A tsunami is a series of fast-travelling ocean waves generated by disturbances like earthquakes, volcanic eruptions, landslides and even meteor impacts. On reaching shallower water a tsunami can create large onshore waves and unpredictable water flows, putting boats, coastal structures and people at risk.
Warning signs of an approaching tsunami can include extreme changes in water depths – especially a sudden receding tide – or an earthquake that is felt in a coastal area.
A boat in deep water that's well clear of the coast may be able to ride out a tsunami event safely. When a distant event has triggered a tsunami, there may be time to move a boat to deeper water. Before doing so, consider:
- The weather
- That conditions can change rapidly in a tsunami; and
- How long you'll be at sea – waves can keep coming for several hours, with the highest waves often arriving some time after the first ones.
If a tsunami is generated near New Zealand, there will be no time to move a boat to deeper water as the tsunami waves could arrive within minutes. In this case the safest strategy is to leave the boat and follow local tsunami evacuation procedures to get to safe ground.
It may be dangerous to attempt to move smaller boats from within a marina or a harbour. If there is time to do so safely, move trailered vessels to higher ground outside the evacuation zone.
- If you are already in deep water, stay out until the tsunami warning is lifted.
- Harbours can be affected for a long time following the initial tsunami impact.
- Listen to broadcasts by Maritime Radio, Coastguard, AM/FM radio stations and local civil defence for further safety information.
Tutukaka Marina is particularly prone to the effects of tsunami events. A tsunami warning system for small craft – consisting of a siren and a yellow quick-flashing all-round light – is on the marina's breakwater. When activated, it means that the marina entrance is unsafe to pass (both in and out) – skippers should contact the marina on VHF Channel 07 for further advice.
Tsunami warning light at Tutukaka Marina.