Background

Wetland maintenance

Dredging of the wetlands is done infrequently (more than 10 year intervals), although wetlands are monitored regularly for litter removal and annually for sediments. Pump maintenance is approximately every six months. A Continuous Deflection System, which traps gross pollutants (litter, leaves, etc.) unit has been installed upstream of the wetland at Styles Reserve. Streamwatch testing is done by Leichhardt High School students.

Mosquito mitigation measures include: riffle zones and elimination of dead-ends to reduce still water habitat; water level controls including the ability to drain one or more cells; and a 1:4 slope to eliminate wet edge habitat.

What is a catchment?

The wetland contributes to improved water quality and highlights the natural water cycle and the effect of our actions within an urban catchment. A catchment is the geographical area that drains down into a river of creek. The Whites Creek catchment comprises 161 ha of land above the wetland, most of which is covered by urban development.

Notes on Whites Creek

The creek was concrete-lined in the 1930s. The channel is designed to withstand a one in three year flood event (current design standards are for a 1 in 20 year flood event) and is an example of aging stormwater infrastructure. During one king tide the water level rose to just below the bridge over the canal. The width of the channel varies between 5m to 8m, and the height varies between 1.4m and 2m. A 1 in 100 year flood would rise 1.5m above the top of existing channel and engulf the wetland.

Snapshot of the wetland

The site area is 1,200m² and consists of five ponds and a settling pond. The water is channelled from the creek into the pump well and then pumped into the sedimentation pond. Mean depth of ponds is 0.3m; maximum depth is 0.5m. Each pond is designed with a different habitat type: shallow marsh, deeper marsh, and meandering stream.

Operation of the wetland

Water flow through the wetland site can be varied from 6 to 25 litres per second. Expected dry weather flow in the Whites Creek channel is 50 litres per second. The wetland helps to treat stormwater by slowing its flow, prolonging its exposure to soil, sun, and plants, allowing contaminants to settle out and nutrients to be filtered.