North Canterbury switches to single tsunami zone for easier evacuation

The colour has changed but the message remains the same when it comes to tsunami risk, says Waimakariri's civil defence spokesperson.

The old yellow, orange and red tsunami evacuation zones in North Canterbury have been changed to a single blue tsunami evacuation zone, as part of a nationwide move to make it easier for people to know what to do.

Waimakariri District Council's civil defence portfolio holder, councillor Jason Goldsworthy, said around 10,000 of the district's residents were living within the new blue tsunami evacuation zone.

"A tsunami could arrive within minutes or a couple of hours.

"If you're near the coast and feel a strong earthquake, don't wait for an official warning or an emergency mobile alert.

"You should immediately make your way outside of the blue zone."

While a tsunami triggered by an earthquake in South America could take at least 12 hours to arrive in New Zealand, an offshore tsunami could arrive within minutes, meaning there may be no warning.

Cr Goldsworthy said residents should be aware that congestion could become an issue, should a tsunami hit on a hot summer's day.

"There may be hundreds of people at our beaches needing to evacuate at a moment's notice.

"If you can, choose to walk, run or cycle rather than drive."

The Canterbury coastline has been hit by five damaging tsunamis since European settlement, with four originating from South America, according to Environment Canterbury.

The largest was the 1868 Arica Tsunami, generated by a magnitude 8.5-9.0 offshore earthquake near the Peru / Chile border.

The tsunami took 17 hours to reach the Canterbury coastline, but it damaged jetties, bridges, fences, houses and boats in Banks Peninsula and Pegasus Bay river mouths.

Other tsunamis originating in South America in 1877, 1960 and 2010 did less damage, but caused strong currents and inundated land in similar places to the 1868 tsunami.

The 7.8 magnitude earthquake in November 2016 is the only damaging local-source tsunami since European settlement.

The first waves reached the Kaikōura coast within 10 minutes and deposited debris, seaweed and sea life up to 6.9 metres above sea level.

Waves also hit Banks Peninsula about 1.5 hours later, inundating land in Pigeon Bay and damaging a cottage at Little Pigeon Bay.

In the Hurunui district, residents in Claverley / Conway, Gore Bay, Motunau, Hurunui River mouth, Amberley Beach and Leithfield Beach are now in the blue tsunami evacuation zone.

Some Leithfield residents who were previously in the yellow zone (low risk) are no longer in an evacuation zone.

Residents from Ashworths Beach to Woodend Beach, including Waikuku Beach and Pegasus, and Kairaki, The Pines Beach and low-lying parts of Kaiapoi are now in the blue tsunami evacuation zone.

But several parts of Kaiapoi which were previously in yellow or orange zones have not been included in the new blue tsunami evacuation zone, so residents should check council maps.