Hexham Swamp Rehabilitation Project

The Hunter-Central Rivers Catchment Management Authority (CMA) is coordinating a partnership between private landholders, industry groups, local community and state and federal government agencies to rehabilitate Hexham Swamp and restore it to a healthy, functioning wetland.

The Hexham Swamp Rehabilitation Project aims to restore the once thriving estuarine wetlands through the staged opening of floodgates built more than 30 years ago on Ironbark Creek to keep out tidal waters from the Hunter River.

For more information about the Hexham Project, please contact the CMA on phone (02) 4930 1030 or email hcr@cma.nsw.gov.au.

Planning Approval
The Minister for Planning, Hon Frank Sartor MP, approved the Hexham Project on 30 November 2006 under Part 3A of the Environmental Planning & Assessment Act 1979. To access the Environmental Assessment and supporting documents, as well as the Minister’s determination and Conditions of Approval, go to the Hexham Project (number 05_0193) at the Department of Planning website.

Construction Works
Before opening of the Ironbark Creek floodgates commences, the CMA is required to carry out works to mitigate the effects of saltwater intrusion on private property within Hexham Swamp.
Construction will take place for the Marsden Street bund, which is situated on the site of Hunter Water’s Shortland Wastewater Treatment Plant, at the Broadcast Australia’s radio masts adjacent to the floodgates, at Hunter Wetlands Centre Australia, and at a number of properties at Shortland.
Gleeson Civil Engineering has been contracted to undertake these works, which will commence on 24 September and extend for a period of 18 weeks. View public notice for full details. If you have any complaints regarding the carrying out of these works, Gleesons can be contacted via post: PO Box 124, Carrington NSW 2294; email: office@gleesoncivil.com.au or 24 hr phone: 0400 249 004.

Where is Hexham Swamp?

Breathing life back into Hexham Swamp

Hexham Swamp is the Hunter's largest and most biologically diverse wetland and one of the largest in New South Wales. But after thirty years of limited tidal exchange in the swamp, resulting from the operation of floodgates at the mouth of Ironbark Creek, the estuarine, aquatic and terrestrial ecosystems of the wetland are severely degraded.

Lack of tidal flushing, vital to the health of an estuarine wetland, has dramatically changed the swamp's environment. A freshwater system has largely replaced the extensive mangroves and saltmarsh communities which once thrived throughout the swamp, significantly reducing vital aquatic and terrestrial habitat for native species.

Protecting the home of important species

The mangroves and saltmarsh of Hexham Swamp once provided a major nursery for commercial species of fish and prawns and many other aquatic species. Much of this fishery habitat has been lost due to impeded tidal flows in Ironbark Creek.

Both commercial and recreational fishing industries are keen to see the swamp rehabilitated and vital fish habitat reinstated. The local fishing industry will benefit when Hexham Swamp is rehabilitated.

The extensive floodplain of Hexham Swamp attracts numerous native waterbirds and terrestrial fauna—some of them rare and endangered. Six species of migratory wading bird, protected under Federal Government agreements with China and Japan, visit Hexham Swamp.

But the number of water birds and other bird species using the swamp has decreased dramatically in the past twenty years, from around 200 species to only 40 today.

Community expectations are very high regarding the rehabilitation of Hexham Swamp. The people of the Hunter have already indicated their commitment to wetland regeneration through their support of the Kooragang Wetland Rehabilitation Project.

Community and environmental organisations supporting the project include:

• Hunter bird-watching groups
• Commercial and recreational fishing groups
• Ocean Watch
• Nature Conservation Council
• The Wetlands Centre, Australia
• Kooragang Wetland Rehabilitation Project

The project has generated significant interest at a regional, state and national level.

Wide stakeholder support for the rehabilitation of Hexham Swamp ensures the wetland's future. The federal and state governments have provided $2.4 million and $2.7 million respectively for land acquisition and restoration works.

A management plan guides the project to rehabilitate Hexham Swamp.

The Hexham Swamp Rehabilitation Project involves:

• Acquisition of some private land and easements over other land
• Modification to the operation of Ironbark Creek floodgates
• Regeneration of native vegetation
• Continued management of the floodgates to exclude Hunter River floods
• Wetland management to reduce mosquito habitat

Hexham Swamp—Vegetation in Transition

From the small plane, I was impressed by the extent of Hexham Swamp. A drop in the bucket compared to the Macquarie Marshes or Kakadu, but at 2 500 hectares, Hexham is one of the largest wetlands on coastal New South Wales.

