坡度与降雨强度对狗牙根草地产流的影响

Effects of slope and rainfall intensity on runoff of Cynodon dactylon lawn

通过室内人工降雨模拟试验,对不同暴雨条件下坡度和降雨强度对狗牙根草地产流的影响及整个产流过程中径流系数的动态变化规律进行研究。结果表明:1)狗牙根草地径流量和场降雨径流系数均随着坡度、降雨强度的增大而增大,径流量最大可达33.77 L/m2;其他条件不变的情况下,随着降雨强度的增大,不同坡度间的径流量以及径流系数差距逐渐缩小;2)初始产流时间随坡度和降雨强度的增加而缩短,各降雨条件下从开始产流到降雨结束,整个过程径流系数动态变化规律都是呈先快速增加,最后趋于稳定的趋势;从产流开始到径流系数达到稳定所需要时间最短的为降雨强度90 mm/h、坡度5°的降雨条件,所需时间最长的为降雨强度30 mm/h、坡度5°的降雨条件;3)运用灰色关联度分析得到降雨强度、坡度对径流量的关联度分别为0.61和0.60,关联度较好,降雨强度对产流影响程度略大于坡度;4)回归分析得到径流量与坡度和降雨强度的线性回归方程,且相关性显著,R2达到0.89,拟合结果较好,降雨强度、坡度与径流量均呈极显著相关水平。

By the ways of rainfall simulation,we studied the effects of different slope gradients and rainfall intensities on runoff and runoff coefficient of Cynodon dactylon lawn,and the dynamic laws of runoff coefficient during the whole runoff process. The results showed that： 1） runoff and runoff coefficient of the C. dactylon lawn increased with the increasing slope gradient and rainfall intensity,and the biggest runoff volume（ 33. 77 L / m^2） appeared under the condition of rainfall density 90 mm/h and slope degree 20°. If keeping other conditions unchanged,the differences in runoff volume and coefficient at different slope gradients would decrease. 2） The initial runoff time was shortened with the increase of slope gradient and rainfall intensity; the initial runoff time occurred 60 min after rainfall at the density of30 mm / h,while it was 30 min after rainfall at 60 mm / h and shortened to 20 min after rainfall at 90 mm /h. From the onset of runoff producing to the end of rainfall,the change of runoff coefficient followed a pattern of increasing rapidly at first and tending to be stable afterwards,which means that it increased at least 50% at first. Compared with other rainfall conditions,the coefficient at the 30 mm / h rainfall density increased fastest,then tended to be steady after a certain period in the whole process; the coefficient increased as the slope degree and rainfall density increased,with a small difference within 0. 05 when the slope degree or rainfall density were kept unchanged. 3） Based on grey correlation analysis,we come to the conclusion that the correlation degrees of rainfall intensity and slope gradient with runoff were 0. 61 and 0. 60 respectively,indicating that the rainfall intensity has more effect on runoff than slope gradient.The maximum correlation degree between rainfall intensity and the runoff was 0. 84,while that between slope gradient and runoff was 0. 91. 4） A linear equation between runoff,slope gradient and rainfall intensity was fitted by regression analysis,with the R2 value 0. 89,suggesting a good fitting. The significant level of slope gradient and rainfall intensity with the total runoff volume was less than 0. 01.