Sustainable Drainage Design Guidance
Devon County Council
Contents
Introduction
3
1. Legislative and Policy Background
4
2. What are Sustainable Drainage Systems?
5
3. Designing SuDS
7
4. Maintaining SuDS
9
5. Construction
10
6. Education
10
Information and guidance for Planners and Developers
11
Flood Risk Assessments
11
Information required for the assessment of SuDS
12
Works in the vicinity of a watercourse, the sea or any
flood defence
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Devon County Council
Introduction
Devon County Council (DCC) is the Lead Local
Flood Authority (LLFA) as defined by the Flood and
Water Management Act 2010 (FWMA) and as such
we have a duty to manage flood risk throughout
Devon; this includes the risk of flooding from new
development and redevelopment. This guide is
intended to be used by designers, developers and
planners to ensure a consistent approach to
Sustainable Drainage Systems throughout Devon
as well as helping us to fulfil our duties under the
FWMA whilst supporting growth in a sustainable
way.
There is a wealth of information available relating
to the design and construction of SuDS and this
guide does not attempt to rewrite existing
documents. What it does do is provide a summary
and signpost relevant information to make it
easier to find the information needed as well as
providing a local context.
This document will be constantly reviewed and
updated as necessary. Feedback and input is
always welcomed. We can be contacted via the
following email: floodrisk@devon.gov.uk
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1. Legislative and Policy Background
Flood and Water Management Act (2010)
(FWMA)
The Flood and Water Management Act was
introduced in response to concerns raised in the
Pitt Review following the 2007 floods. The Act
makes the lead local flood authority (a
responsibility which sits with the upper tier
authority) responsible for coordinating flood risk
management within its area; the LLFA for Devon is
therefore Devon County Council.
Water Framework Directive (WFD) – 2000/60/EC
The Water Framework Directive is European
legislation which was introduced to improve and
protect the quality of water bodies. It aims to
ensure that water is more effectively and
sustainably managed for the benefit of both
society and the environment.
The WFD requires that all inland and coastal
waters are at least of ‘Good’ ecological status by
2015. Well-designed SuDS can help achieve this by
filtering out diffuse pollution before it reaches
water bodies.
National Flood and Coastal Erosion Risk
Management Strategy
Produced by the Environment Agency under the
FWMA, the National Strategy aims to ensure that
flood and coastal erosion risk management is
properly managed and co-ordinated. The
Standards recommend the use of SuDS in
developments and redevelopments to manage
surface water flood risk.
National Planning Policy Framework (NPPF)
The NPPF requires that development is
undertaken in a sustainable manner and has a
presumption in favour of sustainable
development. Further detailed information on
how this should be applied is provided in the
Technical Guidance to the National Planning Policy
Framework.
Devon County Councils Local Flood Risk
Management Strategy (2014-2020)
It is a requirement under the FWMA that LLFAs
produce a local strategy which focuses on local
issues.
In determining planning applications Local
Planning Authorities should ensure that
development avoids flood risk to people and
property, does not increase flood risk elsewhere
and, where possible, reduces flood risk; this should
take account of the impacts of climate change.
DCCs strategy recommends that new
developments have an effective and robust
surface water drainage system and should not
increase flood risk elsewhere which should be
undertaken in accordance with SuDS principles.
The Local Planning Authority will consult the LLFA
as a statutory consultee on major developments
with surface water drainage implications.
Sustainable Drainage Design Guidance – v.3 2015 (DRAFT)
Non-statutory technical standards for SuDS
(DEFRA – Draft 2015)
The Department for Environment, Food and Rural
Affairs have developed non-statutory technical
standards for SuDS which Local Planning
Authorities are required to give due regard when
determining planning applications. Where National
Standards are referred to in this guidance they will
be denoted with S, not all standards will be
referenced and they may not be reproduced
verbatim.
All new development must comply with at least
the Technical Standards and, where relevant, any
specific Local Standards.
Local standards and policies
Local Development Plans (LDP) for Local Planning
Authorities identifies their expectations in relation
to sustainable development and SuDS. In addition
Local Planning Authorities may choose to publish
their own surface water management guidance;
where this is the case links will be provided in this
guidance.
This document sets out the Local Standards
required by DCC which may form the basis of any
LPA requirements.
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2.1
Types and selection of SuDS
(Section 4 & 5, SuDS Manual)
2. What are Sustainable Drainage
Systems?
Surface water should be managed on or as close to
the surface as possible. Following this approach
gives the opportunity to integrate biodiversity and
amenity improvements within the site as well as
dealing with surface water runoff and managing
water quality. On this basis, underground storage
and conveyance systems are not truly sustainable
as they are only normally designed to deal with
flow and volume.
In the natural environment, rain falling on the land
can be absorbed into the ground, taken up by
plants and trees, evaporate or can find its way to
rivers and streams.
Subsequent urbanisation has involved covering
permeable ground with hard, non-permeable
surfaces modifying the natural water cycle. The
subsequent surface water runoff has been dealt
with in subterranean piped systems, designed to
keep the flows out of sight and prevent localised
flooding by moving surface water downstream as
fast as possible. This approach can cause
downstream flooding through the concentration of
flows and localised flooding when the capacity of
the system is exceeded, additionally this approach
does not deal with pollutants and can therefore
cause degradation of water resources.
Every site is different with varying characteristics
and not all SuDS techniques will be suitable for all
sites, it is therefore not possible to apply a one
type suits all approach. A good early assessment of
the site is essential to identify what may and may
not be accommodated within a particular site; this
will help when justifying the approach when
applying for planning permission. Typical SuDS
component are summarised below and designers
will typically utilise a number of these methods
when dealing with surface water.
Well-designed SuDS should aim to manage surface
water close to where it falls and in a way which
works with, and mimics, the natural environment.
Dealing with surface water in this way can have
the following benefits:



