Effect Simulations of Land Use Change on the Runoff and Erosion for a Gully Catchment of the Loess Plateau, China
黄土丘陵小流域土地利用变化对水土流失的影响

Based on the calibration of LISEM (Limburg Soil Erosion Model), five land use scenarios consisting of the previous in 1975 (LU75), present in 1998 (LU98) and future land use pattern were used to simulate the effects of the land use change on runoff and erosion at outlet of the Da Nangou catchment on the Loess Plateau, China. The future land-use maps were made based on three land-use scenarios in which cropland areas are restricted to slope gradients smaller than 25 (FA25), 20 (FA20) and 15 degrees (FA15). Two stages were recognized based on the comparison analysis on these five maps. In the first stage from LU75, LU98 to FA25, the area of the wood/shrub land increases while those of the wasteland, fallow land and cropland decrease, and the orchard/cash-tree land remains the same. During the second stage consisting of the FA25, FA20 and FA15, there is a gradual decrease in the cropland and fallow land and a gradual increase in the orchard/cash-tree land; the other land-use types remain the same. According to the simulation, the predicted peak-velocity, runoff and erosion at outlet decrease significantly if the slope cropland and fallow land are replaced by other types of land use. The peak-velocity, runoff and erosion show the same sequences for different land use patterns in the following order: land use in 1975 (LU75) > land use in 1998 > 25-degree-limit scenario > 20-degree-limit scenario > 15-degree-limit scenario. The runoff and erosion for LU75 and LU98 with much more cropland and fallow land is significantly greater than that for the three degree-limit scenarios with sharp increases in area of wood/shrub land. However, there is little difference in runoff and erosion among the three degree-limit scenarios since there is only a gradual decrease in the cropland and fallow land and a gradual increase in the orchard/cash-tree land. Based on the comparison with the land use in 1975, the predicted peak-velocity, runoff and erosion decrease by about 5-10% for land use in 1998, while the predicted decreases for the three slope-degree-limit scenarios are much larger, ranging between 40% and 50%.