Application of level spreader – grass filter strips in South East Queensland, Australia for discharge reduction and passive irrigation

Abstract

A WSUD practice that has been implemented in the United States is the level spreader – vegetated filter strip (LS-VFS). A typical LS-VFS incorporates a concrete channel with a level control weir (level spreader) that evenly distributes flow to a downslope vegetated filter strip designed for stormwater infiltration. The application of LS-VFS in Australia has generally received little attention. Given the absence of local information, this paper provides a ‘proof of concept’ analysis of LS-VFS as applied to South East Queensland conditions. The main focus of the analysis is to determine how compatible LS-VFS are in terms of meeting the prescribed WSUD frequent flow targets for urban stormwater discharges. Key LS-VFS design requirements were identified from the literature. A MUSIC model analysis was performed to evaluate the expected runoff reduction associated with a LS-VFS receiving stormwater from a Brisbane residential subdivision. Indicative criteria are proposed for design discharges, soil suitability and sizing of the filter strip dimensions. The potential of LS-VFS to provide ‘passive’ irrigation was recognized and the application of LS-VFS for sustaining green cover within urban open space was also analysed. Recommendations are made on further research and investigations on the Queensland application of LS-VFS technology.