西昌安保公司后山火后泥石流成灾特征  

Study on Disaster Characteristics of the Post-fire Debris Flow in Security Firm Back Hill,Xichang

作　　者：黄忠 蒲敏 唐鹏 HUANG Zhong;PU Min;TANG Peng(Sichuan Institute of Metal Geological Survey,Chengdu 611730)

机构地区：[1]四川省金属地质调查研究所,成都611730

出　　处：《四川地质学报》2024年第2期278-283,共6页Acta Geologica Sichuan

摘　　要：火后泥石流是指火烧迹地附近发生的与林火密切相关的泥石流。以四川省凉山州西昌市安保公司后山沟为研究对象,通过无人机航拍、现场勘查和室内分析等方法,对火烧迹地、沟道流域和物源特征进行阐述分析,对火后泥石流成灾特征进行论证研究。结果表明,安保公司后山沟过火面积达到流域总面积的100%,其中重度火烧区占流域的51.8%,灰烬层厚度在3~5cm,扰动土层厚度4~6cm;中度火烧区占流域的44.4%,灰烬层厚度在2~4cm,扰动土层厚度3~5cm;火烧迹地灰烬层和火烧扰动土层厚度与火烧烈度呈正比。火后泥石流的启动方式由坡面径流冲刷和浅层滑坡组成,两种启动方式共同作用引发。火后泥石流表现出暴发频率高,火灾后第一个汛期就暴发了4次泥石流灾害,且多为当地常见的中到大雨激发,说明火后泥石流沟启动降雨阈值降低、暴发频率高。通过对火后泥石流沟成灾特征的研究,为火后泥石流的治理提供科学依据。The post-fire debris flow refers to the debris flow closely related to forest fire near the burned land.In this paper,taking the Back Hill gully of Security Firm in Xichan,Liangshan Prefecture,Sichuan Province as the research object,the characteristics of burned land,gully watershed and provenance were described and analyzed by UAV aerial photography,field investigation and indoor analysis,and the characteristics of debris flow disaster after fire were demonstrated and studied.The results show that the fire area in the Back Hill of the safety company is 100%of the total area of the basin,and the heavy fire area accounts for 51.8%of the basin.The thickness of the ash layer is 3~5cm,and the thickness of the disturbed soil layer is 4~6cm.The moderate burning area accounted for 44.4%of the basin,the thickness of ash layer was 2~4cm,and the thickness of disturbed soil layer was 3~5cm.The thickness of the ash layer and the disturbed soil layer in the burned area is proportional to the fire intensity.The starting mode of post-fire debris flow is composed of slope runoff erosion and shallow landslide,which are caused by the joint action of the two starting modes.After the fire,debris flow showed a high frequency of outbreak,and four debris flow disasters broke out in the first flood season after the fire,and most of them were triggered by the local common medium to heavy rain,indicating that after the open fire,the rainfall threshold of debris flow trench was reduced and the outbreak frequency was high.The research on the disaster characteristics of debris flow gully after fire provides scientific basis for the treatment of debris flow after fire.

关 键 词：火后泥石流 火烧迹地 火烧烈度 灰烬层 成灾特征 

分 类 号：P642.23[天文地球—工程地质学]