At 1.30pm on Thursday, January 7 the water level at Lake Cathie reached 1.611m, according to the Manly Hydraulics Laboratory.

The Lake Cathie Opening Strategy outlines the lake is only to be opened when the lake water level is at, or exceeds, 1.6m or falls below 0.2 metres with high salinity, if optimal conditions allow.

The waterway opened in May last year after the sand berm was scraped between Lake Cathie and the ocean, in response to a council vote.

Read more: Lake floodwater at Lake Cathie released to the sea after epic seven hour dig

The lake was also artificially opened to the ocean in July 2018 when the water level had risen beyond the 1.6m trigger point.

"Council has a management responsibility in terms of flood mitigation particularly in respect of private property and major infrastructure which is triggered at 1.6 metres, in accordance with the Lake Cathie Opening Strategy that is currently under review," a Port Macquarie-Hastings Council statement released on Thursday said.

"A traditional lake opening will not be undertaken but rather the high sand berm will be scraped back to a level of 1.6m, allowing floodwater to escape before flooding sewer infrastructure.

"Ideally, the water level will remain high and allow the lake to continue to repair itself, locking up the iron in the sediments and avoiding further exposure of acid sulphate soils.

"The community should also be aware that if works are undertaken heavy machinery will be used to scrape the beach berm, and it is advised to keep clear of the work area to ensure their personal safety.

"Infrastructure including footpaths and stormwater drains may already be flooded, however residents can be reassured that homes are not deemed to be at risk at this point in time and there is adequate buffer before sewer infrastructure is inundated."

The water quality in Lake Cathie and Lake Innes has previously been impacted by the exposure of acid sulphate soils resulting in a visible red substance on the surface of the lakes.

Read more: Lake Cathie/Lake Innes water investigated after red substance raises concern

Read more: Lake Cathie advocacy groups say waterway is a public health risk

Revive Lake Cathie president Danielle Maltman said scraping the berm north to south is the preferred option, rather than digging a channel from east to west.

"The main issue is acid-sulphate soils and as a group we aren't looking at any more man-made expansions such as an opening of the lake," she said.

"The reasoning behind that is when the lake is opened it activates the acid-sulphate soil in Lake Innes. As the tide comes in it poisons everything in its wake like sulphuric acid.

"The more and more we intervene with mother nature, the more it is going to react in a bad way until the sulphate issue is addressed. So we have to wait for council to complete the Coastal Management Plan, at the directive of the state government, so the quicker they can get that done the better."

Lake Cathie resident and Saving Lake Cathie member Stewart Cooper said the entire process is incredibly frustrating for local residents.

"We're very frustrated with the lack of communication on this whole thing. We wrote to council in September to ask them to work out what they'd do when it floods again - they acknowledged it and we received no response," he said.

"Where are they getting this information that the lake will repair itself, because they've refused to fund any studies into acid-sulphate soils.

"When are they going to start communicating with the community in advance of these things rather than reacting to these things. It's incredibly frustrating, they appear to be doing everything possible to delay doing anything realistic with the lake.

"Our suspicion at the moment is that scraping of the ocean berm down to about 1.5m would at least alleviate flooding and retain water in the lake. But council need to get these studies done so we know the best way to fix the lake and can access government funding."

Tourists and local residents have been continuing to use Lake Cathie for swimming and fishing during the post-Christmas holidays, despite current warnings not to.

Members of the public are advised not to swim in Lake Cathie or Lake Innes or eat any products from either of the lakes until further notice, according to NSW National Parks and Wildlife.

A safety alert for poor water quality in Lake Cathie and Lake Innes was applied from July 3, 2020 and reviewed on November 19 last year.

NSW Health advice recommends members of the public not to swim within 24 hours of heavy rain at ocean beaches and within three days in estuaries or rivers.

Thank you for valuing local journalism with your subscription. While you're with us, you can also receive updates straight to your inbox from the Port Macquarie News. To make sure you're up to date with all the news, sign up here.