What also struck me, from my bird's eye perspective, was the broad expanse of cream-coloured land that filled my vision. This was the common reed, Phragmites australis, in its winter colour. Phragmites Reed Swamp now dominates Hexham. As recent as 30 years ago this was not the case.

So what was Hexham's vegetation like before Europeans started building around and through it? We don't know, but we can be sure that it was markedly different before changes in hydrology were brought about by the construction of the Main Northern Railway line in 1857, the Richmond Vale-Pelaw Main railway in the late 19th century, and the water pipeline in the 1930s-40s.

For the first half of the 20th century, stock grazing was the prime use of the predominantly freshwater wetlands in the south and west of the swamp. Estuarine vegetation communities were restricted to areas along Ironbark Creek and its small tributaries. However with dredging of the north arm of the Hunter River and creation of Kooragang Island in the 1950s and 60s, tidal intrusion pushed further into Hexham Swamp threatening the highly-valued freshwater pastures. Pressure from landholders in the swamp led to the construction, and subsequent one-way operation, of floodgates at the mouth of Ironbark Creek in 1970.

Changes in Hexham's vegetation pattern since this time are well documented. Briggs (1978) identified four vegetation types (her study used 1976 aerial photos, that is, five years after the floodgates were installed). These were:

Zone 1 - Southeast section. Dominated by saltmarsh (Sporobolus virginicus, Paspalum vaginatum and Sarcocornia quinqueflora) and mangroves (Avicennia marina). Patches of paperbark forest (Melaleuca quinquenervia and M. styphelioides) and she-oak woodland (Casuarina glauca) were also present.

Zone 2 - Central section. Reed community dominated by Fimbristylis ferruginea. Phragmites dominated some areas but was relatively minor.

Zone 3 - Southwest section. Fresh meadow and seasonal fresh swamp. Common species were Typha orientalis, Schoenoplectus litoralis and Eleocharis sphacelata. Water hyacinth (Eichhornia crassipes) was also common.

Zone 4 - West of old railway line. Grass swamp dominated by Paspalum paspalodes (now P. distichum) and Eleocharis equisetina.

Of the fourteen coastal wetland types occurring in NSW (described by Goodrick, 1970), eleven were present in Hexham, with nine of these being freshwater communities (NSW NPWS, 1996).

In studies for the Ironbark Creek Total Catchment Management Committee (HCMT, 1996), Conroy and Lake (1992) documented the vegetation distribution and compared their findings with Briggs (1978). In Briggs' Zone 2, within thirteen years, Phragmites had become dominant where Fimbristylis had previously comprised 80% of the vegetation.

Mangrove and saltmarsh communities, mapped by Briggs in Zone 1, had by 1992 contracted from some 180 hectares of mangroves to 20 hectares (i.e. 11% of their former extent) and saltmarsh had suffered an even more dramatic reduction from 640 hectares to virtually none. These trends are confirmed by more recent studies (WBM, 1996, and Morrison, 2001).

Much of Hexham Swamp has changed from a diverse mosaic of wetland types to almost half of its area being now occupied by a monospecific community.

The next challenge for Hexham is adjusting to a renewed saline regime when the Ironbark Creek floodgates are once again opened. The eight gates will be progressively opened over several years, with tidal intrusion monitored between gate openings to gauge the effects.

What will happen to the dense stands of Phragmites? Will they be killed off as the salt water penetrates further into the swamp? We're not sure about that one. Will the mangrove and saltmarsh communities re-establish in the areas where they previously occurred? Here we have better evidence, gained from the Kooragang Wetland Rehabilitation Project and other sites. Mangroves readily establish once tidal inundation returns to an area and saltmarsh has regenerated well.

Keep watching for the next 30 years as Hexham Swamp comes full circle—back to a diverse, healthy and vibrant wetland.

References

Briggs, S V (1978) Hexham Swamp - Vegetation and Waterbird Habitats. NPWS

Conroy B A and PM Lake (1992) A vegetation analysis of Hexham Swamp by Department of Biological Sciences, Univ. of Newcastle. Report to Ironbark Creek TCM Committee.

Goodrick, G N (1970) A Survey of Wetlands of Coastal New South Wales. Tech. Mem. No5, CSIRO Div. Wildlife Research.

Hunter Catchment Management Trust (1996) Ironbark Creek Total Catchment Management Strategy, Vols. 1 and 2. Ed. Ironbark Creek TCM Committee.

