in slope between the two marsh zones to enable the wetland to freely drain (minimum grade = 1:150) (Figure 21). Figure 21 Typical macrophyte zone bathymetry showing the marsh and open water zones. Configuration The length of the macrophyte zone must be at least four times the average width of the macrophyte zone to ensure that the stormwater flows through a sequence and mix of submerged, shallow and deep marsh zones arranged in bands perpendicular to the direction of flow. Macrophyte zones must have an inlet and outlet pool (located at opposite ends of the macrophyte zone). The inlet pool must be sized to dissipate the energy of inflows and to collect sediments that are not trapped by the sediment pond. The macrophyte zone may also have intermediate pools located between the inlet and outlet pools. The inlet and outlet pools must be less than 1.5 m deep, and the intermediate pools less than 1.2 m deep. In situations a macrophyte zone has multiple inlets, major inlets (i.e. those draining more than 10% of the catchment to be treated), must be located within the first 20% of the macrophyte zone. Inlet connection The connection between the sediment pond and macrophyte zone may comprise of pit and pipe, culvert or submerged weir. The connection must be sized such that (Figure 22): All less than the peak three month ARI event are transferred into the macrophyte zone when the EDD in the macrophyte zone is at NWL, and 60% of the peak 1 year ARI flow overflows from the sediment pond into the bypass channel/pipe when the water level in the macrophyte zone is at TED. Figure 22 Conditions for sizing the connection between the sediment pond and macrophyte zone – 3 month ARI flow check. Figure 23 Conditions for sizing the connection between the sediment pond and macrophyte zone – 1 year ARI flow Velocities It is important that velocities through the macrophyte zone are considered during the design process to protect the accumulated sediment, biofilms and macrophytes from scour. Maximum allowable velocities within the macrophyte zone are: less than 0.05 m/s for the peak three month ARI less than 0.5 m/s for the peak 100 year ARI flow Refer to the Melbourne Water Constructed Wetland Manual for guidance on undertaking velocity checks within the macrophyte zone.
Appendix A: Plant species suitable for WSUD treatment assets Bioretention systems: form Scientific name Common name Filter bed (<50 m2) Filter bed (>50 m2) Batter Grasses Amphibromus neesii Southern Wallaby-grass ✔ Amphibromus nervosus Common Swamp Wallaby-grass ✔ ✔ Imperata cylindrica Blady Grass ✔ Lachnagrostis filiformis Common Blown-grass ✔ Poa labillardierei * Common Tussock-grass ✔ ✔ ✔ Poa morrisii Soft Tussock-grass ✔ ✔ Poa poiformis Coast Tussock-grass ✔ ✔ Poa sieberiana Grey Tussock-grass ✔ ✔ Rytidosperma caespitosum Common Wallaby-grass ✔ ✔ Themeda triandra Kangaroo Grass ✔ ✔ Sedges/Rushes Carex appressa * Tall Sedge ✔ ✔ ✔ Ficinia nodosa * Knobby Club-sedge ✔ ✔ Gahnia filum Chaffy Saw-sedge ✔ ✔ Gahnia sieberiana Saw-sedge ✔ ✔ Juncus amabilis Hollow Rush ✔ ✔ Juncus flavidus Gold Rush ✔ ✔ Juncus sarophorus Broom Rush ✔ ✔ Juncus semi-solidus Pale Rush ✔ ✔ Juncus subsecundus Finger Rush ✔ ✔ Lepidosperma laterale * Variable tall sedge ✔ ✔ Lomandra filiformis Wattle Mat-rush ✔ Lomandra longifolia * Spiny-headed Mat-rush ✔ ✔ ✔ Lomandra longifolia var 'Tanika' Spiny-headed Mat-rush ✔ ✔ Groundcovers Atriplex cinerea Coast Saltbush ✔ ✔ ✔ Atriplex semibaccata Berry Saltbush ✔ ✔ ✔