Environment Agency / Defra: Investigating current policy

Objectives: Current Defra/EA guidance requires all flood management plans to allow for climate change by incorporating within a sensitivity analysis an increase in river flows of up 20% over the next 100 years. The objective of this research is to use the latest evidence, including UKCP09, to re-consider the existing guidance and provide evidence for policy makers to help set new allowances depending on catchment vulnerability.

• How they used UKCP09

Rather than taking a scenario approach to a climate change impact assessment, arbitary climate changes were selected for a large number of catchments to provide sensitivity surfaces describing the climate/catchment dynamic in a scenario-neutral way. This approach identified the most vulnerable catchments.

• The 11-member RCM data was then used to consider where on the sensitivity surface for each catchment these different climate model realisations occur.

• The IPCC AR4 models were also used to evaluate what change they indicate with respect to the sensitivity surfaces.

• From this, a broad picture is built up about the vulnerability of each catchment and the potential impact on river flows togther with the likelihood of that change occuring.

• What could they do next?

• A potential range of change can be determined together with how the Hadley centre's 11-member RCM projections compare with the other global climate models.
• Using this evidence, the current guidance and climate change allowances for flood risk management can be reconsidered.

• What they learnt about UKCP09

• The lack of potential evapotranspiration projections in the probabilistic projections is a limiting factor to the study.
• The Weather Generator does provide potential evapotranspiration, however, it is as yet unknown how to best utilise the Weather Generator because of the large spatial information required to study a large catchment.

• Contact details: Bill Donovan, Environment Agency, Karl Hardy, Defra Flood Management, Nick Reynard, CEH Wallingford

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