controls the quantity and rate of runoff
from development;
improves the quality of runoff;
enhances the biodiversity and amenity
value of the site.
Figure 1 - Natural vs. Urban Catchment
(CIRIA C687; 2010 )
Green roofs – these are roofs constructed with a
soil and vegetative layer designed to absorb and
store rainfall, thereby reducing runoff.
Rainwater Harvesting – rainfall runoff can be
stored in water butts or tanks and utilised in a
number of different ways including watering the
garden or toilet flushing.
Permeable Paving – Porous surfacing can allow
rainfall and runoff to soak through into the
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substrate where it can be stored or allowed to
infiltrate; care must be taken where there is risk of
concentrated pollutants.
Soakaways – soakaways are most suited to sites
with permeable soils. They are created by filling a
pit of pre-determined size with aggregate or crate
system to increase the void ratio and give storage
capacity whilst allowing the water to infiltrate.
Soakaways should be designed in accordance with
BRE 365.
allow sediments to settle pollutant to be taken up
by the vegetation.
Underground Storage – runoff can be stored
underground using a variety of methods and
discharge controlled using appropriate methods.
Priority must be given to above-ground methods,
however it is recognised that underground storage
may be the most suitable method available. The
use of this method must be clearly justified and
will be assessed on a site-by-site basis.
Filter Strips – filter strips are designed to allow
runoff to flow across a vegetated area, normally
grass, allowing infiltration and removing
contaminants.
Swales – swales are vegetated ditches which are
design to convey surface water flows. They can
also be used to filter, create infiltration
opportunities and be used for storage in extreme
events.
Ponds – ponds can be used to store and treat
surface water runoff. They can be designed to be
permanently wet and provide additional
biodiversity benefits, or dry when there is no
rainfall. Discharge can be through infiltration or
through other controlled discharge methods.
Graphic
Wetlands – wetlands consist of shallow ponds and
marshy areas planted with aquatic vegetation
which help to filter and cleanse contaminants in
the runoff. They should therefore be designed to
retain surface water runoff for longer periods to
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3. Designing SuDS
Well-designed SuDS can enhance the local
environment, provide a multitude of benefits and
have a positive impact on new developments.
Considering drainage implications late in the
planning process often leads to poorly designed
SuDS which can be visually intrusive and offer little
benefit apart from meeting planning obligations.
Before the site layout is fixed it is recommended
that the drainage infrastructure is designed taking
advantage of any pre-existing, natural flow paths
within the site or ‘Blue Corridors’ and natural
topography.
The design and construction of SuDS in Devon
should be in accordance with the following, unless
otherwise stated through local standards:
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
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
3.1
Non-Statutory Technical Standards for SuDS
(DEFRA – Draft 2015)
The SuDs Manual (CIRIA C697)
Code of practice for surface water
management for development sites
(BS8582:2013)
BRE Digest 365 Soakaway design
Dealing with runoff
Rainfall should be dealt with as close to where it
falls as possible. SuDS should mimic the natural
environment and is therefore best managed on
the surface using the ‘SuDS Management Train’
approach Figure 1. The key elements of the SuDS
Management Train are explained below:
Sustainable Drainage Design Guidance – v.3 2015 (DRAFT)
Figure 2 - 'SuDS Management Train' CIRIA; 2015
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

