Coastcare Issues
Dune erosion
Did you know that...
- Over the last century, 70% of the world’s beaches were retreating due to erosion.
- Beach and dune erosion have occurred on much of Australia’s sandy coast. Most of the east coast and South Australian beaches are eroding and some east coast beaches disappearing at a rate of about two metres a year.
Our beaches are under threat from several sources that combined could prove disastrous.
Natural cycles: The Australian beaches like to travel as sand is naturally moved by the action of the waves. The same process eventually replaces lost beaches, but nature does it in its own sweet time. To meet the needs of both the environment and people, major engineering work is often necessary to replace shifting sands.
On the Gold Coast the so called “long shore drift” moves an estimated 500,000 cubic metres of sand per year between Lismore in NSW and Brisbane in Queensland. That's about 13 million cubic metres disappearing from the southern part of this coastline over 26 years. Quite a lot to replace!
Global warming: Global warming could cause sea levels to rise dramatically over the next 100 years and are likely to cause more extreme storms and even changing wave patterns. The rise in sea levels, more extreme weather and even changes in wave directions are predicted to cause extensive coastal erosion in Australia and the rest of the world.
Human activity: Human activities can accelerate the natural processes that cause the erosion of sand dunes. 4WD, trail bikes, horses and uncontrolled pedestrian access can disturb or strip a sand dune of vegetation, so wind blown sand can no longer be trapped by plants. Mining, grazing, fires, sea walls and groynes can all affect beach dunes and many have been lost to human developments.
Development: A survey carried out by the Surfrider Foundation and supported by Coastcare found that 1 in 20 beaches surveyed had completely lost their dunes to beachfront development paving the way for severe erosion during tidal surges and storms and the loss of native plant and animal life.
The survey also found 72% of beaches surveyed had property or infrastructure development within 250 metres of the high tide mark, with the most common types being roads, car parks and houses. These developments can be severely damaged during storms as sand is eroded from beneath them.
Seawalls: Many beaches have walls built along the shore to protect building and roads behind beaches from waves and storms. These ‘protective’ walls can actually cause the loss of the beach in front of them. The beach erodes and during storms the waves pound across the lower beach with plenty of energy to remove more sand. Sometimes the walls themselves cave in. In some areas beaches lose all their sand, leaving only a rocky or clay base.
What can I do to help?
Our beaches are delicate and with thousands of people trampling on them all the time they tend to waste away. So, if you see beach regeneration areas, don't interfere with them. The dunes depend on grasses and plants to hold them in place.
Join one of the 2000 Coastcare groups in Australia. Two approaches are now being taken in the bid to protect our beach dunes. Careful management of healthy dunes can reduce the need for expensive and time consuming rehabilitation in the future.
Healthy dunes are managed by:
- locating developments well back from dunes to prevent future damage;
- fencing dunes and constructing walkways to prevent erosion caused by people and vehicles;
- keeping out pest plants and animals
Badly degraded dunes are rehabilitated by some or all of the following processes:
- rebuilding the damaged dune with earthmoving equipment;
- removing weeds and replanting the dune following the natural pattern of vegetation;
- fencing the planted areas to allow the vegetation to establish;
- keeping introduced animals, like rabbits, out of the dunes;
- careful location of walkways to prevent erosion from foot traffic;
- continuing maintenance to ensure that the vegetation, fences and walkways continue to protect the dune.
