Deeside villagers fear plans to rebuild a flood bank which collapsed during a storm and left homes and businesses swamped could be fatally flawed.
And they want Aberdeenshire Council to rethink its proposals for reinstating a vital bund which burst near Ballater Golf Course.
The flood bank – built to withstand a one-in-200 year weather event – could not hold back the surging River Dee and a 4ft tide of water rushed through the community.
The bund was built in the 1990s – but the Ballater Flood Group believes a like-for-like replacement may not protect them because of changes to the river channel since Storm Frank at the turn of the year.
The floods in Ballater in December have been identified as a one-in-500 year event by experts.
Members of the group also fear the temporary sand bag defence installed between Ballater Golf Club and Salisbury Road will be removed if the embankment is reconstructed, leaving the village exposed if there is another deluge in the future.
Ballater Flood Group’s co-ordinator, Tony Cox, said a replacement of the old bank would not be “fit for purpose” following Storm Frank, which may have “invalidated the bund” as it was originally designed.
He said it had been constructed taking account of the river channel as it was when it was designed, but added the floods had “completely changed” the river.
Mr Cox said the group had consulted Professor George Fleming of EnviroCentre, who designed the original flood bank.
He added: “Significantly, the council are about to repair a 40-metre (130ft) section of the golf club bund.
“They are involving themselves in a project where the design is not robust.
“The worry we have is the work Aberdeenshire Council are doing seemingly justifies their decision to remove the deflecting sandbag barrier put there after the flood.
“We have asked Aberdeenshire Council to give us evidence to support the work they are doing.
“We are very, very unhappy and very concerned that essential protection is being removed and that work is being done with very little validity. Unless somebody cares to prove to the contrary.”
He added: “We are not a bunch of amateurs, we are qualified and we have one hydrologist who is very experienced on flooding.
“The citizens of Ballater are really, really, really nervous about the on set of winter.”
The group hopes the sandbags can be replaced with an “alternative barrier”.
About 600 homes and 100 businesses are estimated to have flooded across Aberdeenshire in the days following Storm Frank – 367 properties in Ballater alone.
The village’s flood group has proposed raising funds for a flood alleviation scheme through a public-private partnership or private finance initiative with the Scottish Government.
The first priority would be a 2ft Hesco flood barrier running from Sluivannachie, where the golf course was breached, to Ballater’s Royal Bridge.
Aberdeenshire Council’s head of roads, landscape services and waste management, Philip McKay, said: “In the context that Storm Frank was considered to be an exceptional weather event, the bund is being reinstated to provide its previous level of protection after modelling showed it would still provide protection from lesser flood events.
“To do anything else other than reinstate what was there before will require detailed study to understand any adverse impact on other locations along the river – a time-consuming process.
“Some of the work to repair the embankment along the golf course was done in January and we are about to proceed with the repair of a further 40-metre section.
“Armour stone will be placed at the toe of the embankment, earthworks will be done to reinstate the embankment to its existing profile and erosion control material installed.
“The tender also includes removal of the existing one-tonne sandbags on Salisbury Road, improving the area’s visual appeal.”
The Ballater Flood Group will write to First Minister Nicola Sturgeon to ask to have work to protect the village made a regional priority.
Members said they were taking the matter to the Scottish Government with “heavy hearts” because they had hoped to make more progress with the council.
They are also organising a meeting with Scottish Environment Minister Roseanna Cunningham.
Mr Cox said it was “simply ridiculous” Ballater was currently fifth in line for a council flood protection scheme given the events of Storm Frank.
He said: “We have suffered the worst per populous, we have suffered the worst damage in the UK. This can’t be ignored.
“We are talking about human beings, we are not talking about just cost-benefits analysis. The social impact of flooding has to be taken into account.”