Morrison, Danielle (2001) In Press. Honours Thesis, University of Newcastle.

NSW National Parks and Wildlife Service (1996) Draft Plan of Management for Kooragang Nature Reserve and Hexham Swamp Nature Reserve.

WBM Oceanics Australia (1996) Blue Gum Hills Catchment Management Strategy. Report prepared for Newcastle City Council. 

WBM Oceanics Australia (2000) Draft Environmental Impact Statement for Rehabilitation of Hexham Swamp, for Hunter Catchment Management Trust (unpublished and incomplete).

Hexham Swamp Factsheets

Information about Hexham Swamp Rehabilitation Project.

Factsheet 1

Hexham Swamp covers an area of 3800 hectares. These rich estuarine wetlands have become degraded over the last 30 years after floodgates were constructed on Ironbark Creek to keep out tidal waters from the Hunter River. The Hexham Swamp Project will see the staged opening of these floodgates to increase tidal flushing of the swamp. A restored estuarine habitat will encourage the return of migratory wading birds, fish and prawns.

The project also involves the purchase of land within the swamp. A total 800 hectares of private and public grazing land that may become inundated when the floodgates are opened is being purchased by the Hunter-Central Rivers CMA.

Funding for the project has been provided by the CMA and the federal and state governments have provided $2.4 million and $2.7 million respectively for land acquisition and restoration works. An Environmental Assessment (EA) was submitted under Part 3A of the EPA Act 1979, and the project was approved by the Minister for Planning on 30 November 2006.

Factsheet 2

In the past, Hexham Swamp was characterised by extensive mangrove and saltmarsh communities and was dissected by deep, winding tidal creeks. According to local fisherman Dennis Hirst, Hexham Swamp was one of the most important breeding grounds for fish, prawns and crabs in the Hunter Estuary. Hexham was also extremely important for birds with many waders using the swamp during their annual migrations to Australia.

The construction of floodgates at the mouth of Ironbark Creek in the early 1970s and their operation to exclude tidal flushing has greatly decreased the area of estuarine wetlands and impacted significantly on the fish and birds that depend on them. The swamp is now comprised mainly of freshwater wetlands and pasture. The once extensive saltmarsh plains have been replaced by dense stands of common reeds, which provide limited food and habitat value for fish and bird communities. The mangroves that once lined the creeks have either died, or are in a poor condition. Mangroves provide habitat for fish and other marine life as well as being an important source of leaf litter, which is a key component of many estuarine food chains.

Dennis Hirst says he is looking forward to the staged opening of the floodgates as part of the Hexham Swamp Rehabilitation Project, as he believes there will be a significant increase in estuarine wetland habitat in the Swamp, as well as an increase in fish, prawn and crab populations in the Hunter Estuary.

Factsheet 3

Since floodgates were installed at the mouth of Ironbark Creek in the early 1970s, water quality in the creeks that run though Hexham Swamp has declined dramatically. Ironbark Creek is also affected by our activities in nearby suburbs as runoff carries pollutants down into the swamp.

Installation of floodgates on Ironbark Creek has seen Hexham Swamp turned into a mostly freshwater system where the water is often of poor quality. Pollutants from Ironbark Creek catchment have had a big impact on Hexham Swamp. Increased nutrient levels cause algal blooms and encourage weeds such as alligator weed. Organic pollutants (such as leaves and dog droppings) greatly reduce oxygen in the water, which is vital to fish and other aquatic organisms.

The effect of poor quality water flowing from the catchment is worse during dry periods when stream flows are low, as tidal flushing of the swamp is prevented by the floodgates. Many of the creeks in Hexham Swamp are also becoming much shallower than they once were because of silt build-up. Land use in the catchment has increased erosion and the floodgates at the mouth of the creek restrict tidal flows.

When the floodgates are opened and a regular tidal regime is restored to Hexham Swamp, the creeks are expected to become much healthier. This will help the rehabilitation of important estuarine wetland habitat in the swamp.

To date, over 90% of private land in Hexham Swamp (670 hectares) has been purchased for the Hexham Swamp Rehabilitation Project. Negotiations are nearing completion with owners of the remaining private land in the swamp about purchase of any of their land that will be affected when the floodgates on Ironbark Creek are opened.

The EA assessed issues such as the extent of tidal inundation, its effect on grazing land and neighbouring suburbs, and any changes in mosquito numbers. Information has been collected over several years on these aspects of the swamp, and its vegetation, fish, birds, water quality, weeds and feral animals.

