Red-alert calendar now available

NIWA’s annual Storm-tide Red-alert calendar is now available for 2014.

The calendar predicts when especially high tides, known as king tides, may lead to flooding of roads and properties in low-lying coastal areas.

The calendar, which has been issued for about 10 years, provides an early warning for residents, civil defence staff and coastal and stormwater managers.

NIWA Programme Leader for Hazards and Risk Rob Bell says that when the high tide predictions coincide with a low pressure system, high swells, storm surges or strong winds the chances of coastal flooding are high.

“This is a very simple forecasting tool that enables people to do some planning and make decisions ahead of time.”

Dr Bell advises people to keep a close eye on weather forecasts when a red-alert tide day is predicted.

Higher tides are expected to become more common as sea levels rise and the calendar also helps raise awareness that this will be the first indication of climate change at the coast.

Sea levels have risen by an average of 2 cm per decade over the past 100 years, increasing more recently to 3 cm per decade.

In Auckland, in January 2011 a storm surge occurred on a red-alert tide day flooding houses and roads and exceeded the previous highest storm tide in 1936 by 14 cm.

Meanwhile, Auckland Council is encouraging residents to photograph red-alert high tides predicted between 1 and 4 February as part of a community project aimed at raising awareness of rising sea levels.

People can take photographs of the coast during king tides and upload their images to the internet (www.auckland.kingtides.org.nz), or via social media using Instagram/kingtidesakl. Follow the project on Twitter using #kingtidesakl or on Facebook/kingtidesakl. The longer term goal of the initiative is to target one or two king tide events per year, and expand the project to other regions.

Scott Speed, Principal Specialist Coastal, said similar projects were operating in California and parts of Australia and were a fun way of demonstrating how a “normal” tide might look like in the future with projected sea level rise.

“These tides give people an opportunity to be coastal time travellers and give them a glimpse of the future.”

The NIWA Storm tide Red-alert calendar is available free online at
www.niwa.co.nz/our-science/coasts/tools-and-resources/tides and also provides dates of “carefree tides” – when the lowest neap high tides occur with no worries of coastal flooding.

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