Geographic information system-based assessment of mitigating flash-flood disaster from green roof systems

Urban flooding is a severe problem and a growing development challenge for many cities around the world. However, urban impervious areas have sharply increased owing to booming construction activities, and this land-use change leads to more frequent flood inundation in urban flood-prone areas. A green roof system is regarded as an effective mechanism to manage rainwater and reduce flooding disaster, as it is capable of retaining rainwater, thus reducing rainfall-runoff. There is still a lack of assessment of this stormwater management tool for flash floods. The issue of flood inundation associated with green roof systems needs to be explored and developed. To evaluate the effects of green roofs on urban flood inundation, this paper aims to construct a framework for modelling urban inundation integrating a hydrological model of green roofs. The approach addresses both urban rainfall-runoff and underground hydrological models for traditional impervious and green roofs. To accurately calculate the spatial variation, we have proposed a hydrological model to evaluate regional runoff on the basis of a catchment mesh. The Deakin University Waurn Ponds campus in Geelong was then chosen as a community-based study case. From geographic information system (GIS) simulation, the results reveal that the green roofs generated varying degrees of mitigation of urban flash floods with storms of different return periods.