Rainfall intensity and slope gradient effects on sediment losses and splash from a saline–sodic soil under coastal reclamation

Abstract

Rainfall intensity and slope gradient play important roles in soil erosion processes. This study was conducted to investigate the effects of rainfall intensity and slope gradient, as well as of their interactions, on splash and overland flow transport on saline–sodic soil slopes. Rainfall intensities of 85, 95, 110 and 125mmh−1 were applied to slope gradients of 6°, 11°, 22° and 35°. Splash was partitioned into four directional components. Runoff, sediment and splash samples were collected throughout the rainstorms and infiltration was calculated. The final infiltrations under the lower rainfall intensities of 85mmh−1 were the largest for every slope gradient, but they decreased by 39.3% as the slope gradient increased from 6° to 35°. However, the final infiltration rates exhibited an increasing–decreasing trend for rainfall intensities higher than 85mmh−1 as the slope gradient increased. The critical slope gradient was about 11°. The influence of rainfall intensity on runoff was considerably reduced at the higher slope gradients due to increased infiltration. The influence of slope gradient on sediment loss was reduced as rainfall intensity increased, while the effect of rainfall intensity on sediment losses was greater on the gentler slopes than on the steeper slopes. The upslope splash (mean value) initially increased from 4.8 to 7.2gm−1h−1 before it decreased to 3gm−1h−1 as the slope gradient increased. The maximum measured value occurred when the slope gradient was 22°. Total splash increased to maximum levels as the slope gradient increased to 11°, but decreased with further increases in gradient. These results indicated that the effects of slope gradient and rainfall intensity on sediment losses, runoff and splash were interconnected.