Christchurch businessman Antony Gough is "sore and bruised" after falling asleep at the wheel of his BMW and crashing down a bank.

The rich-lister rolled his white SUV near a bend on the Christchurch-Akaroa Highway on Tuesday afternoon.

The car ended up between two trees in a creek, 10km south of Tai Tapu.

Gough was hospitalised but was discharged last night.

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The multi-millionaire city property owner told of his lucky escape on Facebook.

"Water started to come in and then it started to fill with smoke," he wrote.

"I was worried we would either drown or be caught in a fire. The car felt like it was going to roll onto its roof. Very scary."

His partner Vicki Holland was also in the car at the time but is also fine.

His BMW is a write-off, which Holland said would be her third one.

- additional reporting by Christchurch Star