Mining permit holder Daniel Midgley, of Cromwell, said he owned the 600kg gold dredge, which went missing on Monday.
"I still think it’s up the Nevis somewhere," he said last night.
The Nevis River was flowing at 188 cumecs on Monday as a result of heavy rain.
"It usually flows at 10 cumecs ... the river came up about 3m or so."
Mr Midgley believed a dead tree floating down the river ripped the dredge from its mooring.
He doubted the $30,000 dredge, which his family had owned for about three years, would be found.
The family built the "prototype dredge", which had been "working well".
For commercial reasons, he declined to reveal how much gold the dredge had harvested.
The 24km gold claim the family owned in the Nevis Gorge exited near the Nevis Bungy, he said.
Two cargo boxes with diving and camping equipment were also washed away. If the dredge was not recovered, the family would build another one, Mr Midgley said.
The family owned two dredges so the mining operation was able to continue. In a statement, police warned river users to take care because of concern someone could hit the missing dredge. It was moored 1km down from the bridge at the bottom of the dell in Nevis River. Police wanted to hear from anyone who had seen the dredge or boxes.
● Cromwell police (03) 445-1999.
