Investigation And Risk Assessment Of Flood Disasters In Small And Medium River

Flood disaster is a problem that has plagued human beings for thousands of years.Compared with the relatively comprehensive flood control planning and construction of big rivers,the flood control situation of small and medium-sized rivers is a weak link,which causes frequent disasters.The flood related research field is developing rapidly,but the flood of middle and small rivers is still not perfect in the flood research field because of its large quantity and wide distribution.In order to respond to the national call to transition from"flood control"to"flood risk management",provide scientific and non-engineering measures for flood control and disaster reduction,supplement the study cases of domestic small and medium-sized rivers,take the lower reaches of Ashe River in Harbin as the research object,carry out flood disaster investigation and statistics in areas lacking data of small and medium-sized rivers,and use Mike model to carry out flood numerical simulation in the study area.Based on the analysis of flood risk in the study area using geographic analysis software,the degree of impact of floods with different return periods on the study area was determined.The main research content and achievements of this article are as follows:（1）Investigate the historical flood data of Ashe River Basin,analyze the causes of flood disasters of Ashe River from three aspects:hydrology,topography and human activities,and calculate the designed flood peak and flood volume data of different return periods combined with the historical data of Acheng hydrographic Station.Among them,the design flood peak value of each frequency P=20%is 450m³/s,P=10%is 792m³/s,P=5%is 1182m³/s,and P=2%is 1736m³/s,which provides data basis for flood simulation.（2）Construct a hydrodynamic model of flood evolution of Ashe River,and propose solutions to problems in the process of model making such as lack of data in the study area.The Mike11 HD one-dimensional research model and Mike21 FM two-dimensional research model of the study area were constructed by designing Flood in different recurrence periods.The Mike Flood model was coupled to the one and two-dimensional models in the way of lateral connection,and the rationality of the simulation results of the study area was verified.The data analysis of the simulation results showed that the inundated area of 5-year one-time flood was 0.861km².The occurrence is 1.148km² in 10years,1.968km² in 20 years,and 3.53km² in 50 years,which provide the basis for risk assessment.（3）Based on the flood risk analysis research theory,according to the flood simulation results in the study area and combined with the social and economic situation,the economic losses of flood disasters in the study area were calculated as D₅=3.64million yuan,D₁₀=7.97 million yuan,D₂₀=17.106 million yuan and D₅₀=28.772 million yuan.Based on the flood risk and carrier vulnerability,a comprehensive flood risk assessment index system was established,the analytic hierarchy process was used to determine the specific gravity,and the flood disaster risk assessment was carried out in the study area combined with GIS software.The study area was divided into danger area,major disaster area,medium disaster area,light disaster area and safe area according to different degrees of flood impact,so as to provide scientific basis for flood control and disaster reduction measures.