Interim beach works at Semaphore and Largs Bay

Frequently asked questions

Sand is being moved from Semaphore and Largs Bay to West Beach and Henley Beach South periodically 2-3 times per year (autumn and spring) in 2020 and 2021.

In response to community feedback in Semaphore as a trial, the department is moving sand from Semaphore to West Beach closer to winter with works commencing in May 2021. 

Why is sand being collected from Semaphore and Largs Bay?

The state government’s long term strategy to manage the erosion at West Beach and Henley Beach South includes a commitment to match the rate of sand loss at these beaches by moving sand in the short term while new sand is sourced from outside of the Adelaide beach system and a sand recycling pipeline from Semaphore to West Beach is built. 

Due to the natural northward movement, sand builds up at Semaphore. Much is captured at the Semaphore South breakwater. Sand has also accumulated at beaches between the Semaphore and Largs Bay jetties and further north. Sand is being collected from the beach between the Semaphore jetty and Largs Bay jetty to supplement the amount of sand collected from the Semaphore South breakwater. Sand may also be moved from north of the Largs Bay jetty.

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Image: Semaphore beach looking north to Largs Bay

Did you know?

Sand has been collected from Semaphore and moved south to eroding beaches since the 1970s. Sand is quickly moved back into the area by the natural littoral drift process without significant environmental impact.The approach for managing Adelaide’s beaches is based on decades of research, monitoring and international best practice.

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Image: Sand movement works at Semaphore jetty in 1981

When will sand be moved from Semaphore next? 

Sand is normally moved in spring to provide sandy beaches for summer and again in autumn to protect the coast through winter.

In response to community feedback in Semaphore as a trial, the department is moving sand from Semaphore to West Beach closer to winter with works being undertaken from May - July 2021

The department regularly meets with community representatives and council to help guide the Semaphore sand movement works.

How much sand is needed at West Beach each year?

Research undertaken by independent consultants DHI estimates that approximately 100,000 to 115,000 cubic metres (m3) of sand is lost on average from West Beach each year. The sand naturally moves north by wind and wave action. 

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Image: Regularly replenishing sand at erosion hot spots such as the area at Rockingham Street is required to protect the road and infrastructure from damage.  

How is sand collected and moved?

  • Sand from the beach between the Semaphore and Largs Bay jetties is skimmed using a land plane attached to a tractor from between the high and low tide mark. No sand is collected from the dunes.
  • The land plane deposits the sand next to the Semaphore jetty.
  • A conveyor belt system is used to move sand under the Semaphore jetty, in conjunction with trucks along the beach to Point Malcolm.
  • The sand is then trucked by road to West Beach. 
  • All work is undertaken from Monday to Friday only (no weekend works).

Sand will be scraped from the beach surface using a land plane.

Image: Sand is skimmed using a land plane attached to a tractor from between the high and low tide mark

Community safety

  • Community safety is a priority. Safety signage is in place on the beaches during works. 
  • The community and beach users are asked to please take extra care on the beaches while the works are underway and adhere to all safety signage and flagging in place during operations.

Qualified contractors are employed for the works. The successful contractor is required to develop a job safety plan and a thorough risk management plan. This includes safe management between the work and members of the public.  

  • Traffic control complies with relevant Australian Standards and Code of Practice. Traffic controllers and/or signage is provided where necessary.
  • We liaise with Surf Life Saving SA and the Semaphore Life Saving Club regarding beach safety.

safety-signage

Truck speed limits on beaches

Sand movement works on the beaches are undertaken by a contractor on behalf of the department. Safety is of paramount importance when undertaking works along our beaches. As such, the contract includes stringent conditions regarding the speeds that the equipment (trucks and other machinery) can operate at when moving along the beach.

Speed of vehicles on the beach shall not be greater than:

  • 40 km/h unless within 50 metres of any person or animals
  • 25 km/h between 10 metres and 50 metres of any person or animals
  • Must stop within 10 metres of any person or animal
  • 5 km/h within 20 metres of Semaphore Jetty

In addition, all vehicles must give way to all other traffic on the beach including pedestrians and animals. They must stop when pedestrians or animals wish to cross the line of movement of the trucks along the beach.

GPS monitoring is used to make sure the contractor’s trucks are not speeding. The department also has a full time supervisor on site at the beach monitoring compliance with these conditions. 

What environmental assessments have been undertaken?

The beach replenishment will put sand on our most vulnerable and eroded beaches at West Beach and Henley Beach South, with benefits to other beaches as sand naturally moves northward. This has been informed by research completed in 2018 by external consultants DHI. 

