Flooding and Climate Change - A picture of increasing resolution
30 July 2021
In the aftermath of the extreme flooding we witnessed in recent weeks across central Europe, which has scarred the landscape and our conscience in respect to the destructive effects of climate change, we witnessed scenes earlier this week closer to home. Extreme rainfall in London saw a catastrophic impact on the property and infrastructure of the city. The images of these events serve as a timely reminder to the politicians and policy makers of the ever growing importance of their active engagement in the forthcoming UN Climate Change Conference (COP26) in Glasgow, to share a common view that the need for change is urgent.
In the assessment of flooding in the UK, with respect to understanding the impact of development, the effects of climate change has been an important consideration for a number of years. A precautionary approach is taken and policy makers have caught up with trying to impose a requirement to not only make a development safe, but also to design developments in a manner that reduces flood risk elsewhere, with an allowance for the effects of climate change over the lifetime of that development. Only through a cumulative contribution to betterment through catchment management and well-designed development will we be able to off-set the likely increase in big rainfall events we will see in coming decades.
Using improved climate models (UKCP18-2.2km) the Environment Agency have published this week updated climate change allowances to apply to river flows and the assessment risk for all new development in England. The updated guidance further dissects the country into smaller river basins and acknowledges the fact that the effects of climate change on flooding is likely to have significant regional variation. To help communicate the changes, the Environment Agency have published a very useful map portal which provides the % increase in river flows for your area of interest.
In summary, flood predictions have increased in some catchments and reduced in others, but what is consistent is that the allowances to be applied to essential infrastructure and Nationally Significant Infrastructure Projects (NSIP) have increased significantly in many areas and could form a considerable constraint.
Clearly it is no coincidence that the government have coordinated the launch of this guidance with the publication of the updated National Planning Policy Framework (NPPF), to ensure that Climate Change remains fully imbedded in the planning system. The new NPPF states:
“All plans should apply a sequential, risk-based approach to the location of development – taking into account all sources of flood risk and the current and future impacts of climate change – so as to avoid, where possible, flood risk to people and property.”
The new climate change guidance has moved the goal posts overnight and has the potential to impact on Local Plan site allocation and site specific planning applications that have not yet been completed. Although disruptive in the short term to the planning process, the introduction of better data on climate change predictions to inform good decision making and design is a positive step to building a more resilient future.