Investigations for the EA suggest that all eight floodgates should not be opened at once, but rather opening should be staged with one or two gates opened at a time. In this way, the effects of each gate opening on plants, animals and water flows can be monitored and actions taken should anything unexpected occur.

Hexham Swamp is listed in the Directory of Important Wetlands in Australia, and under State Environmental Planning Policy No.14 - Coastal Wetlands. Also, international agreements on migratory wading bird habitat in the Swamp have been signed by Australia with China and Japan.

Hexham is a special place—that's why we carefully assessed changes that are likely to occur in the swamp when the floodgates are opened.

Hexham Swamp is home to many native plants and animals but, unfortunately, weeds and feral animals also call Hexham home.

Two of the main animal pests in Hexham are foxes and wild pigs. Foxes are a major threat in wetland areas where they feed on frogs and birds. This can be especially damaging when rare or threatened species are present.

A coordinated effort is underway to control foxes in the Hunter Estuary. During October each year, baits are laid in areas surrounding wetlands at Hexham, Kooragang Island, Tomago and Fullerton Cove. This project is being coordinated by NSW National Parks and Wildlife Service and involves the Hexham Swamp and Kooragang Wetland Rehabilitation Projects, Port Waratah Coal Services, Energy Australia and Maitland Rural Lands Protection Board.

At times, pigs also cause problems in Hexham Swamp. They destroy wetland habitats by digging up the ground and can turn creek banks and wetland pools into mud beds.

To ensure these unwelcome pests in Hexham Swamp are managed appropriately, the Hexham Project has developed a strategy to control them. This strategy sets out how we will work with our neighbours to ensure feral animals are controlled.

The CMA owns a large area of land in Hexham Swamp, some of which is affected by a range of environmental weeds. Some of these weeds have been declared noxious in NSW including water hyacinth (Eichhornia crassipes), pampas grass (Cortaderia selloana) and alligator weed (Alternanthera philoxeroides). These weeds are considered noxious as they have the ability to spread quickly and could easily dominate environments like Hexham Swamp, affecting habitat for native flora and fauna and reducing the overall value of rehabilitation works.

As well as these significant noxious species, there are many other common weed species in the project area including fireweed (Senecio madagascariensis), purple top (Verbena sp.), fennel (Foeniculum vulgare) and various thistles. While these weeds reduce habitat values in wetland areas, they are less likely to become a threat to the wetland ecosystem.

However one weed that could pose a major threat once the tidal regime is returned to Hexham Swamp, is spiny rush (Juncus acutus). This rush thrives in saline conditions and has the potential to become widespread throughout the swamp once tidal flushing is returned.

Through the Hexham project a strategy has been developed with Newcastle City Council and the NSW Natioanl Parks and Wildlife Service to control both weeds and pest animals in the swamp.

Living near natural areas can be very rewarding as they provide refuges for plants and animals and offer many benefits to people. These benefits include pleasant views, open space to observe native animals in their natural environments, and opportunities for recreation near our homes. However, there can be less desirable aspects associated with living around natural areas. For instance, in Hexham Swamp and many other areas, snakes become active in the warmer months.

The dominant species of snake in Hexham Swamp is the red-bellied black snake (Pseudechis porphyriacus), a relatively shy species that usually only attacks if provoked. Red-bellied black snakes feed mainly on frogs, which is why wetlands and streams are so attractive to them. Numbers will vary from season to season depending on the amount of water and food available, but we can usually expect to find them in and around areas like Hexham Swamp. Interestingly, red-bellied black snakes prey on brown snakes which are highly venomous and whose bite can be fatal. So areas with healthy populations of black snakes often have very few brown snakes.

Most bites occur when people try to kill or catch snakes. While no human fatalities have been recorded from the bite of the red-bellied black snake, it should be noted that they are venomous and can inflict a painful bite. Red-bellied black snakes want to get away from humans rather than attack them, so give them a wide berth if you encounter them. If a snake poses a risk to life, a volunteer from the Native Animal Trust Fund may be available to capture and remove it. You can phone them on 0500 502 294.

Photo courtesy of: Reptiles & Amphibians of Australia. H Cogger. 1996. p.667

Hexham Swamp is located in an extremely important position in terms of the lower Hunter Valley’s biodiversity.

