Guide to rehabilitation

Kerryn Stephens

Estuarine Ecologist

Department of Environment and Climate Change

Along parts of the NSW coast up to 70% of wetlands have been destroyed over the last 200 years (for example, the Illawarra region, Merrin and Chafer 2000). In heavily populated areas, such as the Sydney region, even greater losses of wetland types such as saltmarsh have occurred (Stricker, 1995). In many cases remaining wetlands have been severely degraded. Degradation of coastal wetlands has resulted from poor catchment management practices, land reclamation, pollution of surface and groundwater, agricultural drainage works and construction of navigation channels, ports and canals.
In some locations wetlands continue to be degraded through urban encroachment and vandalism. Impending climate change is likely to further threaten these fragile environments. Action undertaken by communities now to recognise vulnerable areas and implement rehabilitation measures will provide the best chance to help these remaining wetland systems to adapt into the future.
The NSW Department of Environment and Climate Change and NSW Department of Commerce have prepared the Saltwater Wetlands Rehabilitation Manual to assist coastal communities to rehabilitate and manage degraded saltwater wetlands.

What is the Saltwater Wetlands Rehabilitation Manual?

The Saltwater Wetlands Rehabilitation Manual has recently been completed by the Department of Environment and Climate Change (Estuary Management Program) and Department of Commerce (Manly Hydraulics Laboratory). The manual provides not just an understanding of saltwater wetlands, including their hydraulic, physical, chemical, biological and ecological processes, but also guidance in undertaking the rehabilitation process from planning to implementation to maintenance and monitoring.

Saltwater wetlands are those wetlands whose inundation regime and vegetation characteristics are influenced by brackish or saline waters. These wetland types include swamp forest, saltmarsh, mangrove forest and seagrass beds.

The range of services derived from saltwater wetlands are substantial and varied, they include habitat value, food production, waterway and riparian protection, nutrient cycling, flood control, water quality improvement and recreational amenity. The importance of individual wetland types are briefly summarised below.

Swamp forests are generally associated with clay-loams and sandy loam soils, where the groundwater is saline or sub-saline, on waterlogged or periodically inundated flats, drainage lines and estuarine fringes associated with coastal floodplains. As a buffer between dry land communities and the estuary the community is important in terms of habitat value, riparian protection, flood control and water quality improvement. The structure and species composition can vary considerably based on physical factors, however in NSW, many will consist principally of swamp oak (Casuarina glauca), paperbark (Melaleuca spp.) or swamp mahogany (Eucalyptus robusta), the understorey is characterised by vines, shrubs, and a groundcover of forbs, sedges, grasses and leaf litter.

Saltmarshes occur at the upper levels of the intertidal zone. They are not subject to daily tidal inundation but are flooded by larger tides. Saltmarshes have a number of important structural functions including flood and erosion control, buffering storm surges, and improving water quality by filtering pollutants and excess nutrients. They support a rich and diverse community of invertebrates, provide roosting sites for many species of birds, and also provide habitat for juvenile fish when inundated. In NSW, saltmarshes are characterised by herbaceous species such as samphire (Sarcocornia quinqueflora), saltwater couch (Sporobolus virginicus) and rushes (for example, Juncus kraussii).

Mangroves grow along the shorelines of many NSW estuaries in areas subject to regular tidal inundation. In addition to structural functions such as erosion control and buffering of storm surges, mangrove forests are important habitats for fish, molluscs, crabs, bats and birds, and the trees provide large amounts of organic matter as a food source for the estuarine system. The two most common species in NSW are grey mangrove (Avicennia marina) and river mangrove (Aegiceras corniculatum).

Seagrasses occur in the subtidal zones of estuaries. Seagrass meadows are important in sustaining recreational and commercial fisheries, maintaining sediment stability and water quality in estuaries and providing food and shelter for fish and invertebrates. The most common species in NSW are eelgrass (Zostera spp.), paddleweed (Halophila spp.), strapweed (Posidonia australis) and sea tassel (Ruppia spp.).

It is estimated that over 60 percent of the coastal wetlands of NSW have been lost or severely degraded over the last 200 years (Bowen et al., 1995).

In conjunction with the growing awareness of the ecological significance of wetlands in recent years there has been an increase in the amount of information available in Australia regarding the design, use and management of constructed and rehabilitated wetlands. As such techniques used in all aspects of wetland rehabilitation including construction, propagation and planting, and monitoring are increasingly being used and reported on. The NSW Estuary Management Program (now part of the Department of Environment and Climate Change) with Manly Hydraulics Laboratory (Department of Commerce) has brought together information relevant to saltwater wetland rehabilitation into the form of an easy to use manual to guide the wetland rehabilitation process.

Given the aim of the Saltwater Wetland Rehabilitation Manual is to provide technical information and guidance to assist with the rehabilitation of saltwater wetlands, the manual was prepared as a complementary volume to The Constructed Wetlands Manual (Department of Land and Water Conservation, 1998). The Constructed Wetlands Manual provides readers with guidance to plan, design, construct and operate a freshwater constructed wetland. Whilst The Constructed Wetlands Manual is useful in providing guidelines and general information on wetland rehabilitation, it does not specifically address the rehabilitation of saltwater wetlands.

If you require general information on saltwater wetlands or are embarking upon a rehabilitation project the Saltwater Wetland Rehabilitation Manual has been prepared in order to provide not just an understanding of the functioning of saltwater wetlands, but also guidance throughout the rehabilitation process from planning to implementation to maintenance and monitoring.

• 
  sufficiently detailed information is required to design, implement, manage and monitor a saltwater wetland rehabilitation project;
  
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  a logical and robust process for wetland rehabilitation, capable of accommodating developing technologies, information, concepts and ideas should be applied; and
  
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  detailed information is required to convey the complexity of saltwater wetlands ecosystems to assist with planning and management of wetland rehabilitation projects.
  

Guidance on the rehabilitation process from planning to data collection and design, plan preparation and implementation through to operation and maintenance is provided. Where possible, the manual includes simple guidelines to address some of the tasks involved in wetland rehabilitation.

The manual has been prepared for an audience that includes:

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  technical staff in Local government (engineers, planners and landscape architects);
  
• 
  technical staff in government agencies;
  
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  consulting firms and construction companies;
  
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  potential operators, managers and owners of rehabilitated saltwater wetlands (private landholders, agencies, Local councils, community groups and schools); and
  
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  community groups.
  

The ‘Saltwater Wetland Rehabilitation Manual’ is structured into three sections:

1. 
   Overview of saltwater wetlands;
   
2. 
   Planning and implementation for rehabilitation projects, including:
   

Operation and maintenance;

Monitoring and reporting;

3. 
   Characteristics and processes of saltwater wetlands, specifically:
   

Groundwater;

Soils;

Chemistry;

Legislation and Policy.

The production of the Saltwater Wetlands Rehabilitation Manual has involved contributions from numerous people with skills in various saltwater wetland related disciplines, including: Kerryn Stephens (Department of Environment and Climate Change), Dayle Green, Dr Pia Laegdsgaard, Dr David Rissik, Andrew Rawson, Susan Fox (Department of Natural Resources), Dr Ian Turner (University of New South Wales, Water Research Laboratory), Peter Nelson and Ann Finnigan (Shortland Wetlands Centre), Dr Julie Phillips (EcoAlgae Research Pty Ltd) and Phil Anderson, Dr Brian Wallace, Michael Barratt (Manly Hydraulics Laboratory).

Bowen, R., Stephens, N. and Donnelly, P. (1995). SEPP 14 - wetland protection and the role of mitigation. Wetlands (Australia), 14: 6 - 12.