Fiordland's Deep Cove hostel has been closed to overnight accommodation until further notice, after a preliminary report has found the site to be potentially at risk.

The report, commissioned by the Department of Conservation, followed a heavy rainstorm in the area on 1st June which sent water, trees and debris down a valley, washing out a section of the Wilmot Pass Road, demolishing part of the hostel's shed and damaged their hydro electric intake.

Debris blocks a section of Wilmont Pass Road after a heavy rain event near the Deep Cove hostel in June this year. Photo: Supplied

Trust chairman Mike Macmanus said that while DOC had judged the immediate risk tolerable to fix the road, the report looking at the general area had been "quite sobering" to read.

MacManus said the report highlighted the possibility that in a similar event, where logs jammed in different places, the entire site could be at risk.

"We've got maybe approximately $4 million worth of buildings."

"Someone's got to do the calculation and go what's the likelihood," he said.

"Without those numbers we're all just playing guesses, and nobody wants to play guesses with children and people's safety."

MacManus said that while he hoped it won't be a long and drawn out process, the hostel's facilities could still be used during the day.

Visitors and volunteers would however have to stay either on a boat or possibly at West Arm.

"We have probably on average had about 20 [volunteers] every weekend for the last nine weeks," he said.

MacManus said the Deep Cove Outdoor Education Trust had considered what the report could mean and if there were alternative positions buildings could be put.

"We're certainly looking at those options.. [but] to put some mitigation in place is going to be a lot easier," MacManus said.

St Peter's College in Gore had been due to send their Year 8s to the hostel.

College Principal Tara Quinney said students had been studying Deep Cove as part of their social study classes, and while really disappointed for their students, they understood that health and safety had to come first.

She said the camps were hugely important for students bonding and growth.

"Most of the kids have never been on a boat or out in a lake [or] experienced that kind of beautiful natural habitat."

"It's just such a fantastic experience."

"Having an overnight in a far away place, away from their parents, and how they learn to work together - we actually see the benefits of Deep Cove for the next five years," Quinney said.

Quinney said they had experienced similar cancellations with COVID so knew how to adapt, and were already looking at alternative camp places for Term 4.

The Deep Cove Hostel has a full time manager and caters to around 2,500 children every year, with most coming from Southland and Otago.