The Tasman District Council says it could take months to clear up the damage from the week's flooding and bad weather.
The council says it will work with residents to manage changes to the Aorere River after the flood.
The river has permanently changed its course after the worst floods in the region for 150 years.
Mayor Richard Kempthorne says managing the river's new route will be a top priority for the council in coming days, along with repairing roads and bridges.
The river peaked at its highest level in more than 30 years, rising 11 metres, spreading 1km wide and flooding farms.
The council says that in early December, the Aorere was flowing at nine cubic metres of water per second, but at the height of the flooding, it increased to nearly 3600 cubic metres per second.
A spokesperson for the council, Chris Choat, says there has been significant damage to houses and roads and some bridges have been washed away.
He says the council is focusing on restoring water and sanitation to affected residents.
Mr Choat says the residents have been doing their bit by cleaning up their own properties and helping their neighbours.
He says until the silt can be cleared it will be difficult to tell the extent and total cost of the damage.