Climate Change

An allowance for rainfall intensities changing due to climate change should be incorporated into storage capacities.

In February 2019 the Government updated it’s 'Flood risk assessments; climate change allowances' document. This guidance provides updated climate change figures which should be used for flood risk assessments and drainage strategies to help minimise vulnerability and provide resilience to flooding and coastal change in the future. Within this is an update on the Peak Rainfall Intensity Allowance in small and urban catchments as shown in the table below. The climate change allowance required is dependent on the lifespan of the development after it has been completed. The LLFA take a conservative, risk adverse approach to flood and water management and therefore expect the Upper End figures to be used.

Table below showing the peak rainfall intensity allowance in small and urban catchments (use 1961 to 1990 baseline)

Applies across
all of England
Total potential change
anticipated for the ‘2020s’ (2015 to 2039)
Total potential change anticipated for the ‘2050s’ (2040 to 2069) Total potential change anticipated for the  ‘2080s’ (2070 to 2115)
Upper end 10% 20% 40%
Central 5% 10% 20%

Page updated: 17/02/2020

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