Civil Defence, Natural hazards  |  23 Feb 2021

Christchurch and Banks Peninsula residents who live or work near waterways or the coast are being encouraged this month to find out if they are in a tsunami evacuation zone.

“Living close to the water means that we do need to be prepared for tsunamis,’’ says Christchurch City Council Head of Civil Defence and Emergency Management Rob Orchard.

“In the past 18 months we have updated the tsunami evacuation zones to reflect new tsunami modelling that Environment Canterbury, in collaboration with the Christchurch, Selwyn and Waimakariri councils, commissioned GNS to do for Christchurch and Banks Peninsula.

“That modelling indicates significant damage could be caused by flooding from a distant or regional source tsunami. In some scenarios the modelling shows that we could get flooding further inland than previously thought.

“We are working with affected communities to help guide them with their tsunami evacuation planning, but I would really encourage everyone to go onto the Council website and check whether their property or their workplace is in a tsunami evacuation zone,’’ Mr Orchard says.

The website has an interactive property search function that allows you to see which evacuation zone, if any, your property is in. It also has advice about what steps you should take to prepare for an evacuation.

In Christchurch and Banks Peninsula there are three main evacuation zones – the red evacuation zone ,the orange evacuation zone, and the yellow evacuation zone.

The red tsunami evacuation zone is the area that is most likely to be affected by a tsunami. It includes estuaries, rivers, beaches and harbours, where a tsunami of any size could cause strong currents and surges in the water.

The orange tsunami evacuation zone covers areas on land that could be flooded in the event of a large tsunami.

The yellow zone is an area that is least likely to be affected by tsunami, but could be flooded or isolated in a very large tsunami.

“If you are in a tsunami evacuation zone, it is important that you find out what you need to do in the event of an evacuation and start putting a plan together,’’ Mr Orchard says.

“Nature is unpredictable and we could find ourselves in an emergency situation at any time. People need to be prepared for a tsunami event and have a plan of action.’’

Mr Orchard says while there is likely to be some warning of a distant or regional source tsunami hitting our coastline, there is likely to be very little warning of a local source tsunami.

“If you’re near the sea or in the red or orange evacuation zones and feel a rolling-motion earthquake for longer than a minute or a strong earthquake that makes it hard to stand up, you need to leave. When the shaking stops, head immediately to the nearest high ground or as far inland as you can, out of the red and orange tsunami evacuation zones,’’ he says.