Effects of Soil and Water Conservation Measures under Natural Rainfall on Water Erosion Control: A Meta-Analysis of Erosion Plots in China

The efficacy of current soil and water conservation measures (SWCMs) in managing runoff and sediment has been confirmed at the plot scale. However, the effectiveness of conventional measures has been challenged by extreme rainfall and steep slopes, and systematic assessments of the benefits of combined measures are lacking. This study conducted a meta-analysis of 1399 runoff pairs and 1117 soil erosion pairs from 87 studies (2000–2025) to evaluate the effectiveness of various SWCMs and the moderating effects of slope and rainfall. SWCMs were categorized into single measures (biological measures [BMs], engineering measures [EMs], and soil management measures [SMs]) and combined measures (e.g., BMs + EMs). Findings indicate that SWCMs reduce runoff by 58.5 % and soil loss by 82.4 % on average. Runoff and sediment reduction benefits peak on 15–20° slopes when considering slope gradient, and under heavy rainfall when considering rainfall intensity; however, they generally decline under extreme rainfall. This suggests that the combination of steep slopes and extreme rainfall further reduces the protective benefits of these SWCMs. Under slope gradients of 15–20° and I30 < 60 mm/h, combined measures show noticeably greater benefits than single measures; the BMs + EMs approach performs the best. Overall, this study proposes a climate-adaptive “slope-measure” synergistic architecture to provide a scientific basis for optimizing SWCM structure and addressing extreme rainfall erosion risk intensified by steep slopes.