LPA Process Note
Environment Agency Standing Advice to Local Planning
Authorities on Development and Flood Risk
Operational Development (+1ha) within Flood Zone 1
Process
Formal EA response for Green Box (development over 1ha) on the local matrix =
‘LPA to use the advice below’. (Environmental Impact Assessment (EIA)
development would be subject to ‘Red Box’ consultation).
Advice Note
We recommend consultation with the Lead Local Flood Authority (LLFA) and/or your Land
Drainage section, to provide information to support the production of and review of the
Flood Risk Assessment (FRA).
Sources of information might include the Preliminary FRA, Strategic FRA, surface water
management plans, pluvial flood maps or areas susceptible to surface water flooding.
Historic flood records should also be utilised.
Requirement for a Flood Risk Assessment
The National Planning Policy Framework (NPPF) requires a site specific FRA for
development proposals of 1 hectare or greater in Flood Zone 1. We would refer you to
paragraph 103 of the NPPF which states that ‘when determining planning applications,
local planning authorities should ensure flood risk is not increased elsewhere...’.
Where a FRA is not submitted with the application or the FRA is not accepted by the LPA
we would recommend that the LPA considers either deferral or refusal of planning
permission. Where the LPA is minded to refuse the application, the following standard
response paragraphs may be applicable.
A) Failure to submit a FRA The proposed development may present a significant flood risk from the generation of
surface water run-off but is not accompanied by a FRA as required by the National
Planning Policy Framework (NPPF). See Table 1 ‘Flood Zones’ in sub-section 25 within
the Flood Risk and Coastal Change Section of the PPG / local plan policy ‘xxx’.
B) Inadequate FRA The flood risk information submitted in support of the application is not acceptable for the
following reasons: [add omissions / areas for clarification / more detail etc as appropriate].
A proper assessment of flood risk has not been undertaken as required by the NPPF See
Table 1 ‘Flood Zones’ in sub-section 25 within the Flood Risk and Coastal Change Section
of the PPG / local plan policy ‘xxx’.
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FRA requirements
The PPG contains a useful checklist for FRAs at sub-section 26 of the Flood Risk and
Coastal Change Section. To be acceptable as a FRA the applicant should confirm as a
minimum:
Surface Water Risk
1. That it will be feasible to balance surface water run-off to the greenfield run-off rate
for all events up to the 1% (1 in 100 year) storm (including additional climate
change allowance*) and set out how this will be achieved, or achieve betterment in
the surface water runoff regime; ensuring that surface water runoff will not increase
flood risk to the development or third parties.
2. How sustainable drainage system techniques (SUDs) will be used with any
obstacles to their use clearly justified. (This should include, where appropriate,
provision for the adoption of drainage infrastructure and maintenance contribution to
that party).
* Climate Change - An allowance for climate change needs to be incorporated, which
means adding an extra amount to peak rainfall (20% for commercial development, 30%
for residential).
3. The residual risk of flooding needs to be addressed should any drainage features
fail or if they are subjected to an extreme flood event. Overland flow routes should
not put people and property at unacceptable risk. This could include measures to
manage residual risk such as raising ground or floor levels where appropriate.
Fluvial Flood Risk
4. Some watercourses have not been modelled on our Flood Zone Maps. An
assessment of flood risk associated with these unmodelled watercourses will also
be necessary (Note - our Flood Zone Maps primarily show flooding from main
rivers, not ordinary watercourses with a catchment of less than 3km 2). Should the
detailed FRA demonstrate that the site is actually within Flood Zones 2 or 3
you should refer to our consultation filter and flood risk matrix to check if we
should be consulted.
Other Risk
5. Other sources of flooding e.g. groundwater.
INFORMATION:
Climate Change
The PPG refers to EA guidance on considering climate change in planning decisions
which is available via our Flood Risk Standing Advice online: https://www.gov.uk/flood-riskstanding-advice-frsa-for-local-planning-authorities. Here you can download the document
‘Climate Change Allowances for Planners’
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-
Table 2 of the document indicates that surface water FRA should include for an
increase of 30% in peak rainfall intensity for developments to be still in existence by
2085 (20% for developments with a life expectancy which ends prior to 2085).
SUDS
Surface water run-off should be controlled as near to its source as possible through a
sustainable drainage approach to surface water management (SUDS).
SUDS seek to mimic natural drainage systems and retain water on or near to the site,
when rain falls, in contrast to traditional drainage approaches, which tend to pipe water off
site as quickly as possible.
SUDS offer significant advantages over conventional piped drainage systems in reducing
flood risk by reducing the quantity of surface water run-off from a site and the speed at
which it reaches water courses, promoting groundwater recharge, and improving water
quality and amenity. The range of SUDS techniques available means that a SUDS
approach in some form will be applicable to almost any development.
Government policy set out in paragraph 103 of the NPPF expects LPAs to give priority to
the use of SUDS in determining planning applications. Further support for SUDS is set out
in the PPG at sub-section 21 within the Flood Risk and Coastal Change Section, and subsections 2 and 5 within the Water Supply, Wastewater and Water Quality Section. It is a
requirement of the Water Framework Directive (WFD) that there must not be any overall
deterioration in water quality or the ecological status of any waterbody. The inclusion of
SUDS can help deliver the aim of ‘good status’ by 2027.
