Rising sea levels, taller waves and bigger storms caused by climate change could lead to South Australia's famous Robe obelisk falling into the sea in as few as five years, with the cape it is on set to disappear by 2051.

A committee formed to decide on the future of the obelisk has recommended letting it tumble into the Southern Ocean and building a replica on a hill further from the state's rugged south-east coast.

The cost of the proposal is unknown, along with when it will be needed.

It is a similar problem for much of the Limestone Coast, where erosion is causing escalating and unpredictable costs.

Erosion getting worse

Flinders University researcher Patrick Hesp, who is studying wave and current intensity off Robe, said climate change was causing the sea level to rise.

Professor Hesp said it was causing waves to get higher in the ocean and at the beach, causing more erosion of the soft rock that made up the Limestone Coast.

"We're possibly starting to see a tipping point where a number of things are acting in concert," Professor Hesp said.

The Robe obelisk was installed on Cape Dombey, west of the town, in 1855 to act as a beacon to guide ships into the calmer Guichen Bay.

Professor Hesp's research found the cape was eroding at 24 centimetres per year and that, at the most, the obelisk could stay standing until 2047. 

Replica preferred option

A consultant has been employed by local councils and the state's Coast Protection Board to develop a coastal adaptation strategy to work out what the coast will look like by 2100 and how to respond to the expected changes. 

A draft version of his report shows a 50 per cent chance the whole of Cape Dombey will have disappeared by 2051.

With the council under financial pressure because of the large number of historic buildings and other assets it has to maintain, it decided earlier this year not to take efforts to save the obelisk.

A backlash from locals led to the Robe Obelisk Working Party being formed to decide once and for all what to do.

It has dismissed ideas to move the obelisk or shore up the cape that it is on because of the cost and risks involved. 

Instead, it has recommended that the District Council of Robe build a replica, possibly made of concrete to save costs, opposite the ruins of the old gaol on a hill that is higher than Cape Dombey and more protected from the ocean.

Decisions to make

Working party chair Richie White said it would be up to the council to make a decision at a meeting on Wednesday.

He said the new site would be safe from erosion.

"It's probably a thousand-year site as opposed to right down there near the current obelisk, which is at max a 100-year site, possibly," he said.

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The council is also set to decide how the new obelisk could be paid for and when to start building it.

For some time, there could be two obelisks about 400 metres apart.

"We can rejoice in that old iconic structure as it is and, when it's no longer there, we can then concentrate on this new one," Mr White said.

Council chief executive Nat Traeger hoped money for it could come from donations and the state government.

"Certainly [there is] no intention that Robe's ratepayers foot the bill, and of course once we have a known concept, we'll be able to seek grant funding, which will be very helpful as well," she said.

Problems along coast

State and federal government funding has focused so far on protecting properties like beach houses at Kingston South East. 

There is no money to protect private assets like the Cape Jaffa marina that has been clogged with sand from storms, costing the small local council more than a million dollars to dredge this year alone.

It would cost even more to protect the salty Pool of Siloam at Beachport from becoming part of the sea, which could happen within 20 years. 

"Life does change, things evolve and maybe that's what will happen, but it would be very sad for the town," swimmer Susan Altschwager said.

Push for action soon

Local Mark Wheal said he would like a seawall installed along the bay known as the Salmon Hole to stop the dunes eroding and covering a scenic drive along the coast.

He said the cost to fix the problem now would be much less than waiting until it got worse.

"There's a point where you've got to actually say, 'Right, we need to do something about this now'," he said.

"We can't look at it in 20, 30 years' time because it will be gone and the cost of doing that will be so far surpassed of what it would be now.

"Why wouldn't you do it now?"

But Professor Hesp said more research was needed to fully understand the effect climate change was having on erosion.

"Just chucking in a seawall isn't necessarily going to solve the problem, particularly when you don't have good background data on how does the system work," he said.