An independent assessment looking at the impacts of moving sand from the northern beaches is currently underway.

  • Phase 1 has been completed and assessed the impacts of the 2020-21 interim sand movement works, including the spring 2020 and autumn 2021 works. The assessment confirmed that the beaches will recover quickly and continue to grow despite the short term impacts of moving sand.  Read the Phase 1 report
  • The longer term impacts of the sand recycling pipeline (to be constructed from Semaphore to West Beach by 2023) are also being assessed.
  • A working group including community representatives has been involved in the process. (See: Community Engagement – Impact assessment on moving sand from the northern beaches)

At the location between the Semaphore and Largs Bay jetties, and north of the Largs Bay jetty, the government's beach profile data indicates that there is sufficient dune volume buffer and the area will steadily build up again through natural processes. A team of environmental specialists monitor and assess Adelaide's beaches regularly.

The department works with Birdlife Australia to ensure any impacts to shorebirds are avoided or minimised.

See also:

Can’t the sand just be moved from the Semaphore South breakwater?

The Semaphore South breakwater is the primary source of sand to replenish Adelaide’s eroding southern beaches. It is designed to trap approximately 50,000m3 of sand each year.

  • Sand will be moved from the Semaphore South breakwater to the eroding West Beach in autumn/winter 2021.
  • Sand was moved from the Semaphore South breakwater northwards to replenish the Semaphore South dunes in March/April 2021 (see: Semaphore South dune replenishment)

At times the breakwater area needs time to naturally replenish with sand. 

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The dunes at Semaphore Park were an erosion ‘hot spot’ in the 1980s and 90s and required regular beach replenishment. The dunes have built up since the Semaphore South breakwater was built in 2005. Download poster

How much sand has already been moved to West Beach from Semaphore and Largs Bay?

Since October 2018 approximately 178,000m3 of sand has been moved from the Semaphore South breakwater to West Beach and Henley Beach South.

Since November 2019, 40,000m3 of sand has been moved from between the Semaphore and Largs Bay jetties to West Beach.

The sand moved from north of the Largs Bay jetty (in April and May 2020) was used to restore the eroded dunes at Semaphore South. See: ‘Semaphore South dune restoration

What about sand from the beaches further north, like North Haven?

Historically, testing of sand at the northern end of Largs Bay has shown that it would be uneconomic to use it to replenish beaches further south on the Adelaide coast. This is because it is finer and would wash away much more quickly.  The most recent analysis shows that while suitable sand can be found to just north of Largs Bay jetty (to Strathfield Terrace, Largs North), the build-up of sand beyond that would not be an economically viable source for replenishing West Beach or its adjacent beaches.

The properties of Adelaide’s natural beach sand has been thoroughly investigated to inform beach management decisions and help identify suitable sources of sand for beach replenishment. 

What will the likely impacts be to the dunes at Semaphore and Largs Bay?

An independent assessment of the impact of moving sand from the northern beaches confirmed that the beaches will recover quickly and continue to grow despite the short term impacts of moving sand. 

The dunes in between the Semaphore and Largs Bay jetties vary from 80 metres wide to over 100 metres wide, and sand will be sourced from the beach where the dunes are wider.  

Any indication of foredune erosion at this location would be closely monitored to ensure the foreshore remains protected and the wider dune system maintained.

It is expected that this impact will be short-term until the beach naturally replenishes with sand that moves north, enabling the foredune to rebuild. 

How will the impacts to the dunes be managed?

We acknowledge the great work that dune care groups do to look after our beaches and their extensive local knowledge of the dunes.

Assessments by both the department and an independent consultant have concluded that the impact of the sand movement works on the dunes will be minor. No high value native vegetation or dune care group plantings will be affected. 

There will be opportunities in the future for community groups to partner with the local council for dune care grants to further improve the coastal biodiversity.

We will continue to monitor the beaches and dunes to ensure the foreshore remains protected. 

Has an assessment of the dune vegetation been done? 

In March 2020, the department engaged independent ecologists to undertake a vegetation survey to assess and map the flora along 5km length of coast between Semaphore Surf Life Saving Club and Strathfield Terrace, Largs North. The field assessment includes gathering information about native species present, weed species present and their cover category, native plant life forms, native/exotic understorey biomass and tree health. This information has been used to help inform these and future works. 

Why is sand under the surface of the beach grey or black in colour?

The sand collected from Semaphore and Largs Bay is coloured grey to black because of the naturally decomposing seagrass content. This is particularly noticeable if you dig below the surface of the beach in areas where seagrass wrack accumulates. This quickly dries and turns white/yellow after being exposed to the sun, wind and rain.

More information