Wakatu is the largest land owner in the valley.
District councillors have cut their funding for refurbishment of the stopbanks from more than $16 million to $5 million in its draft long-term plan.
Councillors say planning is due to begin in 2017, with the project to be completed by 2030.
But Wakatu Incorporation chief executive Paul Morgan says investigations show the some of the existing stopbanks are poorly compacted and cannot hold water for more than six hours.
Substantial flooding would cause millions of dollars of damage for businesses and homeowners in the area, so the project needs to be given priority, he says.
Mr Morgan says that when councillors meet on Wednesday he will urge them to change their minds.