Earthquakes, landslides, and other geographic disturbances that have the potential to generate tsunamis can happen at any time with little to no notice. Having a plan for what to do when a tsunami is generated is key to ensuring the safety of yourself, the crew, your passengers, and the vessel.
Generally, it is NOT recommended that boaters try to take their vessels offshore before or during a tsunami if you are on land, tied up at dock, or nearshore. In those situations, your personal safety should be the priority, and the best way to ensure that is to leave the boat and move towards higher ground. If you are already offshore when you receive a Tsunami Advisory or Warning, it is recommended that you remain at sea and get to deep water; do not try to re-enter the harbor until local officials indicate it is safe to do so. If you have to remain at sea, you should move to a safe depth until the danger has passed. Safe depths vary by region, but the minimum safe depth for the United States is 30 fathoms (180 feet). For more specific guidelines, take a look at this table or contact your local harbor master or port captain.
Tsunamis are a series of waves with strong and unusual currents which create hazardous ocean and harbor conditions for days. In order to prepare for tsunami events, build an emergency kit to ensure you can be self-sufficient onboard your vessel. These kits should have enough food, fuel, and supplies to last at least three days. If you live on your vessel, ensure you have up to two weeks of emergency supplies located outside the inundation zone. If you’re on land when a tsunami is expected, make sure you know your local evacuation routes and establish a kit in that safe location.
Tsunami alerts are important for understanding the severity and timing of an incoming tsunami. Tsunami Warnings indicate tsunami wave heights exceeding 3 feet along with very strong, dangerous currents and inundation of dry land. A Tsunami Advisory indicates wave heights of 1-3 feet, along with strong and dangerous currents in harbors and channels. A Tsunami Watch can be a precursor to a Tsunami Advisory or Warning and indicates that an incident occurred that may generate a tsunami far from your location, so be prepared for additional information that could lead to safety actions.
It’s critical to have a reliable way to receive tsunami alert information while at sea. When a Tsunami Advisory or Warning is issued, the U.S. Coast Guard will broadcast the information on your marine VHF radio channel 16. Additionally, make sure you talk with your harbor master or local emergency services office to find out what notifications you can sign up for locally. The latest tsunami forecast information can be found on the tsunami.gov website and will be broadcast on NOAA Weather Radio.
Sources:
Guidance for Safe Minimum Offshore Depth for Vessel Movement for Tsunamis