The swamp is part of a vital corridor between the forests and bushland of the Watagans and Lake Macquarie, the wetlands of the Hunter Estuary, and the coast at Stockton Bight.

The main links from the bushland to the west of Hexham Swamp through to the swamp itself are small areas of undeveloped land to the south of Beresfield and near Minmi. Both of these areas were identified as significant local and regional habitat corridors by Newcastle City Council in its Green Spaces Strategy.

These links between the forests and the wetlands provide important areas for birds and animals to move through the landscape. For example, swamp wallabies use the bushland around the Watagans during the day to rest, while at night they move into Hexham Swamp to feed. These corridor links also promote healthy populations of a variety of species and allow animals to move out of danger during emergencies, such as fires or droughts.

As well as its value at a regional level, Hexham Swamp is recognised as a wetland of national and international importance. It provides feeding and roosting sites for at least fifteen species of migratory birds that are protected under agreements between Australia, and Japan and China.

Hexham Swamp makes up 40% of the 6000 hectares of internationally-acclaimed wetland in the Hunter Estuary.

Some people think of wetlands as smelly swamps, infested with mosquitoes. However, mosquito infestations and odour problems are usually a result of human interference with the natural processes of wetlands.  

These problems can occur when there is no water movement through a wetland. Mosquitoes are a natural part of wetland systems. They are also extremely important in the food chain that supports native fish, prawn and crab species. On the other hand, they can present health concerns to humans, through the spread of arboviruses, and can be irritating to those living on the fringes of wetlands. 

Kooragang Wetlands and the Hexham Swamp rehabilitation projects are working with the NSW Premiers Department and local councils on mosquito management in the Hunter Estuary. This cooperative approach will identify hot spots and guide wetland managers in reducing mosquitoes in trouble spots.

It is expected that once tidal flows have been fully restored to Hexham Swamp, predation on mosquito larvae by fish, and the fact that water will be moving in and out of the swamp on every tide, may even decrease numbers of mosquitoes in the swamp in the long term. The Hexham Project will continue to monitor mosquito numbers as the tides are returned to the swamp. But remember, mosquito control is up to all of us—make sure you don’t allow water to collect in your yard—this is an ideal breeding ground for mosquitoes.

The Hexham Swamp Rehabilitation Project is one of very few projects in Australia that aims to restore a degraded tidal wetland. That’s why it is important to study and fully document the recovery of these wetlands to provide valuable guidance to other projects in the future. 

Since it started in 1997, the Hexham Project has collected information on water flows, vegetation and birds—similar information will be collected after the floodgates are opened so that a comparison can be made.

The Hexham Project has engaged additional consultants to look at benthic invertebrates (creatures that live in the swamp’s soils), fish and frogs. This information will also serve as baseline data for the before/after study. Monitoring of water flows, vegetation and animals will continue until well after the floodgates are opened to ensure that changes brought about by the project are fully documented.

Mosquito and fish populations have also been monitored in the swamp in two separate studies, and further monitoring will be carried out. The results from these studies will also be used to determine the impacts of opening the floodgates.

The Hexham Project is also working with the University of Newcastle in order to acquire specific knowledge needed to properly manage the Swamp.

The Hexham Swamp Rehabilitation Project owes its success to date to the enthusiasm and support of a broad range of people and organisations.

Community concerns at the deteriorating estuarine values in Hexham Swamp came to the fore in the late 1980s, when groups such as the Hunter Wetlands Trust (now Hunter Wetlands Centre Australia) advocated increasing tidal flushing of Ironbark Creek. The CMA took up the challenge and established the Ironbark Creek Total Catchment Management (TCM) Committee, with a charter to investigate and report on the catchment and particularly on Hexham Swamp. The TCM Committee completed its report in 1996 and its key recommendations supported the case for returning the tide to Hexham Swamp.

The first step in achieving a rejuvenated swamp was to secure funding for the purchase of private land within the swamp for wetland rehabilitation. Support came from both Federal and State Governments, which committed substantial funding of $2.7 million each over three years, allowing the Hunter-Central Rivers CMA to begin its land acquisition and environmental assessment programs.

Endorsement of the Hexham Project has come from Federal, State and local government representatives and agencies, environmental groups, commercial fishing interests, researchers, neighbours of Hexham Swamp, and residents of the lower Hunter. These groups are represented on the Hexham Project Committee and continue to make a valuable contribution to the implementation of the project.

Without the input and commitment of these individuals and organisations the Hexham Project may have just remained a good idea—but together, we’re making a difference.