Urban Waterlogging Vulnerability Analysis And Drainage Scheme Optimization Based On MIKE FLOOD Model

In recent years,with the rapid development of China’s economy and the rapid acceleration of urbanization,the problems in the urban drainage system are gradually exposed in the face of heavy rainfall,and the waterlogging disaster is becoming increasingly severe.Therefore,it is necessary to analyze the vulnerability of urban waterlogging,and more intuitively understand the complete process of the damage degree of the system when it is attacked by rainstorm from scratch to gradually reduce,so as to provide scientific guidance for disaster prevention and mitigation.In this study,the MIKE model was used to simulate the one-dimensional inspection well overflow,pipe network fullness,and two-dimensional surface overflow in a certain area of Xishi Street,Shangrao City,under various design rainfall scenarios.Then,the water accumulation situation was quantitatively analyzed,and the water accumulation index was calculated to reflect the vulnerability of the system.Secondly,from the perspective of influencing factors,the vulnerability of the system to waterlogging was studied and analyzed.Finally,through pipe network transformation and LID "green" transformation,Based on the surface water accumulation,total water accumulation,and peak water accumulation index,compare and analyze the drainage effects of different reconstruction schemes,providing a certain idea for designing the reconstruction research area.The main research conclusions of this article are as follows:(1)The preliminary waterlogging conditions of the study area under five different design rainfall scenarios(1a,5a,10 a,20a,and 50a)were analyzed.The larger the design rainfall return period,the larger the total surface runoff and the larger the comprehensive runoff coefficient.Based on the analysis of pipe network load,the larger the design rainfall return period,the more and more overflows and overloaded pipelines are distributed in inspection wells,but the gap between the overflow node ratio and the pipeline overload ratio is gradually decreasing.Based on the analysis of the surface inundation situation in the study area,it can be concluded that the largest inundation area with a surface water depth of 0-0.03 m but greater than0.5m still exists,with a high risk,and the inundation area of different water depth levels increases with the increase of the design rainfall return period.(2)The vulnerability of waterlogging in the study area under different design rainfall scenarios was analyzed.The water accumulation index is used to quantitatively analyze the vulnerability of the system.The water accumulation index decreases with the decrease of the design rainfall return period,and the larger the design rainfall return period,the larger the maximum water accumulation index value and the later the maximum value appears,indicating that the more fragile the system is,the higher the degree of damage.When the degree of damage reaches the maximum,the degree of recovery of the system increases with the increase of the design rainfall return period,and the ability of the system to fully recover to a waterlogged state mainly depends on the recovery during the rainfall period,and the smaller the return period,the more dependent the rainfall period.(3)Analyze the impact of design rainfall patterns and duration on urban waterlogging vulnerability.The smaller the rain peak coefficient,the more fragile the system is,and the higher the degree of damage is.Moreover,the smaller the rainfall peak coefficient,the smaller the final value of the ponding index,and the greater the degree of recovery of the system compared to the highest degree of damage.Comparing the degree of recovery of the system during rainfall and non rainfall periods,the complete recovery of the system depends on the rainfall period.For rainfall with a smaller return period,the more attention should be paid to rainfall with an earlier rainfall peak time.The longer the design rainfall duration is,the smaller the peak value of the ponding index is,and the later the time to reach the peak value is,indicating that the system is more vulnerable.When the degree of damage reaches the maximum,the more slowly the system recovers as the rainfall duration increases.Comparing the recovery degree of the system during rainfall and non rainfall periods,the complete recovery of the system depends on the rainfall period,and the larger the design rainfall recurrence period is,The smaller the peak reduction rate of the ponding index between different rainfall durations.(4)The drainage effects of the two schemes were compared and analyzed from three aspects: two-dimensional surface overflow results,total water accumulation,and peak water accumulation index.The results show that the water accumulation situation in the pipeline network renovation scheme has improved somewhat compared to that before the renovation,but the vulnerability of the system has not been significantly reduced,and there is room for improvement in the drainage effect;The water accumulation situation of the LID "green" transformation scheme has significantly improved compared to the current conditions,compared to the only pipeline network transformation scheme.Combining the LID "green" transformation scheme,the system’s waterlogging vulnerability has been reduced to a lower level,and the drainage effect has been significantly improved.