淤地坝对次洪事件侵蚀动力及输沙的调控作用

Regulating effect of check dams on erosion dynamics and sediment transport during flooding

淤地坝对流域产沙的调控作用是黄土高原水土保持与治理研究中的焦点问题。该文以黄土高原岔巴沟三川口站的控制流域为例,采用一维沟道非平衡输沙模型,研究了单座淤地坝对次洪事件的水沙调控作用。结果发现:无坝和有坝情形的计算域出口径流侵蚀功率与输沙模数之间均为幂函数关系,但无坝情形下的幂函数关系不能推广到有坝情形,体现了淤地坝的调控作用,并且淤地坝淤积状态、洪水频率是淤地坝调控作用的重要影响因素。进一步研究发现,淤地坝存在拦沙失效淤积比例,对于特大洪水到一般洪水,失效淤积比例在88.3%~93.6%之间,而工程中的经验常数值仅适用于小洪水情形。

The regulating effect of check dams on the sediment transport in a watershed is important for improving soil and water conservation and watershed management of the Loess Plateau. The effect of a single check dam during flooding is studied here using a one-dimensional non-equilibrium sediment transport model for the Chabagou watershed of the Loess Plateau. The results show a power function relationship between the runoff erosion rate and the sediment transport modulus for cases with and without a check dam, but the relationship with no check dam cannot be extended to cases with a check dam due to the regulating effect of the check dam. The regulating effect of the check dam varies with the flood recurrence frequency and the siltation stage. Furthermore, there is a threshold siltation rate above which the check dam does not trap sediment during flooding. The threshold siltation rate changes from 88.3% to 93.6% for a catastrophic flood to a regular flood. This study shows that the widely used empirical constant threshold siltation rate is only applicable to small floods.