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Prevention; good housekeeping and site
design should be employed to manage and
reduce runoff and pollution.
Source Control; rainfall should be dealt with as
close to where it fell as possible.
Site control; runoff managed in a network
across the site using above ground conveyance
methods.
Regional Control; downstream management
of runoff on a site and catchment scale.
Surface water should be discharged using a
hierarchy of discharge solutions; runoff should be
managed as high up the hierarchy as is practicable
with justification given for progressing through the
hierarchy.
S1 – Where not collected for re-use, surface water
must be discharged as high up the following
hierarchy of drainage options as possible :
1. discharge into the ground (infiltration);
2. discharge to a surface water body;
3. attenuation system with discharge to a surface
water sewer, highway drain, or another
drainage system;
4. attenuation with discharge to a combined
sewer.
Integrating the SuDS Management Train approach
into a development is best achieved by considering
drainage early on in the planning process. At this
stage it is easier to consider how natural features
can be utilised to manage surface water on the site
and how SuDS can be most effectively integrated
into a site.
Risks from pollution should be considered at each
stage and appropriate treatment stages provided
before surface water infiltrates or reaches water
resources. In the natural greenfield environment
the first 5-10mm of runoff would not flow off the
site. Therefore the first 5-10mm of runoff should
be retained and treated on-site using appropriate
SuDS features; this has the added benefit of
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avoiding concentrated pollutants from reaching
water bodies.
S12 – The drainage system must be designed and
constructed so surface water discharged does not
adversely impact the water quality of receiving
water bodies, both during construction and when
operational.
3.1.1 Managing Flood Risk outside the
development
Introducing impermeable surfaces will lead to an
increase in the frequency, rate and volume of
runoff; significant changes to greenfield runoff
characteristics must be mitigated.
When considering the drainage strategy for a site
it must be demonstrated that flood risk will not be
increased up or down-stream of the proposed
development and where possible betterment
should be achieved.
S2 – The design of the drainage system must
mitigate any negative impact of surface runoff
from the development on the flood risk outside
the development boundary.
Climate Change
There is increasing evidence that the global
climate system is changing. In the UK, amongst
other impacts, this is likely to lead to more
extreme weather events and have a particular
impact on the intensity of rainfall events. When
designing drainage systems an allowance must be
Sustainable Drainage Design Guidance – v.3 2015 (DRAFT)
made for climate change to ensure that the likely
impacts are catered for. This is addressed by
increasing the peak rainfall depth by 30 percent in
calculations.
Proposals must be accompanied by a climate
change statement which explains how the SuDS
will accommodate and adapt to climate change,
this is not limited to dealing with increased
volumes but should also include the effects of
drought on the structures, soils and vegetation
integral to the system.
Peak Flow Control
Greenfield runoff rates should be estimated using
the methods described in section 4.2 of The SuDS
Manual for events up to and including the 1:100
year return period. Post-development discharge
rates must be equal to or less than these figures.
S4 - SuDS should be designed to discharge at the
greenfield runoff rate (+30%) up to and including
the 1:100 year storm event.
S5 – Where brownfield sites are being developed,
peak flow control should still be based on the
greenfield runoff rate (or as close as possible) as
described above and must not exceed the rate of
discharge prior to redevelopment.
Volume Control
S6 – The runoff volume for the 1:100 year, 6 hour
event (+30%) must not exceed the greenfield
volume for the same event.
Long-term storage should be provided to deal with
excess volume, this should be discharged through
infiltration or, where this is not feasible, at a
maximum rate of 2 l/s/ha.
Critical Drainage Areas
A critical drainage area is an area within Flood
Zone 1 which has been identified as having critical
drainage problems and has been notified to the
Local Planning Authority by the Environment
Agency.
All off site surface water discharges from
development
should
mimic
greenfield
performance up to a maximum 1:10 year
discharge. On-site all surface water should be
safely managed up to the 1: 100 year (+30%)
conditions. To satisfy the above will require
additional water storage areas to be created
within the site compared to the normal SUDS
design thereby contributing to a reduction in
flooding downstream.
The Environment Agency must be consulted on
applications in areas with critical drainage
problems.
3.1.2 Managing Flood risk within the
development
New development should be safe from the risk of
flooding, consideration must be given to
exceedance routes within the development to
ensure that people and property are not put at risk
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in the event that the drainage system fails or
storms in excess of those designed for are
experienced.
Unless an area is designed to hold or convey
water, flooding within the development must not
occur under the following circumstances:



