Flooding Risk

Some 140,000 properties in Wales (12% of the total housing stock) are thought to be at risk from flooding by rivers or the sea. Experience of recent years suggests that the incidence of problems due to flooding may be increasing in both frequency and scale, largely due to climate change. Therefore, development in Wales must be planned sensitively using a robust risk-based approach. To this end, the Welsh Assembly Government produced Technical Advice Note 15: Development and Flood Risk (TAN 15) in 2004. The aim of TAN 15 is to provide technical guidance which supplements the policy set out in Planning Policy Wales, 2002 (PPW).


Flooding exampleTAN 15 provides guidance on development and associated flood risk. It provides a framework within which risks arising from both river and coastal flooding, and additional rainfall run-off from development, can be assessed. In order to gain planning permission, all new development in Wales has to be tested against TAN 15 for flood risk. The aim is to direct new development away from high risk areas or to justify development in high risk areas.

Sustainable Drainage Systems (SuDS)

Managing flood risk is an important part of achieving sustainable development. SuDS have a key role to play in flood management for new (and existing) developments, and TAN 15 recognises this. All types of land use change impacts on the natural hydrological cycle and development should not increase flood risk. Section 8 of TAN 15 sets out recommendations for the use of SuDS, referencing the National SuDS Working Group’s Interim Code of Practice for Sustainable Drainage Systems (2004) for appropriate guidance.