How do you prepare for a flood?

Short answer. Learn your country's flood warning levels and sign up for them, keep a kit with water and supplies for several days ¹, and never enter moving floodwater: 6 inches (about 15 cm) of fast-moving water can knock an adult over and 12 inches (about 30 cm) can carry away most cars ². After the flood, treat the water, the food it touched and the building as unsafe until checked ¹⁶⁸.

What do flood warnings mean, and what should you do at each level?

Flood warnings are graded. Each level tells you how much time you have, so the useful habit is to know in advance what you will do at each one.

In England, the Environment Agency uses three levels ⁴:

The UK Floodline is 0345 988 1188, available 24 hours ⁴.

In the United States, the National Weather Service uses a different ladder ³:

• Flood Advisory (be aware): a forecast event "may become a nuisance" ³.
• Flood Watch (be prepared): "conditions are favorable" for flooding ³.
• Flood Warning (take action): flooding "is imminent or already happening" ³.
• Flash Flood Warning (take action): "a flash flood is imminent or occurring" ³.

Under a flood warning, Ready.gov says to find safe shelter right away ¹. The names differ between countries, but the logic is the same: the first level means prepare, the next means act.

How deep does water have to be to be dangerous?

Much shallower than most people expect. The figures below come from official sources; centimetre values in brackets are conversions from the U.S. figures.

The U.S. and UK figures agree closely: roughly 30 cm of moving water is enough to move a car ²⁵. The National Weather Service, citing the CDC, says over half of all flood-related drownings occur when a vehicle is driven into hazardous floodwater ². The Environment Agency calls driving through floodwater "the number one cause of death during flooding" ⁵. U.S. agencies sum this up as "Turn Around, Don't Drown" ¹².

Canada adds that fast water on foot "could sweep you away even if it appears shallow", and that you should not drive through flood waters or underpasses ⁶. Germany's BBK warns that underground garages can become deadly traps when flooding threatens, and that staying in a cellar during a flood is life-threatening ⁷.

What should be in a flood kit?

A flood kit is your general emergency kit with a few flood-specific additions.

• Water and food for several days. Ready.gov advises gathering non-perishable food, cleaning supplies and water for several days ¹. Recommended water quantities vary by country; see the Phaenyx guide on water per person.
• Documents. Canada advises making copies of important documents (or digitizing them) for your kit, and storing important documents at a higher level in the home to protect them from flood damage ⁶. The Environment Agency lists insurance documents among the things to gather at the flood alert stage ⁴.
• Medications. Gather them at the first warning level ⁴.
• A kit in the car. Canada recommends keeping a kit in your vehicle and taking your kit with you if you evacuate ⁶.
• Cleanup supplies. Ready.gov includes cleaning supplies in its flood preparation ¹.

How do you prepare your home before a flood?

Most preparation is planning and small measures, not construction.

• Check whether your area receives flood warnings and register for them. In England you can sign up for flood warnings by phone, text or email ⁴.
• Plan how you will respond at each warning level and where you will go ⁴⁶.
• Canada suggests considering a sump pump and a backflow valve or backflow preventer in the basement, and planning where you would place sandbags before an emergency ⁶.
• Germany's BBK advises switching off electrical appliances and heaters in rooms that could flood, and keeping the risk of electric shock in mind ⁷.

Permanent flood protection for a building, such as barriers, raised utilities or structural changes, is a matter for a qualified engineer or contractor and local permits. Phaenyx does not give construction instructions.

What should you do during a flood?

• Go to higher ground or an upper floor if water is coming in ⁴.
• Turn off gas, electricity and water only if it is safe to do so ⁴. Canada is explicit: do not attempt to shut off electricity if any water is present ⁶.
• Do not touch electrical equipment if it is wet or if you are standing in water ¹.
• Avoid wading in floodwater, which can be contaminated and contain dangerous debris ¹.
• Do not drive through flooded roads ⁷. In Germany, the BBK advises having a vehicle towed if the water reached above the wheels ⁷.
• Follow emergency services' instructions and call your emergency number if your life is in danger ⁴.

What are the dangers after the flood?

The water going down is not the end of the risk. Floodwater is contaminated, buildings may be damaged, and electrical systems may be live.

Returning home. Return only when authorities say it is safe ¹⁶. Flood-damaged buildings may be structurally unsafe ⁶. If the main power was not shut off before the flood, Canada advises not re-entering until a qualified electrician has confirmed it is safe; flooded appliances pose a risk of shock or fire when turned on ⁶.

Food. The FDA says not to eat any food that may have come into contact with floodwater, and to discard food and drinks that are not in a waterproof container, including cardboard boxes and home-canned food ⁸. Commercial cans and retort pouches can be saved: remove labels, wash with soap and water, then sanitize by boiling for 2 minutes or soaking for 15 minutes in a solution of 1 cup of bleach per 5 gallons of water, and air dry for at least 1 hour ⁸.

