SHhhh! For those of us not “Living in the Real World,” more Climate Change updates for CPBC to ignore!

Ian Joyner, Associate Director and lead on Flood Risk . writes;

To little fanfare, and amongst a host of other announcements today, the Environment Agency released updated climate change allowances for flood risk and new development in England, bringing their guidance in line with UKCP09 climate change scenarios.

https://www.gov.uk/guidance/flood-risk-assessments-climate-change-allowances

However evidence-based and necessary this new advice may be, the changes in river flows under certain scenarios mark a significant departure from the existing 20% increase in a flood flow with an annual chance of 1 in 100 (1%), currently  used to plan for new development.

The change, which broadly appears to apply to all developments not already submitted for planning, means that the existing well-resourced stock of Environment Agency climate change simulations are now outdated, leading to a short-term need for developers to undertake (and the Environment Agency to review) their own climate change modelling.

Furthermore, the disconnect between the online Flood Map for Planning (which sets the Flood Zone extents based on present day risk) and the climate change flood events (to which buildings and mitigation measures are designed) has increased following this change. This could make planning more challenging at the edge of Flood Zones.

A fairly significant change then, which will require careful thought from regulators, developers and their advisors.

Arbitrary percentage increases in peak flows bring about their own problems (where flood volume is important for example) and there are likely to be theoretical limits in very urban catchments where an increase in storminess instead leads to an increase in surface flooding across a catchment where sewers do not have sufficient capacity to convey this increased flow directly to rivers.

It could also be argued that the change, whilst bringing requirements in line with current climate change scenarios, does nothing to address the main criticism levelled at flood risk management over this winter; that climate change is already influencing river flows in the present day and this is not factored into current estimates.  Addressing this would require a more fundamental look at the way pooled hydrological data recorded in the (relatively recent) past is used to predict future extremes.

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One response to “SHhhh! For those of us not “Living in the Real World,” more Climate Change updates for CPBC to ignore!

  1. Editor
    It is times like this that it is worth revisiting to fully understand the Flood Risk Guidance that supports the NPPF

    Guidance Applying the Sequential

    Test in the preparation of a Local Plan
    What is the aim of the Sequential Test for the location of development? The Sequential Test ensures that a sequential approach is followed to steer new development to areas with the lowest probability of flooding. The flood zones as refined in the Strategic Flood Risk Assessment for the area provide the basis for applying the Test. The aim is to steer new development to Flood Zone 1 (areas with a low probability of river or sea flooding).
    Where lower flood risk may not be suitable for development for various reasons and therefore out of consideration, the Sequential Test should be applied to the whole local planning authority area to increase the possibilities of accommodating development which is not exposed to flood risk.
    More than one local planning authority may jointly review development options over a wider area where this could potentially broaden the scope for opportunities to render a range of options in the site allocation process, using the Strategic Flood Risk Assessment to apply the Sequential Test and the Exception Test where necessary. This can be undertaken directly or, ideally, as part of the sustainability appraisal.
    Where other sustainability criteria outweigh flood risk issues, the decision making process should be transparent with reasoned justifications for any decision to allocate land in areas at high flood risk (Flood Zones 2 and 3) and other areas affected by other sources of flooding where possible. Application of the sequential approach in the plan-making process, in particular application of the Sequential Test, will help ensure that development can be safely and sustainably delivered and developers do not waste their time promoting proposals which are inappropriate on flood risk grounds

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