This study proposed two methods, boundary-type and pond-type, to link overland and underground space in urban flood modeling. The boundary-type treats the exit of underground space as an interface for inflow of floodwater by imposing open boundary condition and pond-type considers underground space as an underground pond by configuring pond terrain. The effect of underground space in urban flood inundation was examined by coupling one-dimensional (1D) stormwater management model (SWMM) and two-dimensional (2D) overland flood model. The models were applied to the Hyoja drainage basin, Seoul, Korea where urban flood occurred due to heavy rainfall in 21 September 2010. The conduit roughness coefficient of SWMM was calibrated to minimize the difference between observed and predicted water depth of pipe. In addition, the surface roughness coefficient of 2D model was calibrated by comparing observed and predicted flood extent. Then, urban flood analysis was performed on three different scenarios involving a case not considering underground (Case 1) and cases considering underground, boundary-type (Case 2) and pond-type (Case 3). The simulation results have shown that the boundary-type is simple but robust method with high computational efficiency to link overland and underground space in urban flood modeling.

In this study, kriging and moving average method were applied in order to comprehend temporal and spatial characteristics of rainfall in Seoul area. Errors were estimated depending on weights of weighted moving average model and exponential moving average model for analyzing temporal characteristics of rainfall. According to the results of the analysis of rainfall database of the Seoul Meteorology Station and AWS(Automatic Weather Station) by using the weighted moving average model having minimum errors, rainfall was concentrated in the summer months except for the rainy season and tend to increase the total amount of rainfall. The kriging was applied for analyzing spatial characteristics of rainfall and the spherical model well depicted spatial distribution of urban heavy rain in target area. And parameters were calculated and analyzed in accordance with rainfall intensity. The result show area-averaged rainfall using kriging reduced risk of overestimation of area-averaged rainfall using Thiessen weighting method.

In this study, 2D finite volume model, which can apply to the mixed meshes that is effective to treat the complicated topography such as a natural river, is developed. To do so, an algorithm for finding the neighbouring cell of a computational cell is introduced, and fluxes are computed using the HLLC approximate Riemann solver at each interface between a computational cell and it's neighbouring cells. Moreover, in order to numerically treat the bed slope which has important effect on the balance between flux gradients and sourte terms, different formula to compute the bed slope for rectangular and triangular mesh are applied. The developed model is applied to analyze dam-break in an experimental channel with 90°bend and Malpasset dam-break in France. The two cases consist of mixed meshes and the suggested method is validated for the experimental channel and natural channel by comparison with the experimental data, field data and computed results.

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