Rock falls and slips at Cape Kidnappers were identified by the Department of Conservation as a "significant" and "unacceptable risk" a decade ago, documents obtained by RNZ show.

Photo: Supplied / Hastings District Council

The walk along the Cape Kidnappers beach under the cliffs to the famous gannet colony at its point attracts thousands of visitors a year.

But the walk has been closed to the public since two South Korean tourists were swept out to sea and seriously injured by a massive slip on 23 January.

An investigation into the department's "risk assessment and consultation processes" was now being carried out, DOC said.

A risk assessment of the walk dated 6 September 2017, released under the Official Information Act, identified rock falls, slips, tidal and rogue waves and seals, all as "unacceptable risks" to the public.

A prior assessment in 2009 also identified rock falls, slips and tidal waves as "unacceptable risks".

The 2017 assessment, done just one day before the launch of a multi-million dollar campaign promoting Cape Kidnappers as a Great Walk, recommended a geotechnical survey of the hazards be carried out.

Engineering firm OPUS was engaged to do this, but only for DOC's assets, including the cliff top track, toilets and lookout. An assessment of the hazards relating to the beach walk was not done.

The OPUS report, which was was not completed until two months after the campaign launch, advised relocating the track and DOC facilities because of erosion issues along the cliff tops and because the current facilities may not cope with the expected increase in visitor numbers.

OPUS' investigations were based "primarily on a desktop study and site walkover. No sub-surface testing was conducted," its report stated.

About 25,000 people a year visited Cape Kidnappers and 15 percent of those, or 3750, opted to walk along the beach to see the gannet colony, DOC estimated.

Visitor numbers were predicted to "triple" in the coming years, it said.

Gannet Beach Adventures, which runs tractor tours to the colony, said it warned DOC about the dangers of including Cape Kidnappers in its Great Walks campaign because of the unstable cliffs and the danger it presented to the public.

Emails between DOC staff members in September 2017 show they were also concerned about the "significant risks" to the public.

"This site has a number of considerable visitor risks issues that will only be raised with the proposed promotion," a DOC technical adviser said in an email to a colleague.

Gannet Beach Adventures owner Colin Lindsay said he was never consulted about the proposed campaign and only found out after it was launched.

Consultation documents released by DOC show Gannet Beach Adventures was consulted, though DOC admits "the timing of consultation is unclear and this process is being reviewed."

DOC also had "concerns about the risk assessment", it said in a statement to RNZ.

"We take this matter and the safety of visitors extremely seriously.

"Immediately after the incident we initiated an internal investigation to examine our processes, identify underlying causes and inform future work" DOC heritage and visitors director Steve Taylor said.

DOC would not be in a position to comment until this investigation was complete, it said.

Cape Kidnappers beach remained closed until a geotechnical survey commissioned by Hastings District Council was completed. That report would be presented to the council at its next meeting on 5 March.