Saturday, 7 January 2017

Climate change allowance for flood risk assessments

DCC's objection to Aggregate Industries' Hillhead ROMP application says:
Following the publication of the Flood Risk Assessments: Climate Change Allowances document (dated 19th February 2016) by central government, the applicant will be required to use a climate change uplift value of 40% when sizing the proposed surface water drainage management system for this development.
The same authority raised issues over the proposals for Straitgate back in 2015; proposals that were looking to permanently change the landscape and surface water runoff above a town with a long history of flooding. In response to that application, DCC said:
The surface water management is inextricably connected to Flood Risk Management/ Airport safeguarding and the need to maintain and recharge watercourses. This issue is so important in terms of the likely significant impacts of the proposal the MPA would wish to ensure that a SWM scheme can be designed to meet all of the requirements identified in advance of the determination of this application.
Based on the Environment Agency's advice at that time, this was the allowance that Amec made for climate change in that application:

The Environment Agency has since issued new advice on flood risk assessments and climate change:

To see why a 10% allowance was grossly inadequate, here's just one graph from the UKCP09 climate projections, for the change in winter precipitation in the South West for a high emissions scenario: