1
Crichton, D., 2005. “Floods and SUDS in Scotland and
Elsewhere. 44 frequently asked questions.” 46pp.
Sustainable Drainage Systems (SUDS): planning and
insurance issues
By David Crichton
Fellow of the Chartered Insurance Institute
Chartered Insurance Practitioner
Visiting Professor, Middlesex University Flood Hazard Research Centre
Visiting Professor, Benfield Hazard Research Centre, University College London
Honorary Research Fellow, University of Dundee
2
Preface
Under Scottish Planning Policy (SPP7), every local authority must establish or participate in Flood
Liaison and Advice Groups (FLAGs) which include an insurance representative.
The author has been funded by the insurance industry since 1996 to attend regular meetings of
FLAGs (formerly called “flood appraisal groups”) all over Scotland to advise them on insurance
issues. He is a member of all 19 such groups involving 28 local authorities, covering 98% of the
Scottish population. He has attended more such meetings than anyone else, and has been able
to help to spread information and best practice. This guidance note is intended to answer some of
the most frequently asked questions on SUDS and drainage issues that have arisen during Flood
Liaison and Advice Group meetings over the last ten years.
Recent publications by David Crichton include:
Crichton, D., (2005) “Flood risk and insurance in England and Wales: are there lessons to be
learnt from Scotland?” Technical Paper Number 1, Benfield Hazard Research Centre, University
College London. Available for free downloading from www.benfieldhrc.org
Crichton, D., 2005. “Flood Risks and Insurance Fact File” Chartered Insurance Institute, fourth
edition, London, June 2005. Available for downloading (for CII members and subscribers only)
from http://www.cii.co.uk/is/factfiles/flood_insurance.php
Crichton, D., 2005. “Insurance and Climate Change”. Proceedings of a Conference on
Climate Change, Extreme Events, and Coastal Cities: Houston & London. Houston, Texas, 9 th
February 2005.
The paper is available from: http://www.benfieldhrc.org/SiteRoot/activities/publications.htm#pres
Meyer, A., and Crichton, D. January 2005. “Contraction and Convergence”. Post Magazine
Weather supplement, 29th January 2005. London.
Crichton, D. January 2005. “The role of private insurance companies in managing flood
risks in the UK and Europe.” In Urban Flood Management, eds. A. Szöllösi-Nagy
(UNESCO) and C. Zevenbergen. ISBN 04 1535 998 8, 2004, 160 pp. A.A. Balkema
Publishers, Leiden, Netherlands. Available from www.balkema.nl or www.tandf.co.uk .
Roaf, S. Crichton, D., and Nicol, F. , 2005. “Adapting Buildings and Cities for Climate Change”
361pp. Architectural Press and Elsevier Press, London. ISBN 0 75065 9114
3
Contents
Introduction
Frequently Asked Questions
Q1. When should one ask for SUDS? Should SUDS be considered for very small developments,
for example, gap sites?
Q2. Why would a site not be suitable for SUDS?
Q3. How should detention basins be used?
Q4. Can SUDS be used outside urban areas?
Q5. Can SUDS be used on brownfield sites?
Q6. What powers do SEPA or EA have regarding SUDS?
Q7. What if the development does not have enough land for SUDS?
Q8. Should SUDS apply to a flood management scheme as well?
Q9. Who is responsible for maintenance of a SUDS scheme?
Q10. One aspect of SUDS is that swales and detention basins may be needed to hold the water
until it can drain through a controlled outlet with infiltration or dry out naturally. Elected council
members have expressed reservations about such features and also about retention ponds on the
grounds of the possible risk of children falling in and drowning. Is there a serious safety issue?
Q11. Should SUDS be to a 1 in 50, 1 in 100, or 1 in 200 design standard?
Q12. If SEPA approve a SUDS scheme, does that mean they consider the scheme will have a
neutral impact on run off?
Q13. Can SUDS lead to pollution?
Q14. What is the position regarding culverts?
Q15. How do Building Regulations and Building Control fit in with SUDS?
Q16. If the water authority/company take on responsibility for a SUDS scheme, will they provide
the engineering expertise?
Q17. It takes a long time for the water authority/company to approve a SUDS scheme. If the
designer is a qualified engineer, is it not possible for the engineer to certify it as meeting the
requirements?
Q18. Can rainwater be recycled?
Q19. What issues arise with phased developments?
