Under natural conditions, beaches are constantly changing. Beach replenishment is required when the natural process of sand movement is inhibited due to foreshore development or to address erosion caused by storms. It involves taking sand from beaches where it is building up and placing it at beaches that would otherwise erode. If action isn’t taken, ongoing erosion could result in extensive damage to reserves, roads and buildings built on the foreshore. The state government and many coastal councils undertake beach replenishment activities by sand carting or pumping using specialised infrastructure. Find out more about how we are replenishing Adelaide’s metropolitan beaches.
Sand dunes play a vital role in protecting our beaches, coastline and infrastructure from the destructive forces of coastal storms, wind and waves. They also provide a future supply of sand to our beaches and an environment for many coastal plants and animals. Dune rehabilitation is carried out by councils and volunteer groups across South Australia.
Structures like groynes, breakwaters and seawalls can be used where appropriate to help trap sand and protect infrastructure:
- Groynes are structures built across a beach, usually from dry land out into the water, to trap sand on the updrift side in what is called a fillet. Small groynes are useful for raising beach levels on a small scale.
- Breakwaters are usually built parallel to the beach to interrupt the alongshore movement of sand. At Semaphore Park, a trial geo-textile sand bag breakwater was built in 2004. The trial proved so successful at trapping sand that the breakwater was armoured with heavy rocks in 2009. This area provides a source of beach replenishment sand to beaches further south.
- Seawalls act as a last line of defence and protect coastal infrastructure and property from storms. Since the 1960s most seawalls have been built and repaired using large boulders and rocks to absorb wave energy. Ongoing beach replenishment along Adelaide’s metropolitan coast has slowed the damage to local seawalls, however many of the older structures will need repair in the future.
Harbours, marinas and boat ramps are valuable tourism and commercial assets. Their presence can also impact on local coastal processes. These impacts are considered during the planning stages of a project and minimised. Management of harbours and marinas includes:
- Sand bypassing using various methods such as trucks, pumping infrastructure and dredging.
- Dredging to remove built-up sand and sea grass wrack and to prepare the harbour for winter storms. This is frequently required at some marinas and boat launches, such as Glenelg and West Beach.
Ensuring new and proposed development is sustainable is an important aspect of coastal management. In 1991, the South Australian Government adopted the Coast Protection Board’s Policy on coast protection and new coastal development. The components of the policy relevant to coastal development and land use were then incorporated into South Australia’s planning system in 1994. Any new development proposal or substantial changes to coastal land is referred to the Coast Protection Board for comment. Find out more about coastal planning and development.
Coastal climate change adaptation
The Coast Protection Board factors in the need to adapt to a changing climate into every aspect of its work. A key aspect of the Board’s coastal development policy is the requirement for new coastal developments to allow for sea level rise. New developments must now be protected against 0.3m of sea level rise (projected for 2050), and be capable of being protected against a further 0.7m of sea level rise (projected for 2100).
The Coast Protection Board and the department undertakes annual monitoring and evaluation to collect valuable data to inform management decisions. Learn more about these monitoring programs.