Flash Flooding

Did you know that one in six properties in England and Wales will be affected by flooding in the future? Read this guide for steps you can take to protect your premises.

What is flash flooding?

Flooding takes two forms:
  • Fluvial – from overflowing natural watercourses
  • Pluvial – from surface water run-off (SWRO) after rain
This second, increasingly more common, form of flooding, Pluvial, is also known as flash flooding. 
Flash flooding is on the increase due to prolonged periods of wet weather caused by climate change and the growth of development of land on flood plains. The latter can result in reduced land drainage capacity and quicker build of up surface water which cannot drain away quick enough.

Are you at risk of flash flooding?

Flash flooding can happen miles away from established watercourses and can occur when there is no history of previous flooding problems. So, it is hard to predict if you are at risk.

What can you do to try to predict the risk?

  1. Complete a flood assessment of your site to determine the risk of fluvial and pluvial flooding. The Government’s Environment Agency has published helpful advice on how to do this
  2. You can check whether your premises are low, medium, or high risk via this government tool 
  3. You can also get alerts of potential fluvial flooding in your area

How do you manage the risk of flash flooding?

Use the Government’s advice (mention above to create a Flood Plan. The plan should include:
  • Details of key contacts in the event of a flood
  • A site plan showing the location of service cut off points so these can be easily isolated
  • Vulnerable property and high-risk areas
  • Clearly detailed evacuation procedures
  • Key contacts including the emergency services, your insurance company, electricians, Gas Safe registered contractors, security providers and plumbers. 
  • Regular inspection of drainage systems on your and neighbouring premises 
  • Contact your local council to check drains on surrounding roads are being inspected and cleared as required
  • Inspect and maintain guttering at least once a year
  • Specify suitable continuity arrangements to support the recovery of your organisation if flooding does occur
  • Implementation and regular inspection of any flood defence products implements as part of the plan

Preventing damage from flash flooding

There are a number of flood resistance measures that you can implement including:
  • Flood barriers
  • Sandbags
  • Airbrick covers
  • Non-return valves on drainage systems
If it is inevitable that water might get in, you should move valuable property above ground floor level.

Example building measures

  • Fit horizontal plasterboard or lime bases plaster instead of gypsum
  • Introduce drainage systems within cavity walls
  • Use tile flooring instead of carpets
  • Use built in units manufactured using stainless steel, plastic, or solid wood rather than chipboard
  • Locate appliances on plinths raised off the floor
  • Raise the height of damp proof coursing
  • Raise electrical sockets and boxes to at least 1.5 metres above floor level
  • Raise the height of door sills
  • Introduction of suction pumps in lower ground areas
  • Locate critical infrastructure/plant away from flood prone areas