Q20. In places like Singapore, Los Angeles, and Madeira, they have large storm drainage
channels to take surface water away. Could this not be tried in the UK?
Q21. One developer has been told by SEPA that they don’t need SUDS because only roof water
is involved so there are no water quality issues.
Q22. Who can enforce remedies for a breach of a SUDS design?
Q23. Some householders are complaining that their gardens are always waterlogged and they
want them to be drained.
Q24. What about roads issues?
Q 25. If someone’s property is damaged by flood or drainage surcharge, can they sue the local
authority or the water company?
Q26 What are insurers’ concerns about SUDS?
Q 27 Some insurers are now refusing to cover houses within 50 metres of a river or pond. Will
this be a problem?
Q 28 What are the implications of Marcic v Thames Water for insurers?
Q 29 Will SUDS make it harder to obtain a mortgage?
Q 30 The public has perceptions of how a pond should look based on experience of ponds in
parks and the grounds of stately homes. Will the public demand aggressive management of
ponds (dredging, weed removal etc) rather than leaving them to stabilise naturally?
Q31 Can soakaways be positioned near to the boundary of the curtilage?
Q32 How much will Scottish Water charge for maintenance?
Q33 What are CSOs?
Q34 What is source control?
Q35 Is groundwater a problem?
Q36 Is planning permission needed to build a pond?
Q37 Are there any guidelines for planting SUDS areas?
The following questions (38 – 44) arising in FLAGS relate specifically to Scottish Water
issues and the answers have been supplied directly by Scottish Water
4
Q 38 Will Scottish Water try to discourage SUDS schemes that have a high maintenance cost in
the future?
Q 39 Scottish Water is less concerned about habitat than SEPA. Will they seek hard engineering
solutions rather than soft solutions? For example they will now accept hydro cells in some areas.
Are we going to end up with plastic boxes everywhere?
Q 40 When “SUDS for Scotland” is agreed, will SW take on the responsibilities for monitoring
surface water quality currently held by SEPA? Will SW have responsibilities for preventing diffuse
pollution under the WFD/WEWS?
Q 41 There seems to be conflict already within SEPA between those responsible for WFD, and
those concerned about flood protection, despite the fact that WEWS emphasises the over riding
importance of liaison between all the agencies concerned to ensure sustainable flood
management. (It must be emphasised that in Scotland, WFD has not been transposed without
modification as it has in other countries). What is SW policy on this? WFD or sustainable flood
management?
Q 42 Will SW take into account the issue of insurability in their new construction standards and
vesting conditions? Have they consulted the insurance industry about insurers’ concerns? Will
this also apply to design standards? For example a common problem is waterlogged gardens
because of inadequate drainage. Also as new developments mature, residents are likely to build
conservatories, extensions, paved patios and driveways etc, which will increase run off. This is
often not allowed for in the original design.
Q 43 What allowance is made for climate change by Scottish Water?
Q 44 Will SW say that the capital and maintenance costs of SUDS are too high to be justified for
a particular site? Can Councils argue when they need affordable housing for low-income
families? As SW has no legal obligation to accept surface water drainage into their systems,
presumably this would prevent the development from proceeding?
Miscellaneous questions for debate
Appendix 1 Extract from the CIRIA Maintenance Framework Agreement for Scotland
Appendix 2: Extract from the residential property section of the ‘insurance template’
Appendix 3: Greywater
Appendix 4: Design of Drains and Sewers
Appendix 5: Marcic v Thames Water Utilities
Appendix 6: Model letter to developer
(Courtesy of Aberdeenshire Council)
Appendix 7: Results of a survey of insurers.
References.
DISLAIMER
It should be noted that the following is written mainly from an insurance perspective, in the light of
the expiry of the flood insurance guarantee, which will make it increasingly more difficult and
expensive to obtain household insurance in flood hazard areas. It is mainly intended to assist
insurance company underwriters and local authority planners, concerned about drainage and
flooding issues.
It is not professional advice and should not be relied on as such. Nor does it necessarily represent
the views of the Benfield Hazard Research Centre, Middlesex University Flood Hazard Research
Centre or the University of Dundee.
The author would be grateful for comments and suggestions.
Acknowledgements
The author is very grateful to the Scottish Environment Protection Agency (SEPA), Scottish Water
(SW), the Scottish Executive, and the Environment Agency (EA) for their helpful comments and
suggestions regarding the content of this note. This should not be taken to imply that the note
necessarily reflects their official policy, (in some cases it specifically does not) and if in doubt,
reference should be made to the relevant agency.
