TAN15 Wales Flood Risk Policy Updates 31 March 2025

The Welsh Government has released a long-awaited update to Technical Advice Note 15 (TAN15), changing how flood risk is assessed and managed in planning decisions across Wales. The new guidance introduces updated flood maps, revised zones and stricter policies that will significantly affect future development, particularly in areas previously considered low risk.

Key Takeaways

• Development Advice Mapping (DAM) has been discontinued with DAM references and DAM Flood Zones ((C1, C2, B and A) removed
• Flood Map for Planning (FMfP) shows more land at risk of flooding in comparison to DAM
• Inclusion of  a new ‘Defended’ Flood Zone and associated policies for new development within a defended area
• There have been alterations to the vulnerability classifications, including category changes
• Removal of the Justification Test (Sequential Test) in favour of defining acceptability criteria of flood consequences
• No new highly vulnerable development will be permitted in Zone 3, regardless of the conclusions of a Flood Consequence Assessment, with the exception of proposals essential to the Development Plan Strategy
• New development on greenfield sites at risk of flooding will face greater scrutiny and is likely to be strongly discouraged.
• Redeveloping existing, previously used land in flood-prone areas might be more acceptable under specific conditions, likely involving robust flood resilience measures
• There is now a greater emphasis on detailed assessment of flood depths and velocities within Flood Consequence Assessments
• Developers must now consider compensatory flood storage for potential displacement of floodwater up to the 1 in 1,000-year event, plus climate change allowance. This should be provided on a ‘like for like’ and ‘level for level’ basis where feasible. Importantly, any proposals must also assess the potential impacts of displaced floodwater on surrounding areas to ensure no increased flood risk elsewhere

The Development Advice Map (DAM) has been discontinued and replaced with Flood Map for Planning (FMfP). DAM is to be retained on DataMap Wales for a period of 8 weeks to inform planning schemes currently being determined. It will be removed from this viewer sometime after May 2025.

The TAN15 update includes a new Defended Flood Zone. TAN15 Defended Zones are protected by defences that shield against at least one major source of flooding, whether from the sea, rivers, or sometimes both. However, some areas within these zones could still be at risk from other flooding sources, so it’s crucial to evaluate all potential risks. Additionally, any new development within TAN 15 Defended Zones must incorporate resilience and resistance measures to ensure it remains safe, flood-free, and adequately addresses the requirements outlined in the Flood Consequences Assessment.

The old Justification Test has been replaced with a greater focus on a plan-led approach to decision-making regarding development in flood risk areas.

The old Justification Test required developers to demonstrate that the location of a proposed development in a Flood Zone was necessary (for example, to support a regeneration initiative or strategy for sustaining an existing settlement, or for specific employment needs) and cannot be located in a lower-risk area.

The revised methodology within TAN15 prioritises a decision-making framework through a comprehensive understanding of flood risk. It stresses the necessity for Local Development Plans to strategically allocate land for development, integrating flood risk considerations based on the Flood Map for Planning and SFCA evidence.

The assumption is that flood risk considerations are expected to be integrated from the earliest stages of the planning process. This approach offers greater flexibility for redevelopment of previously developed land within flood risk areas, whilst tightening the rules for new development within the floodplain

In summary, TAN15 has replaced a criteria-based “Justification Test” with a broader, more strategic plan-led approach to development in flood risk areas. This approach emphasises integrating flood risk management into the planning process from the outset, with a focus on sustainable development, regeneration through the understanding of flood consequences.

In terms of how the flood risk will be applied to your planning application will depend on the vulnerability classification, flood risk zone, whether the site is defended and whether it is greenfield or previously developed.

Zone 1

In Zone 1 all vulnerabilities of use will be acceptable in principle provided that there is no increase in flooding elsewhere and flood-resistant and resilient design in locally defined areas of future or current flood risk are included.

Zone 2

Planning applications in Zone 2 require careful consideration and must be consistent with the acceptability considerations. They must also be accompanied by a FCA which clearly describes the flood risk and the risks must be acceptable. 

Applications for new highly vulnerable development on greenfield land are only appropriate where the site has been allocated in adopted Development Plans.

Proposals for redevelopment on brownfield land of any vulnerability will need to assist, and be consistent with, the Development Plan strategy to regenerate an existing settlement or achieve key economic or environmental objectives. 

Where proposals for redevelopment include residential use, local authorities should ensure that such uses do not occur at the ground floor level; they will also need to be compatible with the tolerable conditions and exhibit resilient flood design.

Zone 3

Planning applications in Zone 3 require the strongest justification. 

No new highly vulnerable development on greenfield land should be permitted in Zone 3, regardless of the conclusion of any Flood Consequences Assessments and NRW will not consider these conclusions.

Other proposals will only be appropriate if they are essential to the Development Plan Strategy to regenerate an existing settlement or achieve key economic or environmental objectives. Any redevelopment proposal must be consistent with the acceptability considerations set out in TAN.

Water-compatible development is acceptable in all flood zones.

In addition, proposals which include residential development must ensure that such uses do not occur at the ground floor level.

Defended Zones

Applications for new development on Greenfield sites are not appropriate in Defended Zones unless they are allocated in development plans. 

On brownfield sites, redevelopment proposals should not over-intensify use, nor should they reduce the area’s ability to absorb flood water, nor cause problems with flooding elsewhere.

All applications should consider opportunities to incorporate flood resilient design as appropriate, and any proposal involving highly vulnerable development must be compliant with the tolerable conditions.