Plot-based experimental study of raindrop detachment, interrill wash and erosion-limiting degree on a clayey loessal soil

Abstract

Better understanding of raindrop detachment, interrill wash and erosion-limiting degree in interrill processes is critical for accurately modelling interrill erosion and implementing proper anti-erosion strategies. Simulated rainfall experiments were conducted on a clayey loessal soil at three rainfall intensities (42, 60 and 90 mm h−1), five slope gradients (7°, 10°, 15°, 20° and 25°) and rainfall duration of 40 min. Results showed that raindrop detachment rate initially decreased rapidly within a few minutes and then reached a relative steady state during rainfall. The initial and steady raindrop detachment rate increased with increased rainfall intensity. Interrill wash rate peaked early and then decreased to a relative constant rate during the rainfall. The initial, maximum and steady interrill wash rate increased with increased rainfall intensity and slope gradient. Erosion-limiting degree (ELD), defined as the ratio of interrill wash rate to raindrop detachment rate, ranged from 10.99% to 35.70% under experimental conditions, indicating that interrill erosion system was transport-limited. The ELD decreased with rainfall intensity and increased linearly (R2 = 0.90) with slope gradient. The higher the rainfall intensity, the stronger the transport-limiting in interrill erosion processes; the steeper the slope gradient, the weaker the transport-limiting in interrill erosion processes. Raindrop detachment is the dominant process in detaching soil particles, whereas interrill flow contributes to washing out detached sediments. The findings of this study, especially ELD, largely improved the understanding of interrill erosion processes.