Changes to flood risk guidance in Wales

April 30, 2025

Understanding both current and future flood risk in Wales is essential for helping planners, developers and landowners understand how flood risk is assessed within the planning process, ensuring that new developments are resilient and sustainable.


Originally published in 2004, the Welsh Government recently published a significantly revised Technical Advice Note (TAN) 15 on 31st March, detailing critical changes to flood risk guidance.



What are the key updates?



  • Development types: 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.


  • A risk-based approach: The new TAN15 adopts a risk-based plan-led decision-making approach that incorporates advancements in flood risk mapping technology and climate change assessment.


  • Flood Map for Planning: The new TAN15 utilises the Flood Map for Planning rather than the previous Development Advice Maps (DAM) to evaluate the suitability of developments based on flood risk zones.


  • Flood Consequence Assessments: 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.


  • Planning applications: The new TAN15 applies to all planning applications made on or after 31st March 2025. Applications submitted before that date are considered under the previous TAN15. However, Local Planning Authorities are encouraged to adopt the principles of the new TAN15 during the transitional period.


  • Design considerations: 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.



The role of Envireau Water


At Envireau Water, we work closely with clients across Wales to navigate and understand these critical policy changes. If you're unsure how the updated TAN 15 may affect your site, get in touch on info@envireauwater.co.uk.. We're here to help!




About Envireau Water


Envireau Water is a team of expert water scientists and engineers who provide guidance on the management and regulation of natural water systems across the UK. By working collaboratively with our clients and the regulators, we deliver robust, sustainable solutions that meet the requirements of all stakeholders. With a loyal client base and our ability to work seamlessly throughout the four nations of the UK, many of our clients know us individually and trust us to find resolutions to their water problems for years to come. 

Share

By Rachael Plant July 10, 2025
We're always excited to see our team grow, and we are thrilled to welcome Hannah to the team. Hannah joined our Scotland office at the end of June to gain some hydrogeological experience alongside completing her university studies, and we look forward to welcoming her officially in September where she will begin her career as a Hydrogeologist. Prior to joining, Hannah completed a BSc in Environmental Sciences at University of Glasgow and is currently working towards completing an MSc in Hydrogeology at the University of Strathclyde. During her masters and undergraduate degree, Hannah has participated in various fieldwork activities where she developed an in-depth understanding of applied hydrology, soil analysis and mapping techniques.
By Rachael Plant July 8, 2025
Our team just keeps on growing and we are delighted to welcome Rob Pickersgill as our newest member! Rob joined us at the end of June, bringing extensive experience across both hydrology and civil engineering, with a particular focus on hydraulic modelling, Flood Risk Assessments (FRAs), and Discharge Impact Assessments. Rob's academic background stems from the University of Nottingham, where he completed a MEng in Engineering, followed by an MSC in Global Urban Development and Planning at the University of Manchester. Rob joins our specialist surface water team and will be based at the RSK Group office in Bristol, providing hydrological services to a range of projects for our diverse client base, primarily within the development sector.
By Rachael Plant June 17, 2025
Desertification and drought are two of the most pressing environmental challenges of the 21st century. Exacerbated by climate change, the devastating effects of both can be felt across the globe, with an estimated 40% of the world's population impacted by water scarcity events. As global temperatures continue to rise, and severe weather events increase, regions across the globe face the potential for increased frequency and severity of droughts, often progressing rapidly and unexpectedly. As of 29th May this year, a drought was officially declared in parts of the UK, having experienced the driest start to Spring in over 130 years. Whilst the recent rainfall at the start of June has helped to stabilise concerns, uncertainty for the months ahead still remain. How is the UK landscape affected by drought?
Show More
By Rachael Plant July 10, 2025
We're always excited to see our team grow, and we are thrilled to welcome Hannah to the team. Hannah joined our Scotland office at the end of June to gain some hydrogeological experience alongside completing her university studies, and we look forward to welcoming her officially in September where she will begin her career as a Hydrogeologist. Prior to joining, Hannah completed a BSc in Environmental Sciences at University of Glasgow and is currently working towards completing an MSc in Hydrogeology at the University of Strathclyde. During her masters and undergraduate degree, Hannah has participated in various fieldwork activities where she developed an in-depth understanding of applied hydrology, soil analysis and mapping techniques.
By Rachael Plant July 8, 2025
Our team just keeps on growing and we are delighted to welcome Rob Pickersgill as our newest member! Rob joined us at the end of June, bringing extensive experience across both hydrology and civil engineering, with a particular focus on hydraulic modelling, Flood Risk Assessments (FRAs), and Discharge Impact Assessments. Rob's academic background stems from the University of Nottingham, where he completed a MEng in Engineering, followed by an MSC in Global Urban Development and Planning at the University of Manchester. Rob joins our specialist surface water team and will be based at the RSK Group office in Bristol, providing hydrological services to a range of projects for our diverse client base, primarily within the development sector.
By Rachael Plant June 17, 2025
Desertification and drought are two of the most pressing environmental challenges of the 21st century. Exacerbated by climate change, the devastating effects of both can be felt across the globe, with an estimated 40% of the world's population impacted by water scarcity events. As global temperatures continue to rise, and severe weather events increase, regions across the globe face the potential for increased frequency and severity of droughts, often progressing rapidly and unexpectedly. As of 29th May this year, a drought was officially declared in parts of the UK, having experienced the driest start to Spring in over 130 years. Whilst the recent rainfall at the start of June has helped to stabilise concerns, uncertainty for the months ahead still remain. How is the UK landscape affected by drought?
By Rachael Plant June 12, 2025
Envireau Water is delighted to welcome Tom Onslow to our North Office in Richmond! Tom joined us at the start of the month from Western Australia, where he gained experience working as a Field Hydrogeologist. Prior to this, Tom graduated from Newcastle University with a Master of Earth Science (MEarthSci). Tom is experienced in both field and desk-based activities, including the supervision of water exploration drilling programs, conducting hydrogeological sampling and logging, carrying out pumping tests and analysis and designing and installing groundwater monitoring networks. Tom has also built a strong foundation in technical reporting, having contributed to a wide range of water-related projects, particularly across the mining sector. At Envireau Water, Tom will continue to develop his hydrogeological expertise and provide technical support across a range of sectors both on site and in the office.
Show More