**3.2 On-line/offline wetland operation**

Standard wetland designs in Victoria include two typical layouts: online wetlands with the sediment pond receiving unrestricted flows and the macrophyte zone receiving controlled flows, and alternatively, offline wetlands where flows into the wetland can be restricted using a diversion pit [16]. Online flows include the total runoff from a catchment area. Offline flows divert a volume of the flow up to a certain amount, and the remaining flow bypasses the wetland. If a wetland does not include a sediment pond, then the bypass can be managed via a pit arrangement with suitable baffle, invert levels and pipe sizes to suit the urban catchment area.

Wetlands that are receiving an online flow passing through the Macrophyte zone are at risk of having collected sediments and nutrients dislodged and washed

**Figure 3.** *Schematic diagram of a constructed wetland, adapted from [16].*

downstream during peak flows [16]. Standard wetland design practice includes a bypass channel to prevent this occurrence as shown in **Figure 3**.
