The new National Flood Risk Assessment (NaFRA) is a game-changer for landowners and developers, offering the most detailed flood risk data yet. Flood expert, Brendan McCarthy, explains how for the first time, it integrates climate change projections, uncovering previously unmapped risks and highlighting increased threats in many areas. With sharper insights into site-specific flood hazards, NaFRA helps developers plan smarter and landowners protect their assets more effectively.

What has changed?

The new NaFRA brings significant changes compared to the previous flood mapping by using updated data and improved modelling methodologies to provide a more accurate and detailed picture of flood risk across England, such as:

• Higher resolution mapping – now improved to a global 2m resolution for better accuracy.
• Detailed flood depth data – provides insights into the probability of specific flood depths occurring.
• Climate change integration – for the first time in England, NaFRA2 incorporates the latest UK Climate Projections (UKCP18), giving a clearer picture of future flood risks and incorporating both present-day and climate change projections.

So far, the Environment Agency (EA) has updated the following items as part of their long-term flood risk mapping (available here: Technical map – Check your long term flood risk – GOV.UK):

• Rivers and sea – this essentially shows the risk of flooding, including any local flood defences. It’s important to note that this is not the Flood Map for Planning (that dictates the flood zone classification of a site), which is due to be updated as NaFRA2 on 25 March.
• Surface water – this has been a hot topic over recent years due to the increased focus of the Sequential Test on assessing the risk of flooding from all sources, leading to a lot of red line boundaries being needlessly redrawn. Thankfully, the revised NPPF confirms that a more pragmatic approach should be applied. However, surface water is still a key site constraint – the latest mapping results in a 43% increase in the total number of properties at risk from this source of flooding. A quick look at the mapping suggests buildings are at a greater risk of flooding and roads are at a reduced risk.
• Reservoirs – this shows the expected flood extents due to reservoir failure when river levels are normal, and a worst-case scenario when there is also flooding from rivers. Due to the high standards to which UK reservoirs are required to be maintained under the Reservoirs Act, this layer is mostly academic unless working in disaster planning or looking to justify maintenance costs.

It is clear from the Risk of Flooding from Surface Water mapping that the methodology used in its development has significantly changed; what’s not so clear is how it has changed. The technical detail underpinning the updated flood modelling is fundamental to understanding the limitations and potential applications of the outputs, which guidance advises “are generally not suitable for property level assessment; instead they estimate flood risk to an area of land.”

A promising revision

Focusing on the positives, this latest iteration of mapping includes climate change outputs; this is a big step forward and will allow for a better assessment of the future risk of flooding in support of planning applications, local development plans and climate risk assessments. Currently, only a single climate change scenario is available, but it is expected that more are on the way:

“A near-term epoch (2040 – 2060 “2050s” epoch) and central allowances are being used initially, to support short and medium-term decisions informed by the highest flood likelihood projections.”

“More precise flood data enhances risk assessments for new developments and supports better planning and decision making. Greater detail means we can provide more detailed assessments in less time and at less cost. Improved understanding of flood risk will provide asset owners with the information needed to protect and maintain their portfolios and safeguard any critical infrastructure. This initial release is a promising first step and presents some great opportunities to deliver increased value for our clients; there is more to come, in the form of the updated Flood Map for Planning, surface water modelling methodology and further climate change scenarios.”

 

Brendan McCarthy, Flood Risk Partner

If you’d like to know more about the new National Flood Risk Assessment (NaFRA) and its application, or about our wider flood risk management service, please contact Brendan McCarthy at brendanmccarthy@ridge.co.uk