基于熵权变异系数融合算法和FLO-2D的朱家沟流域泥石流危险性评价

Risk assessment of debris flow in Zhujiagully watershed based on entropy weight coefficient of variation fusion algorithm and FLO-2D

岷县朱家沟是青藏高原东北缘的典型泥石流小流域,受地震与极端降雨影响泥石流灾害频发,严重威胁县城安全,亟需开展泥石流危险性评价。本文采用熵权与变异系数融合算法评价流域内各支沟泥石流易发性,并选取高易发支沟及主沟进行泥石流事件数值模拟。以“7·18”朱家沟泥石流为例验证精度高于74.12%后,将此评价体系应用于极端降雨条件下的朱家沟泥石流危险性区划。结果表明:沟口单宽清水流量峰值、沟道长度和浅表层岩组是泥石流易发性主要影响因素,流域主要支沟:哈固沟、朱林沟、松树沟和郎家沟均为高易发沟;百年一遇强降雨条件下朱家沟泥石流堆积物会堵塞洮河,威胁沟道、沟口及洮河对岸城区居民生命财产安全,其中高危险区为主沟沟道和沟口,中危险区为哈固沟、朱林沟和松树沟,低危险区为郎家沟。研究成果可为青藏高原东北缘泥石流灾害提供评价方法和防治依据。

Zhujia gully in Min County,a typical debris flow small watershed on the northeastern margin of the Tibetan Plateau,is a serious threat to the safety of the countyseat because of the frequent debris flow disasters caused by earthquake and extreme rainfall. Therefore,it is essential and urgent to carry out debris flow risk assessment.In this study,the fusion algorithm of entropy weights and variable coefficients is employed to evaluate the susceptibility of debris flow in each branch gully of the watershed,and the high prone branch gullies and main gully are selected to conduct a numerical simulation of debris flow events. After taking the“7·18”debris flow in Zhujia gully as an example,the simulation results are proved to have an accuracy higher than 74.12%,and the assessment system is applied to the Zhujia gully debris flow risk zoning under extreme rainfall conditions.Results show that the peak single-width clear-water flow at the gully mouth,gully length and shallow rock group are the main factors affecting the susceptibility of debris flow,and the major branch gullies in the watershed,Hagu,Zhuling,Songshu and Langjia gullies,are all high prone to debris flow.Under the once-in-a-century torrential rainstorm,the accumulation of Zhujia gully debris flow will block the Tao River,threatening the safety of the lives and properties of residents along the gully,at the mouth of the gully and the urban area on the opposite bank of the river. Among them,the high-risk areas are main gully and gully mouth,the medium-risk areas are the Hagugo,Zhulin and Songshu gullies and the low-risk area is the Langjia gully.The research results can be used to formulate an evaluation method and provide a control basis for debris flow disasters on the northeastern margin of the Tibetan Plateau.