EVALUATION OF STORMWATER RUNOFF REDUCTION BY GREEN INFRASTRUCTURE DURING SHORT-TERM HEAVY RAINFALLS

Abstract

 Green infrastructure (GI) is a global, innovative stormwater runoff control measure in response to urbanization and climate change. This study quantified GI performance in improving the urban hydrologic environment. Storm Water Management Model was employed to simulate stormwater runoff in the Yazawa and Maruko River basins in Setagaya, Tokyo, Japan. Under the 75-mm/h rainfall scenario, the existing GIs were found to be incapable of controlling runoff at the government-specified rate of 10-mm/h. Furthermore, while simulating 1–10-year return periods of rainfall with 1–3-h durations, the reduction of runoff depth and peak runoff was less effective when rainfall intensified. A negative relationship was obtained using regression analysis between rainfall depth and the reduction rate of runoff depth and peak runoff. Meanwhile, rainfall duration positively and negatively correlated with the runoff depth reduction and peak runoff reduction rates, respectively. Furthermore, the reduced surface runoff considerably reduced the combined sewer overflow in the 1-year rainfall return period.