Emergency services at the scene of the crash. Photo: Wyatt Ryder
The man has been airlifted to Dunedin Hospital after being treated at the scene for more than two hours.
The cyclist was travelling down Severn St about 11.30am when he cycled into the deep drain and came off his bike, Acting Sergeant Neil Rushton said.
He suffered a laceration to the head and a broken arm.
Nobody else was involved in the incident, he said.
Hato Hone St John spokesperson said they were treating one patient in critical condition.
One ambulance and a first response unit attended the accident along with the rescue helicopter.
