Sandy beaches experience phases of erosion and accretion over a range of time intervals.
In the short term beaches experience erosion in seasons when storms are more frequent.
This is especially so during an extreme weather event such as a tropical cyclone.
The accretion of sand is a slower process than erosion.
It tends to happen in seasons when weather conditions are calmer.
Over long time frames rising sea levels lead to phases of erosion
whereas falling sea levels are associated with long term phases of accretion.
Human activity also has a big influence on rates of erosion.
Urbanization and tourism development near the coast puts a lot of pressure on beaches and dunes.
Most of Australia's urban centres are located close to the coast.
There are many examples of erosion taking place where buildings have been built on or near the beach.
Human activities such as mining, the development of marinas
and dredging sand for canal developments all result in sediment being removed from the sea.
The damming of rivers also reduces the volume of sediment reaching the coast.
All these activities interfere with natural processes such as longshore drift
whereby beaches can be deprived of its naturally replenishing sand.
Human efforts to deal with coastal erosion include a range of options that have had
varying degrees of success and many drawbacks.
Beach renourishment is the artificial placement of sand on the beach.
Natural processes then spread the new sand along the beach.
The problem with this solution is that the removal of sand from another beach
may have environmental impacts for the beach the sand was sourced from.
Another issue is that natural erosion processes mean sand
must continually be replaced at the receiving beach which requires ongoing funding.
Another way of preventing the loss of sand from a beach is to construct groynes.
These are structures built usually extending from the shore
out to sea that are designed to catch the sand that is transported by longshore drift.
Groynes can be built from materials such as wood, steel, concrete, rubble or sandbags.
On the positive side sand gets trapped on the up-drift side of the groyne and a wider beach is created.
However the effectiveness of groynes has some limitations.
On the down-drift side of the groyne the foreshore is even more susceptible to storm erosion.
Groynes also fail to prevent sand movements offshore from the groyne.
A seawall is a structure built to prevent the erosion of dunes and protect buildings.
Sea walls are an expensive option and require ongoing maintenance.
Waves hitting the wall are reflected.
The backwash reflected from the wall drags away sand from the beach.
The base of the sea wall is eroded over time.
Sea walls also destroy the natural look of a beach.
Alternatively some councils place large rocks in gabion baskets on the beach to try and protect it.
Some councils may choose to construct an offshore breakwater.
This is a structure parallel to the shore and placed in the water at a depth of about 10 metres.
By doing this waves will break in the deeper water reducing wave energy and erosion at the beach.
The down side of offshore break waters is that these structures require many large boulders
and can be very expensive.
Surfing communities are also opposed to this
solution because it destroys the availability of surfable waves.
Given the failure of sea walls and other hard structures new approaches have been taken to coastal management.
One of these is a managed retreat from the coastline.
A council may buy coastal properties and remove any buildings threatened by erosion.
This makes it easier to manage as it allows coastal processes to continue.
But buying properties is very expensive and it still does not solve
the long-term problem of the loss of land to the sea.
It is important that people look after sand dunes.
They form a natural barrier to wave erosion.
They are also home to endangered shore birds such as the little tern that lay their eggs there.
Vegetation is essential for stabilizing dunes.
It is a vegetation that traps the sand and holds it in place.
If the vegetation cover gets removed winds will remove the sand leaving a blowout.
If the natural vegetation cover is removed dunes can also advance inland.
Human activities on the dunes such as the driving of four-wheel drive vehicles on the beach
walking
and fires
threaten the vegetation cover of coastal dunes and thereby enhance erosion.
Councils have met these challenges by fencing off the dunes
and by conducting revegetation projects.