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SES urges private owners to check their dams as Echunga flood risk over

A dam in the Adelaide Hills threatened dozens of homes this week, raising questions over how privately-owned dams are managed.

About 40 people from the town of Echunga were forced to leave their homes on Wednesday after a wall in a dam slipped and was threatening to fail.

The State Emergency Service (SES) were able to pump out enough water from the dam for it to be declared safe on Thursday afternoon.

So who is responsible for private dams in South Australia and what is the likelihood of a similar situation happening in the future?

The first thing to know is most of South Australia's privately-owned dams are in the Hills.

The Hills and Fleurieu Landscape Board general manager, Michael Garrod, said about 20,000 of the state's 30,000 privately-owned dams were in the region, the "vast majority" of which were on rural properties.

Mr Garrod said dams required ongoing maintenance and encouraged landholders to complete a review.

"If people do see anything that's unusual or alarming in terms of dams, please just get in touch with us and we can help navigate what can be sometimes a pretty complicated set of arrangements around dams and water management across the state," he told ABC Radio Adelaide on Thursday.

The SES and Department for Environment and Water provide guidelines on dam maintenance and emergency management.

While the owner of the Echunga dam has been praised for his actions, the SES took the opportunity to remind landowners to conduct regular inspections and maintenance to ensure the structural integrity of their dams.

"We'd like the owners to go and inspect their dams so we don't have the same sort of situation happening again," SES incident controller Craig Brassington said on Thursday.

Who is responsible for private dams?

Dam owners are responsible for any damage caused if their dam fails.

They are also responsible for the maintenance of their dam.

Craig Brassington said the SES could only be made aware of issues with private dams if the owner reported them.

He said the Echunga dam owner had been "very proactive" and "cooperative" and would now be working with the relevant authorities.

"He'll be speaking to the Landscape Board and also the [local] council to rectify the dam there, plus also mitigate any other risks that might happen," Mr Brassington said.

"He'll be working with SA Water because they'll make contact with him, and they'll basically follow it through that whatever he does to it gets done."

Premier Peter Malinauskas said the government would discuss the issue with the SES.

"But the fact that the landowner was able to report this matter through to the appropriate state government agencies, that allowed us to respond," he said.

Environment Minister Susan Close said she had asked the Department for Environment and Water for advice on what, if any, additional measures were required.

"It looks to me that there is a bit of a policy gap here," she told ABC Radio Adelaide on Thursday.

"So in the absence of any requirements or any monitoring by any external parties … then really it just falls back on the people who own the dams."

Independent Adelaide Hills MP Dan Cregan said it was important that "we're not casting additional and unworkable obligations on landowners".

"Most farmers are very, very careful custodians of all of the assets on their property and they're regularly inspecting every corner of every paddock," he said.

Echunga situation 'rare'

The SES and Adelaide Hills MPs all agree the situation at the Echunga dam was rare.

"With dams, we don't get too many of them," Mr Brassington said.

"Maybe because they're not so close to towns, if they happen on farms and things like that may happen and we don't even know about them.

"But something that's got a dam so close to town, it is one of the rare things."

Adelaide Hills Liberal MP Dan Cregan said the Echunga dam was built decades ago.

"These dams have been constructed according to the same methods over a long period of time," he said.

"And circumstances of the risk of failure in the way we've seen overnight are really very rare."

What causes dams to fail?

In the case of the Echunga dam, the SES said the Hills had received plenty of rainfall over the wet season and catchments were soaked.

"It's basically been caused by the rain and everything making the ground soft so it's just got a point where it normally has a spillway on the side which will allow excess out, it didn't," Craig Brassington said.

"So it almost overtopped the dam."

Engineers Australia president John McIntosh said in general, ensuring the embankment "stays watertight and doesn't leak" was key to mitigating risks of dam failure.

"Because as soon as you get leakage coming through the dam then that can erode the dam and cause failure," he said.

He said leakage could be caused by several reasons, but dams can be designed to avoid such failures.

Dr McIntosh said issues can also occur due to weather events that exceed the dam's capacity.

"Of course these [aspects] are taken into consideration when engineers are involved in designing the dams," he said.

"But engineers don't always get involved in designing the dams when it's a small dam."

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