By SIMON COLLINS



"Everyone who hears these words of mine and puts them into practice is like a wise man who built his house on the rock. The rain came down, the streams rose, and the winds blew and beat against that house; yet it did not fall, because it had its foundation on the rock.



"But everyone who hears these words of mine and does not put them into practice is like a foolish man who built his house on sand. The rain came down, the streams rose, and the winds blew and beat against that house, and it fell with a great crash."



(Matthew 7, 24-27)

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Building on sand has not had a great reputation for the nearly 2000 years since Jesus delivered that homily in his Sermon on the Mount.



But on the sandhills at Cooks Beach on the Coromandel, where the invading sea has undermined a makeshift seawall, beachfront bach owner Ray Clarke recently turned down a $700,000 offer for his land because a section further along the beach sold this year for $1 million.



Plenty of people are still prepared to pay for a sea view, even at the risk of their houses falling "with a great crash".



New Zealand's erosion problem is not just a matter of soil being washed into the sea at 10 times the world average - a problem likely to be worsened by the cyclonic storms that are expected to become more frequent as the world's weather heats up.



The other half of the problem, which New Zealand shares with the rest of the planet, is that the warmer weather has raised the average sea level at the Port of Auckland by about 14cm in the past century and is expected to raise it by a further 30cm to 50cm by 2100.



Coastal erosion, which already affects 80 per cent of the world's coastlines through purely natural processes, is tipped to worsen as the rising seas bring higher storm waves.



A Government report last year warned: "Sea-level rise will eventually lead to permanent inundation of very low-lying margins, episodic sea flooding of higher margins, increased coastal erosion, salinisation of adjacent freshwater, drainage problems in adjacent low-lying areas, and further coastal squeeze where shorelines are held and constrained by structures such as seawalls."



A map prepared by Professor Terry Healy of the University of Waikato classifies most of the North Island coastline as "erosional", including most of the west coast north of Wanganui, much of eastern Northland, Auckland's east coast, the northern Coromandel, Waihi Beach, Matakana Island and most of the East Cape.



Cooks Beach is shown as "accretional (with episodes of erosion)". But that is not how it seems to Ray Clarke, who has owned his seaside bach there for 39 years.



"Every year the tides are getting higher and stronger," he says.



In 1978, a big storm swept away the bach's front lawn and upstairs balcony.



"The volunteer fire brigade got all the furniture to the back to stabilise the house," Mr Clarke says.



He and his wife and other beachfront bach owners got trucks in and laid rocks along the front of their houses. Mr Clarke put up a timber frontage to hide the "untidy" rocks - only to return from a day in Whitianga to find the rocks undermined by the waves and the timber largely washed away.



Thames-Coromandel District Council forward planning manager Peter Wishart says the wall was built on public property without a consent, and is illegal.



Property owners, led by Auckland lawyer Peter Kemps, have developed a plan for a new wall, but Mr Clarke says he would have to contribute $38,000 to it. Few have signed up to the plan.



Ron Dale, who built his family bach a few doors down from the Clarkes in 1964, walks 17m out to sea to show where his front lawn once ended. The last 4m disappeared just six months ago.



But he pays $2400 a year in rates and refuses to pay $30,000 for the new wall.



"They want megabucks," he says. "In Wellington it cost only $40,000 to do the lot [to protect a whole beach]."



At Wainui Beach near Gisborne, another rock wall was installed after a 1992 storm grabbed 8m off the lawns of property owners such as Margaret Jefferd, whose family has owned the section for 50 years and lived there for 20 years. "When we bought the section there was quite an area of grassy sandhills in front of it. One had a paddock with cows," she says.



But when the Herald visited a month ago, the waves were lashing the rock wall just below Mrs Jefferd's terrace and almost engulfing Gisborne District Council engineer Dave Peacock on some wooden steps that once led to the beach.



In between, the sea has waxed and waned several times. After the 1992 storm, the beach was spared for several years - until this year. "We can see the old tree stumps that we haven't seen since 1992," Mrs Jefferd says.



At Wainui, as at Cooks Beach and around the world for at least the past 2000 years, the only certainty about the sea is that it is constantly changing.



Despite its history, property values on the Wainui beachfront have doubled in the past three years. Some people, it seems, will always choose to live on sand.



* Tomorrow: Councils urge "retreat"



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