| In recent years,with the continuous acceleration of urbanization in China and the rise in global temperatures,frequent extreme rainfall events have led to severe waterlogging disasters in many regions and cities in China,resulting in huge social,property,and economic losses.Reducing the loss of waterlogging disasters can be achieved by accurately and timely simulating urban waterlogging in real-time and issuing warning information.It can also simulate the process of urban hydrological disasters by inputting design rainfall scenarios,analyzing the causes of waterlogging,and proposing waterlogging prevention and control plans.Based on this,this paper takes the old urban area of the sponge city construction pilot area in Xiushan County,Chongqing as the research object,and constructs a one-dimensional drainage pipe network model,a twodimensional surface overflow model and a MIKE FLOOD coupling model.According to the rainfall process predicted by the meteorological radar chart,the urban rainfall runoff is simulated in real time,and the infrastructure waterlogging risk level Three methods are used to evaluate the risk of waterlogging,including pedestrian safety risk level and road traffic operation level.At the same time,a comprehensive evaluation was conducted on the drainage capacity of the current pipeline network,surface water accumulation status,and waterlogging risk level in the study area by designing rainfall scenarios with different recurrence periods.Based on the evaluation results,two waterlogging prevention and control plans were proposed,and the reduction effect of the two plans on urban waterlogging was explored.The main research conclusions are as follows:(1)A one-dimensional drainage network model and a two-dimensional surface overflow model were constructed for the research area,and connected and coupled through MIKE FLOOD.The model was calibrated and validated using measured data such as the water level process of the inspection well and the depth of waterlogging at the waterlogging point.The model results were well fitted with the measured values.Among them,the Nash efficiency coefficients NSE are all greater than 0.7,and the relative error of waterlogging depth at waterlogging points is less than 20%,indicating that the coupled model has good reliability in urban waterlogging simulation.(2)Taking the short-term rainfall process predicted from the meteorological radar chart as the rainfall boundary condition of the coupled model,the urban waterlogging risk under the predicted rainfall is simulated.Research has shown that under the predicted rainfall conditions on September 6,2021,the risk level of infrastructure waterlogging in the study area is mainly mild,the risk level of pedestrian safety waterlogging is mainly I,and the traffic operation level of the road section is mainly smooth.(3)Using the rainstorm formula and Chicago rainfall pattern,five rainfall scenarios with different return periods were designed,and the impact of rainfall with different return periods on pipe network drainage and urban waterlogging process was analyzed.The results indicate that as the rainfall return period increases,the number of overflow nodes increases,and the length of the full flow pipeline also increases.50.01% of the pipeline network’s drainage capacity does not meet the design standards for a 5-year return period or above.(4)The simulation results of surface water accumulation show that the depth of surface water accumulation is mainly concentrated in the range of 0.05-0.15 meters,and the spatial distribution of water depth under different return periods of rainfall is generally consistent.The submergence duration is mainly concentrated in the range of 60-90 minutes,and the water flow velocity is mainly concentrated in the range of greater than 0.8 m/s;The infrastructure waterlogging risk in the entire region is mainly minor,with pedestrian safety waterlogging risk level being mainly level Ⅰ,and the traffic operation status level of road sections being mainly level smooth.The areas with severe waterlogging risks are mainly concentrated at the intersection of Yuxiu Avenue and Fengxiang Road,as well as the intersection of Shilian Road and Binhe East Road.(5)Based on the current evaluation results,two waterlogging prevention and control plans are proposed.Plan A is based on the local pipeline network renovation,and Low Impact Development(LID)measures are implemented for the areas near the two areas with severe waterlogging risks.Plan B is based on the local pipeline network renovation,and LID measures are implemented for all areas that can be renovated in the research area.The degree of mitigation of waterlogging in the research area by both plans is analyzed.The study found that under the two schemes,the overflow quantity of inspection wells decreased by 13.18%～23.84% and 49.04%～76.44%,respectively,and the surface waterlogging inundation area decreased by 31.84%～46.82% and 77.95%～91.46%,respectively.The depth of surface waterlogging and water flow velocity significantly decreased,and the waterlogging time significantly shortened.Both schemes can effectively reduce the three types of waterlogging risks and have good control effects on urban waterlogging.The control effect of Scheme B is better than Scheme A,but the control effect of both schemes gradually weakens with the increase of rainfall return period. |
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