While parts of Queensland's iconic coast will likely be reshaped by the now category 1 system, things could have been a lot worse, beach erosion expert Dr Darrell Strauss said.

"The forecast three days ago was looking pretty bad," he said.

"Obviously we have very high waves with the cyclone sitting offshore but fortunately it decided to change its course."

A combination of king tides, massive waves and storm surge has pushed water higher up the beach than normal, eating into the coast.

"It is a little bit early to tell but it will definitely be reshaped, it will be noticeable," Dr Strauss said.

"Our beaches were in really good condition prior to this event they were in a good condition to withstand what is happening and a lot depends on the state of the beach before the storm hits."

Extra sand dumped on parts of the Gold Coast ahead of last year's Commonwealth Games likely saved the world famous coast from more disastrous erosion, he said.

"I think a lot of it will depend on what happens next and what type of weather arrives after the event.

"If we return to mild weather for an extended period of time, then the sand that has moved offshore at the moment could come back."

Bureau of Meteorology Queensland manager Bruce Gunn said Cyclone Oma is “a very large cyclone” about twice the diameter of Cyclone Debbie, and while now rated a category 1 system, was forecast to re-intensify to Category 2 strength and maintain this strength for some time.

"We will certainly continue to keep a close eye on this cyclone, until it no longer poses a threat,” he said.

"The main impacts are damaging winds along the coastal fringe and big seas, well into next week. We're observing waves of 3-4 metres waves along the Sunshine, Gold and Tweed coasts with offshore waves in excess of 10 metres.”

The latest BoM bulletin said abnormally high tides and dangerous surf conditions were expected along the southern Queensland and far northern New South Wales coasts into early next week.

"Beach erosion is likely to continue with the hazardous marine conditions," the bulletin read.

But Dr Strauss said the coast has endured worse erosion.

"This is not the biggest we have seen. Since the mid-'90s there has been four or five bigger individual storm events," he said.

"In 2009 and 2013 we had a series of storm events fairly close together so the combined affect can be as big as a single storm.

"But it has to be remembered that the catastrophic forecast is entirely possible still, so I think it was a good reality check for everyone."

Cyclone Oma weakened and was downgraded on Thursday night, resulting in the weather bureau cancelling its cyclone and flood warnings.

However, the huge swell and associated beach erosion were expected to continue along the southern Queensland coastline, with all beaches on the Gold Coast and most on the Sunshine Coast closed.

Premier Annastacia Palaszczuk warned residents from the central Queensland coast down to the New South Wales border against camping, boating, fishing, swimming or surfing this weekend.

Gale force winds with gusts greater than 90km/h, are still expected to pummel parts of the southeast Queensland and far northern New South Wales coasts during Saturday.