Drinking water. If your water may be unsafe, the FDA advises boiling it for 1 minute, or adding 1/8 teaspoon (8 drops) of unscented 5.25% household bleach per gallon of water; the FDA notes that boiling kills most disease-causing organisms, while bleach kills some but not all ⁸. Do not use well water until your local health authority advises on cleanup, disinfection and testing ⁶.

Mould. Canada advises cleaning up within 48 hours where possible to avoid mould growth, and getting professional help for extensive mould ⁶.

Generators. Run portable generators at least 6 metres (20 feet) from homes or buildings, and never in flooded areas ⁶.

What official agencies recommend

• England (Environment Agency): three warning levels (alert, warning, severe warning), each with its own actions; 30 cm of flowing water can float a car ⁴⁵.
• United States (NWS, Ready.gov): advisory, watch, warning and flash flood warning; 6 inches of moving water can knock you down and 12 inches can carry away most cars; "Turn Around, Don't Drown" ¹²³.
• Canada (Get Prepared): do not walk or drive through floodwater or underpasses, return only when authorities allow it, clean up within 48 hours, generators at least 6 m from buildings ⁶.
• Germany (BBK): do not stay in cellars or underground garages during a flood, switch off appliances in rooms that may flood, do not drive through flooded roads ⁷.
• Food and water (FDA): discard food that touched floodwater unless in a waterproof container; boil water 1 minute ⁸.

The agencies agree on the essentials. They differ mainly in how they name warning levels and in how much detail they give on cellars, cars and cleanup.

Frequently asked questions

Is it safe to drive through shallow floodwater?

No. About 12 inches (30 cm) of rushing water can carry away most cars ², and the Environment Agency says 30 cm of flowing water is enough to float a car ⁵. The NWS, citing the CDC, says over half of flood-related drownings occur when a vehicle is driven into hazardous floodwater ².

What is the difference between a flood watch and a flood warning?

In the U.S., a watch means conditions are favourable for flooding; a warning means flooding is imminent or happening ³. In England, a flood alert means flooding is possible and a flood warning means it is expected ⁴.

Can I eat canned food that was under floodwater?

Commercially canned food and retort pouches can be kept if undamaged, washed and sanitized as the FDA describes; home-canned food and anything not in a waterproof container should be discarded ⁸.

When can I go back home after a flood?

Only when authorities say it is safe ¹⁶. If the power was not switched off before the flood, Canada advises waiting until a qualified electrician has checked the home ⁶.

Should I stay in the basement during a flood?

No. Germany's BBK says staying in the cellar during a flood is life-threatening ⁷. Move to an upper floor or higher ground instead ⁴.

Next step: check your kit against your country's list

Flood kits share a common base, but each country's official list differs in its details. Start from what your own emergency agency lists, then let the Phaenyx plan count it for your household. Build your Phaenyx plan.

Sources

1. Ready.gov (U.S. Department of Homeland Security / FEMA) — Floods — https://www.ready.gov/floods (accessed 2026-10-20)
2. U.S. National Weather Service (NOAA) — Turn Around Don't Drown — https://www.weather.gov/safety/flood-turn-around-dont-drown (accessed 2026-10-20)
3. U.S. National Weather Service (NOAA) — Flood Warning vs. Watch — https://www.weather.gov/safety/flood-watch-warning (accessed 2026-10-20)
4. GOV.UK (Environment Agency) — Flood alerts and warnings: what they are and what to do — https://www.gov.uk/guidance/flood-alerts-and-warnings-what-they-are-and-what-to-do (accessed 2026-10-20)
5. GOV.UK (Environment Agency) — Driving complacency: 74% of drivers would risk life in flood water (19 December 2019) — https://www.gov.uk/government/news/driving-complacency-74-of-drivers-would-risk-life-in-flood-water (accessed 2026-10-20)
6. Government of Canada — Floods – Get prepared — https://www.canada.ca/en/services/policing/emergencies/preparedness/get-prepared/hazards-emergencies/floods/how-prepare.html (accessed 2026-10-20)
7. Bundesamt für Bevölkerungsschutz und Katastrophenhilfe (BBK), Germany — Vorsorge und Handeln bei Hochwasser - Was tun bei Hochwasser? — https://www.bbk.bund.de/DE/Warnung-Vorsorge/Vorsorge/Mit-Naturgefahren-umgehen/Hochwasser/_documents/hochwasser-handeln_dossier2.html (accessed 2026-10-20)
8. U.S. Food and Drug Administration — Food and Water Safety During Power Outages and Floods — https://www.fda.gov/food/buy-store-serve-safe-food/food-and-water-safety-during-power-outages-and-floods (accessed 2026-10-20)