Characteristics of flash flood-debris flow disaster induced by the'23·7'rainstorm in Hantai Village,Changping District,Beijing
[Objective]In recent years,affected by extreme rainfall events,flash flood-debris flow disaster have occurred fre-quently in the western and northern mountainous areas of Beijing,causing huge losses to local lives and properties.The disaster process and Characteristics of flash flood-debris flow disaster induced by the'23·7'rainstorm in Hantai Village,Changping District,Beijing are analyzed in this paper,which provides basic support and reference for disaster prevention and improvement of disaster response capacity in small watersheds.[Methods]Taking the Hantai Section of Gaoyakou Valley in Changping District research area,a combination of'regional disaster investigation,on-site investigation in severely affected areas,and indoor evalu-ation analysis'was used to identify the characteristics of rainfall and disaster in the research area.Based on the sedimentary structure,physical damage forms,and inherent characteristics of fluids,the disaster process and characteristics of flash flood-debris flow in the Hantai Tributary was analyzed,preliminarily explores the causes of this disaster.The disaster prevention meas-ures and suggestions is also proposed.[Results]The results show that:(1)The catchment area of the upper reaches of Hantai Village is about 0.1 km2.According to the rainfall data from 12:00 to 13:00 on August 31,2023 at the Wangjiayuan Reservoir automatic station,the estimated total hourly flood volume in the upper reaches of Hantai Village is about 6 870 m3,which con-tains a very large destructive power.(2)From the top of Hantai Tributary to the southern entrance of western Hantai Village,typical debris-flow characteristics are observed.Within 120 m from the southern entrance of Hantai Village,there is debris flow accumulation covering the flood deposits,with typical front characteristics of debris flow accumulation.From the front edge of debris flow accumulation to the north entrance of Hantai Village(the mouth of Hantai Tributary),there are obvious characteris-tics of flash flood disasters,with an inundated depth of＞5 m,with an inundated area of about 33 940 m2.(3)The extreme heavy rainfall caused by the residual circulation of No.2305 Typhoon'Dusurui'moving northward is the direct disaster-causing factor.Moreover,it is influenced by factors such as regional topography,flash flood-debris flow,and residents'understanding of the geological environment.[Conclusion]The heavy rainstorm and flood disaster in Gaoyakougou Valley of Changping District is a compound disaster event of flash flood and debris flows caused by an extreme rainstorm.The sudden increase of surface runoff caused by short-term heavy rainfall is the direct cause of this disaster.Preliminary speculation suggests that the debris flow oc-curred later than the flash flood,or it may have formed during the weakening stage of the flash flood.The area from the top of Hantai Tributary to the south entrance of western Hantai Village(about 1.4 km)develops debris flows.The area of about 120 m from the southern entrance of Hantai Village is the front edge area of debris flow accumulation,with flood characteristics at the edge areas.The area from the south entrance to the north entrance(tributary mouth)of western Hantai Village is affected by flash flood disaster.
global climate changeextreme precipitation'23·7'Beijing-Tianjin-Hebei heavy rainstormflash flood-debris flow disasterdisaster processdisaster characteristicsHantai Tributary of Gaoyakou Valleyflood prevention and disaster reduction
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