The findings have prompted Tamworth Regional Council, which built the dam in 1959 and still owns it, to announce it wants to move 11 owners from properties shown to be at risk from a dam break or a flood catastrophe.

The study shows those 11 properties are at high risk of loss of life because of the depth and velocity any break or flood would cause down from the dam wall.

The properties are within about 10km of the dam, down the valley towards the Port Stephens Cutting turnoff.

Those owners have been told by TRC this week that there are two options for them – the council will buy the whole property and knock down the houses on them or the council can pay them a certain amount of money to rebuild somewhere else off the property or if there’s higher ground above the flood height, then relocate there.

Either way, they can’t continue to live where they do, although there is the prospect they can continue to farm the land if they want.

Another nearly 40 properties have been assessed as being at lower risk – where the owner’s places might be inundated through dam failure or high rainfall leading to flooding but not a high risk to life – and the council wants to help them build “refuges” on higher ground where they can evacuate to during the flood.

Long-term resident and retired stock and station agent Doug Rixon has been there since 1969. His family has owned it since 1952, but the home dates back to 1885.

He reckons he’s got 10 acres of his 90 acres that is high enough to be beyond the flood height risk, so he’s contemplating a move up the hill.

“The value of the house would have to be acceptable and they would have to give us the money to spend to build another house, but I don’t know. It will be subject to the valuation but I would like to stay here,” Mr Rixon said on Tuesday.

“Yes, it would have to be a fair value and consideration included for my having to move house and build a new one.”

The Dungowan farmers were shocked to hear the outcome of the study this week – they’d turned up to a meeting thinking TRC was going to give them new early-warning system sirens, They’d been issued with sirens years ago under earlier risk assessments, the last one in 1984.

The latest study, according to TRC water director Bruce Logan, takes into account better technology allowing more accurate flood modelling and detailed analysis. 

Mr Rixon said he thought most would accept that, but like him, understand the history and lessons from the deadly Brisbane and Toowoomba dam flooding and big flash-flooding events in 2011. 

“We know the dam will probably never break but if we get big storms then there’s that sort of event to consider. And I know I’m vulnerable and you remember Wivenhoe and the Lockyer Valley, so you can’t be silly about it.”

Rixon’s property is about 7km from the dam wall. There’s about six properties above him closer to a dam that holds some 6300 mega-

litres at top level, although this week it’s sitting at about 40 per cent. By comparison, Chaffey Dam holds nearly 10 times that capacity when it’s full.

The first of the open briefing sessions starts today at Dungowan Dam between 2.30pm and 7pm and again on August 28. 

The council has invited the high-risk 11 owners, another 37 at lower risk, and about 50 other landowners who live around there.

Basically they live on Dungowan Dam Rd, on Ogunbil Rd, on the Tamworth-Nundle Rd between Dungowan Creek Rd and Dungowan-Woolomin Rd, and along the Dungowan Creek Rd.

One of those landowners, further down the road, described some of the options as impossible and laughable this week. He dismissed the relocation or refuge options as unrealistic too, saying people would be stranded up hills without any access, exits or supplies.

“And the wall has been fixed. They spent about $14 million doing that upgrade didn’t they, to make it safe? Where I live, I’ve got more chance of being killed on the freaking road than the dam wall breaking,” the landowner said. He wouldn’t be identified.

As well as being able to get up close and personal with TRC staff like Bruce Logan, those who attend will get the chance to ask questions, and receive an individual property info pack – and personal briefings. They’re designed to give landholders the nitty gritty on their place in the valley and the risk assessments.

The council has said it wants to move quickly on the buyback or relocation risk project – it’s hoping to have buildings knocked over within 12 months of reaching agreements with those involved. Obviously it also wants to get the refuge constructions underway quickly. 

The dam risk assessment for Dungowan was required to be completed by the state government. As it owns Chaffey, it has its own risk criteria and analysis. Under that, it has chosen to build extra spillway capacity to ensure it doesn’t get overtopped in extreme events. That’s part of the $43m upgrade and augmentation it has been undergoing. 

CORRECTION: A story yesterday outlining the new flood risk for Dungowan Valley farm owners mistakenly said Doug Rixon and his late wife had raised four children at their home near the creek. We are mortified to admit we got that wrong. To borrow from the famous words of Mark Twain, news of that death was greatly exaggerated. We meant of course Mr Rixon’s former wife. The mistake was entirely the fault of the reporter. We apologise and report the woman in question is alive and well.