雨滴打击对黄土坡面细沟侵蚀特征的影响

基于模拟降雨试验和纱网覆盖消除雨滴打击作用的试验方法,研究雨滴打击对黄土坡面细沟侵蚀特征的影响。试验包括3种黄土高原代表性的侵蚀性降雨强度(50、75、100 mm/h)和3个细沟侵蚀发生最常见的坡度(10°、15°和20°)。结果表明,与有雨滴打击试验处理相比,纱网覆盖消除雨滴打击后,坡面径流稳定产流率和含沙量均明显减小;坡面侵蚀量和细沟侵蚀量分别减少28.1%~47.7%和20.2%~38.6%;而细沟侵蚀对坡面侵蚀的贡献率增加。消除雨滴打击后,坡度对细沟侵蚀的影响与有雨滴打击时相同,而降雨强度对细沟侵蚀的影响增加。有、无雨滴打击试验处理的细沟密度和割裂度均随着降雨强度和坡度的增加而增大;而细沟倾斜度的变化较为复杂,所以细沟密度和割裂度可作为描述细沟形态的最佳指标。试验结果还表明,雨滴打击对细沟沟槽形状也有间接影响,即消除雨滴打击后,细沟宽度和深度的变异程度减小,沟槽形状更为规则。同时,有雨滴打击试验处理的细沟宽深比随着坡度和降雨强度的增加而减小,而无雨滴打击试验处理的细沟宽深比随着坡度的增加而减小,随着降雨强度的增加呈微弱的增加趋势。

Effects of Raindrop Impact on Rill Erosion Characteristics on Loess Hillslope

A rainfall simulation study was conducted to examine the effects of raindrop impact on rill erosion characteristics on the loess hillslope. The experimental treatments included three rainfall intensities (50, 75 and 100 mm/h) of representative erosive rainfalls on the Loess Plateau and three common slope gradients (10°, 15° and 20°) of rill erosion occurrence. Each experimental treatment included two surface treatments: with and without raindrop impact through placing the nylon net over the soil pan. The results showed that eliminating raindrop impact caused decreases in stable runoff rates and sediment concentrations; soil loss was induced and rill erosion was decreased by 28.1%~47.7% and 20.2%~38.6%, respectively; the increase in the contribution of rill erosion to hillslope soil erosion was induced. After eliminating raindrop impact, the effect of slope gradient on rill erosion was the same as that in treatments with raindrop impact; but the effect of rainfall intensity on rill erosion was increased. With regard to treatments with and without raindrop impact, both rill density and degree of rill dissection were increased with increase in rainfall intensity or slope gradient; but the changes of rill inclination angle were complex. Thus, rill density and degree of rill dissection were the optimal indicators to describe rill morphological characteristics. The results also indicated that raindrop impact had indirect influence on rill channel shape. That is, the degree of variation in rill width and rill depth was decreased, and rill channel shape was more inerratic after eliminating raindrop impact. With regard to treatments with raindrop impact, rill width-depth ratio was decreased with rainfall intensity or slope gradient increase. For treatments without raindrop impact, rill width-depth ratio was also decreased with increase in slope gradient, but it was slightly increased as rainfall intensity increased.