Analysis on the risk of rainstorm waterlogging in urban area of Changzhou City
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Abstract:
Flood disasters are one of the most serious natural disasters in our country.More than two-thirds of cities across the country have experienced rainstorms and floods of varying degrees.In recent years,with the rapid development of urbanization,a series of problems such as drastic changes in the underlying surface,changes in the law of runoff generation and confluence in river basins,and obsolescence of urban drainage facilities have greatly increased the exposure to flood risk.On average,more than 200 cities have flooded every year,and the phenomenon of "city watching the sea" is getting worse. The mathematical model is the main method to calculate and analyze urban rainstorm waterlogging.The main urban area of Changzhou City is taken as the research object to analyze its rainstorm waterlogging risk.Using InfoWorks ICM,according to the topography,river system,underground pipeline,water conservancy project,and engineering scheduling rules of the main urban area of Changzhou City,the hydrological and hydrodynamic,one-dimensional and two-dimensional,river network and pipe network coupling models of the main urban area of Changzhou City are constructed.The scope of the model covers 179.2 km2 of the main urban area of Changzhou City. To ensure the refinement level and simulation accuracy of the model,the river sections in the constructed model are all measured sections,including 113 river channels and 1 154 sections.The pipeline network model covers the entire compilation range of the main urban area of Changzhou City.During the construction of the two-dimensional model,the road elevation was intensively measured,and the distance between points was controlled to be about 100 m to 300 m according to the changes in elevation.A high-precision DEM data was collected to build a ground model .The hydrological model was used to calculate the confluence process.The calculation results of river water level may also affect the pipe network and ground model.The pipe network,river network,and submerged area may exchange water according to the above process,nesting each other and real-time mutual feed,to realize the one and two-dimensional coupling of the river network and pipe network. The mathematical model was calibrated and verified with the 2017 field prototype observation data,and the 2015 flood simulation situation was compared with the actual submerged area and submerged water depth.The verification results show that the maximum absolute error of the calculated water level and the measured water level are both less than 7 cm,and the shape of the calculated water level curve matches well with the measured water level sequence.Using the calibrated and verified one and two dimensional coupled model of the refined river network and pipe network in the main urban area of Changzhou City to simulate and analyze the flood inundation and pipeline operation load under the maximum 24 h design rainstorm conditions in 50 years,100 years,and 200 years.The results show that:The inundation area is 29.04 km2,31.48 km2,and 34.70 km2,respectively,under the maximum design rainstorm of 24 h.The submerged water depth is mainly distributed in the range of 0.05 to 0.30 m,accounting for about 70% of the total submerged area.The daily maximum rainfall in the region plays a leading role in the process of water accumulation,which is characterized by a large area of waterlogging in torrential rain and a small submerged water depth.Most of the pipelines in the main urban area are overloaded.Among them,the percentages of overloaded pipelines due to the jacking of downstream pipelines were 65.99%,65.65%,and 65.39%,respectively,and the proportions of overloaded pipelines due to the limitation of the flow capacity of the pipeline itself accounted for 33.09%,33.46%,and 33.74%.Short-duration heavy rainfall is the main cause of overloading of the pipeline network.The research results provide a basis for predicting the risk of rainstorm waterlogging in Changzhou City,guiding the decision-making of flood control and drainage,and also provide a reference for the urban development and construction of Changzhou City.
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