The weather event lasted two days but repairing the damage in its wake will take years.
That bleak assessment was given to the Wanganui District Council this week by council staff and rural support teams.
Matthew Smith, council's emergency manager, said the floods and heavy rains that swept through the region and across much of the lower North Island on June 20-21 created the largest event the city's Civil Defence organisation had had to deal with "in living memory" .
He said they were fortunate to have help from other members of the Manawatu-Wanganui Civil Defence and emergency management group who provided rolling shifts of support staff.
"CD staff from Wellington and Waikato also supported our operations centre, while Police, Fire Service, Ambulance, Red Cross, Army and other agencies provided additional resources over an extended period," Mr Smith said.
He said the event also highlighted how easily Wanganui can be cut off from outside support by road.
In the urban area, he said, the flooding occurred when the tides were at their lowest. "If it had occurred the following week, when tides were higher, flooding would have been over a bigger area."
Kevin Ross, council chief executive, said repairing the damage across the region would take from three to five years and most of the work would occur outside this financial year.
He said about 90 per cent of the damage to urban roads would be fixed over the coming summer, while rural repairs would carry on over the next two summers.
Mr Ross said they were hoping to have a complete wrap-up on the damage and costs complete before Christmas.
"But there's a lot of work still going on relating to the event in the city and in the rural area, and that will take a hell of a lot of time to sort through," he said.
Councillors also received an update from the Ruapehu-Whanganui Rural Support Trust, which said two and a half months after the event they were still getting calls from people, mainly asking for some sort of social assistance.
Brian Doughty, Wanganui Federated Farmers president and a member of the trust, said the trust would be offering support to those affected "for however long it takes".
He said the pressure will come on many when the financial year ends "and they haven't finished the recovery work".
"There's still a whole lot of stress and pressure out there in the farming community," Mr Doughty said.