The new National Planning Policy Framework – what next for flood risk and drainage?

Sites adopting a broadly sequential approach to flood risk may no longer need to apply the sequential test as a result of the latest changes to the National Planning Policy Framework (NPPF).  Yet while the strengthening of the wording around this aspect of policy has been well received, there remain some unanswered questions.  In the following article, Director Neil Jaques considers the initial implications for flood risk and drainage requirements. 

Tackling climate change – mitigation and adaptation

Paragraph 162 of the new NPPF sets the scene for a future approach to the role of infrastructure development and protection in climate change mitigation and adaptation strategies.  It states:

“Plans should take a proactive approach to mitigating and adapting to climate change, taking into account the long-term implications for flood risk, coastal change, water supply, biodiversity and landscapes… Policies should support appropriate measures to ensure the future health and resilience of communities and infrastructure to climate change impacts, such as providing space for physical protection measures, or making provision for the possible future relocation of vulnerable development and infrastructure.”

Flood risk and the trigger for the sequential test

One of the most significant changes for developments affected by drainage infrastructure requirements or flooding is the relaxing of the need to trigger the sequential test.  This is underscored by the addition of the new text in paragraph 175:

“The sequential test should be used in areas known to be at risk now or in the future from any form of flooding, except in situations where a site-specific flood risk assessment demonstrates that no built development within the site boundary, including access or escape routes, land raising or other potentially vulnerable elements, would be located on an area that would be at risk of flooding from any source, now and in the future (having regard to potential changes in flood risk).”

This narrow but important exception is a significant step forward from the days when developers might have been tempted to adjust the red line on a plan to avoid triggering the need for a sequential test.  In future, a sequential test will not be required in developments where a site-specific flood-risk assessment can demonstrate that the built development falls outside of any or all flood risk.  This new change will surely be welcomed by the industry.

Sites may still need to satisfy the sequential test where the proposed built development falls within flood zones 2 or 3 and is at risk of surface-water or groundwater flooding.  Here, there appears to be no material difference between how defended and undefended land is dealt with.  Large parts of London are defended from flooding, even if they are technically in flood zones 2 or 3.  In theory, development on these sites might still require a sequential test, although due to the location and availability of other suitable sites, it might be easier to pass that test.  However, this could be yet another hurdle to overcome in the capital.

What constitutes mitigation and an available site?

Another slight ambiguity is in the detail of what could be permitted as mitigation measures to address the reference to ‘now and in the future’.  Some commentators have noted the consultation response which states that the sequential test cannot rely on mitigation measures that would require ‘active maintenance’.

There is a big difference between adjusting ground levels to divert flows around green spaces on the edge of a development compared to, say, storing and controlling the flow with an attenuation basin.  Under the new paragraph 175, a mitigation measure requiring active maintenance could not be relied upon, based on the consultation response.  However, would a strategy to simply divert flows still trigger the sequential test?  No doubt rulings will be obtained in the future on how to apply this, as yet, untested point.

In summary, the sequential test flood-risk criteria have now been enacted by statute, and the increased weight this brings is appreciated.  Additional clarification in any future guidance would help planners and engineers further interpret what constitutes ‘an available site’.  I therefore welcome the commitment to review the Flood Risk and Coastal Change Planning Practice Guidance (PPG).

Sustainable drainage infrastructure – a new threshold?

There is no longer a limit to the size of development where sustainable drainage systems (SuDS) should be considered.  New paragraph 182 states:

“Applications which could affect drainage on or around the site should incorporate sustainable drainage systems to control flow rates and reduce volumes of runoff, and which are proportionate to the nature and scale of the proposal.  These should provide multifunctional benefits wherever possible, through facilitating improvements in water quality and biodiversity, as well as benefits for amenity.  Sustainable drainage systems provided as part of proposals for major development should: a) take account of advice from the Lead Local Flood Authority; b) have appropriate proposed minimum operational standards; and c) have maintenance arrangements in place to ensure an acceptable standard of operation for the lifetime of the development.

Acknowledging the impact on surface water that developments can make regardless of size, this change will mean fewer schemes slip below the threshold.  An expanded definition of SuDS has also been included in the new framework glossary, placing more emphasis on interventions that might be appropriate for small-scale developments.

Practical implementation of the new NPPF

Motion advises clients on flood matters and drainage requirements for a range of sites, each with its own unique set of challenges and restrictions.  Contact Neil Jaques on 01483 531300 if you need expert support with your next project.