Locals had tirelessly constructed the dirt wall, building on areas where the last major flood had approached the southwest Queensland community.
"We had a flood in 2010. They were building around where it came through back then," Thargomindah local Jackie Dare told AAP.
"Everything looked good and it was holding up."
Then the levee broke.
"It didn't roll over the top. The water came through gaps. All of a sudden it just gave," Ms Dare said.
"We had just worked tirelessly making new levee banks, dumping dirt.
"But you can't fight Mother Nature when she is on a roll like that."
Few places in Thargomindah were spared, with more than 90 per cent of homes affected by the flooding.
Every business has been inundated, including the local Foodworks.
The grocery store appeared to be safe after it was rebuilt years ago above the 1974 flood record level.
Water almost one metre high still swept through the shop when the floodwaters came this week.
"This is totally unprecedented," Ms Dare said.
Floodwaters the size of NSW have inundated western Queensland, with some communities expected to be isolated for weeks.
Thargomindah has been one of the worst hit despite the locals' best efforts.
The town's entire population of more than 200 people have fled their homes.
At one stage they all relocated to higher ground at the local airport, spending the night in their cars or campervans as floodwaters threatened.
"Our airport is high and dry," Ms Dare said.
"We did have a moment there where they were a bit concerned and some people went a little bit further out but the airport never went under."
More than 100 people remain based at the local council depots, with the rest choosing to fly out.
Rain has stopped but locals have no idea when floodwaters will recede and they can safely return to their homes.
It is the worst flooding in the town's history, with 7.5m-plus levels inundating the community, eclipsing the 1974 mark of 6.78m.
They have plenty of food, with swiftwater rescue crews helping by gathering what they can from inundated shops and homes.
Ms Dare said it would be hard for some to bounce back.
The local Bulloo Shire Council has organised a GoFundMe account with almost $30,000 raised by late Thursday.
"We are pretty remote, not many people have flood insurance. I think a lot of people will really struggle," Ms Dare said.
Homes have been inundated, communities evacuated and fences destroyed across the region by flooding, triggering fears of significant livestock losses.
About 150,000 sheep, cattle and goats have been lost but the full extent won't be known until water levels eventually ease.
Assistance grants of up to $75,000 have been announced by the state government for affected primary producers.
Widespread flooding is set to continue for weeks in Queensland's central and southern inland but an end is in sight to the rain.
Showers slid through central and eastern Queensland up to the Gulf Country on Thursday with up to 140mm recorded, with the rain set to move northeast.
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