Effects of collection time intervals of surface runoff and sediment on soil erosion analysis during rainfall

In simulation studies of soil erosion, analyzing runoff and sediment curves is important for accurately characterizing soil erosion on hillslopes. The objectives of this study were to measure the effects of surface runoff and sediment collection time intervals (CTIs) on runoff and sediment curves and to determine how CTIs affect soil erosion analyses. Experiments were conducted in runoff plots that were 4 m long and 1 m wide. The slope gradient was 15°, and the soil surface was smooth. Rainfall was applied at intensities of 60, 90 and 120 mm/h, and one short CTI (i.e., 2 min) and four longer CTIs (i.e., 4, 6, 8 and 10 min) were used. The results showed that longer surface runoff and sediment CTIs obviously influenced the runoff and sediment curves and the soil erosion analysis results, especially during the early period of runoff. The amount of accumulated runoff decreased at longer CTIs, and the amount of accumulated sediment increased at longer CTIs. Therefore, it is important to choose an appropriate CTI in simulated rainfall experiments to improve the reliability of soil erosion analyses. The use of an inappropriate CTI will adversely affect the results of such analyses. Based on these results, we suggest using a short CTI to collect surface runoff and sediment measurements during the rising period of the runoff rate; longer CTIs should be used only after the runoff rate has reached a steady state because the temporal variations in runoff and sediment yield are lower during this period.