Camp co-ordinator Mel Helm said the camp was situated between two fords, crossing the Silver Stream, in Silverstream Valley Rd.
However, heavy rain over the weekend made the fords impassible for much of yesterday.
She said the water was so swift and high at times, not even a four-wheel-drive vehicle could cross the fords.
"I definitely would not cross that ford — no."
She said the people staying at the camp were adults, there for a family celebration, and were not in any danger as long as they stayed at the camp.
Without help, they would have been stuck there until today, when the flood waters receded.
However, some of the campers needed to get out before then in order to return to Christchurch, so they contacted police.
Ms Helm took responsibility for the group and used a little known four-wheel-drive track to access the camp, and ferried all 18 of them out in small groups along the track.
She said they had to leave their vehicles behind and were dropped off in Mosgiel.
They would be able to return during a short weather window today, to collect their vehicles.
"I’d rather that than have them risking their lives going over that ford or anything," she said.
In July 2022, a 29-year-old woman died after her partner drove his new four-wheel-drive through one of the swollen Whare Flat fords and got washed away by the floodwaters.
The weekend’s heavy rain also caused many slips and crashes around the southern regions.
State Highway 90, between Tapanui and Waikoikoi, was closed yesterday due to flooding, and other highways in the region were down to one lane or partially blocked.
Several vehicle crashes were reported on state highways in the lower and central South Island on Saturday morning, and there were also reports of slips affecting the highways, including State Highway 88, between Dunedin and Port Chalmers.
The rain cleared late last night, but more is forecast around the southern regions tonight.
MetService has issued an Orange heavy rain warning for the headwaters of the Otago lakes and rivers, from 1pm today until 9pm.
Between 70mm to 90mm could fall about the main divide and up to 70mm could fall within 15km further east, and peak rates of up to 20mmh could fall about the divide.
People were urged to make sure their drains and gutters remained clear, avoid low-lying areas, and drive cautiously.
"Streams and rivers may rise rapidly. Surface flooding, slips, and difficult driving conditions are possible."
On wet, slippery roads, motorists are advised to reduce speeds, increase following distances, watch their visibility, and brake carefully.
MetService also urged residents living in Queenstown Lakes District, Central Otago, Clutha District (north of Tapanui) and Southland (north of Riversdale) to prepare for strong northwest winds which may approach severe gale in exposed places, between noon and 9pm today.
