Potential reduction in urban runoff by green spaces in Beijing: A scenario analysis

Urban green space provides multiple ecological benefits, among which the reduction of rainfall runoff is important for sustainable urban development, particularly for cities experiencing severe flooding and water hazards. However, the effectiveness of urban green space in mitigating runoff has not been fully determined. We evaluated potential reductions in surface runoff associated with urban green space in central Beijing under a greening scenario using the Soil Conservation Service Curve Number method. The results show that urban green space offers significant potential for runoff mitigation. In 2012, a total of 97.9 million m(3) of excess surface runoff was retained by urban green space; adding nearly 11% more tree canopy was projected to increase runoff retention by >30%, contributing to considerable benefits of urban rainwater regulation. At a more detailed scale, there were apparent internal variations. Urban function zones with >70% developed land showed less mitigation of runoff, while green zones (vegetation >60%), which occupied only 15.54% of the total area, contributed 31.07% of runoff reduction. Runoff reduction by urban green space, however, is influenced by many factors, such as rainfall, soil condition, and urban morphology. In regulating urban runoff, therefore, the priorities and integrating adaptive approaches to urban greening should be combined with compensatory and complementary measures. (C) 2015 Elsevier GmbH. All rights reserved.