四川汉源“7·20”山洪泥石流灾害复盘分析

Review and analysis of “7·20” flash flood and debris flow disaster in Hanyuan, Sichuan

摘要

【目的】2024年7月20日，四川省雅安市汉源县马烈乡新华村发生特大山洪泥石流灾害，造成1500余人受灾，基础设施损毁严重。通过对此次灾害进行复盘分析，探究本次山洪泥石流复合灾害形成机理，分析灾害影响范围及程度，并提出针对性的防灾减灾对策，为未来类似山洪泥石流灾害的防治工作提供参考与借鉴。【方法】采用了遥感测量、现场调查、数值模拟、设计指标对比等方法及手段，在模拟分析中分别利用推理公式法、面积比拟法和分布式水文模拟法等技术手段进行多方法对比分析，综合确定此次洪水重现期。【结果】通过推理公式法计算得出大沟头与马烈沟汇口处30 a一遇设计洪水洪峰为286.00 m³/s;通过面积比拟法基于调查洪痕计算本次灾害洪峰约为263.00 m³/s;利用分布式水文模拟计算本次灾害洪峰流量为249.70 m³/s,经综合分析确定本次洪水重现期约为30 a一遇。【结论】经研究分析，确定强降雨为诱发本次复合灾害的主要原因。流域内不利的地形、地貌和地质条件加重了灾害的危害性，桥涵堵塞雍水则进一步扩大了灾害的影响范围。同时灾害应对中预警系统、应急响应机制及风险管理方面的不足也是导致此次灾害损失严重的重要原因。

Abstract

[Objective] On July 20^th, 2024, a severe flash flood and debris flow disaster occurred in Xinhua Village, Malie Township, Hanyuan County, Ya'an City, Sichuan Province, affecting over 1 500 people and causing severe damage to infrastructure. A disaster review and analysis is conducted to investigate the formation mechanism of this compound flash flood and debris flow disaster, analyze the scope and degree of its impact, and propose targeted disaster prevention and mitigation measures, providing references for the prevention and control efforts of similar flash flood and debris flow disasters in the future. [Methods] Remote sensing measurement, field investigation, numerical simulation, and comparison with design indicators were employed. In the simulation analysis, the inferential formula method, area analogy method, and distributed hydrological simulation method were employed for multi-method comparative analysis to comprehensively determine the return period of this flood. [Results] Using the inferential formula method, the peak discharge of a 30-year return period design flood at the confluence of Dagotou and Malie Gully was calculated to be 286.00 m³/s. Based on surveyed flood marks, the peak discharge of this disaster was estimated to be approximately 263.00 m³/s using the area analogy method. By applying the distributed hydrological simulation method, the peak discharge of this disaster was calculated to be 249.70 m³/s. A comprehensive analysis indicated that the return period of this flood was approximately 30 years. [Conclusion] The analysis confirms that the intense rainfall is the primary triggering factor of this compound disaster. The unfavorable topographic, geomorphic, and geological conditions in the watershed exacerbate the severity of the disaster, while the blockage of bridges and culverts further expands the impact of the disaster. Moreover, deficiencies in early warning systems, emergency response mechanisms, and risk management during disaster response are key factors leading to the severe loss.

关键词

山洪泥石流 / 复合灾害 / 灾害复盘 / 灾害机理 / 四川汉源 / 风险评估 / 洪水 / 数值模拟

Key words

flash flood and debris flow / compound disasters / disaster review / disaster mechanism / Hanyuan,Sichuan / risk assessment / flood / numerical simulation

基金资助

国家重点研发计划资助项目(2023YFC3006702)

中国水利水电科学研究院“五大人才” 项目(WH0145B062022)