steepness and slope length factors were derived using Digital Elevaition Model (DEM). Long-term average annual soil loss rates were estimated by the RUSLE integrated with GIS for 1984, 2000 and 2016. Using satellite imageries, the land use land cover and changes within the watershed during the three periods were obtained through a supervised classification with maximum likelihood algorithim. The results of land use land cover change indicated that the proportion of rain-fed cropland, bare land and built up areas increased by 17.4%, 5.9% and 2.9% respectively over the three study period. In contrast the proportion of bush/shrub land, irrigated cropland, grass land, forested areas and waterbodies decresaed by 15.5%, 4.7%, 3.4%, 2.3% and 0.3% respectively during the same period. Estimated average annual soil loss rates showed an increasing trend from 24.3 ton ha yr in 1984 to 38 ton ha yr in 2016. Increasing trends of average annual soil loss rate is attributed to increased proportion of cropland, bare land and built up areas during those periods leading to decreased protective vegetation cover. Hotspot areas within the watershed require implementation of land management practices to prevent further degradation and expansion of gullies. This study is relevant to demonstrate environmental implication of land use land cover change for future land management practices and land use policy in the Rift Valley of central Ethiopia.
水蚀和风蚀是埃塞俄比亚最关键的土地退化过程之一。位于中部裂谷系统的阿拉盖流域也是如此。本研究旨在评估1984年至2016年期间该流域的土壤侵蚀危害及其与土地利用土地覆盖变化的关系，以实现更好的土地管理。该研究基于应用遥感（RS）和地理信息系统（GIS）来提取修正通用土壤流失方程（RUSLE）的输入因子值。利用1984年的陆地卫星TM、2000年的ETM+和2016年的OLI的时间序列卫星图像进行土地利用土地覆盖变化检测，并确定RUSLE的覆盖管理（C）因子。通过实地调查和二手数据源收集了降雨、土壤特性、土地管理实践（包括流域内的水土保持措施）等生物物理数据。利用数字高程模型（DEM）得出坡度陡度和坡长因子。利用与GIS集成的RUSLE估算了1984年、2000年和2016年的长期年均土壤流失率。利用卫星图像，通过最大似然算法进行监督分类，获得了三个时期流域内的土地利用土地覆盖及其变化情况。土地利用土地覆盖变化结果表明，在三个研究期内，雨养农田、裸地和建成区的比例分别增加了17.4%、5.9%和2.9%。相比之下，同期灌木/灌木丛地、灌溉农田、草地、森林区和水体的比例分别下降了15.5%、4.7%、3.4%、2.3%和0.3%。估计的年均土壤流失率呈上升趋势，从1984年的24.3吨/公顷·年增加到2016年的38吨/公顷·年。年均土壤流失率的上升趋势归因于这些时期农田、裸地和建成区比例的增加，导致保护性植被覆盖减少。流域内的热点地区需要实施土地管理措施，以防止沟壑进一步退化和扩张。本研究对于说明土地利用土地覆盖变化对埃塞俄比亚中部裂谷未来土地管理实践和土地利用政策的环境影响具有重要意义。
