How to Prepare Your Household for a Tsunami

A tsunami is one of the fastest-moving hazards a coastal household can face. Unlike a storm you can track for days, the event that triggers a tsunami — a large undersea earthquake, a coastal or underwater landslide, or a volcanic eruption — can put a wall of water at the shoreline within minutes, sometimes before any official warning has time to go out. Distance from the source is what decides your warning time: a tsunami generated far offshore can give a coastline many hours of notice, while one generated close to shore — including a landslide into a fjord, inlet, or lake — can leave almost no time at all.

That is why a tsunami is the one hazard where the most reliable warning system is often your own senses, not a phone alert. Strong, prolonged shaking near the coast, a sudden and unusual withdrawal of the sea that exposes the seabed, or a loud, unexplained roar from the ocean are all nature's own tsunami warnings — and they take priority over any official alert, simply because they arrive first.

The good news is that tsunamis are also one of the more survivable hazards for a household that has done its homework. Knowing whether you live, work, or holiday in a tsunami-risk area, knowing your fastest route to high ground on foot, and moving the moment you recognise a warning sign — rather than waiting to see what happens — are what separate households that get clear from those that don't. This guide walks through what to do before, during, and after a tsunami.

Understand Your Risk

A tsunami is a series of powerful ocean waves triggered by a sudden, large displacement of water — most often a large undersea earthquake, but also a landslide (on the coast, underwater, or into a narrow fjord, inlet, or lake) or a volcanic eruption. A tsunami is never a single wave: it arrives as a series, and the first is often not the largest.

Because tsunamis can be generated close to shore as well as far away, warning time varies enormously — from many hours down to just minutes. Learn both kinds of warning.

Natural warning signs — act on these immediately, without waiting for anything else:

• Strong or long ground shaking near the coast. If an earthquake is strong enough to make it hard to stand, or long enough that it feels like it won't stop, treat it as a tsunami warning in its own right — see also How to Prepare Your Household for an Earthquake for what to do during the shaking itself, then move the moment it stops.
• The sea suddenly draining away, exposing the seabed, reef, or riverbed far further than a normal low tide would.
• A loud, unusual roar from the direction of the ocean, like a jet engine or an approaching train.
• A sudden, fast-moving rise in sea level rather than a normal wave.

In steep coastal terrain — fjords, narrow inlets, and shorelines below unstable slopes — a large landslide or rockfall into the water is a serious tsunami trigger in its own right, and can generate a wave with almost no warning time at all. If you live, work, or holiday somewhere like this, treat a large landslide or rockfall near the water exactly like the signs above: it is your warning, and it means move now.

Official warnings come from your national or regional tsunami warning authority, usually broadcast through emergency alerts, television, radio, and mobile alerts. Sign up for official tsunami or coastal-hazard alerts for anywhere you live or travel, and keep ReadyEssentials notifications on. Remember that an official warning can only reach you if there is time to issue one — for a nearby source, your own senses will always be faster.

Prepare Before a Tsunami

• Know your zone. Find out whether your home, workplace, school, or holiday accommodation sits inside a mapped tsunami-inundation or evacuation zone, using official maps where your area publishes them.
• Plan your route on foot. Work out the fastest walking route from each place you regularly spend time to high ground or inland — roads can jam, buckle, or wash out, so don't plan to drive unless walking genuinely isn't possible.
• Pick a target. If you don't have an official evacuation map, aim for high ground well above the shoreline (many official guides point to roughly 20–30 metres above sea level as a rule of thumb) or at least a couple of kilometres inland — higher and further is always safer.
• Agree a meeting point. A tsunami can strike while household members are scattered across school, work, or errands, so agree in advance where everyone will head and how you'll reach each other — see How to Prepare a Family Emergency Communication & Reunion Plan.
• Keep a go bag ready. A tsunami evacuation happens on foot and often with no time to pack, so a kept-by-the-door kit matters more here than for almost any other hazard — see What to Pack in a Go Bag: The Complete 72-Hour Evacuation Kit Checklist.
• Build in extra time for anyone who can't move quickly. Older adults, young children, anyone with a mobility limitation, and anyone recovering from illness or injury need a head start — agree in advance who will help them and practise the route together.
• Walk the route at least once as a household, including with children, so it becomes automatic under stress.
• Learn your community's warning signals — sirens, phone alerts — and what each one means before you ever need to act on it.

During a Tsunami

• Move immediately. Don't wait for an official warning if you notice any natural sign, or if you feel a strong or long earthquake near the coast, or see a landslide or rockfall into the water. Every minute matters.
• Go on foot to high ground or inland, following your planned route. Don't stop to collect belongings, and don't drive if you can walk faster than traffic will move.
• If you can't reach high ground or get far enough inland in time, go up instead — the upper floors of a strong, reinforced building, or, as a last resort, as high as you can in a sturdy structure.
• Never go towards the coast to watch or film. If you can see the wave, you are already too close.
• Bring anyone who needs help with you — check on neighbours, older relatives, and anyone with limited mobility along your route, but don't delay your own move to do it alone; bring them with you as you go.
• Stay away from the coast until officials say it is safe. A tsunami is a series of waves, not one, and can keep arriving for hours — the first is often not the largest. Returning to the shoreline after the first wave passes is one of the most common causes of tsunami deaths.

If You're Caught in Tsunami Floodwater

A tsunami surge moves fast, carries debris, and can sweep a person off their feet in seconds — even shallow, fast-moving water is dangerous, and it often hides sharp or submerged hazards. If someone is pulled under, swept off their feet, or stops breathing after being caught in tsunami floodwater, get them out of the water and check their breathing immediately. See the in-app first-aid card Drowning for the step-by-step response to follow while emergency help is on the way.

After a Tsunami

• Wait for the official all-clear. Further waves can arrive hours after the first, so a calm sea is not a safe sea — don't judge it by eye.
• Expect hazards you can't see. Floodwater may be contaminated and debris-laden, and roads, bridges, and buildings can be structurally unsafe even when they look fine from the outside.
• Reunite using your plan. Check on every household member and account for anyone who was away from home, following the steps in your family communication and reunion plan.
• Check on vulnerable neighbours once it's genuinely safe to move around — older people living alone, and anyone who couldn't evacuate quickly, may need help even after the immediate danger has passed.
• Avoid downed power lines and damaged gas lines — report them rather than investigating them yourself.
• Restock your go bag and note what worked (and what didn't), so your household is readier next time.

Keeping Pets Safe in a Tsunami

Include pets in your evacuation plan, not as an afterthought. Keep a leash or carrier near your go bag so you can bring pets with you in seconds, not minutes, and note which of your high-ground or inland options will accept animals. If there truly isn't time, never go back for a pet once you've started moving to safety — a tsunami's timeline doesn't allow it, and a household member re-entering a risk zone is the greater danger.