甘肃天水地区渭河南岸大砂沟泥石流发育特征

Debris Flow Characteristics in Dashagou on South Bank of Weihe River in Tianshui Area,Gansu Province

以天水地区渭河南岸大砂沟泥石流沟为研究对象,通过野外地质调查以及历史资料的统计,初步了解该泥石流的形成条件、松散物源的补给条件、活动历史;详细研究了该泥石流的运动特征,并提出了相应的治理措施。结果表明:该泥石流沟上游三面不稳定斜坡体上的堆积物和大砂沟沟道内的松散堆积物为该泥石流的主要物源;通过统计分析,在极端降雨天气条件下计算得到洪峰流量为355. 26 m3/s。该泥石流沟仍存在暴发大规模泥石流的可能性,一旦泥石流发生,将对下游甘谷县城居民的生命财产安全造成严重的威胁。研究成果可为天水地区泥石流的防灾减灾提供科学依据。

Taking the Dashagou debris flow ditch on the south bank of the Weihe River in Tianshui area,Gansu Province as a case study,we conducted field geological survey and historical data review to investigate the formation and recharge conditions and the past activities of debris flow.Movement characteristics of the debris flow are studied in detail,and possible controlling measures are proposed.The results show that debris-flow deposits on the three unstable slopes upstream of the debris flow ditch and the loose sediments in the Dashagou channel are the main source.Through statistical analysis,the peak discharge calculated under extreme rainfall conditions is 355.26 m3/s,and there remains a possibility of a large-scale debris flow outbreak from the ditch.Once debris flow occurs,it will pose serious threats to the life and property of the residents in the downstream town of Gangu County.Our finding can provide scientific basis for disaster prevention in Tianshui area.