Planning needed to protect coastal properties

Those Auckland seaside properties might have a great view, but with storm surge flooding occurring more frequently when there are king tides, there can be a downside.

A king tide is a high tide that occurs several times a year, and can result in usually dry land being flooded.

Around 65 per cent of New Zealanders live within 5km of the sea,with 12 of our 15 largest towns and cities built there.

NIWA says sea level rises are a prompt for coastal dwellers to consider how to approach future development.

"It's mostly about risk,"says NIWA principal scientist Dr Rob Bell. "Rises of more than a metre by 2100 can't be ruled out, and should at least be considered in assessing the vulnerability of our existing development at the coast."

He says New Zealand's Coastal Policy Statement says the country needs to avoid further increasing risk in the future. Large new subdivisions and developments should be built to cope with even higher rises in sea level.

Dr Bell says there's still time to plan and Auckland Council is already well aware of the risks for this city.

"We've been assisting Auckland Council with storm tide innovation and tsunami warning systems. Sea level rise is going to be one of the ongoing challenges for Auckland, which is a developed city with historic development in the lower-lying coastal areas.

"As sea-levels rise, there will be an escalating risk from sea flooding in low lying coastal areas, where a present-day 100-year flood event could occur every year when sea-level rises by 0.5 m," he says.

Higher storm surges can damage beaches, seawalls, buildings, roads and other infrastructure; they may also affect drinking water supplies in lowland rivers and groundwater.

The New Zealand Climate Change Centre (NZCCC) is holding a two-day conference (May 10-11) looking at the subject of rising sea levels and the challenges this brings. The conference, to be held at Te Papa in Wellington, will include keynote speeches from leading international scientists

Scientists will analyse recent projections for sea-level rise and discuss the uncertainties associated with these projections. Such projections are critical because they are used to identify anticipated impacts on New Zealand's coastal areas and buildings in those areas.

Dr Bell says there are two key things councils need to consider for future-proofing communities.

"One is building-in climate change infrastructure into everyday asset management, for example road upgrades, storm water upgrades. The second is for some of the higher priority areas to come up with long term adaptation plans

"Planners and engineersin New Zealand need sound guidance on what sea-level rises are expected along our shores, working around the key uncertainty about how quickly the polar ice sheets may melt in future," says Dr Bell.

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