The author also wishes to thank Dr Chris Jefferies of Abertay University and Kate Zabatis of
United Utilities for their valuable comments and contributions.
5
Finally the author is grateful to all the insurance companies and Flood Liaison and Advice Groups
around Scotland who have raised all the questions dealt with in the paper, and hopes that the
answers will be of assistance to the planning community not just in Scotland but in the rest of
Britain.
Short Glossary
CAR
Controlled Activities Regulations
COPA 74
Control of Pollution Act 1974
CSO
Combined Sewer Overflow (see Q33)
DIA
Drainage Impact Assessments
EA
Environment Agency
Greywater
See appendix 3 and Q33.
SEPA
Scottish Environment Protection Agency
Ofwat
Office of Water Services
PPG 25
Planning Policy Guidance 25 (English planning guidelines)
SPP7
Scottish Planning Policy number 7 (flood) – replaces NPPG 7
SUDS
Sustainable Drainage System(s)
WEWS
Water Environment and Water Services (Scotland) Act 2003
WFD
Water Framework Directive
(There have been a number of variations in the description of SUDS. Originally it stood for
“Sustainable Urban Drainage Systems”, but it is now viewed as not being restricted to urban and
is called simply “Sustainable Drainage Systems”. The acronym is therefore sometimes shown as
“SuDS” but is generally still shown as “SUDS”).
6
Background
“SUDS” refers to “Sustainable Drainage Systems”, and the use of SUDS is growing in response to
the rapid pace of building development and the desire to avoid overloading existing drainage
systems, many of which are over 100 years old. Surface water can be disposed of in two ways:
 to groundwater using soakaways or ponds, or
 to existing watercourses, standing water (lakes/lochs) or the sea
Almost every new housing development in Britain will in future be likely to have some form of
SUDS (Northern Ireland is currently drawing up guidelines). Some years ago, with the permission
of the Association of British Insurers, the author represented insurance interests on the steering
groups which produced the SUDS manuals used by property developers and local authorities 1.
While he supports SUDS in principle, after having subsequently advised more than 30 local
authorities on the subject, he is concerned about some of the problems arising in practice.
Research by the author into insurance company attitudes to SUDS shows that as at June 2005,
hardly any of the major insurers had heard of SUDS or understand how they work.
It seems clear that the insurance industry is not being consulted about SUDS and is largely
unaware of how SUDS will affect future risks. It is hoped that this paper will help to raise
awareness of the issues.
Application
Although the questions shown in this paper come mainly from Scottish Planners, the notes are
intended to be for the benefit of planning and development control staff throughout Britain, to help
them to deal with drainage and climate change issues effectively. It is also intended to be of
assistance to insurance underwriters, to help them to understand more about the latest
developments in drainage systems.
There are a number of differences between Scotland and the rest of Britain,
Geographic and climatic differences:
1. Scotland has 40% of the land area of Britain but only 9% of the population. However
most of the population is concentrated in urban areas where densities are comparable to
England at around 30 dwellings per hectare.
2. During the industrial revolution, many towns in Scotland grew up around rivers which were
used to provide power for engineering and to treat textiles such as linen and jute.
3. There is a higher risk of snowmelt floods in some areas of Scotland, although this is
reducing due to climate change.
4. Coastal flood risk tends to be lower because shoreline geology is more “rocky” and suffers
less from erosion. Thus while there are now shoreline management plans (SMPs) for the
whole coast of England and Wales to consider issues such as defence versus managed
realignment, in Scotland, it is only necessary to have SMPs in certain areas where the
shoreline is “soft”.
5. In Scotland, sea level rise will have less of an effect because ground levels in the North
and West are rising at around the same rate due to tectonic rebound.
6. Climate change will have a significantly greater effect in England and Wales than in
Scotland in terms of rainfall, droughts and rising temperature.
Legislative and economic differences:
1. Privatised Water Companies operate in England and Wales, whereas there is a single Water
Authority (Scottish Water) in Scotland. (In March 2006, Westminster announced its intention
to privatise Scottish Water, selling it for £2 billion. However the Scottish Parliament
responded quickly to state that Scottish Water was owned by them and not Westminster and
they had no intention of privatising it.)
1
CIRIA Report C521
“Sustainable urban drainage systems. Design manual for Scotland and Northern Ireland”, London 2000.
