The Nugget Point area had 40mm of rain, which caused the slip.
The Clutha District Council was notified at 7.14am about the slip and the road was closed as it was completely blocked.
It reopened to the public at 4pm with a temporary 50kmh speed limit due to the clay residue on the road.
Resident Marilyn Dunn and her husband were out doing their usual morning activities when they noticed the boulders.
The boulders bent the barrier railing and had covered the road, she said.
One of their neighbours could not get to work and had to take the morning off.
"It was just enough to do a bit of damage, that’s for sure", Mrs Dunn said.
The last time a slip this bad happened was about five years ago, she said.
"The boulders from way back then didn’t wash away for years.
"It was definitely a bit of excitement for the day, but there’s always something going on at the Nuggets."
The temporary speed limit for the road will be reassessed this afternoon.
