Our eroding nation: Battle for the dunes

By SIMON COLLINS

There are no signs of long-term coastal erosion at Papamoa Beach. But even here, the local Tauranga District Council wants to define "hazard zones", which would encourage residents to shift back from the seashore.

The Papamoa case, which will go before the High Court this year, raises the question of whether planners are becoming so cautious about erosion that they are blocking development unnecessarily.

Alternatively, it might be seen as a case of rich and privileged property owners seeking to keep living on the beachfront, despite rules which require everyone building from now on to stay well back from the beach.

An aerial view of Papamoa makes the point starkly. Almost right along the 17km sweep of the magnificent white sand from Mt Maunganui to the end of Papamoa Beach Rd, development has been set back well behind the sand dunes.

Only two pockets of buildings have been allowed into the sandhills east of the main road - at the Papamoa Domain (shown in the photograph), and in another pocket around Taylor Rd, Motiti Rd and Karewa Parade (just below the bottom of the photo).

The pocket around Taylor Rd was the first to be developed for housing in 1956. Most of the early buildings were holiday baches, and even today 60 per cent of the 122 beachfront property owners live elsewhere.

All the experts agree that there is a seaward bulge, or "cuspate form", in the coastline at Papamoa where the sand has built up over the centuries behind the shelter of an offshore island, Motiti.

Professor Terry Healy of Waikato University, who has drawn "hazard zones" for councils along the coast at Waihi Beach and elsewhere, says: "I agree there is a tendency for long-term accretion [sand buildup], especially in the lee of that island."

However, Dr Jeremy Gibb, a coastal consultant who drew the hazard zones for Tauranga, told the Environment Court that global warming was likely to bring more storms in the future.

According to the court judgment, he felt this could "cause a reversal from a long-term trend of very slow shoreline advance, and a current state of dynamic equilibrium, to a trend of long-term shoreline retreat".

This long-term trend would be exacerbated by the recent switch from a phase when southwesterly "El Nino" winds predominated over New Zealand from 1977-98 to a new phase of more northeasterly "La Nina" winds, bringing stronger waves in the Bay of Plenty.

On Dr Gibb's advice, the council adopted four zones, ranging from an "extreme risk" zone covering the first 30 to 50 metres at the beachfront back to a "safety buffer zone" stretching as far back as 100 metres in places.

Although Dr Gibb and Dr Healy have been on opposite sides in other court cases, Dr Healy supports the hazard zones because of the coast's inherent volatility.

"The cuspate form could reverse if the sediment transport patterns reverse."

Anyway, he says, a hazard zone does not mean a disaster is guaranteed.

"A hazard zone is a zone in which, on the balance of probabilities within the next 100 years, there is going to be a hazardous situation."

But for Wayne and Annette Skinner, who have lived on the beachfront at Taylor Rd for eight years, the council's decision to draw an "extreme hazard" line through their house has real consequences.

"In the extreme zone we can't remove or prune any native tree, can't build anything, can't excavate. You probably can't even put up a barbecue or build a little patio out the front," says Mr Skinner, a real estate agent who is leading the High Court challenge against the hazard zones.

He says the fact that the council has identified a "hazard" makes it hard for beachfront property owners to get mortgages from banks or insure their homes. Subdivision is prohibited or discretionary, and any new buildings must be relocatable.

"A number of the properties down there are little old baches that have been there for 50-odd years, and a lot of people are looking to upgrade to better houses and some want to subdivide," he says.

"Another effect which is important is the effect these zones have on other property owners' values.

"If these zones are correct and stay in place, then what prudent buyer would buy a property believing that at any time in the next 100 years they could lose 30 metres of their property?"

Mr Skinner and other residents have spent more than $300,000 so far on lawyers and other experts to challenge the council.

Keith Smith of the National Institute of Water and Atmospheric Research (Niwa) gave evidence based on monthly monitoring since 1989 showing that the ebbs and flows of sand at Papamoa were all on the beach itself, not on the residents' properties.

Auckland coastal engineer Dr John Abbott and Australian consultant Dr Terry Lustig said the extent of sand movement in the bay meant that any rise in sea level could be matched by drawing in more sand from offshore, so it would not cause any automatic threat to houses.

Of course, as Mr Skinner accepts, there is some risk living anywhere by the sea. But then, he says, residents in say Rotorua or Wellington accept the risks of living beside geysers or near a fault line.

* Tomorrow: Crop land at risk.

Herald feature: Environment