Study On Urban Waterlogging Characteristics Of Coupling Surface Confluence Model And Rainwater Pipe Network Model

In recent years,frequently extreme weather and accelerated urbanization have resulted in flooding disasters to varying degrees in most cities in China,which has hit the economy and security.Through analysis of urban waterlogging,it is mainly caused by natural climate,ground topography,underlying surface conditions,drainage facilities and so on,from which the risk of waterlogging is significantly different.It is in Hefei that rainfall occurs frequently,and waterlogging often appears in some urban areas.At present,there are a number of research results on the waterlogging factors and waterlogging prevention planning of the city,but less research on the applications of drainage capacity assessment and waterlogging models.The research on urban waterlogging urgently needs to widen the technical means.Based on previous research,this paper analyzes the distribution of accumulated water,confluence process and drainage capacity in a small watershed by generation of the MIKE 21 rapid assessment model and the MIKE Urban rainwater pipe network model.In addition,coupling the two models enables the analysis of waterlogging characteristics.And the main contents and conclusions are as follows:(1)The results of the MIKE 21 rapid assessment model based on the generalization of drainage network capacity demonstate that the distribution of accumulated water in the small watershed is similar under storm scenarios with different recurrence periods.The depth of accumulated water in the study area is mainly 0-0.4m,and the distribution of easily-flooded areas of the four models is consistent.(2)The analysis of confluence process and hydrological runoff in the small watershed before and after the buildings’ construction indicates that the buildings’construction has changed the surface confluence.Before the buildings’ construction,the average length of confluence path was 104.24m,with the stable flow direction,balanced flow distribution in each easily-flooded area,and the concentrated water distribution.While after the buildings’ construction,the average length of confluence path is 86.47m,with the messy flow direction,the poor flow stability,and the scattered water distribution.(3)The assessment of drainage capacity of the current MIKE Urban pipe network in the small watershed manifests that number of pipes with a drainage capacity below 2a standard accounts for 69.29%of the total,and that of 2a to 5a accounts for 25.02%,while that more than 5a standard accounts for 5.69%,and which are large-diameter main pipes in the construction of urban drainage facilities.The analysis of overall assessment shows that the design standard of the pipe network is low,and the current drainage capacity is poor.(4)The analysis of the generalized coupling waterlogging model reveals that under the rainstorm of 10a recurrence period,the risk of waterlogging in small watersheds is dominated by moderate waterlogging,that is,the area where the depth of accumulated water is 15cm-60cm and the process of accumulating water lasts 30min-60min.The distribution of easily-flooded areas matches with that of the rapid assessment model and the historical easily-flooded areas.In addition,the historical water depth is close to the coupling model.The qualitative analysis shows reliability and authenticity of MIKE Flood coupling model.Figure[38]Table[12]Reference[88]...