Officials were repeatedly warned of fears that flood defences in a Lincolnshire town would fail, it has been claimed.
Nearly 600 homes in and around Wainfleet were evacuated after heavy rains caused the River Steeping to burst its banks on Wednesday.
Lindsey Marsh Drainage Board (LMDB) said it had spent the last eight years raising the issue.
The Environment Agency had blamed "unprecedented" rainfall.
The equivalent of about two months' rain fell in two days, forcing 1,000 people out of their homes and flooding nearly 130 properties.
The LMDB is one of 112 internal drainage boards that manage low-lying watercourses around the country.
Chairman Giles Crust said he was "absolutely furious".
"We have been telling the Environment Agency for 20 years that this will happen, but forcefully for the last eight years we have been banging the drum that that wall will collapse," he said.
"It should never have happened in the first place. That bank should have been safe.
"There were ways to prevent that water running through the breach by putting a stop at the end of the cut."
The agency, which is responsible for maintaining the river, said the area was "very low-lying".
Mike Dugher, flood risk manager at the agency, said: "We've got a continual programme of maintenance of the river banks in this area and when you get such unprecedented rainfall with two-and-a-half month's worth of rain in two days then the system just gets absolutely full.
"The system once it's full, becomes overwhelmed and as water has got to go somewhere, it's come over the defence at Wainfleet."
Stuart Peltell, who lives in Wainfleet, said: "They ought to stop trying to make the river a wildlife habitat and turn it back into a proper drainage channel, which is dredged out and cleaned so the reeds and the silt can't hold the water."
The agency said river levels were falling slowly but would remain "very high for the next few days".
Two flood warnings remain in place for the River Steeping.
Husband and wife Kevin and Jean Hart said they "lost everything" in their recently renovated house when it flooded.
"It's pretty horrendous really," said Mrs Hart, "There's water up to our chest."
Mr Hart described how their belongings were "floating" in the house.
"Within the hour it literally went from ankle depth to knee depth and the next day it was up to my waist."
Friends of the Earth campaigner Guy Shrubsole said: "We need to work with nature to reduce flooding, not against it."
People evacuated from their homes may not be able to return until Friday as further rain is expected on Tuesday and Wednesday.
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