S9 – on any part of the development for a 1:30
year (+30%) rainfall event;
S10 – in any part of a building or any utility
plant susceptible to water for a 1:100 year
(+30%) event;
S11 – flows resulting from events in excess of
the 1:100 year event must be managed in
exceedance routes that minimise risk to
people and property.
Dividing developments into sub-catchments and
dealing with surface water in smaller systems
closer to source as opposed to one, large system
can make the system more resilient to failure.
When submitting applications a plan clearly
showing proposed levels and demonstrating
exceedance routes must be submitted. Where
exceedance routes are off-site onto an adjacent
highway or land it must be proven that the
exceedance will not cause flooding and that there
are not existing flooding issues which may be
made worse.
Sustainable Drainage Design Guidance – v.3 2015 (DRAFT)
4. Construction
The proposed SuDS must be installed prior to any
construction works being undertaken in order to
deal with any runoff associated with the work, on
larger sites this can be limited to the SuDS
required for the phase being developed.
Measures will need to be put in place to prevent
silt entering the system during construction. This is
particularly important for buried systems which
can prove difficult to clean out. The SuDS should
be cleaned out prior to the developer leaving site
to ensure that it continues to operate efficiently.
The drainage system must be constructed in
accordance with the approved design, Devon
County Council Officers must be granted access to
inspect the SuDS pre, during and post
construction.
When submitting a planning application an
operation and maintenance plan must be
submitted demonstrating:




