Senior Sergeant Anthony Bond said police monitored large groups of students gathering in the student quarter throughout the evening.
Evening festivities were marred by a 22-year-old student who was taken to Dunedin Hospital in a serious condition after falling from an internal balcony.
He was found unconscious and with blood coming from his ears.
He was currently in ICU in a serious but stable condition, Snr Sgt Bond said.
The incident came hours after a 19-year-old fell from a Castle St roof and was transported to Dunedin Hospital in a serious condition, about 2pm.
About half an hour after that incident unfolded, a nearby flat party on Queen St was shut down early due to the large numbers in attendance.
The occupants were generally helpful and compliant, Snr Sgt Bond said.
About 8.30pm police responded to a report of a man being hit with a glass bottle on Castle St.
Upon investigation the victim was found to have to have fallen to the ground and hit his head on a bottle, he said.
A St John spokeswoman said they transported one patient to Dunedin hospital with moderate injuries.
Later on Castle St, about 10pm, a male student was arrested for using obscene language at a police officer, Snr Sgt Bond said.
The 18-year-old has been referred to the proctor.
A party on Castle St began playing music from a second-storey balcony.
It was quickly shut down about 22.30pm and a large crowd dispersed.
By midnight, Castle St was ‘‘virtually empty,’’ Snr Sgt Bond said.
Police attended a Butts Rd address where music was turned off and a crowd of 100 were dispersed without issues.
The occupants were ‘‘pro-police and great to deal with’’, Snr Sgt Bond said.
Throughout the afternoon large numbers of students, mainly first years, congregated at Brackens Lookout, with 300-400 being noted at 6pm.
The throngs finally dispersed around 10.30pm, Snr Sgt Bond said.
The injuries which marred the day were preventable and tied up emergency services, preventing them from attending other emergency calls throughout the day, Snr Sgt Bond said.
A Castle St resident described the day as ‘‘massive’’ and said he was very hungover.
