Constable Paul Mander, of Omarama, said 31 people were evacuated from the Omarama Top 10 Holiday Park about 5.30am after floodwater swept into the park.
A handful of residents were also evacuated from their homes beside the camp.
A joint operation was run by police, fire and civil defence to evacuate people to safety.
Const Mander said the Omarama Stream was well above its flood-alert level, sending water coursing down State Highway 8 near the town.
The Lindis Pass was closed on Saturday night, with up to a metre of water across the highway in places, and did not reopen until about midday yesterday because of a slip at Killermont.
The sewerage ponds at Omarama were overwhelmed with water, and some people on rural properties were isolated for a short time by floodwaters, he said.
Omarama Top 10 Holiday Park owners Win and Arda Booiman said they went without sleep on Saturday night and had warned guests to be ready to leave.
When the guests were evacuated, they were taken to the Country Time Resort, where they were looked after by civil defence staff.
Their vehicles were moved to higher ground.
Mrs Booiman said yesterday she had never seen the Omarama Stream so swollen.
Hot Tubs Omarama owner Lance Thomas said he woke at 4am to find floodwater surrounding his home and business.
He raised the alarm and rescued his neighbour's two Labradors.
Mr Thomas and his wife, Jan, who opened the business only three months ago, were forced to leave about 7.30am and he said the business would close temporarily to allow repairs to electrical equipment.
A stopbank designed to cope with a 100-year flood was overtopped.
