交通施工扰动对沟道山洪泥石流孕灾风险的放大效应：以四川金阳“8·21”灾害为例

Amplification effect of transportation construction disturbances on disaster-forming risk of flash flood-debris flows in mountainous gullies: A case study of “8·21” disaster in Jinyang, Sichuan

摘要

【目的】山区交通建设等工程的施工扰动常不可避免，可能会增加受影响区的山洪泥石流灾害风险。科学识别和评估施工扰动对山洪泥石流孕灾风险的影响，有助于防御诱发的相关自然灾害。【方法】以2023年四川金阳“8·21”山洪泥石流灾害为案例，根据现场调查和遥感解译，研究分析了施工扰动形式，提出了基于情景模拟对比的山洪泥石流风险施工扰动放大效应识别方法，解析了该事件中施工扰动物源叠加的风险放大效应。【结果】研究表明：(1)供给近程直接物源和占用行洪区域，是施工扰动影响山洪泥石流孕灾风险的主要形式，分别增大了致灾风险度和受灾易损性；(2)在四川金阳灾害中，施工物源供给导致成灾断面最大淤埋厚度增加了2.65 m,是严重损毁施工临时用房的直接原因；(3)该事件中的施工扰动，导致临时用房的成灾风险从近50 a一遇升至20 a一遇，显著放大了山洪泥石流的孕灾风险。【结论】基于情景模拟对比的方法，能有效识别山洪泥石流风险的施工扰动放大效应，强调了山区交通建设等施工应避免在平缓展宽河段的凹岸布设临时用房，减少对岸坡扰动并增强岸坡侵蚀保护，可很大程度上抑制扰动对山洪泥石流孕灾风险的放大效应。

Abstract

[Objective] Construction disturbances from projects such as transportation infrastructure in mountainous areas are often unavoidable and may increase the risk of flash flood-debris flows in the affected areas. Scientifically identifying and evaluating the impact of construction disturbances on the disaster-forming risk of flash flood-debris flows is conducive to preventing induced natural disasters. [Methods] The 2023 “8·21” flash flood-debris flow disaster in Jinyang, Sichuan was taken as a case study. Based on field investigations and remote sensing interpretation, the forms of construction disturbances were analyzed, and a scenario-based simulation comparison method was proposed to identify the amplification effect of construction disturbances on flash flood-debris flow risk. The risk amplification effect result ing from the superposition of construction material sources in this event was elucidated. [Results] The results showed that:(1) supplying short-range direct material sources and occupying flood discharge areas were the main forms through which construction disturbances affected the disaster-forming risk of flash flood-debris flows, respectively increasing the disaster-forming risk degree and the vulnerability of affected areas.(2) In the disaster occurring in Jinyang, Sichuan, the supply of construction-induced material sources caused the maximum burial depth at the disaster-forming cross-sections to increase by 2.65 m, which was the direct cause of the severe destruction of temporary construction housing.(3) The construction disturbances in this event caused the disaster-forming risk of the temporary housing to increase from a 50-year return period to a 20-year return period, significantly amplifying the disaster-forming risk of flash flood-debris flows. [Conclusion] The scenario-based simulation comparison method can effectively identify the amplification effect of construction disturbances on flash flood-debris flow risk. It emphasizes that during transportation construction in mountainous areas, the placement of temporary housing on the concave banks of gently widening river sections should be avoided. Reducing disturbances to bank slopes and enhancing bank slope erosion protection can significantly suppress the amplification effect of disturbances on the disaster-forming risk of flash flood-debris flows.

关键词

山洪泥石流 / 孕灾风险 / 施工扰动 / 数值模拟 / 识别 / 施工物源 / 降雨 / 遥感

Key words

flash flood-debris flow / disaster-forming risk / construction disturbance / numerical simulation / identification / construction material sources / rainfall / remote sensing

基金资助

国家自然科学基金项目(41771112)