Adelaide is known for some greats beaches within a short drive of the city centre, such as at Glenelg, West Beach, Henley Beach and Semaphore.
The beaches though are not stationary, but are impacted by the currents in Gulf St Vincent, which is constantly moving the sand northwards, by a geological process called longshore drift. But the beaches at Glenelg, West Beach and Seacliff Beach are slowly eroding, due to the movement of sand being disrupted by the Torrens River outlet. The outlet is acting like a hydraulic groyne causing the sand to build up to the south of the outlet.
This issue is not unique to Adelaide, in fact it’s common to many beaches around the world.
The outlet was constructed in 1937 and was designed to help prevent Henley Beach and Grange being isolated during floods, and to protect market gardens and properties from flooding.
To protect the beaches a strategy has been developed called Adelaide’s Living Beaches: A Strategy 2005 to 2025. The strategy outlines a number of measures, that if not undertaken, could see the beaches could left barren as clay and rock. This would diminish the recreational uses of the beaches, disrupt the ecological value of the dunes, undermine infrastructure and even expose the nearby houses to erosion
This earthcache will take you on a short journey to identify the key features, and some of the measures being undertaken to keep the beaches in good order.
Waypoint 1 – Posted Co-ordinates (S34 56.292 E138 29.954)
You are now to the south of the Torrens River outlet into Gulf St Vincent.
At the information board, have a look at the photos. You can clearly see the build up of sand that has occurred here since 1949, and how the discharge from the Torrens River has been impacted. Take particular note of the shape and direction of the channel into the gulf.
- The sand dunes acts as a buffer. What benefit does this provide the local community?
- What does the yellow line represent?
Waypoint 2 – Southern Side (S34 56.053 E138 29.881)
As you travel south along Seaview Road you will cross the Torrens River. As you do look to your left (west) and you will see the concrete outlet
Waypoint 3 – Dune Vegetation (S34 55.951 E138 29.839)
Vegetation also plays critical role in the formation and management of the dunes here, and in protecting the beaches from erosion
- What two ways does vegetation help protect and maintain the beaches?
Feel free to take photos of the beach, the outlet and the dunes and add to your log.
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