Study On Rainfall Runoff Control And Impact Of Tidal Backwater In Coastal Cities

With the rapid development of urbanization,urban rainstorms are frequent and runoff pollution is serious.Following this,the construction of the sponge city came into being.For coastal cities,seawater reflow pipe network and tidal backwater problems are common.However,the coupling simulation of rainwater system and external boundary conditions is still lack of researchers' attention.Aiming at the impact of torrential rains and sea tides in coastal cities,taking the construction of sponge city as an opportunity,relying on the online monitoring information platform of Internet of Things,the construction model of rainfall runoff was based on SWMM and GIS.The sponge construction model was selected to establish a sponge model to study the rainfall runoff control and water quality control effects of LID measures.Compare the simulation with the LID measures,statistically analyze the total rainfall runoff control rate under the short-time rainfall events of different rainfall return periods,and view the runoff,node water depth,pipe network load,total discharge load,etc..The results show that the total rainfall runoff control rate is significantly improved and the total pollutant discharge load is reduced in the LID mode,and the low-intensity rainfall control effect is better.LID measures reduce infiltration and interception of rainwater,reduce rainfall runoff and pollutant load,relieve node overflow and reduce pipeline operating load.Therefore,the risk of influx of endogenous water and non-point source pollution is reduced,and the water quantity and water quality control effect are good.The rainwater pipe network system in the sea area was constructed to construct the rainwater system and the tidal coupling model,and the tidal outflow and free outflow were compared and analyzed.On the one hand,the simulation analyzes the adverse damage of the ocean tide tidal backwater to the rainwater pipe network system.On the other hand,adjust the rainfall period to encounter the tidal curve period,study the operational changes of different encounter situations,find the most unfavorable working conditions;propose measures to alleviate the adverse effects of tidal backwater.Studies have shown that the influence of tidal backwater on the drainage network system varies with the tidal water level and the changing law.The tidal outflow caused the water level of the inspection wells in the middle and lower reaches to rise,and the fullness of the pipeline increased,which seriously affected the drainage capacity and increased the risk of internal hesitation.In addition,when the tidal flood peak overlaps with the flood peak,the pipe network is the most serious,which is the most unfavorable situation.When the tidal flood peak lags,the seawater backflow is serious during the rainfall period,and the impact is second.Finally,using the theory of hedging transactions,according to the construction concept of the sponge city,it is proposed to adopt the LID facility to reduce the flood peak flow,delay the flood peak time,cut the peak peak and adjust the peak,and alleviate the adverse effects of the tide backwater.