Study On Flood Evolution In Mengwa Flood Storage Area By Proposed Bridge Project

The distribution of precipitation in China is obviously extremely uneven in time and space,leading to the difficulty in promoting flood disasters and secondary disasters.In recent years,the frequent extreme weather is even worse.The influence of waterrelated buildings on the flood routing process before and after the construction is analyzed to provide scientific support for the real and efficient calculation of bridge engineering on the flood routing process in flood storage and detention areas and the effective development of flood control in flood storage areas.In this paper,the Mengwa flood storage area in Fuyang City,Anhui Province is selected as the study area.In terms of the direct impact of flood,the latest data of regional topography,hydrological data and bridge engineering design are used.The unstructured hydrodynamic model of MIKE 21 is used to simulate the flood evolution process of Mengwa flood storage area in real time.The influence of bridge engineering construction on flood evolution and diversion time,velocity distribution and water level change in flood storage and detention area is analyzed.In terms of secondary influence of flood,mathematical formula is used to calculate Yongshui,river scouring and dike leakage before bridge,and the influence of flood evolution on flood control after bridge construction is analyzed.The main conclusions are as follows :(1)Direct impact of floods.After the construction of the bridge project,under the action of the pier,the flood diversion duration of the flood storage area is 45 s longer than that before the construction of the project.The velocity distribution of the mainstream area near the bridge site is 0.4 ～ 0.6 m / s,and the local velocity change rate is 7.409 %.The flood water body is blocked by the pier.The maximum elevation value of the nearby water level is 0.006 m,and the maximum change rate of the water level is-0.22 ‰.The construction of the bridge delays the flood discharge time in the flood storage area,raises the water level near the pier,and changes the flow velocity distribution near the project,but has little effect on the overall flood storage area.(2)Secondary impact of flood.During flood storage in Mengwa flood storage area,the water level of bridge pier is raised,the length of backwater is about 7.78 m ～ 43.83 m,and the water blocking area of bridge pier occupies 5.02 % ～ 5.58 % of the area of cross section before the project.The change of flood velocity will affect the scour depth of the inland river in the flood storage area.Under the design flood condition,the local scour depth at the bridge site of Mengwa flood storage area is 0.329 m.Under the condition of super flood storage,the local scour depth at the bridge site is 0.330 m;under the condition of flood in 300 years,the local scour depth at the bridge site is 0.362 m.Even affected by the changes of water level,flow velocity and flood inflow time,the Yongshui River,river scouring and dike leakage before the bridge meet the requirements,and basically do not affect the normal operation of Mengwa flood storage area.Figure[40] Table [16] Reference [62]...