Author(s): Dieu Huong Trinh; Ting Fong May Chui
Linked Author(s): Ting Fong May Chui
Keywords: Green roof; Stormwater management; Hydrological model; Runoff retention; Peak discharge delay
Abstract: The impervious surfaces in urban areas significantly increase surface runoff and river discharge leading to flooding issues. Green roof is one possible mechanism in adverting such problems. Up to date, most of the green roof studies are site-specific or experimental-based. This study uses a numerical model to demonstrate and quantify the hydrological behaviour of green roof and to examine the effectiveness of green roof in stormwater management. A one-dimensional hydrological model is built, which consists of all the main hydrological process such as: rainfall, plant interception, evapotranspiration, infiltration and storage reservoir. The base case is a green roof with 21 cm of soil without storage reservoir, which is calibrated with experiment results. The calibrated model is adjusted with various green roof and weather characteristics such as soil hydraulic conductivity, soil thickness, and storage reservoir capacity for a series of one-month simulations. Model results show that green roof have strong hydrological influences, e. g. reducing large runoff fluctuation between wet and dry period and thus urban flooding. Soil with high hydraulic conductivity allows high infiltration rates but small delays in peak discharge; while soil with high thickness retains more water and has longer delay period. Comparing the results between the green roof with and without storage system, the green roof with storage reservoir is shown to be more beneficial to stormwater management in terms of rainfall retention as well as peak discharge delay. However, it has less effect in reducing runoff fluctuation. Overall, this study improves our understanding of hydrological behaviour of green roofs for stormwater management, which is a good foundation for optimizing green roof properties for many urbanized areas.