NORTHERN Beaches residents have expressed their frustrations over the water level at Woolgoolga Lake, and what they say is inaction by council to safeguard nearby properties.

Coffs Harbour City Council artificially opened the lake last week after it reached the trigger height of 1.6m above sea level, however some say council was too slow to act and any rain last weekend would have caused properties to flood.

Sunset Caravan Park resident Pam Berry said the water level was a constant worry for those living nearby.

"When the water gets to 1.6m, we generally have to wait for them to come out and open it up," Ms Berry said.

"If we get a heavy downpour, in half an hour we're flooded.

"We started ringing council on Thursday and across the weekend - we're all there being told it's going to rain and there will be thunderstorms, knowing the water level will rise and there's a threat of flood."

Ms Berry said water quality in the lake and connecting Woolgoolga and Jarrod's creeks was being affected.

"We're constantly asking the council to come and clear the lake," she said.

"The water that's in there now is absolutely putrid.

"It's filthy - there are dead fish all along the creek.

"In about a five metre distance, there were four dead fish.

"The bigger issue here is the harm to the environment.

"I used to swim in the lake when I first moved here - I wouldn't even walk across it now."

Ms Berry said it was time for council to act.

"Council needs to look at the broader picture and not look at us as if we're just whinging.

"I think the lake needs to be opened more often or, even better, I think the whole upper part of Jarrod's Creek needs to be piped.

"I know piping would cost a lot of money but if it were in Coffs Harbour this would be done.

"This is the environment we're talking about."

A council spokeswoman said the 1.6m trigger point for opening the lake had recently been reviewed.

"A NSW Public Works water level gauge continuously monitors the water level of Woolgoolga Lake and council accesses the gauge data online," she said.

"The 1.6m level is a trigger point for council to initiate artificial opening of the lake.

"The trigger level and opening strategy was reviewed during the community consultation in the Woolgoolga Floodplain Risk Management Study and Plan, which was adopted at the last council meeting on February 25.

"The level is a balance between allowing the lake to open through natural processes and minimising flood risk to properties.

"Council was aware of the level of the lake and took action at the appropriate time."

The spokeswoman said recent hot and dry weather was a factor which affected water quality.

"Woolgoolga Lake is an ICOLL - an Intermittently Opening and Closing Lake or Lagoon," she said.

"These are ecologically sensitive coastal features that are protected by state legislation and can only be artificially opened in certain circumstances.

"Generally, ICOLLs open naturally due to rainfall and this also results in a flushing of the lake.

"During dry and hot periods - such as we've been recently experiencing - a breakdown of organic matter can occur which may affect water quality.

"Since the lake has been opened, the resulting flushing action will help improve the water quality."