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Guide

Tsunami: what to do on the Gulf

Checked September 28, 2026 against the National Tsunami Warning Center, the National Weather Service, the National Hurricane Center, NOAA’s National Centers for Environmental Information, the U.S. Geological Survey, the TAMUG Tsunami Research Group, the Governor’s Office of Homeland Security and Emergency Preparedness, the Louisiana Department of Transportation and Development, the Louisiana Department of Health and the parish and city alert pages linked below.

The Tsunami tile repeats what the National Tsunami Warning Center has said. A tsunami on this coast is rare, and this page says plainly what is and is not known about one, what each alert level means, how to get your parish’s alerts, and why the water that usually does the harm here comes from a hurricane instead.

If the Gulf does something strange, go to high ground or inland now. The National Weather Service’s natural warnings: a strong or long earthquake; the sea rising like “a fast-rising flood or a wall of water”, or draining away to show the bottom; or a loud roar from the water. Any of those means a tsunami “could arrive within minutes.” Do not wait for an official warning, a phone alert or this website.

Who warns this coast

The National Tsunami Warning Center in Palmer, Alaska, issues tsunami messages for this coast. NOAA gives its area as “coastlines along the continental United States, Alaska, and Canada”, and that includes the Gulf. Its first messages are built from the earthquake’s location, depth and magnitude, often before any wave has been measured, and they are updated, upgraded or cancelled as more information comes in.

What is actually known about the Gulf

The U.S. Geological Survey’s summary is short: tsunamis on the Atlantic and Gulf coasts “are rare, but the risks associated with these natural hazards are high.” The source studied most is not an earthquake fault but an underwater landslide on the steep continental slope far offshore. The TAMUG Tsunami Research Group, which maps the Gulf’s hazard for NOAA’s National Tsunami Hazard Mitigation Program, writes that assessments by the USGS and the programme “identified underwater landslides as the primary potential source”, that the probability of a massive one is “quite low”, and that the large ancient slides were probably active more than 7,000 years ago. It adds that sediment still empties into the Gulf “mainly from the Mississippi river”, steepening the slope, and that preliminary modelling of sources outside the Gulf, such as earthquakes along the Caribbean plate boundary, has indicated “a very low threat”.

The record agrees. NOAA’s historical tsunami database lists five entries for Louisiana, and none of them is a tsunami from the Gulf. The one with the most deaths, Grand Isle on September 20, 1909, is marked as an error; NOAA’s note begins “Not a tsunami, but a storm surge” and names the Grand Isle hurricane. Two come from the 1964 Alaska earthquake, whose seismic waves set the water sloshing in the rivers and bayous around New Orleans: NOAA’s notes call them seiches, with “peak-to-peak amplitude of approximately 6 ft (1.8 m)”, and say “considerable damage was done to many boats and barges”. One is the 1811 New Madrid earthquake, felt at Lake Bistineau far inland in the northwest of the state. The last is 0.05 metres — about two inches — on the Grand Isle tide gauge after the January 2022 eruption at Tonga, on the far side of the world. Nothing in that record is a warning to wait for, which is why the sea’s own signs above come first.

The map

The Tsunami Research Group has drawn one tsunami inundation map for this coast, for Grand Isle. It shows the combined maximum flooding from nine modelled source events — five identified ancient landslides and four synthetic ones — and it says what it is for: it portrays “the worst case scenario”, gives no estimate of how often such an event happens, and “is intended for local jurisdictional, coastal evacuation planning uses only” — “not intended for site-specific or land-use purposes”. Read it as the outer edge of what is possible, not as a forecast.

What the alert levels mean

In the warning centre’s own definitions and recommended actions:

Getting an official alert

Wireless Emergency Alerts come to a capable phone with nothing to sign up for — the weather service’s words are “No signup is required!” — and it sends them for tsunami warnings, hurricanes and storm surge. They are short. The longer local messages come from parish and city systems, and those you have to register for.

The sign-ups that could be confirmed for the parishes on these boards, west to east (read September 28, 2026):

If you are not sure which system covers your address, ask the parish office of homeland security and emergency preparedness (in Cameron, the Office of Emergency Preparedness).

The water that usually does the harm here

On this coast the dangerous rise in the sea is almost always storm surge from a tropical storm or hurricane. The National Hurricane Center calls storm surge “currently the leading cause of fatalities from hurricanes” and says all locations on the Gulf coast are vulnerable to it. That is the Weather tile’s job and the weather service’s storm surge and hurricane warnings’, not this tile’s.

Two things are worth doing before a storm. The Louisiana Department of Transportation and Development’s evacuation map plans a route from a ZIP code and shows the contraflow routes, and the Governor’s Office of Homeland Security and Emergency Preparedness prints the state’s phased evacuation map in its Louisiana Emergency Preparedness Guide: the first phase, 50 hours before tropical storm force winds, is for the areas south of the Intracoastal Waterway, which it calls “outside any levee protection system”. And for anyone who would need help to leave, the Louisiana Department of Health says to contact the parish office “if assistance is needed during an evacuation or to be added to the parish registry for residents with medical needs for an evacuation.” Jefferson Parish’s Medical Needs Registry is on the same sign-up page as JPAlert.

Sources