Guide · Weather and nature

Flash floods

Flash floods can rise within minutes, sometimes under a clear sky, when heavy rain falls further upstream. Knowing where they happen and how to respond can save lives.

Where they happen

• Narrow valleys, gorges and canyons
• Dry riverbeds and gullies, which can fill suddenly
• Low-lying roads, underpasses and fords
• Below steep slopes and hills that shed water quickly
• Near burnt or bare ground, which soaks up little rain

Warning signs

• Heavy rain nearby or upstream, or a thunderstorm in the hills
• Water rising quickly, or changing from clear to muddy
• Floating debris such as branches and leaves
• A roaring or rumbling sound from upstream
• A sudden change in the flow of a stream, including it drying up suddenly

If you notice any of these, act straight away. Don't wait to see what happens.

What to do

1. Get to high ground immediately. Climb up the sides of the valley, away from the water.
2. Leave your gear if it slows you down. Your life matters more.
3. Don't try to outrun the water along the valley floor. Climb up instead.
4. Stay on high ground until the water has gone down, which may take hours.

Never walk or drive into floodwater

• Just 15 cm of fast-moving water can knock an adult off their feet.
• About 30 cm of moving water can float a car, and 60 cm can sweep most vehicles away.
• Floodwater hides dangers: holes, washed-out roads, sharp objects, open drains and sewage.
• It may be much deeper and faster than it looks.

If your vehicle is caught in rising water and you can safely get out, leave it and climb to higher ground.

Choosing where to camp

• Never camp in dry riverbeds, gullies or at the bottom of narrow valleys.
• Pitch well above the high-water line — look for debris caught in bushes and on banks.
• Choose a spot with an easy route to higher ground, even in the dark.
• Check the weather before you go, and pay attention to rain in the hills upstream, not just where you are.

If you're swept away

• Float on your back with your feet pointing downstream to protect your head.
• Steer towards the bank at an angle, rather than fighting the current head-on.
• Grab anything stable, like a tree or rock, but avoid being pinned against obstacles.

After the flood

Stay away from riverbanks, which may collapse. Don't drink floodwater without treating it. Call your local emergency number (112 in Europe and many other countries, 911 in North America) if anyone is missing or hurt.

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