Abstract:
Gully erosion is a significant form of land degradation in the Ethiopian Highlands, which adversely affects agricultural productivity and environmental stability. The extent of gully erosion was calculated by multiplying the eroded volume by the bulk density of the soil. Physical dimensions of gullies were measured using tools such as GPS, measuring tapes, ranging poles and a digital camera. Remote Sensing and GIS, satellite imagery from 2004, 2014, and 2024 (e.g., Land sat, Sentinel-2) was obtained from USGS. DEMs (e.g., SRTM or ALOS PALSAR) were used to derive slope, flow accumulation, drainage density, and watershed boundary. This study evaluated the spatial and temporal trends of gully erosion in the Angeto micro-watershed, Dera District, over 20 years (2004–2024). The evaluation involved comprehensive field measurements, GPS mapping, and Morphometric analysis of 12 selected gullies. The total gully length measured 2,272 meters, resulting in a gully density of 31.55 meters per hectare and an estimated soil loss of approximately 15,184.94 tons, equivalent to 10.55 tons per hectare per year, far exceeding the acceptable threshold of 2 to 5 tons per hectare per year. The gullies showed significant variations in length, width, depth, and volume, with Gullies 3, 11, and 12 contributing the most to erosion volumes and impacted areas. A strong positive correlation was found between gully length and volume (r = 0.855, p < 0.001), establishing length as a crucial determinant of gully growth. A historical reconstruction, utilizing a power function model (V = 1.092*A^1.014), indicated that both gully volume and cross-sectional area have been increasing at annual rates of 4.12% and 3.84%, respectively. This highlights a notable acceleration of erosion processes over the past decade. Spatial analysis revealed concentrated gully activity in mid- to lower-slope areas, influenced by steep terrain, inadequate vegetation cover, and a lack of soil and water conservation measures. The research concludes that gully erosion in the Angeto micro-watershed is escalating at unsustainable levels, emphasizing the urgent need for targeted interventions. The priority should be given to head-cut areas and large, rapidly expanding gullies. It is recommended that both structural and biological conservation strategies must be implemented to prevent further degradation. These findings provide essential scientific insights for managing watersheds and restoring land in similar highland environments.
Keywords: Angeto micro-watershed, Dera District, Gully erosion, Soil loss, spatial distribution
