九龙县踏卡河流域乌拉溪沟低频泥石流特征与危险性

通过计算分析四川省九龙县踏卡河流域乌拉溪沟的泥石流运动特征参数并结合实地调查,探讨其再次暴发的危险性。研究表明:乌拉溪沟泥石流属于低频稀性泥石流,二十年一遇泥石流的流速为4.35m/s,峰值流量达221.09m3/s,一次冲出固体物质总量为4.18×104m3;流域内物源丰富,总量为527.85×104 m3,多为坡面侵蚀物源,占总量的89.32%;短历时强降雨是该沟爆发泥石流的关键因素,当降雨强度大于32.76mm/h时(二十年一遇),乌拉溪沟泥石流暴发可能性较大,并且会堵塞踏卡河,属于高危险性泥石流。沟道内两处堵溃点及丰富的物源是泥石流危险性放大的主要因素,在防灾减灾中需及时疏通沟道,避免发生堵溃。

Characteristics of low frequency debris flow and its risk analysis in Wulaxi Gully of Taka River Basin,Jiulong County,Sichuan,China

Based on the field investigation,the risk of debris flow at Wulaxi Gully of Taka River Basin in Jiulong County,Sichuan Province is discussed through calculation and analysis of the characteristic parameters of debris flow movement.The results show that the debris flow at Wulaxi Gully belongs to the low-frequency sparse debris flow with the debris flow rate of 4.35 m/s,the peak flow rate of 221.09 m 3/s,and with the total amount of one time washed out solid material of 4.18×104 m 3.Present investigation leads to the recognition that the debris flow provenance in the basin is mainly from slope erosion,which accounts for 89.32%of the total.Short-duration heavy rainfall is the key factor for the outbreak of debris flow in the gully.When the rainfall intensity is greater than 32.76 mm/h(once in 20 years),the possibility of the outbreak of debris flow in Wulaxi Gully is raised.The high risk debris flow will block the Taka River and cause hazards.The two blockage points and abundant material sources in the gully are the main factors for the risk amplification of debris flow.In the disaster prevention and mitigation,the gully should be dredged in time to avoid blockage and collapse.