CIRIA Report C522
“Sustainable urban drainage systems. Design manual for England and Wales”, London 2000. ISBN 0
86017 522 7
7
2. Since 1995 planning policy has been much tougher in Scotland than in England, and the
current planning policy (SPP 7) effectively prevents any building where the flood hazard
exceeds the 200 year return period for housing, or 1,000 years for vulnerable developments
such as hospitals etc, in line with the Insurance Template. By contrast, in England there is a
planning “guideline” (PPG 25), to be replaced soon by a “policy statement” (PPS 25), both of
which allow building in the floodplain if there is nowhere else suitable (the sequential
approach). Thus in England, large scale housing development is planned for the Thames
Gateway area, and PPS 25 says ““It is estimated in the Thames Gateway where more than
90% of the land for development lies in designated flood risk areas, a sequential approach
that allocates housing to the lowest risk areas could reduce potential flood risk losses by up to
52%.” (Section 6 [35] )
3. The Scottish Framework agreement for SUDS (outlined in Q9 and Appendix 1) has no
equivalent in England and Wales, where there are as yet no standard agreements on
construction, adoption or maintenance of SUDS 2. There is however an interim Code of
Practice on SUDS in England and Wales3 which goes some way to provide agreement
methodologies. Background paper 8 for the Making Space for Water consultation exercise 4,
suggests that uncertainty over ownership and responsibility issues constitute a disincentive to
their greater use.
4. Under the Water Environment and Water Services (Scotland) Act 5, which implements the
Water Framework Directive in Scotland, Scottish Water will be obliged to adopt a limited set of
above and below ground SUDS in certain circumstances. This is likely to start some time in
2006.
5. Certain aspects of SUDS such as soakaways will require regular maintenance by the property
owner.
In Scotland the Building (Scotland) Act 6 contains a section on “continuing
requirements” which allow the local authority to specify maintenance requirements in the
building warrant (this has not yet been introduced by the Scottish Building Standards Agency).
There is no similar power in England and Wales. Meantime in Scotland some local authorities
provide house buyers with an “entry pack” which sets out the continuing maintenance needs.
6. Following the Strategic Environmental Assessment EU Directive and the subsequent
Environmental Assessment (Scotland) Act 2005, it is now law in Scotland that the person
commissioning a plan or programme which is likely to have environmental impacts must
produce an Environmental Assessment. In Scotland this has been extended to include a
“Strategic Flood Risk Assessment”. There is no similar requirement in England and Wales
(although it was proposed in December 2005 in PPS 25). In Scotland, insurers can sue a
local authority if they fail in their obligation to undertake a Strategic Flood Risk Assessment.
7. Scottish Water will not sanction any new developments where surface water drains into
watercourses unless the relevant local authority accepts responsibility for the additional
discharge, and presumably any flooding and legal liability which might result.
8. Scotland has Flood Liaison and Advice Groups (FLAGs) where drainage and flooding issues
can be regularly discussed and best practice disseminated. These FLAGS cover 98% of the
population in Scotland and are attended by all relevant stakeholders. There is no equivalent
in England and Wales, although ODPM has recommended that local councils consider
following the Scottish example7.
9. Scotland is subject to the Flood Prevention and Land Drainage (Scotland) Act 1997, which
imposes certain statutory duties for assessing and reporting flood hazards and the
“Framework for Sustainable Urban Drainage Systems (SUDS) in England and Wales.” Available from
www.environment-agency.gov.uk/yourenv/consultation/486641
3
“Interim Code of Practice for SUDS” published in July 2004 and available from www.ciria.org/suds/icop.ht
4
“Sustainable drainage systems (SUDS): summary of policy and suggestions for possible future legislative change.”
Environment agency 2004.
2
5
Water Environment and Water Services (Scotland) Act, 2003. Thanks to energetic lobbying by a group of 32
environmental NGOs led by WWF and RSPB (and assisted by the author), this legislation goes well beyond the Directive
and produces a much more holistic solution to water problems in which flooding hazards are fully taken into account. In
respect of flood risk management, the 2003 Act (Subsections (3) and (4)) requires ‘‘Scottish Ministers, SEPA and the
responsible authorities to work in an integrated fashion and co-operate with each other to promote sustainable flood
management”.
6
Building (Scotland) Act 2003 Available from
http://www.scotland-legislation.hmso.gov.uk/legislation/scotland/acts2003/20030008.htm
CAG Consultants and Oxford Brookes university (2004) “The planning response to climate change –
overview and best practice.” ODPM, Scottish Executive and Welsh Assembly Government, 15 October
2004. ISBN 1 85 1127 15 1.
7
8
10.
