Study On The Assessment Of Urban Waterlogging Risk And Source Control Based On Digital Water

Since the beginning of the 21 st century,the rapid increase in urbanization rate has led to the imbalance of the original hydrological cycle in the city.The old urban drainage system and the backward urban rainwater management concept cannot coordinate the urban development,and the resulting cities are frequent cities.Floods have caused serious damage to residents’ production,living safety and social economy.Therefore,the simulation of urban intrinsic risk and the sustainable control of urban stormwater research can scientifically and intuitively judge the flood disasters of future cities and implement them effectively.The means of control and control are of great significance to the prevention and rescue of urban shackles and comprehensive countermeasures.In this context,the paper takes a certain urban area of Qingdao as an example to carry out simulation research on urban rainwater and conducts research on the feasibility of source control based on simulation results,in order to provide scientific basis for flood control,rescue and comprehensive management of other cities in China.The main research contents and results are as follows:(1)Construction of urban rainwater drainage model based on DWThe Digital Water Simulation(DW)was developed by Beijing Qingkong Institute of Human Settlements and Environment.It can simulate the operation status of urban drainage pipe network,realize the seamless coupling between one-dimensional pipe network and two-dimensional surface,and construct the urban stormwater drainage in China.The model has a strong advantage.Based on the functional principle of GIS and DW system,the urban rainwater drainage model is constructed.Taking the district A of Qingdao as an example,the model is determined by the runoff coefficient method.The results show that the model can better simulate different land use under different return periods.The type of runoff coefficient changes can be used for subsequent urban stormwater simulation.(2)Study on urban waterlogging risk assessmentUsing the scenario simulation assessment method,the urban flood risk level is divided by the depth of water accumulation,the time of flooding,and the grade of land use as evaluation indicators.Based on the A-zone rainwater drainage model,the rainfall conditions of different return periods were designed to evaluate the drainage network capacity and the risk of internal drainage,analyze the causes of internal hesitation and propose transformation measures.The results show that:(1)model simulation of the A-zone drainage network capacity is generally low,can not meet the needs of the city.(2)The risk level of the A area is divided into three categories: low,medium and high,and the risk area in the A area is obtained.The main reasons area are: high impermeability of the underlying surface,flat terrain is not conducive to drainage,the current capacity of the drainage network is low,the catchment area is large,and the pipeline is silted(3)Research on the feasibility of source control——construction of new project indicator systemThe source control is divided into new construction projects and renovation projects according to the type of construction land,and the evaluation target of the source control implementation is determined as the annual total runoff control rate.According to the relevant requirements of Qingdao Municipality,determine the composition of the underlying surface,the proportion of source control measures and other storage volume for each typical plot in the new project.The national standard method and the model method are used to simulate the annual total runoff control rate.The results show that :(1)New types of land parcels are divided into four categories: residential land,public management and public service facilities land,commercial service land,and utility land;there are three types of source control measures: recessed green space,bioretention facilities,and permeable pavement Loading;other storage volume is unified into a reservoir.(2)The simulation results of the model method are generally larger than the calculation results of the national standard method.(3)Under this indicator system,the total annual runoff control rate of public management and public service facilities is the largest,the commercial service industry facilities use the smallest land,all kinds of typical land parcels meet the target requirements,and the indicator system is feasible and effective.(4)Research on the feasibility of source control——the study of the optimal situation of the transformation projectFour source control retrofit scenarios were designed: recessed green space,bioretention facilities,permeable pavement,and a combination of three measures.A typical built-up community is selected.The model method is used to simulate the current situation of the community,the runoff coefficient of the four types of scenarios,the peak flow,and the peak time.The current situation and the annual runoff total control rate of the optimal scenario are simulated.The results show that:(1)All four scenarios can reduce the runoff coefficient,reduce the peak flow and the lag peak current in different degrees,and the optimal control effect is the fourth scenario.(2)The annual average runoff control rate of the optimal scenario increased by 27.2% compared with the current control rate.The value reached the target requirement,and the source control transformation was effective and feasible.