Cyclones AND tsunamis, double trouble! Research highlights need for integrated marine hazard warnings
New research published in iScience into mariners’ experiences during the coinciding 15 January 2022 Cyclone Cody and Hunga Tonga volcanic tsunami events highlights the need for integrated thinking about the combined impacts of these rare but possible events.
The Hunga Tonga Hunga Ha’apai volcanic eruption – the largest eruption in a century –generated a tsunami that prompted a beach and marine threat advisory in Aotearoa New Zealand. At the same time, a severe weather warning was issued for ex-Tropical Cyclone Cody, producing heightened swells along the North Island coast.
While mariners were already sheltering in place with the longer advanced warning for Cyclone Cody, the research suggests marinas and boat owners were less aware of, and therefore less prepared for, the compounding threat posed by the rapid and unexpected eruption of the Tongan volcano. The Tutukaka Marina in Northland was particularly affected by the coinciding events, with several boats severely damaged or sunk.
Research lead author and GNS Science Hazard and Risk Management Scientist Dr Sara Harrison says the 2022 event shows that mariners require information on the combined magnitude of impacts from multiple hazards. They need to understand the danger concurrent hazards pose to the marine environment, including information about expected wave height and arrival time, weather, and sea conditions, so they can best assess and decide their response actions.
“Based on our research, we recommend all agencies involved in communicating about and warning for hazards in New Zealand coordinate closely with each other to provide frequent and focused information on the combined magnitude of impacts from multiple hazards.
“Once warnings are issued, it is up to boaties to assess their own level of risk and follow safe boating practices.
Having information on the timing, location, and impacts from single and multiple threats offers people more certainty to make decisions about their life safety and their property, whether used for business, recreation, or in some cases, a home.
The research also suggests marinas and boating communities should work with their local emergency management groups to develop response plans for both high-magnitude and low-magnitude tsunami threats that pose a risk to life and marine property.
“Ensuring response plans are fit for boaties’ needs and are well socialised before a tsunami threat, can help increase the awareness and response capabilities in boating communities,” Dr Harrison says.
Dr Harrison also recommends response plans should include coordinated and community- or marina-led evacuation drills both by foot and by boat to improve the community’s ability to respond to a tsunami threat.
“This would help boaters make quicker and more informed decisions about when and how to evacuate from the threat area, with or without their boat.”
The research recommends response plans should include:
- information about the tsunami risk to that locality
- how to identify natural warning signs and what to do if they’re observed
- information about the current tsunami warning system in New Zealand
- how people can expect to receive official tsunami warnings
- actions to take when an official tsunami warning is received
- where to go for more information
- if, when, and where boats should go offshore before tsunami arrival, and when to return.
“It’s important that we don’t overlook the threat posed by smaller, more frequent events, and strive to keep boating and coastal communities safe. We can do this by developing effective communication strategies with them so that they are aware of the enhanced risk to them and what to do in the event of a beach and marine threat.”
The National Emergency Management Agency advises that for more information or advice about what to do to prepare for or evacuate from a tsunami, boaties are encouraged to talk to their local Harbourmaster and CDEM group.
The research was funded under the Ministry of Business, Innovation and Employment Global Change through Time programme.