11.
12.
13.
14.
15.
16.
17.
maintenance and cleaning of watercourses and gullies. There is no corresponding legislation
in England.
Scotland is also subject to the Roads (Scotland) Act 1984. Councils can issue an Order 8 to
the landowner or occupier requiring measures to be taken to prevent surface run off from
flooding an adjoining road. There is no corresponding legislation in England.
The EA regards SUDS as having a number of applications, including “flood management”,
whereas SEPA regards it primarily as a means of controlling diffuse pollution.
Building on floodplains has virtually ceased in Scotland, but continues on a major scale in
England, where 56% of local authorities ignore EA advice 9 about flood risks. In 2004, there
were nearly 700 new houses built in flood hazard areas in England against the advice of the
EA10.
A major increase in the programme of flood defence work in Scotland, combined with tight
planning controls is likely to result in a reducing number of unprotected flood plain
developments. In England and Wales, spending on flood defence work is inadequate
according to the government’s own reports, and the number of flood plain developments is still
growing. In Scotland no application for grant aid for flood defences has ever been turned
down due to budgetary constraints, the budget has simply been increased. To encourage
flood defence projects, grant aid has been increased to 80% and there is a national target of
defending all existing properties against the 100 year flood by 2008, taking climate change
into account.
England, Wales and Northern Ireland have transposed the EU Water Framework Directive
(WFD) as it stands, whilst Scotland has transposed it in a more holistic way, giving
sustainable management of flood risks priority. The legislation has to enable Scottish Local
Authorities to fulfil their statutory duties for watercourse maintenance under the 1997 Flood
Prevention Act, as failure to do so would lead to legal liability should floods occur.
Sustainable flood management is essential as climate change impacts result in increases in
rainfall. Often the most sustainable solution is to increase the storage capacity of rivers and
lakes upstream, rather than building flood walls through towns and cities as is proposed for
Carlisle.
In Scotland, flood management is under the control of the local authority, this means that only
the local authority has the power to initiate flood defence schemes, not SEPA. The local
authority is therefore democratically accountable if they fail to defend properties adequately:
they cannot “pass the buck” to SEPA in the way that English local authorities do with the EA.
This is a strong incentive for elected members to refuse to allow building in flood hazard
areas, especially as, unlike England, there are no targets for numbers of new houses in each
council area.
In Scotland, the sewer undertaker is only obliged to accept sewage if there is sufficient
capacity in its system, whereas in England and Wales, the householder has a right to be
connected to public sewers under section 106 of the Water Industry Act 1991, even if the
sewer has insufficient capacity. This means that in England and Wales sewers are much
more likely to be overloaded leading to overflows and sewage flooding, while in Scotland new
building is effectively prevented in areas where the sewage network has reached full capacity,
until there is investment in new sewage infrastructure. Developers are reluctant to pay for
additional sewage capacity beyond their immediate needs because this surplus cannot be
“banked” for future developments, but it also means that if another developer comes along
they can obtain the benefit of this surplus capacity.
The Scottish Executive has powers to insist on resilient reinstatement after a flood or storm.
There are no such powers in England.
Section 99 (1) of this Act states: “The owner and the occupier of any land, whether or not that
land is such as constitutes a structure over or across a road, shall prevent any flow of water or of
filth, dirt or other offensive matter from, or any percolation of water through, the land onto the
road.”
9
Association Française pour la Prévention des Catastrophes Naturelles (AFPCN) and the UK Advisory
Committee on Natural Disaster Reduction (ACNDR) the respective national platforms for the United
Nations International Strategy for Disaster Reduction, (UN/ISDR), conference presentation by Prof.
Handley OBE of Manchester University, held in Paris on the 22nd and 23rd September 2004. Proceedings
not yet published.
8
10
The Environment, Food and Rural Affairs Committee Report on the Environment Agency. UK Parliament, May
2006
9
18. For dams and reservoirs subject to the Reservoirs Act, the enforcing authority in England and
Wales is the Environment Agency while in Scotland it is the local authority. In other words the
enforcement authority is directly democratically accountable in Scotland, but only indirectly in
England and Wales (although the Scottish Executive is considering making changes to this).
