Local government WSUD practitioners regularly raise the challenges that maintenance of raingardens present including: understanding the regime of maintenance works required and the budgetary implications of providing the appropriate level of service.
The City of Manningham, in collaboration with Melbourne Water and the CRC for Water Sensitive Cities, may have the answer for Councils seeking simple streetscale stormwater treatment options – the mowable raingarden, as described in the Zero additional maintenance water sensitive urban design handbook.
At the training for the Adoption guidelines for stormwater biofiltration systems held in Adelaide in July of this year Prof. Ana Deletic and Dr Belinda Hatt from the CRC for Water Sensitive Cities described the nutrient removal performance of a range of plant types including sedges, shrubs and grasses. Some grass species were shown to be extremely effective at the removal of pollutants, and performed well in comparison with sedge species, typically included in raingardens due to their nutrient removal properties.
The project partners, which also included Glen Eira City Council, Monash University and Melbourne Water, have built upon this research, taking advantage of the nutrient removal performance of the humble buffalo grass to develop a raingarden design with ‘zero’ additional maintenance requirements compared to a typical kerb and channel streetscape.
The handbook details a design that features:
- mowable buffalo grass, so residents can mow the raingarden just like they mow their nature strip
- installing channel grooves to trap incoming sediment on the roadway, so it can be picked up by streetsweepers
- adding a protective layer of coarse sand on the surface of the filter media to help prevent the formation of a sediment layer.
(Adapted from CRC for Water Sensitive Cities)