UK Climate Projections: impacts on development and flood risk

The world of development and flood risk has evolved since the first Department of the Environment circular on the matter in 1992. National Planning Policy has been updated a number of times, most recently in July 2018.

Our understanding of the likely impacts of climate change on river flows, rainfall and coastal change has also developed with technological advances in climate scenario modelling. The new UK Climate Projections 2018 (UKCP18) will give us more specific information at a local level to feed into future development plans.

Taking this into account, how can UKCP18 help with the challenges that lie ahead?

  • How do we ensure development is appropriately safe from flooding?
  • How do we ensure development does not increase flood risk elsewhere?
  • How do we ensure that development contributes to the wider collective vision of flood risk, drainage and coastal change for an area?
  • What should the planning policy be in those areas where the viability of any development is questionable in the long term? For example, due to increased flood risk and/or coastal change?

Strategic decision making

Having up-to-date and more reliable projections based on the latest climate science will mean we are better placed to help our clients respond to these challenges. The projections will help make strategic decision making through Sustainability Appraisals, Strategic Environmental Assessment, Climate Change Risk Assessments, Strategic Flood Risk Assessments and Water Cycle Studies more robust.

At a site level, our work with developers on Flood Risk Assessments will also benefit from using the new information. More specific guidance on how the new UKCP18 allowances should be considered in such work is expected in 2019. My colleague Angus Pettit explored this in his blog last week.

Read Angus’ UK Climate Projections: impacts on appraisal of flood schemes blog.

Interdisciplinary thinking

UKCP18 will provide probabilistic information based on different scenarios of change. How can we use probabilistic information in an appropriate manner? For example, how do we use the most likely scenario to inform the allocation and master planning of new developments and following on from this, the design of mitigation measures?

How can we then make those decisions sustainable in the long term and for the life of new developments? And how can we use the less likely, but more extreme, change scenarios to make new developments resilient in future? This requires interdisciplinary thinking. For example, the use of green corridors and infrastructure to safely channel water away from new developments and the innovative design of new housing and commercial units with flood risk in mind.

The revised National Planning Policy Framework (NPPF) places an emphasis on planning for the cumulative impacts of new development at a strategic level. For those catchments at high flood risk and/or where there is likely to be the newest development, what should local planning policy say? What are the most sensitive catchments to target more stringent policies on SUDS and runoff rates and volumes towards? How can achieving the wider benefits of SUDS also assist in ensuring developments are adaptable to climate change. For example, how could water be stored for use in times of drought?

Flood risk management

With climate change on the cards, where does land need to be safeguarded against new development for flood risk management, such as the use of natural flood management upstream of our settlements or opening up inner city culverts?

Where could new developments meaningfully contribute to reductions in risk in these areas? Could land on the sites be put aside for flood storage and/or could developers be required to contribute partnership funding towards flood alleviation schemes? We are working through a number of these areas with local authority clients on Strategic Flood Risk Assessments at present.

Coastal change

Lastly but by no means least, sea level rise poses an additional and even more complex challenge. Losses from coastal erosion are absolute. Major coastal flood events are life-threatening and cause extensive devastation.

New UKCP18 outputs should help Local Planning Authorities (LPA’s) to apply the direction in the NPPF to identify and develop appropriate planning policy for areas vulnerable to coastal change. We have been supporting coastal LPAs with developing long term policy approaches to tackle coastal change, considering the multiple complexities this challenge brings.

Want to know more?

Email Hannah Coogan for more information. You can also find out more at on our flood and water management web pages.

Click here to read all our UKCP18 blogs.

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