Analysing Green Roof Effects in an Urban Environment: A Case of Bangbae-dong, Seoul

Abstract

Green roofs have been considered as an alternative to providing green spaces in urban areas. Recently, many researchers have suggested that green roofs could contribute to urban flood mitigation by reducing the amount of stormwater runoff. However, the stormwater runoff reduction effect has not yet been fully understood. In this study, two analyses have been performed to investigate the stormwater runoff reduction effect and economic feasibility of green roofs. First, as simulated using PCSWMM, the stormwater runoff effect of green roofs was identified and then the rooftop attributes were considered to acquire results that are more precise. As a result, two of three scenarios demonstrated an average 20% reduction of runoff, which is comparatively smaller than the results of preceding studies. Second, benefit-cost analysis was performed to evaluate the economic feasibility of green roofs. Two of the three scenarios had a benefit-cost ratio narrowly above 1.0 over a period of 20 years. Our results seem to suggest that a green roof has benefits that surpass costs; yet it is insufficient to say that it is an economically sound approach. Overall, green roof does have some stormwater runoff reduction effects and economic effects, but these were not as significant as has been previously described.