Climate change is not the only issue yet there are the combinations of many existing factors. Urbanization is one of them and is considering the major criteria. Due to the Rapid Urbanization, land use of the existing watershed is becoming impervious layer and even drainage network system is more complicated. Existing system might not be able to handle the amount of water during the storm events thus, hydrologic impact assessment is necessary for a planned development area in designing detention storage for urban drainage systems to minimize the effect of urbanization. It is advisable to reassess the existing structure to handle and to prevent the threat of flood in the future. For such assessment, single or two hydrologic models can be paired for pre- and post- development conditions. Typical pairings are the use of synthetic hydrograph methods for both conditions or synthetic hydrograph for pre-development and urban hydrology model for post-development condition. This study is aiming to assess the flood impact and suggest the proper technique for future flood prevention. To accomplish, the SWMM was adopted to development areas in Korea. The comparison of results can be done to show the new approach can resolve the irrationalities that can occur with the combination of two different models such as smaller peak flow and longer time to peak for post-development conditions. It is thought that the proposed method will improves the accountability of the flood impact assessment on future development areas

• Ly Sidoeun(Dept of Civil Engineering, Inha University)
• Hyunseok Shin(Dept of Civil Engineering, Inha University)
• Narae Kang(Dept of Civil Engineering, Inha University)
• Kim Hung Soo(Dept of Civil Engineering, Inha University) Corresponding author