Abstract
Upland agricultural expansion and intensification cause soil erosion, which has a negative impact on the environment and socioeconomic factors by degrading the quality of both nutrient-rich surface soil and water. The Haean catchment is a well-known upland agricultural area in South Korea, which generates a large amount of sediment from its cropland. The transportation of nutrient-rich sediment to the stream adversely affects the water quality of the Han River watershed, which supports over twenty million people. In this paper, we suggest a spatially explicit mitigation method to reduce the amount of sediment yield to the stream of the catchment by converting soil erosion hot spots into forest. To evaluate the effectiveness of this reconfiguration, we estimated the sediment redistribution rate and assessed the soil erosion risk in the Haean catchment using the daily based Morgan–Morgan–Finney (DMMF) model. We found that dry crop fields located in the steep hill-slope suffer from severe soil erosion, and the rice paddy, orchard, and urban area, which are located in a comparatively lower and flatter area, suffer less from erosion. Although located in the steep hill-slope, the forest exhibits high sediment trapping capabilities in this model. When the erosion-prone crop lands were managed by sequentially reconfiguring their land use and land cover (LULC) to the forest from the area with the most severe erosion to the area with the least severe erosion, the result showed a strong reduction in sediment yield flowing to the stream. A change of 3% of the catchment’s crop lands of the catchment into forest reduced the sediment yield entering into the stream by approximately 10% and a change of 10% of crop lands potentially resulted in a sediment yield reduction by approximately 50%. According to these results, identifying erosion hot spots and managing them by reconfiguring their LULC is effective in reducing terrestrial sediment yield entering into the stream.
Highlights
Agriculture expansion and intensification often lead to severe soil erosion in the course of altering naturally dominated surface configurations [1,2,3]
The soil erosion rate varied greatly depending on the topography and land use and land cover (LULC) type, and the area located on the steep hill-slope, which is adjacent to the forest severely suffered from soil erosion
We identified that the sediment yields entering the stream were reduced sharply, as crop lands were sequentially changed into forest from the area with the most severe soil loss to the area with the least soil loss
Summary
Agriculture expansion and intensification often lead to severe soil erosion in the course of altering naturally dominated surface configurations [1,2,3]. A large amount of surface runoff from heavy rainfall washes out nutrient-rich surface soil from deforested upland agriculture areas and degrades the soil quality of the agricultural area [6]. The Han River watershed in South Korea experiences extreme downpours that cause severe soil erosion and subsequent water deterioration every summer monsoon season [3,10,11]. These problems are worsening, as upland agricultural areas expand and the intensity of monsoonal rainfall increase due to ongoing climate change [12,13]. The Han River is the primary freshwater source for the Seoul
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