坡面产流过程及产沙临界对立地条件的响应关系

Responses of runoff process and threshold of sediment generation for different vegetation-covered plot

利用人工模拟降雨试验,以黄土高原黄土丘陵沟壑区第三副区黄土为模拟对象,依据45、90和130mm/h降雨强度下共计18个试验组次观测资料,定量研究了裸地、草地和灌木地3种立地条件20°陡坡产流过程及其产沙临界的响应关系。研究表明,高强度降雨条件下,草地和灌木地的减流作用会降低;裸地径流过程具有明显的起涨阶段,而草地和灌木地的起涨阶段不明显,对径流过程具有消波调控作用,同时草地产流量受下渗率的影响比灌木地的大;裸地下渗率比草地和灌木地的明显为小,且其过程波动性强;3种立地条件的初渗率与稳渗率之差以裸地的最大,草地的最小,而且,产流与入渗的关系对降雨的响应是非线性的;断面比能参数可表征为产沙的主导因子,裸地、草地和灌木地的临界断面比能分别为0.074、0.11和0.13cm。该研究对于揭示植被调控坡面产流产沙机理,为生态修复工程建设提供科学依据具有重要科学意义。

Responses of runoff process and threshold of sediment generation for bare plot, grass plot and shrub plot at 20° slope gradient were studied by model test using simulated rainfall intensities of 45, 90 and 130mm/h including 18 experiments based on the third sub-region in hilly-gully region on the loess plateau. The experiment results show that there is a decreasing trend in reduction effects of grass and shrub on runoff under higher rainfall. Runoff process on bare plot has an evident stage of flood rising, but that on grass and shrub plots keeps relatively steady. Thus, grass and shrub can decrease runoff peak and regulate runoff process. Effect of infiltration rate on runoff for grass plot is more significant than that for shrub plot. Infiltration rate on bare plot is obviously lower than that on grass and shrub plots and showed a fluctuanting trend. The difference of initial infiltration rate and steady infiltration rate on bare plot is the highest, and that on grass plot is the lowest. The hydraulic parameter of unit flow energy can be used as a dominant indicator of sediment generation. The critical unit energy of bare plot, grass plot and shrub plot are 0.074, 0.11 and 0.13cm, respectively. The objective of this study is essential to understand the mechanism of vegetation influences on runoff and sediment yield and can offer scientific data for ecological restoration project construction.