The effect of slope on interrill erosion at short slopes

Slope gradient is an important factor that affects soil erosion. This study was conducted to investigate the effect of slope gradient on soil erosion and determine the splash contribution to interrill erosion at short steep slopes. An experimental device was used to make simultaneous measurements of interrill splash and wash at 9, 18, 27, 36, 47, 58, 70, 84, and 100% slopes under a constant rainfall intensity of 67 mm h− 1 in a laboratory setting. The specially designed runoff and sediment collection system provided a means of partitioning total splash into four directional components and interrill sediment transport into wash and splash components. The results revealed that the total splash loss, net downslope splash loss and wash loss all increased with slope, and then decreased after a maximum value was reached. The slope factor equation of short slopes in RUSLE matched the wash loss from this study very well when the slope gradient was less than or equal to 58%. The ratio of net downslope splash loss to wash loss increased from 0.21 to 1.33 as the slope gradient increased from 9% to 100%. Taken together, these results indicate that upslope splash loss was a very important component of the total splash loss on gentle slopes and may be neglected on slopes greater than 36%. Splash transport was a significant part of interrill sediment delivery at short steep slopes.

Research Highlights
► Slope has effects on wash loss and splash loss. The experiments provided by the published references mainly focus on gentle slope. Compared with the published references, this study was conducted to investigate the effect of slope gradient on soil erosion on short steep slopes.
► Few experiments have effectively partitioned total splash into four directional components and interrill sediment transport into wash and splash components and provided the relative contribution of splash and wash to soil erosion in interrill area and its variation with slope. This study effectively partitioned total splash into four directional components and interrill sediment transport into wash and splash components and found that the ratio of net downslope splash loss to wash loss increased with the slope gradient. Splash transport was also a significant part of interrill soil erosion on short steep slopes.