Environment Canterbury (ECan) described the flood event as ''significant''. The campground was extensively flooded by about 1m of water at its peak.
A council spokeswoman said 120mm and 140mm of rain was recorded over a 20-hour period, most of it falling in six to seven hours on January 22.
This is the largest flow in the river since the damaging South Canterbury floods of 1986.
About 30 caravans and tents were on site when the flood occurred and people were evacuated and taken into Otematata.
Waitaki District Council recreation manager Erik van der Spek said while the actual costs of the clean-up were yet to be determined, they consisted of staff and contractor time associated with the evacuation and inspections.
He said the flood banks were badly damaged, the ground's boat ramp was undermined and the channel out to the lake was full of debris.
''The boat ramp and camping ground has been extensively damaged and it will be several months before it is expected to be reopened. People who have season passes have the option to have 50% of the fee refunded, however, they can also choose to use their passes at the other council-owned camping grounds.''
Mr van der Spek said work was now under way to help protect the camping ground. In addition, the NZ Transport Agency was assessing the State Highway 83 bridge, a main entry point to the township.
''It is unlikely the risk will be able to be fully mitigated and we may need to consider if this is a site where camping should continue.''
