"The same thing happened when they cut down some of the willows with chainsaws, and they just threw the branches in the river," said Mr Watt, who has lived in the neighbourhood for over 50 years.
"It ruined the swimming hole. The branches got stuck between the stones, which ruined it for fishing and swimming. Everything's dangerous now.
"It's a really worthwhile area for swimming but people aren't coming much to swim now."
He is also concerned the branches will pose a flood risk.
"The branches will get swept away by the river and the river will get blocked up.
"There can't be that much building up of rubbish in the river, otherwise there will be a flood."
Mr Watt, who often patrols the river banks in search of rubbish, discovered the willow trees were being cut down around six months ago.
"I heard the machines working and wondered what the noise was," he says.
"I took the dog and went to see what it was all about."
He discovered a group of workmen felling the trees, using large machines. At the time, he did not know who the men were working for.
"I got moaned at when I tried to talk to them about what they were doing. They weren't very nice at all."
He says he is angry that, even though the trees were felled some time ago, the resulting mess has not been cleaned up.
"They need to get rid of all the branches, even if they have to get a prison gang in to do it. It makes the area look bad. It's not just bad for me, but bad for everyone. Lots of people go down to the river."
The regional council's Wairarapa flood protection section leader Mike Longworth said the council had assessed the willow trimming at the River Rd entrance to the riverbanks and was disappointed with the outcome.
"We consider the stumps are too long and the debris too coarse for an urban road entrance," he said.
"This needs tidying up. We will get a machine in to lower the stumps and further mulch the branches as soon as possible.
Mr Longworth said the council planted willows for holding riverbanks together and protect them from erosion, and arranged for them to be trimmed if they got overgrown. He said the river had not been blocked by tree felling in the past but the council would assess the area again before summer to check if remaining debris could pose a risk to swimmers.