A large group of rowdy teenagers who have potentially caused tens of thousands of dollars worth of damage to a Whangamata cafe are being described by the local mayor as "self-indulgent brats" who have "cost a family their livelihood".

There was carnage at Williamson Park near the main Whangamata surf beach on New Year's Eve as unruly youths caused chaos by climbing onto the Blackies Cafe roof, throwing bottles into a crowd of roughly 5000, damaging public toilets and knocking over rubbish bins. 

Footage also shows officers in riot gear advancing down one of the town's main roads with shields and batons. Police say behaviour escalated during the evening and 22 people were arrested after the crowd was dispersed.

Thames-Coromandel District Mayor Sandra Goudie described the group as "self-indulgent brats". Williamson Park previously hosted a concert on New Year's Eve, but Goudie says that was canned after issues. 

"We didn't want to start having the sort of riotous behaviour we had about in the earlier 2000s. We totally supported not having any events to avoid this very situation," Goudie told Newshub.

"It doesn't seem to matter what you do, they seem to just get into this self-indulgent behaviour. They have cost a family their livelihood.

"It is just a significant group of young people that were highly intoxicated. They were throwing bottles into the crowd. The breach of the liquor ban was just horrendous. The amount of liquor has just been horrendous. They confiscated enormous amounts."

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The damage to the Blackies Cafe is "horrendous", she said.

The owner told Newshub the roof was broken and the group had got into the freezer. Repairs to the structure could be worth tens of thousands of dollars and an insurance assessor is needed.

Locals had been out since about 6:30am picking up glass from across the large Williamson Park, the owner said, and they were really grateful to staff for pulling together to allow the cafe to open on Friday. 

Goudie said that on top of damage to the normally bustling cafe, youths had damaged the nearby public toilets. 

"That is going to be another unbudgeted cost on everybody's rates."

She paid tribute to the police officers who responded and said they had her full support.

"I am pretty incensed. I am backing the police all the way. Whatever they do. Whatever it takes. I am backing them 100 percent. While we are all sitting safe and sound in our living rooms… they are out there doing the hard yards," Goudie told Newshub.

"The police themselves incurred some injuries. But they are not going to worry about that, they are just getting on with the job."

Overall, police said they were happy with the behaviour of revellers out and about celebrating the New Year across New Zealand despite some disorder jobs. Sixteen people were arrested in the Auckland CBD while two were arrested in Mission Bay.

"No major problems were reported at celebrations in Mt Maunganui despite large crowds.

In Wellington New Year celebrations were generally well-behaved. Police attended a disorder job in the CBD where five people were arrested.

"In Wanaka there were five arrests, the majority were for disorder. There were multiple breaches of the liquor ban and warnings for disorder.

"Police would like to thank those that enjoyed New Year’s celebrations responsibly."