Flash Flooding – what you need to know

Around 1 in 6 homes in England are at risk of flooding – and according to the Environment Agency, as our climate gets warmer and wetter, those numbers are set to increase.

There are different types of flood. For example:

• Floods from rivers bursting their banks
• Coastal flooding, which is typically caused by storm surges
• Groundwater flooding – caused by a prolonged period of rain
• Flash flooding – trigged by torrential rain

In this article we examine flash flooding, reflecting on the July 2021 floods in London. We also offer advice on how to minimise the effects of flash floods on your property.

What causes flash flooding?

Flash flooding and surface water floods are caused by intense high velocity torrents of waters triggered by torrential rainfall within a short period of time.  They can also be caused by a release of water from an upstream levee or dam. They are fast, dangerous and destructive.

What happened in July 2021 in London?

On the 12^th July 2021 nearly a month’s worth of rain fell in parts of London, resulting in over 100 homes in Kensington and Chelsea being evacuated and the closure of eight underground lines. Just five days later on the 17^th July, 76mm of rain fell in 90 minutes, causing floods along Portobello Road, with flood levels reaching 0.45m. Then on the 25^th July torrential rain deluged several locations around the south of England. The wettest area in London was St James Park which recorded 42mm of rainfall on a day. The flooding this caused resulted in two hospitals and eight tune station closures.¹

Why were the floods in London so severe?  

As well as the intensity of the rain the drainage system was overwhelmed so water was flowing into the streets and nearby properties.  This was exacerbated by an increasing number of properties moving from gardens to paving - which only worsened the surface water run off.

There are also many Georgian and Victorian properties which tend to have occupied basements.  Some London properties have multi-level basements which can often hold high value items. The clean-up operation after a basement flood is long lasting and expensive.

A weather alert has been issued – what can I do quickly to reduce the impact of flash flooding on my property?

If a weather alert is issued in your area after a heat wave, we recommend taking the following actions.

• Clear out gutters and if you have water butts make sure they can hold water
• Check any storm drains on your property and out on the street and remove any debris
• Cover and protect outside items
• Check the roof for loose tiles
• Check the roof inside and skylights for signs of water ingress and prepare buckets
• If your home is prone to flooding, check the government website and local flood support agencies for advice.
• Make sure all flood resistance measures are in place and functional.
• Move items off the floor and move valuables upstairs.
• If you park your car in an area prone to flooding, move your car to higher ground.

How can I reduce the impact of flooding in the long term?

While you can never completely eliminate the risk of flooding, you can take steps to reduce the risk of water getting into your property and minimise the damage if it does make it over the threshold. These methods are known as ‘flood resistance’ and ‘flood resilience’. Making sure you implement them can help you both manage the risk of your property being damaged and help to lower your insurance premium.

What is flood resistance? Flood resistance refers to the measures you can take to reduce the risk of water getting into a property. For example: Flood doors or barriers placed over openings Air brick covers Masonry protection, i.e. specialist material that you can apply to the outside of your property to increase water resistance Floor membranes to help prevent damage from rising water Non-return valves Pumps and toilet bungs In addition to this, keeping your property well-maintained is essential. For example, making sure the pointing is in good condition above and below ground, and making sure all entry points are sealed, including cable entries through walls. This will give you the best chance of holding back any water from entering during a flood.

What is flood resilience?

Flood resilience is all about minimising the damage as much as you can if water does get in. By having robust protection measures in place, the idea is that you can get back to normal as quickly as possible once the flood has subsided. Flood resilience includes:

• Using resilient floor and wall materials, such as tiles, solid floors and porous plaster
• Raising electrics so they’re less likely to be touched by water
• Installing a cavity drainage membrane for extra waterproofing
• Using water resilient insulation
• Keeping or storing belongings off the floor at ground level or in the basement as a matter of course
• Moving valuable possessions and any furniture you can upstairs in times of flood
• Pumps

If my property is at risk of flooding what insurance do I need?

The risk of flooding in your area will inevitably have an impact on your home insurance – you may find it challenging and more expensive to find a buildings and contents policy.  However, the more measures you’ve taken, such as raising the electrics and using water-resistant materials, the more likely you are to source a policy including flood cover. We also have access to Flood Re – a scheme run by the government that’s designed to help those with properties in high-risk areas find home insurance subject to meeting the FloodRe criteria. You can read more about Flood Re in our article: Flood Insurance – what is Flood Re?

How can Howden help?

As brokers, we are at the coal face. We are the ones with direct contact with homeowners, so we have a collective duty to educate homeowners; to help and support our clients to reduce the flood risk; to introduce flood resilience measures and improve homeowners’ ability to get flood cover in the future.

To speak to us about flood insurance call 020 8256 4901 or email privateclients@howdeninsurance.co.uk

Sources

1. JBA Risk Management