Abstract

Land use/land cover (LULC) change is an important measure to monitor the land degradation. This study focused on the Sebeya watershed located in the western province of Rwanda to evaluate the soil erosion and sediment yield spatio-temporal pattern from 1990 to 2019 occurred due to LULC change. Multi-temporal LULC maps of 1990–2019 and RUSLE model were used to achieve the objectives. The sediment yield was computed as a product of sediment delivery ratio (SDR) and the gross soil erosion. From the period 1990–2019, each year forestland decreased by 2.6%/yr, whereas the grassland, cropland, and settlement increased by 23.6%/yr, 14.5%/yr, and 81.6%/yr respectively. As a result, the mean soil erosion for 1990, 2000, 2010, and 2019 was 14.7, 28.3, 34, and 34.7 t ha⁻¹yr⁻¹ whereas the total sediment yield was 3254.15, 5029.8, 6814.56, and 9074.04 t yr⁻¹ respectively. Cropland was an exception to the other LULC classes because it has generated soil erosion in very high severity > 50 t ha⁻¹yr⁻¹, while this severity class showed an upward trend. The study demonstrated that LULC change has a significant impact on soil erosion and sediment yield and suggests proper land-use planning and encourages afforestation to arrest soil loss.

摘要

土地利用/土地覆盖（LULC）变化是监测土地退化的重要措施。本研究以位于卢旺达西部省的塞贝亚流域为重点，评估 1990 年至 2019 年因 LULC 变化而发生的土壤侵蚀和产沙量时空格局。使用 1990-2019 年的多时态 LULC 地图和 RUSLE 模型来实现目标。沉积物产量计算为沉积物输送比 (SDR) 和总土壤侵蚀的乘积。从 1990 年到 2019 年，林地每年减少 2.6%/年，而草地、农田和聚居地分别增加 23.6%/年、14.5%/年和 81.6%/年。因此，1990、2000、2010 和 2019 年的平均土壤侵蚀量分别为 14.7、28.3、34 和 34.7 t ha ^-1 yr ^-1而总产沙量分别为 3254.15、5029.8、6814.56 和 9074.04 t yr ^-1。农田是其他 LULC 类别的一个例外，因为它产生了非常严重的土壤侵蚀 > 50 t ha ^-1 yr ^-1，而该严重程度级别显示出上升趋势。该研究表明，LULC 变化对土壤侵蚀和沉积物产量有重大影响，并建议进行适当的土地利用规划并鼓励植树造林以阻止土壤流失。