19. The Scottish Executive has devoted substantial funding to encourage insurance schemes to
provide household contents insurance on a pay with rent basis for low income tenants of local
authority and housing association homes. Most Scottish local authorities now administer such
schemes. There has been no such funding in England and Wales. In Scotland, 43% of
families in social housing are uninsured. In England the figure is 61%.
Introduction
It is estimated that during 2002, insurers spent over £125m on repairs to underground drains
damaged by building contractors, with the average claim costing around £1,000. The Association
of British Insurers established a forum in 2003 to look into ways of reducing such costs. The real
problem for insurers is a widespread lack of understanding of how drainage systems work. This is
particularly evident in the case of drains and rising groundwater as a source of flooding, and the
impacts of source control measures such as SUstainable Drainage Systems (SUDS). The bulk of
the paper takes the form of frequently asked questions about SUDS. Each answer to these
questions is designed to “stand alone” (although there are cross-references where appropriate)
and this will mean some duplication.
It should be remembered that floods are not confined to floodplains. A single rainstorm in
Llandudno on 10th June 1993 flooded 2,500 homes and forced the evacuation of 4,000 residents.
These homes were entirely outside any floodplain, but the rainfall was so intense that the
drainage systems could not cope and insurance claims costs exceeded £5.5m. A very high
proportion of the flood claims arising from the autumn 2000 floods in England related to other
causes than rivers bursting their banks, causes such as surcharge of sewers, and agricultural
runoff from fields where grass had been ploughed up ready for winter cereal crops. In 2001, the
EA published a “Lessons Learned” report on the autumn 2000 floods11 which showed that in areas
where more than 20 properties flooded, the cause in nearly 14% of the cases was drainage
surcharge. Anecdotal evidence, especially from the insurance industry, indicates that the figure
may be much higher.
Research by the author for the government indicates that 40% of inland flood claims are outside
the indicative floodplain maps published by the environment agencies, although this figure falls to
25% if the floodplain map boundaries are extended by a 250m “buffer”. This suggests that some
15% of inland flood claims are due to backup into combined sewers and small watercourses and
is consistent with the EA’s findings. EA’s detailed report on the flooding in Wales (EA Wales,
2001) gives many examples of properties flooded by sewer surcharge or blocked culverts.
Robust data is hard to obtain, because many events are unreported to the water companies, but
the Construction Industry Research and Information Association (CIRIA) estimated in 1998 that
32,500 properties have a one in ten or one in 20 chance of sewage flooding each year (CIRIA
Report C506). According to the Institute of Civil Engineers report 12 “Learning to Live with Rivers”),
at an estimated cost of £50,000 per house, it would cost £1,625m just to cure the problem in this
relatively small number of properties.
The Office of Water Services (Ofwat) Annual Report for 2001-2002 states: “Flooding caused by
blocked or overloaded sewers is one of the worst failures of companies’ activities that customers
experience.” They published a consultation paper on the subject in March 2002, to which the
customer representative bodies, known as “Water Voice” groups have now responded. The
response from “Water Voice Thames” (WVT) is particularly interesting. Thames Water has over
half the properties at risk of sewer flooding in England and Wales, and WVT say they are
convinced that “a continuation of the established approach to correcting the deficiencies in the
Environment Agency, 2001, “Lessons Learned, Autumn 2000 Floods” Environment Agency, Bristol.
Fleming, G., Frost, L., Huntington, S., Knight, D., Law, F., Rickard, C., Macdougall, K., Ferguson, A.,
The Institution of Civil Engineers Presidential Commission Report, “Learning to Live with Rivers” London,
England, November 2001. Available for downloading from www.ice.org.uk/rtfpdf/ICEFlooding.pdf
11
12
10
system will not succeed.” They call for the avoidance of sewer flooding to be given the highest
priority over the next five years. The Environment Agency reported in their web site in February
2002 that one third of the total water industry planned future capital expenditure of £5.1 billion in
England and Wales has been allocated to Combined Sewer Overflow improvements.
Climate Change
Climate change is already happening, and EA and SEPA have undertaken to take this
account. In Scotland, Chief Executives of local authorities have made a special undertaking
their councils will take climate change into account especially with regard to the flooding
(Scottish Executive 2001). The Foresight reports published by the Office of Science
Technology in April 2004 show that
into
that
risk
and
in England and Wales:
• River and coastal flood risk could increase between two and 20 times;
• Annual economic damage could increase from £1bn to between £1.5bn and £21bn by the
2080s, depending on the scenario.
