New TAN15 2025: Flood & Planning Policy Update

According to Rebecca Evans MS, Cabinet Secretary for Economy, Energy and Planning, the updated TAN15

She noted that this guidance

TAN15 2025 ushers in a modernised, climate-responsive approach that aims to ensure communities, infrastructure, and the natural environment are more resilient in the face of increasing flood risk. It encourages proactive risk management through a stronger integration of flood mapping, climate science, and planning policy.

In this blog, we unpack the key changes introduced by the new TAN15, compare them with the previous framework, and explain what this means for planners, developers, and local authorities across Wales.

Key Principles and Detailed Changes in the New TAN15

1. Plan-led and Risk-based Framework
   The new TAN15 is fundamentally plan-led, requiring flood risk and coastal erosion to be considered from the earliest stages of strategic planning. Local Development Plans (LDPs) must integrate flood risk mapping and evidence such as Strategic Flood Consequence Assessments (SFCAs). This reflects a shift from reactive decision-making to strategic, risk-informed planning.
2. Flood Map for Planning (FMfP)
   Replacing the outdated Development Advice Map (DAM), the FMfP is a digital, frequently updated spatial tool managed by Natural Resources Wales. Updated biannually, it provides enhanced layers including surface water, rivers, sea, and small watercourse flood risk. Crucially, it now also identifies TAN15 Defended Zones and areas susceptible to coastal erosion.
3. Defended Zones and Residual Risk
   The policy introduces 'TAN15 Defended Zones' — areas protected by flood defences that meet specific design standards (e.g. 1:100 for fluvial flooding, 1:200 for tidal). Development is not prohibited in these zones but must demonstrate consideration of residual risk, including overtopping and breach scenarios. A Flood Consequences Assessment (FCA) is required regardless of the presence of defences.
4. Refined Vulnerability Classification
   The classification of development types has been updated and expanded. Categories now include Highly Vulnerable, Less Vulnerable, and Water-Compatible developments. Examples of Highly Vulnerable uses include all residential buildings, hospitals, schools, and emergency services infrastructure. This classification determines where development may be acceptable depending on the level of flood risk.
5. Mandatory Flood Consequences Assessments (FCAs)
   FCAs are now compulsory for a wider range of applications — not only in higher-risk areas but also in TAN15 Defended Zones and certain lower-risk zones adjacent to small watercourses. The requirements have become more technical, with applicants expected to address breach, blockage, exceedance, and climate change projections.
6. Coastal Erosion Risk Now Fully Integrated
   For the first time, TAN15 fully integrates coastal erosion risk into development planning. Proposals must align with Shoreline Management Plans (SMPs) and consider the long-term retreat of coastlines. This will be especially significant for regeneration projects and infrastructure in at-risk coastal areas.
7. Stricter Rules for Development on Greenfield Land
   The 2025 Notification Direction requires LPAs to notify the Welsh Ministers of applications for Highly Vulnerable Development on previously undeveloped land within Flood Zone 3. A 21-day notification period follows, during which Ministers may call in the application. This aims to reduce inappropriate development in high-risk areas.
8. Emphasis on Design for Resilience
   New developments must now embed design measures to manage residual flood risk, such as raised floor levels, flood-compatible materials, SuDS schemes, and emergency access planning. Designing for exceedance — planning how water will behave when systems are overwhelmed — is now explicitly required.
9. Transitional Arrangements and Immediate Effect
   The policy applies to all planning applications made on or after 31 March 2025. Applications submitted before that date are considered under the previous TAN15. However, LPAs are encouraged to adopt the principles of the new TAN15 during the transitional period.

What’s Changed Since the 2004 TAN15?

• More Nuanced Decision-Making: The old blanket approach has been replaced by a more balanced framework that accounts for defences, mitigation, and land use type.
• Advanced Mapping and More Risk Categories: The FMfP introduces more comprehensive and frequently updated mapping layers.
• New Referral Requirements: Applications that increase residential dwellings on undeveloped land in Zone 3 now require Ministerial referral.
• Integrated Coastal Policy: Coastal erosion is treated as a primary planning concern for the first time.
• Expanded Scope for FCAs: These are now required in more situations and to a higher technical standard.

Implications for Stakeholders

• Local Planning Authorities (LPAs) must revisit LDPs, consult updated flood and erosion maps, and engage in early dialogue with NRW and Welsh Government for sensitive applications.
• Developers and Housebuilders will face more complex site selection and pre-application processes, particularly on greenfield or coastal sites. Early-stage engagement and robust technical evidence are key.
• Flood Risk Consultants and Engineers will play a pivotal role in delivering robust, site-specific FCAs that satisfy new technical requirements.
• Communities and Landowners will need clear, early engagement — particularly in areas reclassified under FMfP or where regeneration and flood risk overlap.

The new TAN15 represents a turning point in how Wales embeds climate resilience into development planning. It is no longer enough to acknowledge flood risk on paper — developers, planners, and consultants must now show precisely how that risk is being addressed, reduced, or managed. This shift places a premium on robust site assessments, integrated drainage strategies, and early-stage collaboration.

For many stakeholders, these changes will require a significant upskilling in how flood data is interpreted and how proposals are shaped. The emphasis on site-specific evidence means generic or templated FCAs are unlikely to suffice — tailored, technical, and forward-looking assessments are now the expectation.

Moreover, the combination of coastal erosion policy, Defended Zones, and dynamic mapping adds new layers of complexity to an already technical process. It’s crucial for everyone involved in development — particularly in at-risk areas — to become familiar not just with what the new TAN15 says, but how it must be applied.

As Rebecca Evans MS put it, this is "a landmark moment for Welsh planning policy," one designed to ensure decisions are "informed by the best available evidence on climate change and flood risk."