Paul Shaffer, BeFloodReady Project Manager, CIWEM
As we’ve seen over recent months flooding remains one of the most significant environmental risks in England, affecting 6.3 million properties and critical infrastructure. As climate change accelerates and demand for more housing increases the need for updated and accurate flood risk information has never been greater.
The National Flood Risk Assessment 2 (NaFRA2) for England released in December 2024 covering fluvial, coastal and surface water flood sources is a significant update on our national flood risk that delivers enhanced flood modelling, high-resolution mapping, and improved climate change projections.
NaFRA2 is a monumental step forward in understanding and mitigating flood risk. It offers a detailed view of potential flood depths and frequencies, enabling improved planning and response strategies that improve flood resilience. By integrating local information (from local authorities and other risk management authorities) and national data, NaFRA2 ensures that flood risk assessments are both more accurate and relevant, reflecting the true nature of potential flood hazards.
One of the critical aspects of NaFRA2 is the new detailed information on flood depths from improved resolution, modelling and impact calculations. This is helpful for planners, developers, flood risk managers and homeowners. NaFRA 2 indicates that a significant proportion of flooding events are likely to occur below 30cm, particularly in areas with effective drainage systems. However, the risk of flooding above 30cm is substantial in high-risk zones, especially during extreme weather events or in areas with inadequate flood defences.
By providing detailed information on potential flood depths, NaFRA2 enables more informed planning and optioneering for better flood resilience. For instance, it helps in identifying areas that are at higher risk and require more robust flood defences or areas where surface water management, sustainable drainage system (SuDS) or Property Flood Resilience (PFR) could be critical in providing greater resilience.
PFR involves implementing measures that reduce the impact of flooding on people and properties. The approach underpinned by preparedness by those living and working in properties includes measures to keep flood water out, i.e. resistance and approaches to improve the recoverability of properties following flooding. A better understanding of the flood depths and associated hazard from NaFRA2 can help influence the overall flood resilience strategy for property. Supporting design decisions on the balance between flood resistant measures, like installing flood doors, barriers, and non-return valves, which can slow water entering properties, and recoverable measures and building materials like tiled, or concrete floors and re-routing of electrics that can reduce the damage from flooding.
NaFRA2 could play a pivotal role in enhancing PFR, supporting the design stages of the Code of Practice for PFR (i.e. hazard assessment, property survey and options development and design). With more accurate flood depth predictions, professionals and property owners can better prepare properties, improving resilience and reducing the emotional and financial toll of flooding.
NaFRA2’s detailed flood depth data could also support the development of community resilience strategies. By focusing on the most vulnerable areas, understanding flood depths, and residual risk measures like SuDS and PFR can be planned and delivered more effectively.
Combining NaFRA2 with the planning and design of PFR (and integration of SuDS) could support a more resilient future. By leveraging its detailed insights, we can enhance our flood preparedness and ensure that properties and communities are more resilient to the inevitable challenges posed by climate change and flood risk.
