The Gisborne District Council says the damage done by last month's flooding could take more than two years to fix.
An estimated one million tonnes of forestry slash was washed from hillsides onto roads, farms and other properties in the Tolaga Bay area during two bouts of heavy rain.
Six hundred kilometres of road had to be closed and six roads are still shut to everyone but residents.
A council spokesperson, David Wilson, said the initial cleanup would take another three months.
He said complex engineering repairs would then be needed, and that could take up to two years.
There is a heavy rainfall watch for Gisborne south of Tolaga Bay this evening and work crews are on standby.