New flood maps for Wales – Flood Map for Planning

In our third and final blog on the new flood maps coming to Wales, George Baker, Associate Director looks at a flood map that we are expecting to see published in Spring 2021.

As part of the long awaited update of Technical Advice Note 15 (TAN15): Development and Flood Risk, the Welsh Government are now undertaking consultation and development work on a new Flood Map for Planning.

Our understanding of the Flood Map for Planning is based on Welsh Government’s consultation on an updated TAN15 which concluded January 2020, and a recent limited consultation on the presentation of the new map. Both the new TAN15 and associated flood map are still draft and therefore subject to change. However, given recent messaging from Welsh Government, significant changes to the proposed Flood Map for Planning appear unlikely.

What can we expect?

The new Flood Map for Planning will incorporate projections for how climate change will affect flood risk over the next century. This is a major departure from the current Development Advice Map, which shows only the present-day risk of flooding. This is also different to the new Flood Risk Assessment Wales (FRAW) map that we covered in Part 2 of this blog series.

Another major development from the current Development Advice Map is that the Flood Map for Planning is proposed to incorporate Surface Water and Small Watercourse flood risk in addition to the risk from Rivers and Sea. This will necessitate a more comprehensive assessment of flood risk when proposing new development.

The proposed flood map will introduce new flood risk bands to support a more risk-based approach to decision making. Currently our understanding of the new zones is as follows:

  • Zone 1:  greater than 1:1000 annual chance of flooding: no flood risk constraints to development. Zone 1 are areas not covered by any of other zones.
  • Zone 2: between 1:000 and 1:100 (1:200 sea) annual chance of flooding: all types of development subject to TAN 15 tests. Flood Consequences Assessment required.
  • Zone 3: less than 1:100 (1:200 sea) annual chance of flooding: no highly vulnerable development; less vulnerable development subject to TAN 15 tests and a Flood Consequences Assessment required.
  • Defended zones: all types of development subject to TAN 15 tests. Flood Consequences Assessment required. The technical definition of what constitutes a Defended Zone is currently unknown.

Zones 2 and 3 are based on ‘undefended’ flood modelling i.e. assuming no flood defences. Defended Zones will designate if an area benefits from flood defences.

Climate change

At first glance the new Zones when applied to River and Sea flooding are very similar to Zones 2 and 3 of previous Flood Map. The big change here is the addition of climate change. This can have a significant impact on the extent and banding of flood risk, particularly in coastal areas where predicted sea level raise can be game changing.

In fact in many coastal areas (eg. Cardiff, Newport, Port Talbot) large areas previously indicated to be at little or no flood risk will now find themselves in the highest risk category.

What the maps will show

The current draft maps that we have seen show two versions of the Flood Map for Planning:

  • ‘Basic’ version aimed at planners and decision makers with the key policy layers.
  • ‘Detailed’ version that will provide flood risk professionals with a more detail insight into the underlying and contextual data.

Want to know more?

Our understanding and appreciation of flood risk is always changing and improving. With this comes the need to update our tools, technology, processes and policy. We therefore welcome these new flood maps and are proud of our involvement in various aspects in their development.

We hope that this blog series has helped, and if you would like any more information on how JBA can support your projects please contact George Baker.

You can also find out more in Part 1 and Part 2 of this blog series on the new flood maps for Wales.

Leave a Reply