The revised National Planning Policy Framework and its implications for FRAs and SFRAs

JBA SuDS new housing development
SuDS new housing development

The revised National Planning Policy Framework (NPPF) was released on 24 July 2018. So what impact will this have on how flood risk is assessed for planning, both strategically at a Local Planning Authority scale (LPA) through Strategic Flood Risk Assessments (SFRA) and in more detail at a site scale as part of Flood Risk Assessments (FRA)?

General Observations

The new guidance mostly involves a change in emphasis with respect to the considerations that are given to flood risk, primarily with respect to climate change and resilience. The most significant introductions for evidence not previously required are:

  • The requirement to identify policies and physical measures to provide for resilience to climate change effects.
  • The consideration of cumulative impacts in, or affecting, local areas susceptible to flooding.
  • The need to consider the introduction of Natural Flood Management.
  • The specific requirement for sustainable drainage systems and the need to evidence their use in FRAs.
  • The requirement to prepare emergency plans in FRAs.

The sequential approach and ‘flood risk from all sources’

Updated wording suggests that the fundamental premise of the sequential approach to avoiding inappropriate development in areas of high flood risk (by applying the Sequential and Exception Tests) will remain in place.

The requirement to ‘manage flood risk from all sources’ (para 156) is also unchanged. While the sequential approach can in theory be applied to other sources, the level of detail and certainty of risk data and mapping varies for difference sources, and areas at risk often interact or overlap.

Cumulative impacts

JBA New Houses - Upton SuDS
New Houses – Upton SuDS

New to the updated NPPF is the requirement that strategic policies should also now consider the ‘cumulative impacts in, or affecting, local areas susceptible to flooding’ (para 156).

Previous policies have relied on the assumption that if each individual development does not increase the risk of flooding, the cumulative impact will also be minimal. However, if there is a lot of development occurring within one catchment, particularly where there is flood risk to existing properties or where there are few opportunities for mitigation, the cumulative impact may be to change the flood response of the catchment.

The risk of this could be identified at a high level, by comparing potential development site locations with hydrological catchments and areas of existing and historic risk to people and property. These will be the locations where existing communities will be most alarmed at the prospect of further development exacerbating existing problems. Detailed conclusions on cumulative effect however would require certainty on which sites would be likely to be allocated, the size/density of the development, and potentially hydraulic modelling to test impacts downstream.

Climate change and future flood risk

JBA SFRAs diagram to explain Flood Zones
SFRAs diagram to explain Flood Zones

There has been a strengthening of wording on future risk under climate change, in that the ‘sequential approach should be used in areas known to be at risk now or in the future from any form of flooding’ (para 158).

It is not uncommon that the modelled Flood Zone 3a plus climate change estimate is more extensive than present day Flood Zone 2, i.e. falls within Flood Zone 1, and these sites had the potential to fall through the cracks of the Sequential Test in the past.

We have long recommended that SFRAs include screening sites for future risk at a Level 1 stage and have highlighted this future risk to LPAs to include in their Sequential Test for some time now (most SFRAs prepared by JBA have included this evidence).

Natural flood management

There has been an additional reference to the use of Natural Flood Management (NFM) techniques to reduce the causes and impacts of flooding (para 157c).

We developed NFM opportunity mapping for the Environment Agency which is available online and can easily be used to identify NFM opportunities within a particular LPA for an SFRA.

At site level, NFM measures can potentially be incorporated within a site and there is an overlap with Sustainable Drainage Systems (SuDS), but influencing NFM at a catchment scale draining to the site may be more difficult.

Sustainable Drainage Systems

JBA SuDS - Development site underwater
SuDS – Development site underwater

The requirement for SuDS has been strengthened, both in para 163c and also given a full paragraph (para 165) outlining the requirement to:

  • Take advice from the Lead Local Flood Authority (LLFA)
  • Have appropriate proposed minimum operational standards
  • Have maintenance arrangements in place
  • Where possible provide multifunctional benefits.

This is a very welcome addition to planning policy, in the absence of the enactment of Schedule 3 of the Flood and Water Management Act (2010). However, it only applies to major developments and so potentially does not capture circumstances where there ‘is clear evidence that this would be inappropriate’. It is possible that clarity on what evidence is required is subsequently set out in the Planning Policy Guidance (PPG), and that these circumstances would be exceptional.

We would observe that all developments (major and minor) can include SuDS, providing multiple benefits contributing to many of the other NPPF policies – climate change, healthy and safe communities, well-designed places, conserving and enhancing the natural and historic environment.

Where site conditions are more challenging the type of SuDS may need to be adapted to the site’s opportunities and constraints and used in combination with traditional techniques if absolutely necessary.

At a strategic level, this means identifying SuDS opportunities according to geology, soil type, topography, groundwater conditions etc, their potential impact on landtake, and setting out local SuDS guidance and opportunities for adoption and maintenance.

At flood risk assessment/drainage strategy level this means early engagement with the LLFA and the client to set expectations of what SuDS can be used on site, what impact this will have and how their multiple benefits will contribute to meeting other planning policy.

Emergency Plan preparation and agreement

This is considered to be a ‘catch up’ introduction to reflect practice that is already in place. There is a requirement that the plans are now agreed, and consideration will need to be given to the appropriate parties to this agreement. These will vary according to the specific circumstances and the nature of the risk and emergency that is being addressed.

Summary of the influential changes

Things that are different (most involve a change of emphasis)
(149) – There is potentially a requirement to provide further evidence on the infrastructure required to ensure future resilience of communities.
(150) – There is increased emphasis on the requirement to demonstrate that risks can be managed through adaptation measures, introducing the need to quantify the magnitude of the risks and the efficacy and practicality of measures that can be used to manage adverse effects.
(155) – There is greater emphasis in identifying development that avoids risks arising from climate change effects.
(156) – There is a requirement to consider cumulative impacts in, or affecting local areas susceptible to flooding.
(157[c]) – There is a requirement to consider the use of natural flood management techniques.
(162) – There is a greater emphasis on the requirement to consider the Exception Test when submitting FRAs for sites that have satisfied the Sequential Test – this is valid as the Exception Test assessment performed in a Level 2 SFRA can demonstrate that the principle of development can be supported, but when more detail is prepared in support of a specific application then further assessment is required.
(163) [b] and [c] – There is increased emphasis on FRAs including evidence on the need to consider flood resilience and resistance and sustainable drainage systems.
(163[e] – There is now specific reference to the need to prepare and submit an ‘agreed’ emergency plan.
(165) [a-d]– There is now specific inclusion of the requirements that should be included for sustainable Drainage systems

Want to know more?

Email Rachel Brisley for more information on the revised National Planning Policy Framework and its implications for FRAs and SFRAs. You can also find out more on our flood risk assessment web page.

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