Effects of Substrate Types on Runoff Retention Performance Within the Extensive Green Roofs

摘要

Little is known about the water retention performances of different substrate types within extensive green roofs in Malaysia. Thus, this research focused on the runoff retention performance within extensive green roof system with respect to different substrate types in Malaysia. A total of six green roofs were constructed with four being vegetated and two left unvegetated with bare soil acted as control. Four test beds were vegetated with Axonopus compressus (cow grass) and Portulaca grandiflora cultivars (sedum) in both pot soil and burn soil, respectively. The runoff volume was measured volumetrically through connected to an surface runoff harvesting tank under the test beds. Water retention was calculated from the difference between rainfall and runoff volumes from each test bed. Results showed that burn soil was the most effective substrate type in retaining runoff water. The test bed with sedum planted in burn soil performed the best runoff retention efficiency in extensive green roof system in Malaysia.