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Flood management policy guidance

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

1. Rather than taking a scenario approach to a climate change impact assessment, arbitrary 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.

  1. The 11-member RCM data was then used to consider where on the sensitivity surface for each catchment these different climate model realisations occur.
  1. The IPCC AR4 models were also used to evaluate what change they indicate with respect to the sensitivity surfaces.
  1. From this, a broad picture is built up about the vulnerability of each catchment and the potential impact on river flows together with the likelihood of that change occurring.

Next steps

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.

Lessons learned

  • The lack of 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.

Find out more

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