Flood Zones - What you need to know

Key facts
  • Understand the risk and rewards of buying property or land that are in flood zones.
  • One in six homes are located in areas where there is a significant risk of flooding.
  • Use our Flood Zones map layer to help you locate if an area you are buying is at risk of flooding.
  • We want to help to put you in a confident and strong position when it comes to purchasing your land or property.

If you're a professional land buyer or self-builder, make sure you understand what Flood Zones can mean to your investment. 

Types of flood zone 

Flood zones were created by the Environment Agency to understand the probability of flooding, this is used within planning, and by planning authorities, to discover the risk and rewards of development in these areas.

There are three flood zones defined by the EA (Environment Agency), these are Flood Zone 1, 2 and 3. In terms of flood risk, Zone 1 is least and Zone 3 being the most likely to flood.

Flood zones and development 

The good news is that although these areas have a higher risk of flooding, it doesn’t always mean they will flood. Plus, the fact that flooding is normally seasonal, means it makes planning ahead of time possible and ideal locations for developing. Planning authorities know the chance of flooding, too: developments on flood zones may be granted subject to flood defence works and suitable mitigation.

“Despite warnings from the Environment Agency and the Committee on Climate Change (CCC) between 2001 and 2011, 200,000 new houses were built on the flood plain whilst at present, there are almost 500,000 homes that have been given planning permission and are waiting to be built on the flood plain.” (Today's Conveyancer)

Flood zones and planning permission 

Though Local Planning Authorities, in line with the NPPF, would prefer not to have houses built on flood plains, the need for housing is universally recognised. Proposals in Flood Zone 1 are most likely to be approved, Flood Zone 3 the least. If you're planning on building in Flood Zones 2 or 3 (a medium or high-risk area), you'll have to do a Flood Risk Assessment at first instance. Your plan will then have to pass the 'Exception Test' - showing that the development will be safe if flooding occurs, that building it won't increase the chance of flooding, and if there are any features installed to protect the house in the event of flooding, to name a few things.

Understanding Flood Maps for Planning Risk 

Although there are risks when it comes to buying land with flood risks and making planning applications, one in six homes are located in areas where there is a significant risk of flooding.

Our Flood Zone land consideration gives you a detailed assessment for planning any development. Knowing the flood risk in an area will be crucial to create resilience against flooding as well as how to reduce the impact of your land flooding. 

What to consider when self-building in a flood zone

It is possible to build a new home safely in a flood zone. Houses can be proofed against a flood event, and the lengths you go to will likely depend on the annual probability of flooding. Designing a flood-proofed house breaks down into two goals: one, to prevent water from entering the house in the first place and two, to minimise any lasting damage from water flows if they do get in. Building your ground floor above the potential water level is, in theory, the most logical flood protection measure. This can be difficult to implement in practice, though, and English Councils may be reluctant to grant permission for houses much higher than those in the neighbourhood. 'Tanking' is a waterproof layer installed within walls and floors to prevent flood water from seeping in, and is a common means of flood prevention.       

You can also add several design features to mitigate damage if water does get in, from adjustable seals on windows and doors, to non-return valves in plumbing to prevent sewage from being released in cases of flooding.  

Climate change and flood zones 

Flood zones are changing due to climate change. You can find information on the government website of how these changes to our climate affect a flood risk to the area:

“The flood zones do not take account of the possible impacts of climate change and consequent changes in the future probability of flooding. Reference should therefore also be made to the Strategic Flood Risk Assessment when considering location and potential future flood risks to developments and land uses. The EA made revisions in March 2016 to the peak flow rate of rivers in various catchments across the country based on climate change predictions. This guidance is available here.”

Addland
Published: 05 October 2021
Last updated: 19 April 2022

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