Global climate change is expected to affect water cycle of many cities substantially. Not only changes in precipitation but also Sea Level Rise (SLR) is anticipated to modify urban water systems. This is particularly of great importance in South Korea where urban dwellings have densely developed along coastal areas and the speed of SLR is higher than the global average rate. Recent years have witnessed growing interests in Low Impact Development (LID) in urban areas for better stormwater management, but their efficiency has rarely been addressed. In the present study, we simulated flooding patterns of two representative cities in Korea with different intensity of development by employing XP-SWMM 11.0 version. Gunja in Seoul is located in highly developed downtown with high impervious rate, while Songdo is a newly developed town with relatively large buffer zones. Firstly, we constructed models for two sites using input data of land use, DTM, pipeline, and climate. Secondly, we simulated future climate and LID technique assuming SLR of 0.5 m, several rain events that are predicted by a GCM model, and an increase in permeability by 20%. While Songdo does not exhibit any significant changes in flooding patterns by the adaptation of LID, Gunja showed a substantial reduction in flooding regime. Overall results of this study suggests that priority for LID application should be given to old towns with extensive impervious areas, while recently development town with ample buffer zones should focus on maintaining the current status of infrastructure.