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Crimesite: Porters Creek Wetland

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Map of Porters Creek

Map of Porters Creek

A photograph of sedges at Porters Creek. Grasses in foreground, trees in background.

Sedges at Porters Creek.

A photograph of Porters Creek swampland. Grass clumps in foreground, trees in background.

Porters Creek swampland. Photograph courtesy of Kevin Butler.

Porters Creek

Catchment

Porters Creek Catchment is a sub-catchment of Wyong River Catchment. It covers approximately 5500 hectares of gently undulating land north of Wyong and the Wyong River on the NSW central coast. It has very few creeks apart from man-made channels. The largest of the swamp forests is the 500 hectare Porters Creek Wetland. This is the largest freshwater wetland on the NSW central coast.

Town history and pattern of settlement

The Darkinjung and Kuringgai people, the original Aboriginal inhabitants of the area, had trade or ceremonial links with communities up and down the coast and inland as far away as Moree.

The modern town of Wyong was built on Kurringgai land. For many years attempts to destroy the wetland by draining and clearing failed. In recent years Wyong Shire Council has dedicated a large part of it for conservation purposes.

Today Porters Creek Wetland is surrounded by rapidly growing residential and industrial suburbs and rural residential developments.

Topography

Before European land clearing there was no creek but a broad floodplain containing a grand swamp forest. Rainwater seeped or trickled down the hillsides and into extensive wetlands.

Close to half of Porters Creek catchment is floodplain. Most of the remaining half of the catchment consists of low undulating hills, many of which still have their native woodlands.

Ecology

The soil of the floodplains and lower hills of the catchment consists of dense clay which expands when it becomes wet and contracts as it dries. In the areas that have not been cleared, the clay is held together by the roots of wetland trees but over time the expansion and contraction has created a complex network of hollows. These hollows vary in size and can be close to a metre deep, half a metre wide and several metres long. Because of the hollows, the floodplains store large amounts of water creating a habitat for many wetland plants and animals.

Where once rainwater entered the wetland very gently, today, after years of land clearing and building of suburbs with stormwater channels, water flows quickly into the wetland and floods it, even after only a small amount of rain. Because the plants of the wetland are so sensitive to the water conditions, this change has caused swamp forest dieback and tree fall.

Land use

The eastern half of Porters Creek Catchment is a residential area and also provides employment for the NSW central coast. Thousands of new houses are being built and are planned for the catchment in coming years.

Climate

Porters Creek catchment has a temperate climate with mild winters, warm summers and plentiful rainfall. The average winter temperature varies between 5ºC and 17ºC and summer temperature varies between 17ºC and 28ºC.

The average annual rainfall ranges between 1000 mm and 1300 mm.

Flora and fauna.

Porters Creek Wetland and catchment have high biodiversity. There are two hundred different plant species. They include Woollybutt and Prickly Paperbark forest, Redgum, tall Paperbark forest dominated by Melaleuca linariifolia and Eucalyptus robusta (Swamp Mahogany), and low Paperbark forest dominated by Melaleuca ericifolia. In the areas which are usually flooded sedges, rushes and reeds are found. The endangered Wyong daisy, several species of ground orchids and the rare aquatic plant Maundia triglochinoides are also found in the wetland.

The wetland provides a habitat for a diversity of animals including the swamp wallaby, antechinus, microbats, ringtail possums and squirrel gliders. There are many bird species including the Sacred Kingfisher. Sixteen different species of frogs are found, including the rare and endangered Wallum Froglet and the Green and Golden Bell Frog. More common are the Eastern Froglet and Striped Marsh Frog. Bandicoots and the Australian Water Rat nest in levee banks. A small brown yabbie, still an unnamed species, lives in the wetland.

Water quality

While water quality is poor near the ends of urban stormwater drains, the overall quality of water in Porters Creek wetland is good. The water is mildly acidic with low salinity, low dissolved oxygen, elevated nutrients and variable turbidity. Near stormwater drains, the water has higher levels of phosphorous and nitrogen. Turbidity may be high following rainfall.

Issues

The main environmental issues in Porters Creek catchment are:

Catchment management

The Porters Creek Catchment is managed by the Hunter Central Rivers Catchment Management Authority.

Wetland health rating

The wetland health rating for Porters Creek wetland is 5 out of 10.

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