South Australian police responded to several assaults and arrested 121 people during a New Year's Eve crackdown.

Many of the arrests were for disorderly behaviour while another 29 people were reported for behavioural offences during the blitz between 7:00pm and 6:00am.

A person had part of their nose cut off when a group of men gatecrashed a party in Ottawa Avenue at Panorama at 1:45am.

Another of the revellers was stabbed.

In a separate incident, police arrested a man after another man was injured in the back of the head in a glassing attack about 2:30am.

Police say they received 1229 calls for help between midnight and 6:00am, mostly related to unruly behaviour and loud noise.

36 people were reported for drink driving while 15 drivers tested positive to drugs.

New Year's Eve fireworks are also believed to have started a small bushfire which threatened homes near Willunga South.

The fire broke out near the corner of the Victor Harbor Road and St John Terrace about 11:00pm.

New Year cheer

Tens of thousands of people made the most of a mild evening to welcome in the New Year at the beach.

About 30,000 people witnessed the fireworks display at Glenelg.

St John Ambulance says it hopes milder temperatures prevented many people from drinking too much.

Glenelg commander Simon Walter says celebrations seemed a little quieter this year.

"With the crowds we do tend to get a lot of work but it's been good so far this time," he said.

Thousands of revellers also went to Elder Park for live entertainment and fireworks.