黄土丘陵沟壑区人类活动对流域系统[2]侵蚀、输移和沉积的影响

从长期来看 ,在治理度达到 70 %条件下与治理前相比泥沙输移比减小 50 %左右 ,治理的效益是十分显著的。在治理的过程中 ,与治理前相比泥沙输移比变幅明显减小 ,但在短期内由于暴雨洪水侵蚀力大于工程设计标准而发生毁、垮坝或淤平后 ,仍可以将前期滞留的泥沙重新搬运而出现泥沙输移比大于 1的情况。在黄土高原地区治理前后流域系统次暴雨泥沙输移比均可用径流深度比来定量计算获得 ,泥沙输移比变化的动力机制可用径流深度增与减时水流剪切力的变化来解释

Influence of human activities on erosion, delivery and deposit of basin system in hilly-gully loessic area

From long term point of view, sediment delivery ratio of a drainage basin with a control degree reaching 70% can be reduced by around 50% in contrast to pre control conditions. The effect of erosion control is quite significant. In the management process, although delivery ratio drops considerably in comparison to pre control conditions, yet the previous retained sediment can still be carried, resulting in the situation of delivery ratio greater than 1 since erosive strength of rainstorm induced erosion is greater than project designed standard in a short spell following dike breach and scouring. In the loess plateau region, individual rainstorm event related delivery ratio under either pre or post control conditions in drainge system can be obtained by using runoff depth, and dynamic mechanism for changes of delivery ratio can be explained with shear force changes following fluctuations of runoff depth.