Synergistic effects of vegetation restoration and check dams on water erosion in a slope-gully system

Restoring vegetation and constructing check dams are important measures for controlling water erosion in slope-gully systems. However, percolation through the dam body could lead to shortened runoff paths in the gully. Moreover, the synergistic effects of vegetation patterns and siltation-induced runoff path length decrease (RPLD) in slope-gully systems on reducing water erosion remain unclear. In this study, 20 physical models of slope-gully systems were constructed to quantitatively evaluate the synergistic effect of these measures under simulated rainfall. The models included four slope vegetation patterns (no vegetation, up-slope, middle-slope, and down-slope) and five levels of RPLD in the gully (0, 1, 2, 3, and 4 m). Owing to synergistic effects, combined measures led to a more considerable reduction in soil and water loss than a single measure. Furthermore, the synergistic effect was related to vegetation patterns and shorter siltation-induced runoff paths. The mean synergistic effect produced the following runoff yield order: down-slope (2.84%) > middle-slope (2.81%) > up-slope (1.78%); and 4 m (3.18%) > 3 m (2.66%) > 2 m (2.29%) > 1 m (1.78%). The sediment yields were in the following order: down-slope (18.15%) > middle-slope (12.63%) > up-slope (6.67%), and 4 m (14.56%) > 3 m (12.82%) > 2 m (11.73%) > 1 m (10.82%). These results suggest that revegetation of the lower parts of the slope, along with check dams, will be more effective for controlling soil erosion. Such synergistic effects should be considered in future soil erosion modeling.