Little Granity School versus the sea

DEIDRE MUSSEN
Last updated 05:00 25/06/2012

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Spectacular views across the Tasman Sea and wild coastline are a daily offering from Granity.

The only problem is, those views threaten to swallow the tiny West Coast beachfront township.

Granity School is in the midst of a David and Goliath battle with the sea, desperately trying to halt its relentless erosion of land.

This year, it got $60,000 from the Ministry of Education to renew a temporary gravel stopbank, which was finished last month.

However, the sea has already breached the wall in recent storms, highlighting its expensive futility.

Experts have known for at least six years that new solutions are needed to protect the township, but the sea's march inland continues.

A report by the National Institute of Water and Atmospheric Research (Niwa) in 2006 on erosion at Granity said landward migration of gravel barrier beaches was typical.

Doug Ramsay, a Niwa coastal hazard consultant who wrote the report for the West Coast Regional Council, says the main cause is relatively stable sea levels over the past 6000 years. That means insufficient fresh gravel enters the beach system, starving it and forcing its retreat at a rate of about 40 centimetres a year at Granity.

"For most of the coast around New Zealand, there isn't much fresh sediment coming in," he says.

Storms also destroy the gravel barrier, worsening erosion. In 2006, he noted the school's gravel stopbank was near the end of its life.

"However, given the location of the school and swimming pool relative to the retreating beach, there needs to be serious consideration given to the landward relocation of these buildings/facilities," he wrote.

He also warned property owners, particularly at the northern end of Granity, to plan an exit strategy as erosion worsened.

In 2007, Mr Ramsay wrote a report for the ministry about the school's erosion issues, again recommending moving some buildings and the pool as a long-term solution.

"The school has always tried to push the coastline out and the sea is fighting back," he says. As a result of the school's stopbank, its property protrudes further out into the sea than neighbouring areas "and the sea doesn't like that".

The stopbank would be a "very short-term" solution and rising sea levels will worsen the problem.

New Zealand's sea level has risen about 16-17cm in the past 100 years and while it is unclear if climate variations rather than global warming have caused it, scientists predict it will speed up, he says. Unfortunately, erecting permanent barriers, such as a seawall, can cause erosion in neighbouring areas, as another West Coast township discovered earlier this year.

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Mr Ramsay suspects the seawall protecting Punakaiki properties is partly to blame for Punakaiki's beach vanishing in a big storm in April.

Granity School principal Megan Rich says the gravel stopbank at the front of the school hadn't been topped up for about four years, but the ministry funded the $60,000 price tag to strengthen it over about a month after Easter.

The school board has been considering options to address the erosion and another idea has been some planting. It plans to discuss the issue further with the regional council and ministry to work out a more permanent solution.

Ms Rich makes it clear there is no chance of the sun setting on this school while she is at the helm.

"Where there's a heart, there is a beat."

- The Timaru Herald

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