Flood Submerging Simulation And Evaluation Based On MIKE11 In Small Watershed Of Hilly Regions

In recent years,with the frequent occurrence of extreme weather and the acceleration of urbanization,the frequency of flood disasters is getting higher and higher.However,hilly areas will cause more serious mountain torrents disasters due to their special landform conditions,which will bring serious economic and property losses to local governments and people.Liubu Town of Licheng District is located in the southern mountain area of Ji'nan,which lies to Jinyang River.With the effect of heavy rains and imperfect flood control engineering measures,flood disasters occurred repeatedly in this place,causing the submergence of riverain residents and farmland.In this paper,three small watersheds of Liubu Town were selected as the study object,and the model of flood submerging simulation was established by coupling the HD model with the NAM model using MIKE11 software.It completed the simulation and analysis of rainstorm-runoff-flood routing-flood submerging under different five modes,and a comprehensive evaluation on the present situation of flood control along the riverain village based on the simulation results also be made.The main conclusions are as follows:(1)The simulation results of runoff-conflux model show that: the relative error of each index is smaller and less than 10% in calibration periods.In the validation period,the simulation effect is slightly worse.But in general,the simulation results are in good agreement with the export flow process of the basin,and all parameters meet the accuracy requirements,which can be used for further modeling.(2)In the hydrodynamic model,segmentation setting for the roughness parameters according to the characteristics of the river bed and the water flow.The range of the overall roughness is 0.03~0.045.When the river turn suddenly,the river bed is uneven or the section is irregular,the value of roughness is larger,otherwise the value is smaller.(3)Through the simulation of four typical rain flood process,we know that the effects of the four floods on each basin are different.The verification results of coupled model show that the simulated maximum flood level from upstream to downstream changes with the downward trend of the river longitudinal profile,the simulated form of the water surface line and the maximum flood level are similar with actual measurement.Therefore,the overalleffect of simulation model is believable.(4)According to simulation results under five different calculation schemes,we know that submerged water surface line change with the topography of the river and rise gradually with the increase of the magnitude of the flood,but the increase is not obvious;With the increase of flood magnitude,the highest flood level in each section and the peak flow rate will also increase,and the flood peak flow of Liu buzhong village located at the intersection in100-year flood recurrence is more than 1000m3/s;The highest flood level in the main stream and the tributaries gradually decreases from upstream to downstream,and the variation trend of peak flow is the opposite;The submerged depth of each section increases with the increase of flood magnitude,and some submerged depth reach more than 4.5m.(5)The comprehensive evaluation results of the flood control show that there are 20 villages,1003 households,3756 person in the research area,among them,the village number of the flood control capacity over the 100-year flood recurrence is 11,between the 20-years and 100-years flood recurrence is 4,between the 5-years and 20-years flood recurrence is 5,in addition,the flood control capacity of the main stream is best,Toke river is in the second place,and Qicheng River is the worst;From macro perspective,most of the population throughout the town are in a relatively safe zone,there are 872 people are in the dangerous area,accounting for about 23.2% of the total survey population.Among them,the threatened population is mainly concentrated in the less-risk area,followed by the high-risk area,there is no perspon in the extremely-risk area.The population of the high-risk area and the less-risk are 190 and 682 respectively.