• The number of people at high risk of river and coastal flooding could increase from 1.6
million today, to between 2.3 and 3.6 million by the 2080s.
• Inadequate drainage will be a much bigger problem
– (7th August 2002, five mainline stations closed in London)
While in Scotland
• 2 hour duration rainfall intensity in East Scotland could increase by 60%.
• Annual average economic flood damage could increase from £90m to between £200m
and £400m by the 2080s, depending on the scenario.
SUstainable Drainage Systems (”SUDS”)
In March 1999, SEPA and the EA published a joint booklet entitled “Sustainable Urban Drainage:
an introduction”. This booklet gives an excellent introduction to SUDS and the reasons for it.
There is also a video13 available from the EA or SEPA, which also provides an excellent
introduction to SUDS. During 2000, CIRIA published comprehensive manuals on sustainable
urban drainage (C521 “Sustainable urban drainage systems design manual for Scotland and
Northern Ireland” and C522 “Sustainable urban drainage systems design manual for England and
Wales”). These were the culmination of extensive work to establish guidelines for “SUDS”. A
further “best practice” manual was published in October 2001 (CIRIA Report C523).
(These manuals provide many good reasons for implementing a SUDS strategy, and there is no
need to repeat these here. The purpose of this note is mainly to address some of the questions
that have arisen.)
The Scottish Executive published its Scottish Planning Policy guideline number 7 (SPP 7) on
flooding in February 2004. It states that:
“Generally, drainage will be a material consideration and the means of draining a development
should be assessed. Sustainable drainage will be required whenever practicable and
watercourses should not be culverted.”
This indicates the Executive’s policy on this matter and it is anticipated that SUDS will increasingly
be a standard requirement for new developments in Scotland whenever possible.
In England and Wales, there are still a number of practical problems with SUDS, especially issues
such as adoption and maintenance14. Uncertainty over these issues is a disincentive to the
spread of SUDS in England and Wales15 and legislation may be required.
Shot in the Dark Centre for Environmental Communications (2002) “Designs that hold water:
Sustainable Urban Drainage Systems Explained” Video production (25 minutes) sponsored by SEPA, The
Environment Agency, and the Institution of Civil Engineers.
14
“Framework for Sustainable Urban Drainage Systems (SUDS) in England and Wales.” Available from
www.environment-agency.gov.uk/yourenv/consultation/486641
And the “Interim Code of Practice for SUDS” published in July 2004 and available from
www.ciria.org/suds/icop.ht
13
11
One of the issues which has led to increases in flood frequency is the question of “urbanisation”
which leads to the covering up of the ground with impermeable roofs, roads, and car parks. This
speeds up the rainwater run off from the site, causing potential flooding elsewhere. It can also
cause pollution of watercourses. Initially, SUDS were mainly intended as a source control
measure to ensure that building developments have a neutral effect on rainwater run off by
keeping water on the site to the same extent as (but not necessarily more than) if the site was not
developed. In other words, that the site was sustainable from a drainage point of view. But SUDS
can do much more. By moving away from hard engineering solutions to more natural “soft”
solutions, modern developments can look more natural and provide a better environment for
people and wildlife.
So different bodies support the SUDS initiative for different reasons:
Scottish Water and the water companies in England and Wales
SUDS can reduce the increase in the load on surface water drainage. For areas with combined
surface water and foul water drainage pipes, SUDS can reduce the impact of new developments
on already overloaded sewers, reducing the risk of sewer overflow. Insurers should therefore
welcome properly designed SUDS schemes as they are likely to reduce flood hazard.
Unfortunately, there seems to be no co-ordinated approach to mapping such schemes or their
effects on surface water run off and there are no plans to do so. Local councils would be well
advised to keep records of all SUDS schemes in their area on a GIS for future reference.
EA and SEPA View of SUDS
Environment Agency
The Environment Agency view of SUDS is stated as follows:
“Sustainable drainage is a process for achieving integrated surface water drainage design with the
objectives of: reducing the flood risk from development within a river catchment;
 minimising diffuse pollution arising from surface water runoff;
 minimising environmental damage, e.g. bank erosion, and damage to habitats;
 maintaining or restoring the natural flow regime of the receiving watercourse;
 maintaining recharge to groundwater subject to minimising the risk of pollution to
groundwater;
 achieving environmental enhancements, including improvement to wildlife habitats, amenity
and landscape quality;
 minimising the amount of surface water runoff and infiltration entering foul and surface water
sewerage systems."
