The purpose of this research is to examine the environmental effects of the proposed Songpa new town development built along the urban growth boundary in South Korea. The project evaluates the proposed development plan from an environmental perspective, which can be easily ignored during a planning process. With the logistic regression model considering accessibility and physical constraint factors, future development in the proposed new town and infill development in two existing alternative areas are simulated based on the assumption that future development will follow past development patterns. The project examines changes in runoff volume directly affecting water quality and flooding in and around the study areas. Pre-development and post-development runoff volumes are estimated through hydrologic analysis using land use, soil type, and average rainfall data.