Building a rock wall in front of Stockton Surf Life Saving Club could further damage the beach, increase erosion, cause issues for the caravan park and it was "highly likely" to end in further loss of beach amenity.

A leaked letter from an independent expert panel set up to advise the NSW government on coastal issues, directly foreshadowed the deepening erosion crisis that has played out at Stockton over the past month.

The advice, from the NSW Coastal Panel [now Coastal Council], to City of Newcastle in July 2016 "strongly recommended" against building the controversial rock wall.

Dr Carolyn Davies, acting chair of the Coastal Panel, described the proposal as "well-intentioned, but ill-conceived".

Her letter, addressed to City of Newcastle's then acting director of infrastructure Ken Liddell - who is now leading the response to Stockton's worsening erosion crisis - warned of increased scarping at each end of the wall and further loss of sand in front of it.

Dr Davies scathing assessment of the rock wall proposal went even further. She warned if it was built the wall would "highly likely" result in the need for more hard structures needing to be built along the fading coastline.

"The REF [Review of Environmental Effects by council's consultant Royal Haskoning] document is extremely limited, failing to identify and address key issues such as the potential for increased erosion from end effects of the structure and the potential loss of beach amenity in front of the structure," she wrote.

"Council are very familiar with the scale of these problems which have been apparent from the exposure of the Mitchell Street seawall immediately to the north on several occasions... It is strongly recommended that Newcastle City Council does not proceed with the proposed structure at this stage and incorporate a more considered position of how best to manage the Stockton beach area."

Despite the strongly-worded advice, City of Newcastle built the rock wall - that stretches along the main entrance of the beach from the surf club to the caravan park - as part of a $3 million beach restoration program.

It followed extreme storm surges in June 2016 that stripped Stockton beach to a thin ribbon of sand and threatened the surf club. About 9000 cubic metres of rock was used to build the seawall that has an expected lifespan of about 50 years.

In February, north-east swells and high tides combined to create deep erosion scouring at either end of the wall, forcing the emergency removal of cabins from Stockton Beach Holiday Park at one end and sand bagging at the other to secure an unstable sand cliff.

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About 30 metres of beach frontage was secured by sandbags at the southern end of the rock wall to protect the caravan park and a severely eroded 20-metre section north of the wall, at Dalby Oval, was stabilised with sand bags.

"It is disappointing that the REF notes a response might be to monitor the coastline in front of the caravan park to the south in the event that coastal protection might also be needed there as well," Dr Davies wrote.

"It is highly likely that end effects of the proposed structure will indeed necessitate a proliferation of continued hardening of the foreshore and further loss of beach amenity into the future rather than successfully retiring assets that come under threat over time."

The surf club was built in the early 1970s and concept plans for a major overhaul and extension of the ageing facility were made public last year.

An emergency operation to remove three holiday cabins at imminent risk of being washed into the sea was carried out at Stockton caravan park in February. The caravan park is operated by Australian Tourist Park Management, a subsidiary of NRMA. The council estimates the caravan park contributes between $8.4 million and $16.8 million to Newcastle's economy annually. It returned just over a $1 million to the council in 2019.

Former professional lifeguard Noel Burns, who spent 37 years patrolling Newcastle beaches, described the Stockton surf club rock wall as a "nightmare". Mr Burns, a life member and former president of Stockton Surf Life Saving Club, spent years measuring the impact of erosion on Stockton beach as part of his daily job, and said since the rock wall was built the erosion was "much worse".

"For more than 20 years there were sand bags there and we never had anywhere near this level of damage around them," he said. "It was cutting in a bit during major events, but nothing like what has happened since the rock wall went in. I think they needed to put in more sandbags until they got sand on the beach. You only have to look at the beach now to see the impact the rock wall has had."

Aerial drone pictures taken by Stockton resident John Chesworth reveal severe scouring at either end of the rock wall and at both ends of the Mitchell St seawall.

City of Newcastle did not answer a question about why it didn't take the Coastal Council's advice, instead a spokesman said the wall was built to save the surf club.

Successive studies dating back to the 1970s have outlined the need for a long-term solution to the continuing loss of sand, but still no decision has been made on how to save the beach.

Stockton resident Lucas Gresham said inaction over decades on a long-term solution had led to the current crisis.

"The people we look to who should help provide us with a better future have let us down," he said. "Where we are right now is a direct reflection of that."

In her letter, Dr Davies outlined the long history of the problem. "Members of the Panel are quite familiar with the Stockton Beach area and its erosion history since the mid-1990s," she wrote.

"The sand-filled geotextile structure in front of the Stockton Surf Life Saving Club was itself installed during this period as a temporary measure to buy time whilst longer term consideration was given to updating and relocating threatened assets nearing the end of their serviceable life."

According to new research revealed by the Newcastle Herald last month, the erosion problem is a lot worse than previously predicted.

A comparison of NSW government seabed survey data found that between 2000 and 2018 on average 85,300 cubic metres of sand, or 136,500 tonnes, was lost from the beach every year, which is more than double previous predictions.

Severe scouring and massive sand loss at the northern end of the Mitchell Street seawall resulted in the demolition of Stockton's only child-care facility earlier this year.

The southern end of the seawall has been reinforced by emergency sandbagging.

Former Australian board paddling champion John Anderson, who has spent 50 years training on Stockton beach, said the Mitchell Street rock wall "always struggled to have a beach in front of it".

"I can only comment on the changes I've seen being a prolific user of the beach and I don't see either rock wall working," he said.

"At either end of both rock walls you see areas that are severely eroded and there is no beach in front of them. There is a lot of talk about needing a rock wall as a last line of defence, i'm not too sure about that. The beach needs sand, the state it is in now is because there is no sand."

The Mitchell Street rock wall, that was meant as a temporary solution, is the only thing that stands between the ocean and a row of beachfront homes.

Long-term Mitchell Street residents Alan and Kerrell Metcalfe and Di and Jimmy Newton said the wall had dropped about 1.5 metres since it was built in 1989.

In 2009, environmental and water consultants DHI investigated building a 2.16-kilometre seawall, north and south of the Mitchell Street wall, from the Stockton breakwater to the sewage treatment ponds.

It concluded the negative impacts of the seawall, without sand nourishment, outweighed the benefits.

Concerns included increased erosion in front of the wall and worsening erosion downdrift of the wall.

The study concluded that without sand nourishment the wall would have an unacceptable impact on the social and environmental value of the beach.

A City of Newcastle spokesman said despite the resignation last month of its chief coastal scientist Mark Manning, who was in charge of the Coastal Management Plan to identify a long-term solution for Stockton, it was on track to have the plan completed by June 30 after the NSW government brought the deadline forward.

"The only way to meet the NSW government's new deadline is to complete the CMP on a condensed scale," he said. "Through the city's existing engagement with the Stockton Community Liaison Group, we understand [sand] nourishment is a preferred long-term option of the local community."