What - an overview of the SuDS features
and the management aims for the site;
How - How will they be accessed and the
scope of the activities;
Who - Who will be responsible for
maintaining them;
When - When and how often they need
maintaining.
The drainage system must be designed to take
account of the construction, operation and
maintenance requirements of both surface and
subsurface components, allowing for any
personnel, vehicles or machinery access required
to undertake the work. Consideration must also be
given to how waste materials resulting from the
maintenance will be dealt with.
5. Maintaining SuDS
(Section 22, SuDS Manual)
The on-going maintenance requirements of SuDS
are an important aspect of the planning and design
stages.
It is the responsibility of the developer to put in
place suitable management arrangements for the
SuDS for the lifetime of the development. It is
essential that the drainage system is maintained to
ensure that it continues to function as designed.
6. Education
(Section 24, SuDS Manual)
It is important that those who will ultimately
benefit from and use the SuDS understand what
they are and how they work as they are more
likely to accept and embrace SuDS when they are
fully aware of the benefits. This can be achieved
through information provided to new owners via
leaflets, information/interpretative signage at
strategic locations and community groups.
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Quick Reference and general guidance
for Planners and Developers
Flood Risk Assessments
Planning Practice Guidance (PPG) contains detailed
information on the preparation of flood risk
assessments (FRA) and includes a useful checklist
under the Flood and Coastal Change section.
In developing the flood risk assessment to support
all aspects of the planning process, including
outline, Environmental Impact Assessment and
detailed submissions, the applicant should
demonstrate consideration of the following as a
minimum:
Surface Water Flood Risk
 That it will be feasible to balance surfacewater runoff to the greenfield rate for all
events up to the 1 in 100 year storm plus
an allowance of 30% for climate change,
unless the site is in a Critical Drainage Area
which are subject to more stringent
criteria. It should be set out how this, or
betterment, will be achieved and that
flood risk will not be increased elsewhere;
 How Sustainable Drainage Systems (SuDS)
will be integrated into the proposed
development with any obstacles to their
use clearly justified.
 An operation and maintenance plan
detailing the maintenance requirements
Sustainable Drainage Design Guidance – v.3 2015 (DRAFT)


for the SuDS, who will undertake the
maintenance and how it will be funded;
The surface water discharge hierarchy has
been considered and justification given for
discounting options;
The residual risk of flooding needs to be
addressed should any drainage features
fail or if a storm event over and above the
design event is experienced. Overland flow
routes should be identified and should not
put people or property at risk.
Fluvial Flood Risk
 The Environment Agency’s flood risk maps can
be used to determine the risk of flooding from
watercourses, these primarily show flood risk
from Main Rivers. Consideration should also
be given to the risk of flooding from Ordinary
Watercourses, which include all ditches and
channels that convey flows.
Other Flood Risk
 Other sources of flooding e.g. groundwater.
Graphic
Devon County Council
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Devon County Council
SuDS Component
Green Roofs
Description and Key Design Considerations
Green roofs are systems which cover a building’s roof with vegetation. Laid over a drainage layer with other layers they can
provide protection, waterproofing and insulation as well as reduced runoff and water quality improvements.
• Designed for interception storage
• Minimum roof pitch of 1 in 80, maximum 1 in 3
• Multiple outlets to reduce risk from blockages
• Lightweight soil and appropriate vegetation.
SuDS Manual Ref:
Chapter 6
Excavations filled with aggregate or a Used to store runoff and allow it to infiltrate back into the ground.

Soakaways
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Infiltration testing carried out in accordance with BRE Digest 365, the test must be allowed to drain beyond the 25%
effective depth;
Maximum depth 3m for ease of maintenance;
Fill material should provide >30% void space;
Base of soakaway at least 1m from groundwater level;
Minimum of 5m away from foundations and highways;
Maximum gradient of surrounding land 10%;
Below ground attenuation devices must be provided with adequate monitoring devices to allow for inspection in relation
to functioning and performance.
Chapter 6
Wide, gently sloping areas of grass or other dense vegetation that treat runoff from adjacent impermeable areas.
Filter Strips

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
Recommended minimum width of 6m;
Runoff must be evenly distributed across the filter strip;
Slopes not exceeding 1 in 20, minimum of 1 in 50.
Chapter 8
Broad, shallow channels covered by grass or other suitable vegetation used to convey and slow down flows, store runoff and
infiltrate the water into the ground where conditions allow.
Swales

