Research On GIS-based Model For Flood & Waterlogging In Urban Area

It is a hot topic to build numerical models, not engineering measures, to simulate and predict the process of the stormwater, flooding and waterlogging in the urban area. Those models always be established based on advanced computer technology and information technology, latest algorithm theory, which have great economic and social benefit comparing to the engineering measures. In this paper, a flooding and waterlogging model was developed using the theory of CFD and the ComGIS technology, which can simulate the whole flooding process in urban rivernet and the waterloging process in urban area .The main works of this paper are as follows.First, according to the three-step method, 1-D unsteady flow model in river network is introduced. A new topological structure is presented to describe and store the topology information and data in river network ,which realises the connection between GIS and the numerical program of hydraulic calculating and turns the program into a universal one .A new formula of internal boundary conditions with double-recursion algorithm is deduced, and the relationship of recursive coefficient between imaginary channel length and non-imaginary channel length is presented ,which makes sure that the model can comprise the numerical simulation of the internal boundaries such as side pipe outflow ,barrage, slice gate and drainage pump station.Secondly, the model of 2-D overtopping unsteady flow based on finite volume method(FVM) is presented the weir formula is used here to realize the coupling calculating of three step method and FVM. the generating algorithm of the data structure of grid is developed.Based on the COM theory,the third part introduces the GIS technology into the model,and presents related algorithm to realise the visualization of topology data structure of river network ,the automating input and output of the program,which make the model easily to be widely applied.The storm in Wenzhou in 1999.9.4 is selected as a calculating example ,this part calculates the process of the flood in river network and the inundation preocess when overtopping occured during the period from 23:00.1999.9.4 to 24:00.1999.9.5. Comparing to the testing data of water level ,the result shows that the accuracy of the model is engineering practical and the model can be used widely in urban flood control and disaster prevention.