Monitoring our beaches and coast
Successful management of South Australia’s coastline requires a detailed understanding of local coastal environments and processes. The Coast Protection Board and the department undertakes annual monitoring and evaluation to collect valuable data to inform management decisions. The monitoring includes:
The method of measuring sand levels is called a 'beach profile'. Profile measurements are taken from a permanent starting point and run along a cross-section of the coast over sand dunes, the active beach zone and offshore. Some profile lines extend 5 or even 10 kilometres out to sea.
A network of beach profiles has been established along the South Australian coast at places where beach erosion has been identified as a possible threat to public property and development. The profile lines are regularly surveyed and evaluated for short and long-term changes in sand levels or changes in cliffs.
Brass rods have also been installed in the seabed along the Adelaide coast and are used to measure depth changes from sand movements. Seabed deepening caused by a loss of seagrass is a particular issue along the Adelaide coast.
A surface modelling technique can also be employed along the coast to map and measure large sand movements from replenishment projects or erosion. This technique involves measuring the study area in a grid pattern and then using surface modelling software to create a map of the beach and sea floor surface. Where cliff erosion is an issue, a row of spikes located behind a cliff top at set distances is used to measure the cliff top offset and erosion rates over time.
Coastal monitoring: how we measure the sand on our beaches
Seagrass along the Adelaide metropolitan coast has been monitored by the department since 1987, following the loss of around one third of seagrass over the last half century.
Brass rods installed on the sea floor at a number of locations are surveyed and photographed annually to identify any changes in the seabed level, including observations on seagrass species composition and overall condition.
The monitoring has shown that where seagrass has been lost, there is a deepening of the seabed of up to one metre in places. This has resulted in an increase in the wave energy that reaches our beaches and has contributed to increased beach erosion.
In recent years, because of water quality improvements, the monitoring has also captured seagrass regeneration at various locations along the Adelaide metropolitan coast. These sites are revisited regularly to monitor the slow progression of the recolonising seagrass patches to form more complex meadows.
The Coast Protection Board has undertaken coastal aerial oblique photography since the 1970’s. The aerial photos capture the diversity of South Australia’s coastal landscape. In recent years, these images have been publicly available as a layer on NatureMaps, the department's online mapping and data access site. The photographs are used to inform coastal management decisions and also help natural resource managers, coastal researchers and community groups involved in coastal management.
The department undertakes regular surveys of the Glenelg and West Beach harbors to measure channel depths to ensure the levels are safe for boat navigation. The survey is completed using a boat equipped with high accuracy GPS survey equipment. Dredging of the harbours is carried out if the levels are not suitable for boat navigation.