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Update to ‘Flood risk assessments: climate change allowances’’

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What this is about

On 17th December 2019 our guidance for developers and planners on how to account for climate change in their flood risk assessments was updated – ‘Flood risk assessments: climate change allowances’. The main changes include:

  • Updated sea level rise allowances to reflect latest climate change projections (UKCP18), which have replaced previous projections (UKCP09);
  • Improved clarity and usability of the guidance. This has been informed by a user feedback event in summer 2017, plus general feedback and questions we’ve had since 2016 when it was originally published;
  • Amendments to reflect changes in policy since the National Planning Policy Framework was updated in 2018.

The updated sea level rise allowances are broadly similar to the previous allowances, although now a range of sea level rise allowances is provided so a range of sea level rise scenarios can be assessed.

When UKCP18 was published in November 2018 the Environment Agency shared an interim approach for planners and developers to use to ensure their development accounted for the upper end of sea level rise projections in UKCP18, as appropriate. On this basis, and because the updated allowances are broadly similar to previous allowances, developments approved using previous climate change allowances and guidance should be considered to be robust in the context of UKCP18. 

Future updates

The allowances for peak river flow and peak rainfall in ‘Flood risk assessments: climate change allowances’ are unchanged. This is because research is still underway to assess the impact of the rainfall projections in UKCP18 on peak river flow. In addition, high resolution rainfall projections have only just been published as part of UKCP Local (2.2km) (in September 2019) and work to analyse these projections and update peak rainfall allowances has not been completed. Any updates to these allowances will not be made until 2020. We will provide customers with more information regarding the need to update peak river flow and peak rainfall intensity allowances in due course.

Please note that we are also intending to update the guidance we produce for FCERM schemes in early 2020. ‘Adapting to Climate Change: Advice for Flood and Coastal Erosion Risk Management Authorities’ is unchanged for now. The update will be timed with other planned enhancements to appraisal guidance. Communications will be sent to relevant people in due course.


Please contact Sam Kipling ( if you have any queries.

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