Scientists are using Ghost Crab populations as a measure of human impact upon dunes.
Going to the beach is part of the Australian culture. However, our desire to live and play on the sandy shores can have a
negative impact by causing the degradation of coastal dune systems.
Formation
A dune is a hill of sand built by aeolian processes1. Dunes occur in different forms and sizes, formed by interaction with the wind. Most kinds of dunes are longer on the windward
side where the sand is pushed up the dune and have a shorter ‘slip face’ in the lee of the wind. The valley or trough between
dunes is called a slack. A dune field is an area covered by extensive sand dunes. Large dune fields are known as ergs.
Role
Some coastal areas have one or more sets of dunes running parallel to the shoreline directly inland from the beach. In most
cases the dunes are important in protecting the land against potential ravages by storm waves from the sea.
Erosion
The beach environment is dynamic, undergoing cycles of beach erosion to be followed by periods of sand deposition. The capacity
of the beach to recover from erosion is impacted upon by all kinds of human activities. People walking through the bush or
along grassy dunes to get to the surf are often unaware that the vegetation on sand dunes plays a vital role in maintaining
the sand on beaches.
A fragile ecosystem
The beach is a fragile ecosystem rich in biodiversity and at the same time offering a barrier that protects the land from
the sea. Understanding the processes that shape the coastal sand dunes will help inform coastal communities about using the
beach in a sustainable way to ensure future generations of Australians access to the beach.
Illawarra EEC offers students access to a variety of coastal landscapes and landforms including the Farm Beach, Mystics Beach,
headlands, barrier dunes, coastal lagoon and Minnamurra River.
Port Kembla – Windang – Warilla
The coastline in this area comprises a number of significant natural features: rocky headlands of Port Kembla to the north,
long sandy beaches along Perkins (Windang) Beach, extensive hind dune communities, the entrance to Lake Illawarra, Windang
Island, Warilla Beach, a short sandy beach with minimal hind dune communities and the entrance to Elliott Lake estuary.
Google Earth
An example of a coastal dunes environment can be found at Garie Beach in the Royal National Park on Google Earth2. To move out of street view level and look at the wider area click the yellow person icon in the bottom right hand corner.
This resource will only work in the Google Chrome browser.
Coastal dune systems provide a buffer between natural processes of erosion and deposition.
Movement of sand
During storms sand is washed from the foredune and carried out to the surf zone where it forms sandbars3. Waves breaking over these bars lose some of their force before they reach the shoreline. The impact of the waves on beach
is less destructive. During calmer weather, the sand is washed back onto the beach and eventually blown back to the dune area.
Sand dune vegetation
Foredune plants, in particular the grasses such as Spinifex4 trap this sand and rebuild the front of the dune. However if there are no plants within the foredune to trap the sand the
sand can be transported back into the water and away from the beach. Sand dune vegetation is very important. The plants trap
the sand to allow cycles of erosion and deposition to maintain a healthy dune system.
Layers of defence
Behind the Spinifex grass and Coastal Wattle (Acacia sophorae) there are gradations in vegetation from sand dunes to hind dunes with Coastal Banksia5 (Banksia integrifolia) and Coast Tea Tree6 (Leptospermum laevigatum) appearing as a front row defence of trees against the salt laden winds from the sea. Because of the sandy soil and exposed
nature of the sand dunes the character of the vegetation cover is low and shrubby consisting of drought-resistant plants.
To restore coastal dune systems under threat of excessive erosion a variety of management strategies are undertaken including
planting of native coastal dune species, fencing and signage.
A number of things can damage sand dunes. Some of these are natural while others are caused by humans. The natural processes
that can damage a beach include wave erosion, wind erosion and fire. Other damaging influences on beaches include developments
such as car parks, houses, parks and roads located too close to the beach, access tracks across dunes, vehicles on the dunes,
grazing and in some cases, mining. On-going erosion problems cause the protective vegetation to be destroyed.
High school students practice skills that can only be completed in the field. These tasks include the completion of a transect
to observe, measure and record living and non-living factors across the dunes. Students also complete a précis map to include
the transect site and use a key to record salient features and adjacent human activities.
Examples and resources
Students are provided with workbooks containing coloured photographs depicting current management issues. These issues are
observed and discussed in the field allowing students to assess the success of management strategies. Students also observe
an excellent example of dune revegetation to make inferences about the sequence of actions required to reconstruct dunes to
replicate a sustainable coastal dune system.
Your local Environmental Education Centre
Other Environmental Education Centres providing access to coastal dunes include:
The introduced species Bitou Bush was deliberately planted along the NSW coast to reduce erosion. The spread of Bitou Bush
now poses a serious management issue as it threatens coastal dune vegetation communities along the NSW coastline.
Information on beaches and dunes, with detailed information about abiotic and biotic indicators that can be used to measure
the health of an ecosystem.
