Assement Of Drainage Capacity Of Pipeline Networks And Study On Simulation Of Waterlogging Risk In Typical New Urban Areas Of North China

In the current situation of frequent urban waterlogging,how to simulate the urban rainfall runoff process,accurately identify waterlogging risk areas,and take corresponding waterlogging prevention and control measures in a timely manner is an important issue faced by urban emergency management.This study aims to establish a MIKE21 rapid assessment model and a MIKE Urban one-dimensional pipeline network model to quickly identify waterlogging areas and evaluate the drainage capacity of the drainage network.In addition,this study constructs a MIKE FLOOD one-dimensional and two-dimensional coupled model to simulate the waterlogging situation in the region,and further proposes effective waterlogging prevention and control measures,in order to provide strong technical support for urban emergency management and flood control and drainage work.The main achievements of the paper are as follows:(1)For areas without pipeline network data,this study uses evaporation value instead of pipeline drainage capacity,and combines local rainstorm intensity formula to generate Chicago rain patterns with different return periods as the input conditions of the model.Then,based on the MIKE21 two-dimensional surface overflow model,a rapid assessment model for waterlogging was constructed.The changes in surface inundation under different return period design rainfall conditions were compared and analyzed,and the waterlogging area was preliminarily determined.The simulated inundation location and depth were compared with the survey results,verifying the reliability of the simulation results of the rapid assessment model.(2)This study constructed a MIKE URBAN one-dimensional pipeline network model and evaluated the drainage capacity of the pipeline network based on two evaluation indicators: pipeline fullness and node overflow obtained from simulation.From the perspective of pipeline filling index,under the design rainfall conditions of once every year,once every two years,once every three years,and once every five years,the length of pipelines with insufficient drainage capacity accounts for 83.7%,87.9%,89.3%,and 91.1% of the total pipeline length,respectively.From the perspective of node overflow index,under the design rainfall conditions of once every year,once every two years,once every three years,and once every five years,the number of node overflows accounts for 55.4%,66.8%,70.7%,and 74.6% of the total overflows,respectively.It can be seen that the current drainage capacity of the pipeline network is poor.(3)Based on the above constructed MIKE21 surface overflow model and MIKE URBAN one-dimensional pipeline network model,a MIKE FLOOD coupling model was constructed under different return period design rainfall conditions.According to the simulation results of the model,the study area was divided into three different risk categories,with low risk area,medium risk area,and high risk area accounting for 5.29%,8.6%,and 2.06%respectively,with medium risk area accounting for the largest proportion.Based on the risk of waterlogging in the research area,this study proposes corresponding engineering and non engineering waterlogging prevention and control measures.From the perspective of the implementation effect of green roof measures,after the implementation of green roof measures,the proportion of areas with a submerged depth of more than 0.3m decreased from8.73% before the implementation of green roof measures to 4.69%.It can be seen that green roof measures can effectively improve the waterlogging situation in the research area.