Research And Ayalysis Of Urban Flooding Simulation In Coastal City Based On The Example Of Jin’an River Basin

Affected by human activities,global climate change and urbanization jointly lead to extreme rainstorms.When coastal cities were hit by typhoons,short-term heavy rainfall quickly forms surface water,which causes serious urban waterlogging.Then normal traffic and production and life were hindered,resulting in huge economic losses and casualties.The establishment of local urban flooding model to simulate the degree of disaster under different rainfall conditions,and the formulation of scientific and effective scheduling scheme based on the working conditions of reservoirs and lake sluice stations in the basin have become powerful strategies under the background of smart water affairs.Taking the Jin’an River Basin in Fuzhou City as an example,this paper investigates the historical flood disasters and current flood control standards,takes into account the natural climate,topography,river network and underlying surface distribution.Based on the integrated drainage software of Info Works ICM,a pipe network model,a river channel model and a two-dimensional surface waterlogging simulation model are constructed.Based on two measured typhoon rainfall data,the infiltration,roughness and water storage coefficient of depression in sub catchment area of the basin are adjusted,and the calibration and validation of the model are completed.By designing eight rainfall scenarios in the recurrence period,the inundation range,submerged area,inundation depth,pipe fullness and pipe network overflow of the study area under different conditions were simulated.According to the statistical analysis,if the recurrence period is less than 3 years,the pipe network has a strong capacity to hold rainwater.The flood discharge capacity is better when the recurrence period is less than 10 years.When the recurrence period is more than 10 years,the intensity of the rainstorm exceeds the current flood control standard of drainage facilities,the water level of the river flows to the surface,and the storm water pipe network has a large amount of overflow.Further analysis shows that the enhanced impermeability of the underlying surface,the lagging flood control standard,the flood discharge in the upstream mountainous area and the tidal backflow from the outer river constitute the cause of waterlogging in the study area.Combined with economic benefit and management cost,from the perspective of off-peak regulation and storage,this paper proposes a joint dispatching scheme of the reservoirs,lakes,sluices and pumps.Before the rainstorm,the reservoir and lake channel space should be vacated in advance,and the discharge and discharge time should be controlled under the premise of ensuring the safety of the reservoirs and lakes.Give full play to the drainage function of the downstream riverside sluice station.When the water level of the inner river is higher than the water level of the outer river,the pumps will be opened to drain waterlogging.When the water level of the inner river is lower than the water level of the outer river,the sluice gates will be closed to prevent the river water from flowing backward.The simulation results show that the flood area can be reduced by 19.5%,the average water depth of main waterlogging points can be reduced by 0.23m,and the total overflow flow can be reduced by 24.71%.The results of this study can provide theoretical and technical support for the urban water system scheduling in Fuzhou urban area,and have important reference significance and reference value for other coastal cities to deal with twaterlogging disasters and achieve scientific scheduling.