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Flash Flooding

Flooding is the most common and widespread natural hazard in the UK. One type of flooding that can occur is flooding from river levels or surface water rising very quickly in response to very heavy rainfall. These types of events are rare but can be very dangerous. Examples of flash floods include Lynton and Lynmouth in 1952, Boscastle in 2004, Sidmouth in 2012 and Tipton St John in 2023. This type of flooding is termed flash flooding.

Across England the Environment Agency have identified 384 ‘Rapid Response Catchments’, with over 75,000 properties being identified as being vulnerable to this risk.

Flash floods occur extremely quickly – much faster than other forms of flooding – and with massive force. They can move rocks, tear out trees, sweep away vehicles and destroy buildings and bridges.

They tend to happen when heavy rainfall runs off land and quickly swells rivers and streams. Water can also build up quickly in urban areas when rainfall is unable to drain away.

Across Devon and Cornwall there are a large number of communities where this type of flooding could happen. Most major flash floods occur in places where there have been none in living memory, so it is vital that, even if flooding hasn’t happened in your community for a long time, you know what to do and how to stay safe.

How to recognise a flash flood:

· heavy rainfall
· a short time between the rainfall and flooding
· large amounts of fast flowing water
· damage to buildings and structures
· dangers presented by debris
· there is an urgent threat to life.

Flash flooding can happen suddenly. You may have to act before the Environment Agency can issue a warning, or before emergency services can reach you.

People particularly at risk are those:

· In basements or single-storey properties
· In a mobile home, tent, caravan, boat or wooden structure
· Unfamiliar with the area e.g. tourists.

What can you do now?

· Although the Environment Agency won’t always be able to issue a flood warning in time, it is worth checking if you are at risk and signing up to receive a flood warning: Sign up for flood warnings – GOV.UK (www.gov.uk)
· Register to the Met Office’s Severe Weather Warning Service: Weather warnings guide – Met Office
· Check the Environment Agency’s 5-day Flood Forecast: Check for flooding in England – GOV.UK (check-for-flooding.service.gov.uk)
· Check to see if your insurance covers flooding
· Know how to turn off gas, electricity and water supplies.
· Download and print this document and keep somewhere handy

What can you do when you get a Flood Alert or you think Flash Flooding is likely?

· Check that your family, neighbours and pets are okay.
· Move important things upstairs or to higher shelves, so they don’t get covered in dirty flood water.

Three steps to safety


Be aware and know the signs. Signs to watch for:

· Heavy rain or severe weather reports.
· Rising water levels with churning dark water.
· A build up of debris in rivers or streams.


· Do not walk or drive through flood water.
· If you are in a building with at least two storeys and you believe it is safer to stay where you are, you should move to a higher storey.
· Call 999 if there’s a risk to life, or if you are trapped.


· Call 999 if you’re in immediate danger.
· Follow advice if you’re in immediate danger.
· Keep yourself and your family safe.

21 August 2023
Last Updated
21 August 2023