Proof of concept analysis of level spreader – grass filter strips for runoff reduction

Proof of concept analysis of level spreader – grass filter strips for runoff reduction

A Water Sensitive Urban Design (WSUD) practice that has been implemented in the United States, mainly in North Carolina and Pennsylvania, is the level spreader – vegetated filter strip (LS-VFS). A typical LS-VFS incorporates a bypass structure that diverts excess stormwater flows, usually to a grassed swale and a concrete channel with a level control weir (level spreader) that evenly distributes flow to a downslope vegetated filter strip designed for stormwater infiltration.
Although many of the different elements of a LS-VFS are easily recognisable, the application of LS-VFS systems in Australia has generally received little attention. Given the absence of local information, this paper provides a ‘proof of concept’ analysis of LS-VFS systems as applied to South East Queensland conditions. The main focus of the analysis is to determine how compatible LS-VFS systems are in terms of meeting the prescribed WSUD frequent flow targets for urban stormwater discharges.
The paper provides background information on LS-VFS design and performance, sourced from a literature review. Key design requirements are identified. 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. Recommendations are made for further research and investigation into the application of the LS-VFS technology in Queensland.

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