Surface water drainage
We encourage surface water runoff from all developments to be
treated by sustainable drainage systems
(SUDS) in line with Scottish Planning Policy. SUDS
help to protect water quality and reduce potential for flood risk.
They are appropriate in both urban and rural situations. Cost
effective SUDS solutions can be found for almost every situation,
and can be a cheaper alternative to traditional drainage measures.
SUDS also provide opportunities for increased amenity and
biodiversity value of sites.
Where the alternative is use of combined
systems, SUDS increases capacity in infrastructure for future
developments and reduces the risk of pollution events. Discharges
to combined sewers should be avoided. Scottish Water will only
accept surface water into a combined system in exceptional
circumstances, and we would expect Scottish Water and the applicant
to ensure that all reasonable efforts are made to remove surface
water from the combined sewer.
It is important to ensure that adequate space
to accommodate SUDS is incorporated within the site layout.
Consideration should be given to this matter early in the planning
process when proposals are at their most fluid and modifications to
layout easily made with less expense to the developer.
Each individual type of SUDS facility, such as
a filter drain, detention basin, permeable paving or swale,
provides one level of surface water treatment. For example, surface
water treated by filter drains and permeable paving would be
classed as receiving two levels of treatment. Further guidance on
SUDS devise design can be found within CIRIA’s C697 manual
entitled
The SUDS Manual 
.
The level of surface water treatment required
is dependant on the nature of the proposed development, for example
residential or non residential, the size of development, and the
environmental risk posed by the development. The environmental risk
is principally determined by the type of activity being proposed
(residential, industrial, etc), the available dilution, and the
sensitivity of the receiving waterbody. The levels of
treatment listed below represent best practice. Please be advised
that for mixed use developments, the level of treatment
required will be determined by the use with the highest sensitivity
within the development.
- Residential developments of 50 houses or less and
retail/commercial/business parks with car parks of 50 spaces or
less require one level of treatment for all hardstanding areas
including roads. We encourage this first level of SUDS to be source
control.
- Residential developments of more than 50 houses and retail/
commercial/ business parks with car parks of more than 50 spaces
require two levels of treatment for all hardstanding areas
including roads. An exception is run-off from roofs which requires
only one level of treatment. We recommend, as best practice, the
second level of treatment to be a basin or pond designed in
accordance with Sewers for Scotland Second Edition.
- Industrial developments require three levels of treatment for
hard standing areas and two levels of treatment for roads. An
exception is run-off from roofs which requires only one level of
treatment. We recommend, as best practice, the second level of
treatment to be a basin or pond designed in accordance with Sewers
for Scotland Second Edition.
- All roads schemes typically require two levels of treatment,
except for residential developments of 50 houses or less and
retail/commercial/business parks with car parks of 50 spaces or
less. For technical guidance on SUDS techniques and treatment
for roads please refer to the
SUDS for Roads manual.
In addition to the above levels of treatment, for all
developments, run-off from areas subject to particularly high
pollution risk (eg yard areas, service bays, fuelling areas,
pressure washing areas, oil or chemical storage, handling and
delivery areas) should be i) minimised and ii) directed to the foul
sewer. Where run-off from high risk areas cannot be directed to the
foul sewer we can, on request, provide further site specific advice
on what would be the best environmental solution.
The SUDS treatment
train should be followed which uses a logical sequence of SUDS
facilities in series allowing run-off to pass through several
different SUDS before reaching the receiving watercourse or
waterbodies.
Comments should be requested from Scottish
Water where the SUDS proposals would be adopted by them and, where
appropriate, the views of the local authority’s roads department
and flood prevention unit should be sought on the SUDS strategy in
terms of water quantity and flooding issues.
Scottish Planning Policy
Scottish
Planning Policy (SPP) sets
out the Scottish Government’s policy on nationally important land
use planning matters. The SPP provides policy on surface water
drainage and SUDS in paragraphs 209-211.
Planning Advice Notes
Planning Advice Notes (PANS) provide advice on good practice and
information including PAN 61
Planning and Sustainable Urban Drainage
Systems and
PAN 79
Water and Drainage .
SEPA policy and guidance
Regulatory and best practice advice
The Water Environment (Controlled Activities)
(Scotland) Regulations 2011 (CAR) provides regulation under General
Binding Rules (GBRs) 10 and 11 for surface water and SUDS.
Details of the requirements of these GBRs can be found in the
CAR
Practical Guide to the Water Environment 
(590kb).
Further guidance on the design of SUDS systems can be found
within CIRIA’s C697 manual entitled
The SUDS Manual . For
technical guidance on SUDS techniques and treatment for roads,
please refer to the
SUDS for Roads manual.