A man was rescued from the Reid Falls Flume after falling 50 metres down a cliff near the Otira Gorge Rock Shelter Lookout on the South Island's West Coast.

A tourist spent about 18 hours trapped on a steep, slippery aqueduct – with only a rope and tussock between him and certain death – after falling 50 metres down a sheer rocky cliff on the South Island's West Coast.

Police have apologised for incorrectly saying the man became trapped after ignoring safety signs and scaling a look-out barrier to take photos of the Otira Gorge, where the survival tale took place.

An NZCC Rescue Helicopter spokesman said he fell while hiking on an old "zig-zag road" about 9.30pm on Sunday, landing in a gully above State Highway 73.

NZCC Rescue Helicopter The man remained on the flume for about 18 hours until crews abseiled to him from above.

Badly injured and unable to walk, with his car parked at a look-out back by the highway, the man crawled for about three hours to get down a gully in the hope of being found, he said.

"He knew he was going to die if he didn't get down the cliff," the spokesman said.

Finding a rope in the gully, the man descended onto the Reid Falls Aqueduct.

NZCC Rescue Helicopter A man was rescued from the Reid Falls Flume after falling 50 metres down a cliff near the Otira Gorge Rock Shelter Lookout on the South Island's West Coast.

There, he tied himself to a tussock-type plant to stop himself from falling to the rocky riverbed below.

Tourists at a nearby lookout spotted the man just after 10.30am on Monday.

A Fire and Emergency New Zealand spokesman said four fire crews, police crews and two rescue helicopters attended the scene.

NZCC Rescue Helicopter A man was rescued from the Reid Falls Flume after falling 50 metres down a cliff near the Otira Gorge Rock Shelter Lookout on the South Island's West Coast.

He said helicopter crews found it difficult to rescue the man due to the downdraught at the flume.

An alpine cliff rescue and FENZ lines crew, called in from Christchurch, abseiled down to the man and secured him in a basket to be winched to safety just after 3pm. The man was then flown to Christchurch Hospital with broken bones and cuts.

A NZCC spokesman said the man was lucky to be alive.

"He could have been easily killed in the fall."

A NZCC spokesman said it was a great combined effort between the various emergency teams.

"It was a pretty good operation with a really good outcome," he said.

After the rescue, police said he was trapped for three hours and it was a "timely reminder to all people out walking or climbing to obey all warning signs near rock faces and cliffs – the signs are there for a reason, and if you ignore them, then this is what can happen".

On Tuesday, police conceded their statement now appeared to be incorrect.

"All we can really do at this point is apologise for the error," a spokeswoman said.