Whangamata surfers have called on the Department of Conservation to investigate after a 4m high dune slumped away at a busy beach access, leaving ladders hanging in the air.
Recent storms carved the escarpment and revealed planks that locals say have been buried since the 1980s and 1990s.
Surfer Paul Shanks has called on DoC to step in, saying Thames-Coromandel District Council has directed stormwater to the dunes, adding to their instability.
"DoC is liable for all this infrastructure that is on DoC land and foreshore. It is now endangering the users of Whangamata beach and surf spot," he says.
"Less than 12 months ago the TCDC reconfigured the back of these dunes to take newly sealed car park stormwater. They put in huge soak pit and the rain over the last weeks has been able to concentrate under the dune.
"The dune-sand has become liquefied at a great depth, and so when only a moderate swell touches the dunes, they collapsed."
TCDC coastal scientist Jamie Boyle says the dune erosion is not a manmade problem.
"The dune erosion is completely natural and the active dune that has lost sand is doing exactly what it should be doing and providing a buffer for wave energy. The area is being monitored and the beach accessway upgrades will occur once the current erosion event settles down."
He said the stormwater upgrade work near Williamson Park would ease the increasing demand on this part of the network, and the current beach scarp evident along Esplanade Drive and other parts of the beach impacted by recent storms and swells would have "very little influence" from one stormwater outlet.
"We would expect a small amount of scour within 1-5m either side of an outlet, but not the area-wide erosion that is currently visible."
Further drainage improvement started last week in Lowe St to reduce the impact of water ponding on the road and into low-lying properties. This project would reduce surface flooding draining on to adjacent properties and on to the dunes and beach area, he said.
But Shanks and fellow surfer Taff Kennings are among residents critical of work in the vicinity, including a proposed boardwalk on dunes where the erosion has occurred.
TCDC proposed to build the boardwalk from Whangamata Surf Club through dunes, eventually to Hunt Rd. It wants feedback on a 10m trial section near the erosion zone.
Whangamata pioneer surfer Kennings said planks uncovered nearby had been buried for years, proving infrastructure on top of the dunes was futile.
"But they [the council] keep wanting to build things."
He says the project relies on the advice of coastal scientists: "They just don't seem to want to learn from the residents here who have the knowledge.
"It will come back. But if you keep building things and don't really need them, you're just
creating something that's falling apart every few years."
He said in the 1980s, those on the "dole" had to build fences along the beach to retain the dunes. "This was built then and pops up when this happens."
In December last year TCDC gave residents options to select one of two routes - either higher up on the dunes or closer to the sea.
The Coastal News reported the council's response to concerns over ecological impacts and consultation, that no consent was required since it was a permitted activity in its District Plan.
However, DOC Hauraki operations manager Avi Holzapfel says any activity on DoC-administered land requires an approved permit or management agreement with DoC in consultation with Hauraki iwi.
He said TCDC contacted the department in January 2020 for permission when a title search confirmed the land was under DoC jurisdiction.
"As of today, TCDC has not yet submitted a formal proposal for the boardwalk. The only formal request for approval is the application [for] a short trial section of 10m for three months," he said.
Other than permitting, DoC's primary interests were ecological and ensuring local iwi are consulted and engaged, he said. It had had discussions with TCDC about the wider project since December 2019.
After strong winds last week, the trial section had already been partially covered by sand.
Taff said a hole in the sea in front of the dunes had been "eating" the dunes away and another low pressure was coming across the Tasman this week that would "chew it out more".
An online survey can be found at: www.tcdc.govt.nz/Your-Council/Council-Projects/Current-Projects/Whangamata-Boardwalk-Project/
TCDC says anyone can contact project manager Ross Ashby on 027 510 9079 or email firstname.lastname@example.org.