Advice on rural SuDS can be found at:
https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/291508/sch
o0612buwh-e-e.pdf
Local Planning Authorities should ensure their policies and decisions on applications
support and complement Building Regulations on sustainable rainwater drainage.
Approved Document Part H of the Building Regulations 2010 establishes a hierarchy for
surface water disposal, which encourages a SUDS approach beginning with infiltration
where possible e.g. soakaways or infiltration trenches. Where SUDS are used, it must be
established that these options are feasible, can be adopted and properly maintained and
would not lead to any other environmental problems. For example, using soakaways or
other infiltration methods on contaminated land carries groundwater pollution risks and
may not work in areas with a high water table. Where the intention is to dispose to
soakaway, these should be shown to work through an appropriate assessment carried out
under BRE Digest 365.
Provision for long-term maintenance should be provided as part of any SUDS scheme
submitted to the LPA. Model legal agreements that provide a mechanism for SUDS
maintenance may be accessed on the CIRIA web site at:
http://www.susdrain.org/delivering-suds/using-suds/adoption-and-maintenance-ofsuds/adoption/adoption.html
Further information and references on SUDS can be found in sub-section 21 of the PPG.
The CIRIA website provides advice on design, adoption and maintenance issues and a full
LPA Process Note
overview of other technical guidance on SUDS. CIRIA's web site is available at:
http://www.susdrain.org/
Under the Floods and Water Management Act 2010 a SUDS Approval Body will be set up
in Unitary or County Councils to approve drainage systems in new developments and
redevelopments before construction begins.
Disposal to public sewer
Where it is intended that disposal is made to public sewer, the Water Company or its
agents should confirm that there is adequate spare capacity in the existing system taking
future development requirements into account.
Designing for exceedence
For on/near site flooding, we advise that:
For events with a return-period in excess of 30 years, surface flooding of open spaces
such as landscaped areas or car parks is acceptable for short periods, but the layout and
landscaping of the site should aim to route water away from any vulnerable property, and
avoid creating hazards to access and egress routes. Further guidance is available on
CIRIA’s website. No flooding of property should occur as a result of a one in 100 year
storm event (including an appropriate allowance for climate change). In principle, a welldesigned surface water drainage system should ensure that there is little or no residual
risk of property flooding occurring during events well in excess of the return-period for
which the sewer system itself is designed. This is called designing for event exceedence.
The CIRIA website has further detail on designing for exceedence in urban drainage, via
the following link: http://www.susdrain.org/delivering-suds/drainageexceedance/managing-exceedance/managing-exceedance.html
For off-site flooding, we advise that:
For the range of annual flow rate probabilities up to and including the one per cent annual
exceedence probability (1 in 100 years) event, including an appropriate allowance for
climate change, the developed rate of run-off into a watercourse, or other receiving water
body, should be no greater than the existing rate of run-off for the same event. Run-off
from previously-developed sites should be compared with existing rates, not greenfield
rates for the site before it was developed. Developers are, however,
strongly encouraged to reduce runoff rates from previously-developed sites as much as is
reasonably practicable. Volumes of run-off should also be reduced wherever possible
using infiltration and attenuation techniques.
Other flood risk issues to consider for development in Flood Zone 1 - Dry Islands
There are some areas within Flood Zone 1 that are surrounded by areas at a higher risk of
flooding i.e. areas falling within Flood Zones 3 and 2. In certain cases development within
such 'dry islands' can present particular hazards to public safety and risks such as those
risks associated with maintaining safe access and exit for occupants during flood events.
The distribution of dry islands and risks posed by them in terms of access/exit vary
considerably across the country. (If there is a concern on this issue please contact the
local Environment Agency Sustainable Places Team).
Is the proposal part of a larger development site?
LPAs should be aware that some applications for smaller scale developments in Flood
Zone 1 might be part of larger sites which already have outline permission. In such cases,
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the LPA should ensure that any conditions which were applied to the larger site, in relation
to surface water drainage, are complied with in order to prevent a ‘piecemeal’ approach to
SUDS/drainage schemes.
Note: Development which involves a culvert or an obstruction to flow on an Ordinary Watercourse
will require consent under the Land Drainage Act 1991 and the Flood and Water Management Act
2010. In the case of an Ordinary Watercourse the responsibility for Consenting lies with the LLFA.
In an internal drainage district, the consent of the Internal Drainage Board, instead of the LLFA, is
required for the above works under Section 23 of the Land Drainage Act 1991. An Ordinary
Watercourse is defined as any watercourse not identified as a Main River on maps held by the
Environment Agency and DEFRA. For further information on Ordinary Watercourses contact the
LLFA.
Last updated: October 2014
LPA Process Note
Contact: Environment Agency, Sustainable Places Team, Shropshire Herefordshire Worcestershire & Gloucestershire Area.
shwgplanning@environment-agency.gov.uk