“6·28”矮子沟特大泥石流灾害成因研究

Study on the Causes of “6·28” Aizi Gully Extra Large Debris Flow Disasters

通过对四川凉山矮子沟流域的勘查,结合遥感解译及矮子沟流域的地质活动历史,分析"6·28"矮子沟泥石流的影响因素,在此基础上分析了矮子沟泥石流的成因。"6·28"矮子沟泥石流是在地震、人类活动及干旱影响下,受强降雨激发,坡面及支沟先发生泥石流,支沟泥石流堵塞主沟泄洪通道,强降雨使堵塞体瞬间溃决形成较大山洪,山洪的强大揭底作用使沟床松散固体物质启动,沿途不断有岸坡坍塌补给,中下游段有大块石加入,规模不断增大而形成。采用形态调查法计算的泥石流流量为925.91m3/s,泥石流总量为57.4×104 m3,一次固体物质总量为27×104 m3。通过对矮子沟流域的物源、地形及流域的气候特征研究,得出初步结论:近期泥石流的规模和频率都会降低,但在极端干旱、地震和强降雨的偶然联合作用下,依然可能发生大规模的泥石流灾害。

Through field investigation, remote sensing interpretation and geological activity histo- ry at Aizi Gully we analyze the impact factors of “6 ·28”debris flow, then discuss the cause of “6 · 28”debris flow at Aizi Gully： due to the effect of frequent earthquake, human activity and extreme drought, due to the effect of intense rainfall, debris flow initiated on slope and branches firstly, heavy rainfall makes the block body burst into torrents in short time, as a result of the strong scour capability of torrents, the materials in the gully bed is initiated, during the process of movement bank to be collapsed, material and many boulders are mixed with it along the mid- stream and downstream, finally the severe debris flow is formed. Through morphological investi- gation to calculate the discharge, total volume and one time solid material volume of 6 ·28 debris flow at Aizi Gully are obtained. The corresponding values are 925. 91 m3/s, 5？. 4 × 104 m3 and 27× 104 m3 respectively. Study on the loose solid material condition, topographic condition and climatic characteristics we obtain the preliminary result： in recent years the debris flow frequency and scale at Aizi Gully will lessen, but if extreme drought, earthquake and intense rainfall occurr simultaneously, a large scale debris flow will be triggered.