Flash flooding brought a deluge of pine plantation slash and logs down a Northland river devastating farm properties in its path.

Dairy farmer Greig Alexander reckons he will spend the next two weeks cleaning up the mess and fixing fences and snapped posts after an early-morning downpour yesterday swept pine plantation "rubbish" through his property on Opouteke Rd.

He said more needed to be done to hold forestry owners to account so debris did not enter the Opouteke River, which feeds into the Mangakahia River, and cause damage for farm owners downstream.

The latest flood had swamped some paddocks were Alexander had stock and he was up at 3am yesterday to check they were not being washed away.

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"I looked at one group of cattle and I could see a bunch of eyes staring back and not swimming so I went on to the next lot," he said.

He said he had checked the MetService weather report the night before but said the deluge was unexpected.

As day broke the damage became clear.

"There was the usual debris, slash and logs. There were whole trees and they go through the wires and snap posts," he said.

"Whole trees with root balls get washed down and act like battering rams."

While there was a substantial amount of damage to clean up there was some relief it was not as bad as the July floods two years ago when there were four downpours that continually washed through forest debris.

Alexander, who has been farming the block of land for more than 40 years, said in the early years he did not have such a problem as there were no pine plantations being harvested in the area.

"Once they started harvesting all the cuttings seemed to get in the waterways."

Police had reports of Mangakahia Rd being closed because of floodwaters at about 9.30am yesterday. Vehicles, including a milk tanker, were unable to pass through.