Identification And Risk Early Warning Of Flash Flood Disaster For Ungauged Basin In Jiangxi Province

Mountain torrent disaster is caused by short duration and heavy rain,and its influencing factors are various,mainly including rainfall,terrain and human factors.Mountain torrents flood streams and rivers,and flood roads,bridges,farmland and villages.They not only seriously damage infrastructure and natural environment,but also seriously threaten the safety of people's lives and property.Jiangxi province is a mountain torrents frequent area,every year because of mountain torrents the death toll reaches dozens of people even hundreds of people,the economic loss is also countless.In this paper,the FLOW 3D flood model method is proposed to deduce design flood from design storm?The calculation results are compared with the rational formula method and the instantaneous unit hydrograph method?Taking Huoshiling-Maogongdong small watershed in Zhongyuan Township in Jing'an County as a typical research object,the risk identification and early warning of mountain torrent disaster in mountainous areas without hydrological data in Jiangxi Province are studied.The following conclusions are drawn:(1)Mountain torrent disaster in Jiangxi Province has the following characteristi-cs:1.Strong randomness.2.Obvious regional.3.High frequency.4.Fast disaster, short response time.5.Strong destructive,serious harm.6.Mainly mountain stream flood and landslide.7.Disasters have a wide distribution.(2)This paper studies the method of calculating design flood from rainfall data,analyzes on the method of determining the current flood control capacity with critical flow,and discusses the theory and method of risk zoning with housing and population as research objects.(3)A new method and modeling process for calculating early warning indicators with FLOW 3D hydrological model method were proposed to simulate and calculate the runoff,flood-peak discharge and flood process.(4)The instantaneous unit hydrograph method,the rational formula method and FLOW 3D hydrological model method were used to calculate the design flood of small watershed.The results showed that the results of the three calculation methods were similar.This paper has verified the feasibility and applicability of FLOW 3D hydrological model method to design storm and design flood.(5)In this paper,the FLOW 3D flood model is proposed to calculate the early warning index.Assuming the rainfall value and rainfall time distribution,the design flood-peak discharge is trial calculated in FLOW 3D.When the design flood-peak discharge is close to the disaster flow,the assumed rainfall is the critical rainfall index?(6)Considering the influence of early rainfall and soil moisture content,two critical values Pa=0.5wm and Pa=0.8wm were selected to simulate three calculation conditions:soil moisture(Pa>0.8wm),soil general(0.5Wm?Pa?0.8Wm)and soil drought(Pa<0.5Wm).The results show that the influence of early rainfall and soil moisture content on design flood can not be ignored.The FLOW 3D flood model method has good simulation effect and high accuracy,which provides a new method and technical support for risk identification and early warning of rainstorm mountain torrent disaster in mountainous areas without hydrological data in Jiangxi Province.