多场次降雨条件下覆沙坡面的径流产沙特性试验研究

Experimental study on runoff and sediment yield characteristics on sand-covered slope under the condition of repetitive rainfall

基于可控坡面进行多场次降雨试验，对覆沙坡面的产流产沙特性进行研究，以期为揭示黄土高原风蚀水蚀交错区风水复合侵蚀机理研究提供科学依据。结果表明：覆沙坡面的初始产流时间远大于裸坡，相对延迟了5．3—11．2倍，多场次降雨条件下，产流时间显著提前。首场降雨下，覆沙厚度为1cm，当雨强由1mm／min增加到1．5mm／min，覆沙坡面径流量、产沙量分别增加了0．87倍、0．85倍；雨强为1．5mm／min时，当覆沙厚度由0．5em增加到1cm，首场降雨的径流量、产沙量分别减小了9．6％、12％。相对于裸坡，覆沙坡面产沙量较大，产沙过程较剧烈，首场降雨产沙量占总产沙量的70％以上，是裸坡的8．9—10．8倍，但在多场次降雨条件下，产沙量显著减小，并趋于稳定。研究结果表明坡面覆沙在一定程度上加剧了土壤侵蚀，可为揭示风蚀沉积物对水蚀过程的作用机理研究提供参考。

Based on experiments of controlled repetitive rainfall on slope, the runoff and sediment yield charac- teristics of sand-covered slope were studied,in order to reveal the loess plateau water erosion and provide sci- entific basis for the study on complex erosion of wind water erosion region. Results show that the initial runoff time （tp） of the sand-covered slope is much larger than that of the bare slope,with a relative delay of 5.3 - 11.2 times. Under the condition of repetitive rainfall, tp decreased rapidly. During the first rainfall, the thick- ness of the overlying sand was 1 cm,when rain intensity increased from 1 mm/min to 1.5mm/min, the sand-cov- ered slope runoff and sediment yield were increased 0.87 times and O. 85 times. When the thickness of the o- verlying sand increased from 0.5 cm to 1 cm,runoff and sediment volume were reduced by 9.6% and 12% re- spectively. Compared with bare slope, the sediment yield on sand-covered slope was larger, and sediment pro- duction process was more severe. Sediment yield of the first rainfall accounted for more than 70% of the total sediment yield which was 8.9 - 10.8 times of the bare slope. But under the condition of repetitive rainfall, sed- iment yield decreased significantly, and tends to be stable. The effect of thickness of the overlying sand on slope erosion was more complex. Results show that sandy slope exacerbated the soil erosion of the slope to some de- gree.