北京山区典型低频泥石流特征及危险性研究

通过2015年3月对北京密云水库上游白马关河流域内黄梁根桥沟现场调查,收集该区历史上泥石流灾害事件资料,对该沟的物源特征、降雨激发条件进行了分析;参考该区域其他泥石流沟的堆积物,分别进行了泥石流的密度、流速、流量和总量计算;最后对该沟的泥石流潜在危险性进行了分析,并提出了相应的减灾对策,可为该沟以及该区域其他低频率泥石流防治、预测预报提供参考。结果表明:黄梁根桥沟内物源总量为17.99万m3,大部分堆积在斜坡坡脚,严重挤压主沟道。短历时降雨是该沟以及该区泥石流暴发的主要激发条件,当暴雨强度在31.79~40.20 mm/h时,泥石流暴发可能性较大。受物源体影响,该沟为稀性泥石流沟,流速接近5.0 m/s;20年一遇暴雨条件下洪峰流量为187.41 m3/s,一次固体总量为6.82万m3,超过沟口目前的拦挡坝库容。 

Characteristics of low frequency debris flow and risk analysis in Beijing mountainous region

By investigating the Huanglianggenqiao Gully in Baimaguan River Basin of the upper stream of Miyun Reservoir in Beijing in March 2015, we analyzed the provenance characteristics of the gully and rainfall excitation conditions. Referring to other debris flow gullies in this area, we calculated bulk density, flow velocity, flow rate and debris flow scale of the studied gully. Finally, we analyzed the potential risk of debris flow in this gully and proposed countermeasures for reducing disasters, which would provide references to the prevention, control and forecast of debris flow in this gully and other low-frequency gullies in this area. The results showed that the total provenance in Huanglianggenqiao Gully was about 17.99×104 m3, which was mainly piled up at the bottom of slope and thereby seriously squeezed the main channel. Short-duration rainfall was the main excitation factor for the debris flow of this gully or the whole area. When rainfall intensity ranged between 31.79 and 40.20 mm/h, debris flow was more likely to break out. The gully belongs to diluent debris gully and the flow velocity is close to 5.0 m/s, affected by provenance reserves. Under the condition of 20-year rainstorm, the peak flow was 187.41 m3/s and the debris flow solid scale was 6.82×104 m3, which were beyond the surplus storage capacity.