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四川省汶川县下庄沟“8·20”泥石流成因分析及堵江范围预测
罗玉婷, 唐川, 熊江, 陈明, 张宪政
成都理工大学 地质灾害防治与地质环境保护国家重点实验室, 四川 成都 610059
摘要:
[目的] 探究四川省汶川县下庄沟2019年"8·20"泥石流成因、形成过程及堵江特征,为该区域泥石流灾害防治预警提供科学参考。[方法] 结合野外调查与遥感影像对泥石流物源供给条件及泥石流形成、侵蚀搬运与堵江过程进行了分析,并采用FLO-2D模型开展不同降雨强度下的泥石流堵江范围分析。[结果] 震后泥石流流域部分崩滑体物源持续补给沟道物源,致使沟道物源不断累积,短历时强降雨形成径流不断侵蚀沟道物源,形成沟道启动型泥石流。下庄沟"8·20"泥石流大量碎屑物质搬运出沟口后形成顺河长度达280 m,横河最大宽度110 m的堰塞体,堵江模式为堰塞坝全堵。堵江范围分析结果显示:5年一遇降雨频率下物源滞留在沟道中,无堵江现象;20年一遇降雨频率下,泥石流基本堵断杂谷脑河,极易形成堵江现象;在50年一遇降雨频率下,泥石流完全堵断杂谷脑河,形成堰塞湖。[结论] 下庄沟与杂谷脑河垂直交汇,且沟口建有水电站的引水坝,极易形成堰塞坝堵江现象。在汛期降雨强度较大时仍可能会暴发泥石流造成堵江,今后的泥石流防治还需加强防洪预警等减灾措施。
关键词:  “8䞐”泥石流  崩滑体物源  堵江  FLO-2D
DOI:10.13961/j.cnki.stbctb.2020.06.028
分类号:P642.23
基金项目:国家重点研发计划项目“强震区地质灾害动态演化机制与长期效应”(2017YFC1501004);国家自然科学基金项目“急陡沟道泥石流起动—侵蚀—冲出模型研究”(41672299)
Cause Analysis of “8·20” Debris Flow and Forecast of River-blocking Range in Xiazhuang Gully of Wenchuan County, Sichuan Province
Luo Yuting, Tang Chuan, Xiong Jiang, Chen Ming, Zhang Xianzheng
State Key Laboratory of Geohazard Prevention and Geoenvironment Protection, Chengdu University of Technology, Chengdu, Sichuan 610059, China
Abstract:
[Objective] The origin, formation process and characteristics of the "8·20" debris flow at Xiazhuang gully, Wenchuan, Sichuan Province in 2019 was explored in order to provide a scientific reference for the prevention and early warning of debris flow disasters in the region.[Methods] Based on field surveys and remote sensing images, debris flow source supply conditions, debris flow formation, erosion transport and river blockage process were analyzed. And FLO-2D model was used to analyze the extent of Xiazhuang debris flow blockage under different rainfall intensities.[Results] After the earthquake, part of the debris flow in the debris flow basin continued to erode the source of the channel, resulted in the accumulation of gully material source. Runoff formed by short-duration heavy rainfall continuously eroded the gully material source and formed a channel-initiated debris flow. A large amount of debris from the "8·20" debris flow in Xiazhuang gully was transported out of the ditch, and formed a dammed body with a length of 280 m along the river and a maximum width of 110 m across the river. The blocking mode of the river was full blockage of the dam. Under the frequency of 5-year rainfall, the material source would stay in the channel without blocking the river. Under the frequency of 20-year rainfall, the debris flow basically would block the Zagunao river and form a blocking phenomenon. Under the frequency of rainfall once in 50 years, the debris flow would completely block the Zagunao river and form a dammed lake.[Conclusion] Xiazhuang gully and Zagunao river intersect vertically, and the diversion dam of a hydropower station is built at the mouth of the gully, which is easy to form the phenomenon of dam blocking. During the flood season, when the rainfall intensity is high, debris flows may still cause river blockage. In the future, the prevention and control of debris flows need to strengthen flood prevention and early warning and other disaster reduction measures.
Key words:  “8䞐” debris flow  landslide  river-blocking  FLO-2D