In May 2013 a council officer noticed a digger was working near the river adjacent to the defendant's farm and six separate areas of earthworks were found, involving about 5300 cubic metres of earth. Wilson said he thought he was allowed to do the work.
The court heard his illegal works had increased the river's velocity, increasing flooding and creating more erosion. The excavated material was deposited into the river and had discharged into the harbour.
The work had permanently moved the river channel, increased sediment discharge to the river and increased instability of the river banks. The total cost of remedial works is estimated to be $63,000.
Regional Council Pollution Prevention Team Leader Steve Pickles said the penalties of more than $110,000 sent a powerful message about the potential consequences of carrying out unlawful river works.
"The sentence imposed on Mr Wilson should dissuade any farmers or contractors in the Bay of Plenty who are tempted to embark on an unauthorised stream or river works project with a digger," he said.