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Guide · GUIDE 11

Shelter from flooding

Last reviewed on 05.07.2026

Avoid cellars, underground car parks and underpasses and never walk or drive through flooded water – even about 30 centimetres can render a car unusable. Turn off electricity and gas in endangered areas, leave endangered areas and follow the authorities' instructions. Only return when the authorities clear the area.

In Switzerland, flooding is usually caused by prolonged rain, local thunderstorms or snowmelt – often in combination. Streams and small rivers swell within minutes, large lakes overflow with a delay. The greatest danger does not come from the water level itself but from underestimated water: cellars, underground car parks and underpasses fill within minutes to a depth of several metres – if you want to get something there, you will be trapped. Just a few decimetres of fast-flowing water can knock an adult off their feet, and about 30 centimetres is enough to render a car unusable. That is why one unbreakable rule applies: never walk or drive through flooded water – not even with a car and not even through seemingly shallow underpasses. Before flooding, the Federal Office for the Environment (FOEN) issues warnings; you will find the current situation and a five-level hazard scale in the federal natural hazards portal (naturgefahren.ch); live water levels are on hydrodaten.admin.ch.

Current situation: check the situation dashboard to see whether any warnings are currently in effect for this hazard.

Where do I get flood warning levels?

The Federal Office for the Environment (FOEN) warns of flooding. The federal natural hazards portal (naturgefahren.ch) shows the current hazard situation with a five-level hazard scale – from level 1 (green, no or low danger) to level 5 (dark red, very high danger).

The specific live water levels and discharge data of rivers and lakes are on hydrodaten.admin.ch (also FOEN). Level 4 and 5 warnings can be declared mandatory for broadcast – then licensed radio and television stations must broadcast them.

You will also receive official alarms and behaviour instructions via Alertswiss (FOCP app/website) and via radio. From level 3 (orange) you should keep distance from water bodies and take first protective measures; from level 4 (red) staying near rivers and streams is dangerous.

Before: prepare

  1. Know the hazard map of your municipality (is my address in a zone?)
  2. Move valuables, technology and hazardous items (chemicals, fuels, paints) from the cellar upstairs
  3. Have backflow valves and shafts checked; seal light wells and leaky points
  4. Have sandbags or sealing material, plastic film and a submersible pump ready
  5. Monitor live water levels of FOEN (hydrodaten.admin.ch) and warnings
  6. In case of forecast flooding, turn off electricity and gas in endangered areas

During: rising water

  1. Do NOT enter cellars, underground car parks and underpasses anymore
  2. Turn off electricity and gas in endangered areas in time
  3. Avoid flowing water – even just a few decimetres can knock you over
  4. Do not drive or wade through flooded streets or underpasses – not even with a car
  5. Leave endangered area; listen to radio and follow the instructions of emergency services
  6. In case of evacuation, take your emergency bag

After: return

  1. Only return when authorities clear the area
  2. Document damage (photos) before clearing up
  3. Only turn electrical and gas systems back on after a specialist has checked them
  4. Flush drinking water pipes thoroughly; in doubt, boil water (possible contamination)
  5. Only pump the cellar when the groundwater level is below the cellar floor
  6. Avoid direct contact with flood water – it is often mixed with sewage, heating oil or chemicals

What equipment do I need for flooding?

Have material ready for sealing and pumping before the water comes – in the event it is often sold out.

  1. Sandbags or reusable water barriers, plus plastic film and duct tape
  2. Submersible or dirty water pump with hose (think of emergency power in case of power outage)
  3. Rubber boots and gloves (flood water is often mixed with sewage)
  4. Emergency bag ready to grab in case of evacuation
  5. Drinking water supply in case the supply becomes contaminated

Common mistakes

  1. Driving through a flooded street or underpass with a car – even about 30 cm of water can destroy the engine; from about 50 cm the vehicle floats and is no longer controllable
  2. Going down to the cellar or underground car park at the last moment to rescue something
  3. Wading through flowing water on foot – a few decimetres is enough to be knocked over; depth and current are not apparent from outside
  4. Underestimating the hazard level or ignoring warnings and road closures
  5. After the flood, turning on electricity or gas without specialist inspection or drinking contaminated tap water
  6. Never having looked at the hazard map for your own address
Flood warning levels in Switzerland (FOEN / naturgefahren.ch) and correct behaviour
Level Meaning Behaviour
1 – Green No or low danger Staying near water bodies is unproblematic, but remain alert
2 – Yellow Moderate danger Keep distance from rivers and streams, follow the situation, take first protective measures
3 – Orange Significant danger As a precaution keep distance from water bodies, monitor development, implement protective measures
4 – Red Major danger Staying near rivers and streams is dangerous – stay away; warnings are mandatory for broadcast
5 – Dark red Very high danger Staying is extremely dangerous – stay away, implement protective measures; mandatory for broadcast

Scale and wording: FOEN/naturgefahren.ch or hydrodaten.admin.ch, as of July 2026. FOEN warns of flooding; live water levels at hydrodaten.admin.ch. Level 4 and 5 warnings can be declared mandatory for licensed radio/TV stations.

Frequently asked questions

May I drive or walk through flooded water?

No. Never drive a car or bicycle through a flooded street and do not wade through flowing water. Even a few decimetres is enough to knock a person over; about 30 cm can destroy a car's engine, from about 50 cm it floats and is no longer controllable (TCS). Never drive into a flooded underpass – the depth is not apparent from outside.

What to do on a flood warning?

Monitor the hazard level in the natural hazards portal (naturgefahren.ch) and the water levels on hydrodaten.admin.ch. Move valuables and hazardous items from the cellar upstairs, turn off electricity and gas in endangered areas and have sandbags and a pump ready. From level 3 (orange) keep distance from water bodies and follow the authorities' instructions.

Secure the cellar or go higher?

Secure the cellar only beforehand, before the water comes (backflow valves, sealing, valuables upstairs). Once water enters, do not enter cellars and underground car parks anymore – they fill within minutes. Do not stay in low-lying rooms in endangered areas and leave the area once authorities request it.

How do I find out how dangerous the situation is?

Via the natural hazards portal (naturgefahren.ch) with its five-level scale and the live water levels on hydrodaten.admin.ch. The Federal Office for the Environment (FOEN) is responsible for flood warnings.

When can I return to my house?

Only when authorities clear the area. Electrical and gas systems may only be switched back on after a specialist has checked them. Pump the cellar only when the groundwater level is below the cellar floor, and avoid direct contact with the flood water (sewage, heating oil).

What must I watch out for with drinking water after the flood?

Flush drinking water pipes thoroughly and boil the water if in doubt, as the supply may be contaminated. Follow your municipality's guidance. How to treat water is described in the guide «Prepare drinking water».

Official sources