Study On Flood Risk Simulation And Regionalization Of Flood Control Protected Areas Considering Influence Factor Of Flood Risk

As one of the most important natural disasters,flood hazard has a certain randomness,so that only engineering measures can't guarantee the safety of flood control protection regions.In recent years,China's flood control and hazard mitigation strategy has been changed from flood resistance to flood management,including flood hazard zoning in flood control protection areas,which are importantly used non-engineering measures for flood protection.Dividing the research area according to different risk levels can intuitively express the spatial characteristics of flood hazard and provide a practical and effective basis for flood management.In the past studies on the zoning of flood hazard at home and abroad,the selection index of flood hazard assessment system is relatively simple.Although many factors have been taken into consideration,the selected indicators are not targeted and the spatial scale of evaluation unit is too large to accurately judge the extent of flood hazard.Taking the flood protection areas located in the right bank of Zhangweixin River as object of study,two-dimensional hydrodynamic models were established,and three flood risk indicators were obtained,including submerged duration,submerged depth and flood velocity.In addition,this study established a flood risk assessment system considering hazard-causing environment,such as terrain slope,river buffer and vegetation cover,as well as hazard-bearing body,such as population density,GDP density,main traffic routes and flood control standards of embankment projects.The flood hazard assessment in flood control protection regions was carried out,using three methods,namely AHP,catastrophe theory and stochastic theory.Finally,the zoning of flood hazard in flood control protection regions,based on GIS grid technology and spatial information overlay technology.The main conclusions of this study are as follows:(1)Considering various underlying surface conditions in flood control protection regions,such as landform,bridge,culvert,road,and vegetation cover,two-dimensional hydrodynamic models were established,and relatively reliable flood risk indicators were obtained,including maximum submerged duration,maximum submerged depth and maximum flood velocity.(2)According to the actual situation of flood protection areas located in the right bank of Zhangweixin River,hazard-causing factors,such as submerged duration,submerged depth and submerged flow velocity,hazard-causing environment,such as terrain slope,vegetation cover and river buffer,as well as hazard-bearing body,such as population density,GDP density,main traffic routes and flood control standards,were chosen to establish a more complete flood risk assessment system.(3)In the past,the flood hazard zoning mostly used districts and counties as evaluation units while the space scale was relatively large.In order to improve the performance,this paper based on GIS grid technology,finely divided the evaluation unit into 50 m × 50 m,and used grid pixel technology to accurately judge the extent of flood risk in various areas.(4)Based on the mentioned flood risk assessment system and assessment unit,three methods,namely analytic hierarchy process,catastrophe theory and stochastic theory were applied to study the hazard zoning of flood control protection areas,and comparative analysis was conducted in this study.The results of comparative analysis show that these three methods are reasonable and feasible of flood risk zonation in flood protection areas.Each method has its advantages and disadvantages.However,applying random set theory to zoning research is not only more reasonable theoretically and the calculation results are closer to reality.It also can avoid the subjectivity of catastrophe theory and analytic hierarchy process in judge the importance of the indicator.The result of the finely flood hazard zoning is more realistic.