Research On The Drainage Planning System Based On Urban Drainage Capacity Assessment In A Certain City Of Heilongjiang Province

Due to the continuous development of the city,and the residents demand for municipal infrastructure facilities has further increased.In recent years,a city have built a large number of impervious surfaces.The area of urban hardening has increased,reducing rainwater retention and drainage.However,infiltration,resulting in an increase in surface runoff,the construction of urban drainage systems cannot keep up with the speed of urban development,and cannot meet the requirements of flood control and drainage.Furthmore,urban waterlogging is prone to occur in the rainy season,which restricts the sustainable development of cities.In this study,based on the city’s urban profile,natural conditions,and upper-level planning conditions,combined with the urban rainwater drainage zoning and the current status of drainage facilities,the city’s drainage and flood prevention capabilities and risks were evaluated.First,analyze the rainfall law and the various underlying surfaces on the rainfall data for a total of 11 years in a city from 2005 to 2015.Using infoworks ICM urban rainwater simulation software to simulate the existing rainwater drainage network and other facilities and assess the risk of flooding.The simulation results of drainage capacity show that pipelines with drainage capacity that meet the intensity of a rainstorm less than one year account for 53.74%of the total length;the compliance rate of pipelines that meet the intensity of a rainstorm over three years and above is only 25%.The simulation results of risk assessment show that,as a result of the simulation result of a waterlogging once in 20 years in an urban area,there are 10 waterlogging locations in the four districts,and the area of risk of waterlogging in the future is calculated to be 13.95km~2.The existing drainage pipe network in a city simply cannot meet the drainage demand.According to the evaluation results,the urban drainage(rainwater)pipe network system was planned and designed.Based on the actual situation of the city,the analysis determines that the combined drainage system and the diversion system should be combined.In some areas of the old city,the combined drainage system was changed to a diversion system,while in the old city,a diversion system was adopted.The drainage system of the newly built urban area should be a diversion system.It is divided into five rainwater drainage areas:the southern part of the railway,the western part of the Hulan River,the southern part of the Tiejia River,the northern part of the Tiejia River,and the northeastern drainage area.At the same time,the transformation plan for each district was proposed,some pipelines were transformed,pipelines were laid to reduce the current pipeline load,23 pipelines were added,the total length of the pipeline increased by 2198km,and the water collection area was 10.6km~2.The hydraulic model is used to check and adjust some of the pipelines.The results showed that the full flow capacity of all pipelines can meet the flow rate during a two-year heavy rain.There were no overloaded pipelines.Half-flow pipes and full-flow pipes each accounted for 46.5%of the total pipeline and 53.5%of the main urban areas had no standing water.When the planned rainstorm intensity P was 2,the design parameters of the rainwater pipeline for the drainage system design that met the drainage intensity were reasonable and feasible.In terms of urban waterlogging prevention system planning,after analyzing the urban waterlogging prevention system,considering topography and waterlogging risks,four waterlogging prevention areas were divided.The drainage system planned for a certain city was simulated,and the simulation results were as follows:the evaluation results of urban waterlogging were 5,the area of waterlogging risk area was 3.02km~2,the maximum water depth was 0.3～0.9m,and the maximum water retention was 3582～12873m~3.The simulation results showed that there were still flood-prone points.By estimating the amount of excessive floods,it was found that the flood-discharging capacity of the five flood-prone points was 0.12,0.15,0.05,0.15 and 0.05m~3/s,respectively.According to the simulation results,combined with factors such as urban vertical and receiving water bodies,9 rainwater drainage channels were planned.Arrange urban rainwater storage facilities based on the results of flood forecasts and flood control standards.Among them,the area of wetland,planting plants,and permeable sidewalk paving were 5.9,4.8,and 9.3hm~2,respectively.Perform the final hydraulic simulation of the urban waterlogging prevention system in a city.The simulation conditions were:when the Tiejia River reached the once-in-20-year flood level(recurrence period of the water conservancy department),the urban area would have a short-duration rainfall of once in 20 years(the return period of the municipal department)(2h).The simulation results showed that it met the planning standards for drainage and waterlogging prevention systems.