Mangawhai risks $100 million economic disaster if sandspit fails: warning

RNZ News

15-06-2025

Mangawhai Harbour Restoration Society dredge operator Mark Vercoe on the sandspit where the barge in the background pumps sand along the black pipe beside him, to keep the harbour open and build up the protective sand dune barrier known as a bund wall that protects the sandspit from harbourside-generated erosion.
Photo:
LDR / Susan Botting Local Democracy Reporter Northland
Mangawhai sandspit has recently been confirmed to have lost more than 420,000 tonnes of its locally-unique
non-replenishing sand
.
Many in the community worry about its future as a result.
Mangawhai sandspit is described as "a hotbed of coastal management considerations" by a University of Auckland academic.
The rare landform is one of just five drumstick-shaped sandspits in New Zealand. Its sand was predominantly made hundreds of thousands of years ago from volcanic explosions in the central North Island, delivered by the Waikato River.
It's at the epicentre of competing tensions between seabed sand mining, local and central government bureaucracy, New Zealand's rarest bird, community groups, conservation, harbour health, mana whenua, population growth, tourism, recreation and development.
In the first of a two-part feature, Local Democracy Reporting Northland reporter
Susan Botting
looks at what sort of health report card those connected with the rare landform give it.
New Zealand's fastest-growing coastal settlement risks a more than $100 million economic disaster if Mangawhai Sandspit fails, a community leader warns.
The stark warning is from community group Mangawhai Matters member Dr Phil McDermott, a former Massey professor of resource and environmental planning.
A second breach of the sandspit where sea washed in from the Pacific Ocean would hit the economy on many fronts, he says.
McDermott was among a range of community leaders, councils, coastal experts and government organisations who raised their fears for the spit's future with Local Democracy Reporting Northland.
They have overwhelmingly given the spit's health a bare pass of C report card, pointing to a range of reasons.
Rising sea levels and
intensifying storms
are among the issues sounding warning bells.
Community group leaders Mangawhai Matters' Dr Phil McDermott (left) and chair Doug Lloyd say the settlement's iconic sandspit is highly valued by the local community
Photo:
LDR / Susan Botting Local Democracy Reporter Northland
McDermott said the economic hit would be from plummeting property values, disappearing tourism, and fewer visitors.
"There are so many pressures including significant development," McDermott said.
Mangawhai Matters has successfully legally challenged unfettered Mangawhai development.
The sandspit breached in 1978 after a huge storm. The resulting 600 metre channel split the three kilometre long, 3 square kilometre spit in half for more than a decade. The breach led to today's main northern harbour entrance filling up with sand as Mangawhai Harbour discharged via a new exit point to the sea. Renegade action by the local community known as "the Big Dig" opened the channel.
Looking east across Mangawhai sandspit where sand from adjacent Mangawahi Harbour is piped onto prescribed locations under a formal Department of Conservation concession.
Photo:
LDR / Susan Botting Local Democracy Reporter Northland
The blockage led to stagnating harbour water. House prices fell and properties weren't selling. Banks in some cases did not want to provide mortgage lending.
Work to open the blockage and close the breach finally started in 1991.
Mangawhai Sandspit's at the epicentre of competing tensions between seabed sand mining, local and central government bureaucracy, New Zealand's rarest bird, community groups, conservation, harbour health, mana whenua, population growth, tourism, recreation and development.
Mangawhai Matters community group chair Doug Lloyd said surveying showed the harbour and sandspit were rated the most important feature of their local area.
When Lloyd arrived in Mangawhai in 1989 there were about 600 people there.
Now there are up to 20,000 over the summer peak.
And there are more than 2000 new houses on the cards in several big developments.
Mangawhai Harbour Restoration Society chair Peter Wethey.
Photo:
LDR / Susan Botting Local Democracy Reporter Northland
Mangawhai Harbour Restoration Society (MHRS)'s Peter Wethey chairs the community group credited by many as having had a key role in the spit surviving to the degree it has.
The society runs New Zealand's only dredging operation of its type, sucking up sand blown into the sea from Mangawhai Sandspit and putting it back onto the rare coastal landform.
Wethey said the dredging was about keeping the harbour's ever-filling navigation channels open and protecting the spit with an about 800 metre long harbourside bund - effectively a man-made sand dune strip edging to protect it from future breaching.
Longtime MHRS dredge operator Mark Vercoe said the process of sustainably delivering sand from the harbour floor to the prescribed location, that continued to strengthen spit protection, was an exacting one.
Just over 5000 Kaipara District Council (KDC) Mangawhai Harbour catchment ratepayers pay $80 annually towards the society for its work.
Kaipara Mayor Craig Jepson said that money was well spent to protect the spit, echoing many in the community by saying the group had to navigate significant bureaucracy to do its work.
Jepson said he believed too much of the society's funds and time were being wasted on bureaucracy when they were better spent on taking action.
Mangawhai Harbour Restoration Society pumps sand from the local harbour back onto the spit each year.
Photo:
LDR / Susan Botting Local Democracy Reporter Northland
Northland Regional Council (NRC) governs consenting for the dredge's sand extraction with up to 50,000 cubic metres of sand dredgings allowed annually. More recently that quantity was not fixed but instead dependent on location and dredging depth.
Dredging must take place between April and December each year, depending on where it happens and the values of those locations - outside the fairy tern breeding season.
DoC rules on where the dredgings can go on the spit.
DoC acting operations manager - Whangārei Sarah Newman-Watt, said the Mangawhai government wildlife refuge reserve was protected for its ecological significance, particularly for its critical nesting habitat for New Zealand's
fairy tern/tara-iti
and northern dotterel.
She said the sandspit was the country's largest tara-iti breeding site with fewer than 45 individuals left.
Fairy Tern Trust convenor and Mangawhai property owner of three decades Heather Rogan said the spit was critical for the bird's future. It was currently home to all but one of New Zealand's tara-iti nesting sites.
University of Auckland coastal geomorphologist Professor Dr Mark Dickson said it was about how well the spit would do its job of protecting the Mangawhai community.
The work of the community was essential.
Mangawhai Sandspit's man-made, but looking quite natural, protective 800m long bund wall on the sandspit's western harbour shores.
Photo:
LDR / Susan Botting Local Democracy Reporter Northland
Thousands of sand dune plants, kilometres of sand fencing to trap sand, pest control work and dredgings from the harbour going onto the sandspit towards maintaining its resilience are among this work.
Dickson said the spit would undoubtedly breach again if left to its natural cycles without this community input.
"The spit's not quite holding its own. It requires quite a level of intervention," Dickson said.
Save Our Sands spokesperson Ken Rawyard gave the spit a D health report card.
He said DoC was prohibiting the re-establishment of critical vegetation cover on the spit due to concerns about the fairy tern.
Newman-Watt said this was not the case.
It was actively encouraging the re-establishment of appropriate dune vegetation - where it supported the sandspit's health and resilience and did not conflict with conservation goals.
Fairy terns needed open shell patches with very little to no vegetation for nesting.
"At known nesting sites, DoC removes or limits vegetation to preserve these rare habitat conditions," Newman-Watts said.
Mangawhai sandspit was a dynamic system that required careful, site-specific management.
NRC local coastal south councillor Rick Stolwerk acknowledged there were processes that needed to be navigated before the dredging began.
He said the spit was not faring as well as it could, but community members were doing great work.
Te Uri o Hau Environs representative Cindy Hempsall did not want to comment on Mangawhai sandspit when approached by Local Democracy Reporting Northland.
LDR is local body journalism co-funded by RNZ and NZ On Air.