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
Limit velocities during extreme events to 1-2 m/s;
Maximum side slopes of 1 in 3, where soil conditions allow;
Minimum base width of 0.5m.
Sustainable Drainage Design Guidance – v.3 2015 (DRAFT)
Chapter 10
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Devon County Council
Shallow landscaped depressions or pre-cast units which rely on engineered soil and vegetation to remove pollution and reduce
runoff.
Bioretention/Rain 

gardens

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
Sufficient area to temporarily store the water quality treatment volume;
The water quality treatment event should half drain within 24 hrs to provide adequate capacity for
multi-event scenarios;
Minimum depth to groundwater of 1m, if unlined;
Overflow/bypass facilities for extreme events.
Chapter 11
Pervious surfaces allow rainwater to infiltrate through the surface into an underlying storage layer, where water is stored
before infiltration to the ground, reuse, or release to surface water.
Pervious Surfaces




Pervious sub-base to be structurally designed for site purpose
Temporary sub-surface storage must provide infiltration and/or controlled discharge
Geotextile may be specified to provide filtration treatment
Surface infiltration rate should be an order of magnitude greater than the design rainfall intensity.
Chapter 12
Modular geocellular systems which create an increased void ratio providing below ground infiltration (soakaway) or storage
device opportunities.
Geocellular
Structures



Standard storage design using limiting discharges to determine storage volume;
Structural design should be to relevant standards for appropriate surface loadings;
Use appropriate geotextile (for infiltration) or geomembrane (for storage).
Chapter 13
Infiltration basins are depressions in the surface that are designed to store runoff and infiltrate the water to the ground. They
can be landscaped to provide aesthetic and amenity value.
Infiltration Basin
Detention Basin


Pre-treatment is required to remove sediments and fine silts
Infiltration should not be used where groundwater is vulnerable or to drain pollution hotspots.
Vegetated areas which are normally dry and are designed to detain runoff and either discharge it through infiltration or
through a flow control device at a set rate. Dry basins can be used as multi-functional spaces enhancing the amenity and
biodiversity value of an area.


Chapter 15
Chapter 16
Maximum side slopes of 1:4;
Bioretention and/or wetland/micropools at outlets for enhanced pollution control.
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Provide surface water attenuation and treatment. Permanent ponds can provide amenity and wildlife benefits and help to
remove sediments.
Ponds
Wetlands



Permanent pool for water quality treatment and temporary storage volume for flow attenuation;
Minimum depth for open water areas of 1.2m;
Maximum side slopes of 1:3.
Shallow ponds and marshy areas for attenuation and water treatment. Aquatic vegetation and extended detention allow
sediments to settle and enhance wildlife habitat.

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Shallow, temporary storage for attenuation
Sediment forebay or equivalent upstream pre-treatment
Combination of deep and shallow areas (maximum depth <2m)
Length:width ratio of greater than 3:1, shallow side slopes.
Sustainable Drainage Design Guidance – v.3 2015 (DRAFT)
Chapter 17
Chapter 18
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Devon County Council
Key Design Criteria for SuDS in Devon
On-site it must be demonstrated that there is no risk of flooding to properties for the 1in30year event and that flood risk will not be increased offProtection from
site.
flooding
Overland exceedance flow routes must be illustrated to show how surface water will be managed to control risk to people and property.
Runoff
Flow Control
Volume Control
Quality Control
Amenity
Biodiversity
Runoff should be dealt with as close to where it falls as possible.
Pre-development greenfield runoff should be determined in accordance with The SuDS Manual for the 1in1, 1in10, 1in30 and 1in100 year storm
event.
Brownfield sites should be designed to discharge at greenfield rates where feasible. Where it is demonstrated that this is not feasible betterment
should be achieved.
Off-site flows must be attenuated to match the greenfield runoff for storm events up to and including the 1in100 year event and where feasible
betterment achieved. More stringent requirements apply in Critical Drainage Areas as determined by the EA.
Surface water storage areas should be designed to contain surface water runoff for events upto the 1in100 year event. Surface water volumes
over and above the 1in100 year, 6 hour event must be attenuated on-site and disposed of through infiltration. Where this is not feasible it should
be discharged at a rate of 2l/s/ha.
Surface water should be stored above ground where possible.
Interception storage should be provided so that the first 5-10mm of runoff does not leave the site. Cleansing stages implemented depending on
the use and risk of contamination.
SuDS should be designed to be multi-functional where possible and designed to enhance the aesthetic appeal of the development with
appropriate maintenance regimes.
Community engagement and education should be undertaken to promote understanding and acceptance.
Native planting should be used to provide varied habitats. Designs should closely mimic the natural ecosystem.
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Devon County Council
Information required for the
assessment of SuDS
The LPA has a statutory duty to consult the LLFA
when determining planning application. Statutory
Consultees have 21 days from when they receive
the information required to make an assessment
to provide a substantive response. To ensure that
a response can be made in a timely manner, and
the decision is not delayed, the following
information must be submitted as part of the
planning application. This list is not intended to be
exhaustive and additional information may be
required; this will be assessed on a site-by-site
basis.
Flood Risk Assessment
□ Prepared as previously detailed including a
clear explanation of the SuDS proposal
demonstrating compliance with Devon
County Councils SuDS Guidance and
recommended documents;


