Civil Defence logo. Porirua's Tsunami Risk

This page explains what a tsunami is and Porirua's tsunami risk.

What is a tsunami?

Tsunami produce a series of very low, but extremely fast-moving long waves or surges. They can be an hour our more apart and move at speeds of 600–700 km/hr in the open ocean. At the coast they slow down and steepen up to sometimes produce breaking waves. More commonly though, they cause a very rapid onshore flow of water, like going from low tide to high tide, to a higher tide in minutes. In doing so, they can cause widespread coastal inundation. Much of the damage comes from debris being pushed along in the flow – trees, building materials, vehicles, and boats.

What is Porirua's tsunami risk?

While we face a low risk in the region of a distantly generated tsunami (such as the one from the Japan quake on 11 March 2011), we are still very much at risk from tsunami created by a local source, such as the faultlines off our coast. There are signs of a 15 metre high tsunami dating from the 14th or 15th Century along Porirua's western coast.

However the 14 November 2016 Cheviot earthquake did result in Marine and Land tsunami alerts for the East Coast of the North and South Islands. There was no or a very low threat to Porirua harbour.

For specific tsunami zones in the Porirua region, visit our tsunami evacuation zone page.

For a general overview of tsunami evacuation zones in the Wellington region, read our brochure – It's Easy – Know your tsunami zone (727KB pdf)

Go to the WREMO website for the latest updates, or the Ministry of Civil Defence website.

Watch this video on How Tsunamis work.