Coastal erosion
Coastal Dune Management
Coastal Evolution
Dunes are an integral part of our coastal
environment. They are a basis of important
ecosystems supporting valuable communities of
plants and animals. As such they initially provided
resources and shelter for Aboriginal people,
generating cultural values that remain important
today. More diverse activity resulted from European
settlement providing the basis for another set of
social values.
Around 120,000 years ago when the sea level was
possibly a few metres higher than it is at present, a
powerful, constructive south-easterly swell was the
dominant component of NSW wave climate. At that
time these waves were helping to move large
volumes of sand both along shore and onshore to
form the mix of beach and dune sands that are
present today, at least on the north coast.
Unfortunately, many coastal dunes have been
degraded over the years due to pressures from
urban development, agricultural practices, mining
and recreational activities such as vehicles driving
on beaches.
The result of dune instability and sand drift remains
a serious problem along parts of the New South
Wales coast, as wind-blown sand continues to
advance inland, threatening both natural and built
environments.
However
through
integrated
management,
Government partnerships and grants, ecologically
sustainable development processes and community
involvement through Dunecare and CoastCare,
these valuable ecosystems can be protected and
thrive.
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With the onset of the last Ice Age sea levels fell and
most of the NSW coastline was several tens of
kilometres seaward of its present position. Coastal
rivers were flowing out onto the shelf and depending
on the catchment characteristics, were depositing
sediment onto the coastal plain.
Climate warming at the end of the Ice Age prompted
sea levels to rise until about 6500 years ago. This
rapid rise in conjunction with a prevailing southeasterly swell prompted more onshore and
longshore movement of large amounts of sediment
to form the outer barrier to the beach systems,
creating the beaches and dunes we value today.
Figure 1
Image sourced from, Kidd. R, Department of Land
and Water Conservation, Coastal Dune
Management A manual of Coastal Dune
Management and Rehabilitation, October 2001.
Great Lakes Council Breese Parade (PO Box 450) FORSTER NSW 2428
2 Study Mate 8 Coastal erosion
A functioning beach and dune system can be
classified into different typical features. All of these
features are important to the health and successful
functioning of the dune systems (see Figure 1).
Typically an undisturbed beach will include a fore
dune (frontal dune) and hind dunes, there may also
be an incipient fore dune immediately seaward of
the established fore dune. The incipient fore dune
can grow with new deposits of sand and is normally
colonised by grasses and creepers. During storms
and natural erosion processes these incipient fore
dunes are attacked and sometimes completely
destroyed, only to rebuild with the next deposit of
sand.
The established fore dune lies between the incipient
dune and the hind dune. They are a more persistent
beachscape feature surviving attacks by waves
during severe or prolonged storm events. Their size,
shape and stability are also controlled strongly by
vegetation cover. Typical dominant vegetation in
the fore dune area includes woody shrubs and trees
(see the fore dune walk at One Mile Beach,
Forster).
The hind dune is characterised by tall woody trees,
these hind dunes transition from dune to tertiary
wooded forests.
Without the stabilising effect of vegetation, sand is
easily moved by the wind and the result, sand drift,
can progressively bury both natural and built
environments. Weakening or destruction of fore
dune vegetation can be induced by natural events
such as drought, lightning-initiated fires or storm
waves, and of course through various human
activities, including trampling and the introduction of
weeds.
When dune vegetation is healthy and stable, it acts
almost like a cyclone proof house, as it deflects the
main force of the wind, as seen in Figure 2.
A fully functioning dune system is a vibrant, diverse
and healthy ecosystem, supporting a range of
plants and animals. As such beaches and their
dunes should be protected and enhanced so they
can keep functioning properly.
Figure 2
Image sourced from, Kidd. R, Department of Land and Water Conservation, Coastal Dune Management A Manual of Coastal Dune Management and Rehabilitation, October 2001.
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Great Lakes Council Breese Parade (PO Box 450) FORSTER NSW 2428