冰岩型灾害链动力侵蚀过程与地貌演化响应规律研究
Study on the dynamic erosion process of rock-ice avalanches and the characteristic of geomorphic evolution
【目的】冰岩型灾害链引发的主河道堵溃洪水对下游城镇及重大水电工程极具破坏力。为揭示冰岩型灾害链动力侵蚀与地貌演化、堵江成坝之间的关系，【方法】以藏东南色东普沟为例，利用多源多期光学遥感影像解译、DEM差值、无人机航飞及现场调查等技术手段，探究了冰岩链式运动转换过程及灾害地貌效应。【结果】研究表明：自2010年以来，冰岩崩源区主要集中在海拔4 000 m以上的陡坡之上，最大累计侵蚀深度约为75 m。海拔3 000~4 000 m段的沟谷以侵蚀为主，长达5 km的沟谷最大累计侵蚀深度约300 m,且沟谷最大拓宽宽度超过500 m。海拔3 000 m以下区域为流动堆积区，最大累计堆积厚度超过50 m,堆积堵塞河床导致其抬升高度超过40 m。受沟谷弯曲地形影响，碎屑流/泥石流不仅对基底进行侵蚀，还表现出对岸坡强烈的侧向侵蚀作用，凹岸岸坡失稳体积累计超过4×107 m3,堆积体再运移率达到75%,为灾害体积放大效应提供了物源供给。【结论】冰岩型碎屑流在长距离运动过程中，其高速冲击作用下不仅造成谷底快速侵蚀加深，而且弯道离心力使其对凹岸岸坡造成侵蚀破坏和拓宽，形成的滑坡堆积物再次被铲刮、裹挟，造成灾害体积放大，加速沟谷物质运移和地貌演化。
[Objective] The dam-break floods triggered by rock-ice avalanches in the river channel are highly destructive to downstream towns and major hydropower projects. To reveal the relationship between the dynamic erosion of rock-ice disaster chains, geomorphic evolution, and river damming, [Methods] taking the Sedongpu Gully in southeastern Xizang as an example, the study employed multi-source and multi-temporal optical remote sensing image interpretation, DEM differencing, UAV aerial surveys, and field investigations to explore the process of ice-rock chain movement transformation and its geomorphic effects. [Results] The research indicates that since 2010, the source areas of rock-ice avalanches have mainly been concentrated on steep slopes above 4,000 meters in altitude, with a maximum cumulative erosion depth of approximately 75 meters. In the valley section at an altitude of 3 000~4 000 m, erosion is predominant. The maximum cumulative erosion depth in the 5 km long valley is approximately 300 m, and the maximum widening width of the valley exceeds 500 m. The area below 3 000 m is a flowing accumulation zone, where the maximum cumulative accumulation thickness exceeds 50 m, and the accumulation blocking the riverbed has caused it to rise by more than 40 m. Influenced by the curved terrain of the valley, debris flows/mudflows not only erode the base but also exhibit strong lateral erosion on the bank slopes. The cumulative volume of unstable bank slopes on the concave bank exceeds 4×107 m3, with a re-migration rate of the accumulation body reaching 75%, providing a material supply for the volume amplification effect of the disaster. [Conclusion] During the long-distance movement of ice-rock debris flows, their high-speed impact not only causes rapid erosion and deepening of the valley floor but also leads to erosion damage and widening of the concave bank slope due to centrifugal force at bends. The result ing landslide deposits are subsequently scraped and entrained again, amplifying the disaster volume, accelerating the transportation of valley materials, and promoting geomorphic evolution.
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