Green roofs for stormwater mitigation in Hong Kong

Abstract

Hong Kong often faces stormwater problems during the rainy season. The heavy rainstorm could cause flooding and serious damages to the society. To tackle this, the Government has to make large investment in drainage and flood control projects which have significant socioeconomic implications. The research findings in other countries indicated that green roofs can be an effective tool to help mitigate stormwater problems. The application of green roofs in the buildings can delay the starting time of the stormwater runoff and reduce the magnitude of peak runoff and the total amount of rainwater discharged from the buildings. Also, the roof greening method in urban areas can improve the quality of the built environment and provide useful spaces for community functions. This paper explains the major findings of a research project to study the potential of green roofs for stormwater mitigation in Hong Kong. The rainfall characteristics and stormwater issues in Hong Kong are evaluated. The basic principles of green roof systems for stormwater management are studied. In addition, laboratory test and field studies have been done to assess the effectiveness of green roofs to alleviate the stormwater problem. Finally, the strategy to develop green roofs to improve the quality of urban environment is discussed.