Impacts of infiltration holes on rainfall-runoff production on slopes treated with engineering measures: A simulation study in the Loess Plateau of China

Present slope engineering measures are insufficient to intercept and infiltrate extreme rainstorm runoff in the Loess Plateau of China. The infiltration hole that has specific depth and volume can be used as a supplemental to slope engineering measures to rapidly reduce rainstorm runoff and store them into deep soil layers. In this study, the performance of infiltration holes (60, 80, and 100 cm in depth and 10 cm in diameter) in intercepting and infiltrating rainstorm runoff was evaluated through the field simulation experiment (rainfall intensity of 1.5 mm min-1). The results showed that infiltration holes directly increased the runoff infiltration area by 0.20, 0.26, and 0.32 m2. Before infiltration holes were filled up, all the runoff were intercepted, the reduced runoff were 5.70, 5.85, 8.85 mm, respectively. When runoff reducing rate reached stable (around 110 min), the stable runoff-reducing rates were 0.079, 0.088, and 0.091 mm min-1, and the cumulative reduced runoff were 15.05, 18.11, and 20.97 mm, accounting for 30.41%, 36.59%, and 42.36% of the simulated rainstorm runoff. This implies that filtration holes could, on average, reduce runoff by 70.50, 132.42, and 256.26 mm within 12, 24, and 48 h, respectively. Based on the results, it was verified that infiltration holes could reduce most of the runoff under the scenario of historical extreme rainstorms in the past two decades. Our research determined the rainfall runoff reduced by infiltration holes and verified the effectiveness of infiltration holes under rainstorm events, and provided a prospective technique for regulating extreme rainstorm runoff and decreasing landslides and mudslides risks on the Loess Plateau.