串珠状堰塞湖级联溃决对汶川震区河流演化的影响

Effects of Cascade Failure of Dammed Lakes on the Evolution of Rivers in Wenchuan Earthquake Region

"5·12"汶川地震震后3年多以来,串珠状堰塞湖群的形成和发展,对震区河流演化的影响重大。通过对汶川地震灾区岷江支流——渔子溪的耿达—映秀河段的野外考察发现,堰塞坝对河流挤压造成异岸冲刷,河道横向展宽或弯曲;多堰塞湖河段河床抬升强烈;部分堰塞坝由于未完全溃决而逐渐发育成尼克点,从而形成阶梯状河床。鉴于野外考察的局限性,通过野外水槽实验初步探索了堰塞湖级联溃决的动力学特征,堰塞湖级联溃决放大了山区河流洪水的峰值流量,从而加剧了河流沿程冲淤程度,更有利于梯级河床的形成。探索多堰塞湖河段堰塞湖级联溃决情况下的河床演化规律,旨在为地震灾区河道修复及灾后恢复重建提供科学指导。

A field investigation of Gengda-Yingxiu reach of Yuzixi River, a tributary of the Minjiang River, found that the river was al- ways either squeezed by natural dams, resulting in river bending or broadening ]aterally, or the river was uplift strongly, or developed into step-like riverbed. Considering the limitations of field investigation, the dynamic characteristics of peak discharge of dammed lakes cas- cade failure were explored by field flume experiments. The amplified scale of peak discharge intensified the degree of erosion and depo- sition along the flume, which could be conducive to forming the step-like riverbed.