Surveys/Monitoring
□ Existing and proposed site levels;
□ Seasonal ground water levels covering a 12
month period where infiltration is
proposed.
Assessments
The applicant should demonstrate:
□ Greenfield runoff rate and volume for the
□
Plans
□ Location plan that includes geographical
features, grid reference, street names
catchment identification and watercourses
or other bodies of water in the vicinity;
□ Site plans showing:
 Existing site;
 Proposed site boundary and area
it encloses;
 Development proposals clearly
identifying all aspects of SuDS,
Sustainable Drainage Design Guidance – v.3 2015 (DRAFT)
such as ponds, swales and other
significant features;
Identification of any existing or
proposed structures which may
influence the flow of water
overland or any watercourses
present on the site;
Exceedance flow paths.
□
□
□
site from each of the corresponding 1, 10,
30 and 100 year storms;
Proposals for surface water management
that aims to not increase surface water
runoff rate and volumes from the site as a
result of the development including any
calculations (inclusive of climate change);
Information in relation to existing surface
water systems within the site and their
condition;
Information about other potential sources
of flooding that may affect the site;
Proposed SuDS will not cause any
deterioration to water quality or ecological
status of any water body and where
possible will provide amenity and
biodiversity benefits;
□ Any environmental impacts as a result of
the development and/or provision of SuDS
are mitigated.
Maintenance
□ An operation and maintenance plan
detailing the maintenance requirements
for the SuDS, who will undertake the
maintenance and how it will be funded.
Education
□ Details of proposed community
engagement, information and
interpretative signage.
Flood Risk Asset Register
Under the Flood and Water Management Act
LLFAs have the power to designate features which
have a significant bearing on flood risk.
Where an asset is designated permission must be
sought from the LLFA to undertake works on it.
The LLFA will inform the LPA when it intends to
formally designate a feature and will request the
following information:
□ As Constructed Drawings of all SuDS
features;
□ Asset records for the site;
□ Owners of each SuDS feature;
□ Person/company responsible for
maintenance.
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Devon County Council
Works in the vicinity of a watercourse,
the sea or any flood defence
Development which involves works on or near
main revers or sea and flood defences require
consent under the Water Resources Act 1991, local
bylaws, the Environment Act 1991 and the Flood
and Water Management Act 2010.
Consent must be sought from the Environment
Agency if works are proposed:
 on over, under or near a main river, flood
or sea defence
 to make changes to any structure that
helps control floods
Main rivers are shown on a main river map
available on the Environment Agency’s website.
Ordinary Watercourses
Development which involves works in or near an
Ordinary Watercourse may require consent under
the Land Drainage Act 1991 and the Flood and
Water Management Act 2010. Regulatory
responsibility for Ordinary Watercourses, and
consent for works, lies with the Lead Local Flood
Authority (Devon County Council).
Graphic
An Ordinary Watercourse is defined as any
watercourse that is not designated as a Main River
on maps held by the Environment Agency.
Sustainable Drainage Design Guidance – v.3 2015 (DRAFT)
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