The NSW State Emergency Service (SES) said those living downstream of the dam on Mt Brandon Road, Jerrara Rd and Jamberoo Rd are the residents most likely to be affected.

The community engagement coordinator for the SES, Andrew McCullough, said Jerrara Dam was currently being decommissioned, so the earth dam was already missing part of its wall and the SES was concerned the rest could wash away.  

He said the SES was unsure of what would happen with the dam, so have advised the small number of residents living in the rural community downstream to leave the area as a precaution.

There was no risk to residents of Jamberoo of Kiama, as there was plenty of space for the water to flow to in the area near Swamp Rd.

Flood rescue operators are in the area around Jerrara Dam as a precaution, and the SES is launching the Westpac lifesaver helicopter to do reconnaissance.

It is not the first time Jerrara Dam has overflowed, as Mr McCullough recalled a similar situation in about 2012.

Mr McCullough reminded residents to follow SES’s advice and warnings, such as to avoid driving through floodwaters as they could become trapped and require rescue.

“It is disappointing to see that some residents were ignoring the warnings and continuing to drive across floodwater,” he said.

On Monday night, about 15 rescues had to be performed by the SES across the Illawarra, mainly for people driving through floodwaters.

For people who need assistance with evacuation call the NSW SES on 132 500.