Natural hazards  |  6 Aug 2021

Banks Peninsula and some parts of inland Christchurch will get tsunami warning sirens installed if a recommended upgrade of the district’s tsunami warning system goes ahead.

Currently there are 45 tsunami warning sirens strategically located along the Christchurch coastline between Brooklands and Taylors Mistake.

However, there are no tsunami warning sirens in Banks Peninsula or in the inland areas of Christchurch that could be at risk of flooding in the event of a large tsunami.

“In the last couple of years we have received updated scientific information about which areas of Christchurch and Banks Peninsula could flood if there is a tsunami,’’ says Christchurch City Council Head of Civil Defence Emergency Management Rob Orchard.

“We have updated the tsunami evacuation zones for Christchurch and Banks Peninsula in response to that information as it shows that flooding could occur further inland than previously identified.

“Our existing tsunami warning system does not provide adequate siren coverage for the updated tsunami evacuation zones so we are recommending the Council extend the system,’’ Mr Orchard says.

The exact number of additional sirens that will be required to extend the system won’t be known until the detailed design work has been done.

The cost of the extension is estimated at $3 million and there is money in the 2021-31 Long Term Plan for the work.

Mr Orchard says extending the sirens into Banks Peninsula will fill the void for areas where emergency mobile alerts are not received due to limited cellphone coverage.

“Sirens are not a stand-alone alerting tool, but they are an important part of notifying coastal residents of a tsunami warning. Following the upgrade, when the sirens are activated a pre-recorded voice message will be played. This is an efficient and speedy way of giving instructions to coastal residents.

“The existing sirens will also be upgraded so they can be used for public addresses. This will reduce confusion for people about what action they should take if a distant source tsunami generated from across the Pacific Ocean or a regional source tsunami generated from the eastern North Island is likely to hit our coastline,’’ Mr Orchard says.

“It is important for people to remember though that if there is a local source tsunami, we will not have time to activate the sirens.

“In that case, the best warning sign is the earthquake itself.  If you are near the coast and you experience a strong earthquake that is difficult to stand up in, or lasts for a minute or more, you should evacuate immediately out of the affected tsunami evacuation zones.’’

Find out more about our tsunami evacuation zones and when to evacuate.

The Council will make a decision on whether to proceed with the proposed extension of the tsunami warning system when it meets on Thursday 12 August.

Read the Council report.