With the latest climate change requirements published by the Environment Agency (EA), what do they mean for developments and will this lead to additional assessments being required in the future?
- The EA’s updated climate change allowances impact how rainfall intensity needs to be calculated when designing surface water drainage strategies, with allowances following a similar trend to fluvial climate change, in that this is now a regional approach rather than country-wide.
- There are two main approaches which depend on the size of the site. For all catchments less than 5km² (or urbanised) these updated climate change allowances should be used. In all instances there is either no change, or an increase in the climate change requirements which need to be assessed.
- For rural catchments larger than 5km², guidance states that alternatively the fluvial allowances should be used.
- Interestingly some allowances for earlier epochs (2050s) state higher climate change requirements (in comparison to 2070s), however clarification states that the higher of the two figures should be used for design purposes.
Whilst this guidance is aimed at drainage design, the question may be in the future whether climate change modelling will be required (as per fluvial flooding) to assess the impacts of climate change on surface water (pluvial) flooding using this updated guidance. If this does transpire, a further question remains as to whether strategic modelling will be undertaken by the EA, or will developers need to assess this independently.
What appears true for now is that Lead Local Food Authorities (LLFAs) are requiring the updated guidance to be used for those planning applications not yet submitted, with additional space for attenuation needing to be accommodated.
https://www.gov.uk/guidance/flood-risk-assessments-climate-change-allowances#peak-rainfall-intensity-allowance
If you would like to discuss these potential implications in more detail please feel free to get in contact. Logika Consultants are experts in Flood Risk and Drainage, Biodiversity, BNG, Natural Capital, and Green Infrastructure design. Our sister companies Air Quality Consultants and Noise Consultants are similarly technical experts with regards to air quality and noise assessments.
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