What the latest data tells us about flood risk – and how to manage it

The Environment Agency says better flood modelling techniques have allowed it to build a clearer picture of the threat posed by different types of flooding. In England, around 6.3 million properties are now believed to be at risk of some form of flooding – up from 5.5 million a year ago¹.

Separate research has found an estimated 284,000 properties are at risk in Scotland², around 277,000 in Wales³, and around 85,000 in Northern Ireland⁴.

Understanding different types of flood risk

In order to prepare for the impact of floods, it’s important to first understand how and when they are likely to occur – as there can be significant regional variations in different types of flood risk.

Surface water flooding

Nearly two million properties across England are now thought to be in areas with a medium or high risk of surface water flooding. This term describes scenarios where urban drainage systems are unable to cope with extreme rainfall. As a result, flooding can occur independently of any overflowing water bodies, such as nearby rivers.

Surface water flooding tends to be fairly shallow (usually not more than one metre deep) and build up gradually, giving people time to evacuate, but it can cause significant and widespread property damage.

Surface water flooding is a problem nationwide but presents a particular risk in large towns and cities, where drainage systems are more likely to struggle with intense rainfall. In London, for example, more than half a million properties are at medium or high risk (12.6% of the city’s total)⁵.

River and coastal flooding

While the Environment Agency’s latest data shows a slight decrease in the number of properties thought to be at some risk of river or coastal flooding, there has been a big leap in the number considered to be at high risk of deeper or more frequent floods. 367,900 properties now fall into the high-risk category (up 87% from previous estimates), and nearly half of these high-risk properties are considered likely to flood to depths of over 30cms, which is enough to move a car during heavy rainfall. Yorkshire and the Humber, and the East Midlands, are the regions in England with the highest proportion of properties considered at high risk of either river or sea flooding.

Addressing surface water flood risk – our partnership with Previsico

Although there are flood warning services for river and coastal flooding (see information at the bottom of this article), there is no publicly available flood warning service that accurately covers surface water flooding, which is why Zurich Municipal has partnered with tech company, Previsico, to offer our customers a surface water flood warning service at no extra cost.

Previsico’s model draws on a variety of data sources to provide property-level flood warnings up to 48 hours in advance. It can also predict the time and depth of the flooding, allowing users to take appropriate action to protect their property.

You can find out more about Previsico’s flood warning service, or sign up if you are an existing customer, via the link below.

• Previsico flood warning service

Practical ways to manage flood risk

Once you have established the nature and scale of flood risk in your area, it’s important to consider the different ways floodwater might enter your buildings. This could include through walls, windows, doors and floors, but also drains, sewers and pipework.

Our flood guide contains useful guidance on different types of flood mitigation measures for your property, including wet-proofing, dry-proofing and drain maintenance. Our guide also includes a flood checklist to help you prepare, as well as tips on what to do inside and outside your property.

As well as understanding the different practical measures you can take to reduce flood risk, it’s also important to consider how well flood risk is understood and communicated across your organisation. Creating and sharing a flood emergency response plan is a good starting point. An emergency response plan identifies specific actions to take before, during and after a flood.