SEPA
SEPA primarily promote SUDS on the basis of water quality and NOT flood alleviation, this is
because SEPA do not have the same responsibilities for flood control. In Scotland this is entirely
the duty of the local authority, with SEPA acting in an advisory capacity.
SEPA therefore emphasise the water quality aspects, and regard SUDS as primarily a means of
enhancing natural biological attenuation and so improving water quality. It is SEPA policy for
SUDS to be favoured over traditional systems in all new developments (Policy 15)
SEPA point out that it is not practical to pursue a policy of using SUDS on a site-by site basis to
resolve a flooding problem. This is a valid point, given the nature of flooding at a catchment scale
and the dependency on the location and timing of runoff. In other words, SUDS are just one
aspect of source control See also Q11.
Planning and Development Control
Background paper 8 for the Making Space for Water consultation exercise, “Sustainable drainage systems
(SUDS): summary of policy and suggestions for possible future legislative change.”
15
12
There is no statutory compulsion to adopt SUDS in new developments16, but planners are
increasingly insisting on it as a condition of planning consent, at least in Scotland. In the author’s
experience this is not usually a problem for developers so long as they know the score at the
outset and can build SUDS into initial designs and feasibility studies. If maintenance is not agreed
at the outset then this can store up major problems for the future.
Benefits
There are many benefits for the community in having SUDS schemes:
 Amenity value is higher. SUDS features such as swales, ponds and natural watercourses are
aesthetically more attractive for the community than culverts and paved areas.
 The risk of flooding due to blocked culverts is eliminated.
 Wildlife habitats are enhanced, and biodiversity is improved
 Permeable surfaces dry out more quickly after rainfall.
 Infiltration systems can reduce the risk of pollution of groundwater and watercourses.
Problems
 If not properly maintained the systems can become an eyesore
 The public often abuse the systems, for example filling in soakaways for car parking
 Land values are so high that there is often resistance to taking up valuable land with
ponds and soakaways.
 Affordable housing offers particular challenges as housing density is higher.
 Smaller gardens increase the risk of escape of surface water into neighbours’ gardens,
leading to possible liability, especially if SUDS is used for greywater.
 Gardens are often waterlogged, reducing amenity.
 Flooding risks can be increased, especially for new housing subject to level access
requirements.
Insurance
While SUDS were not originally intended for flood alleviation, if the surface water from new
developments was all to end up in existing watercourses, downstream and upstream flooding
would be more likely. Also if the water were to end up in our existing drainage and sewage
infrastructure, it would not be able to cope in many areas, and there would be more instances of
sewage backup and overflow, again causing flood damage. For these and other reasons, it is
important that insurance companies understand and support SUDS, for example by not excluding
liability arising from SUDS features in householders’ gardens in the standard household policy.
Another insurance issue arises from the fact that SUDS could result in higher water tables and
rising groundwater. This is not covered under a standard household insurance policy, and there
may be increasing pressure on insurers from mortgage lenders to add this cover. It should be
noted, however that rising groundwater could cause heave, which is covered under a standard
policy.
Another issue for insurers is the increased risk of subsidence from a SUDS installation, due to
watercourses being starved of water by upstream SUDS installations during a dry spell.
The results of a survey conducted by the author in June 2005 are shown in Appendix 7.
Developers and Builders
SUDS developments can be more attractive to the buyer than hard standing and pipes, especially
in prestige developments. SUDS can also often be cheaper than laying pipes and drains, although
of course maintenance costs need to be considered if the SUDS is not adopted. In England and
Wales, the developer may well incorporate maintenance responsibilities into the title deeds,
putting the responsibility onto the buyer of the property. However there may be some concerns
over dangers to children from ponds (see Q10) and also concerns about waterlogged gardens
(see Q 23).
For some years now, developers in Scotland have had no alternative but to implement SUDS, not
only because of the policies of SEPA, but also in cases where Scottish Water state that they
cannot accept any additional surface water in their drainage systems.
16
Although it will in due course become a statutory requirement in Scotland under the Water
Environment and Water Services (Scotland) Act, 2003.
13
This is because in Scotland, the sewer undertaker is only obliged to accept sewage if there is
sufficient capacity in its system, whereas as mentioned above, in England and Wales, the
householder has a right to be connected to public sewers under section 106 of the Water Industry
Act 1991. This means that in England and Wales sewers are much more likely to be overloaded
leading to overflows and sewage flooding. The House of Lords has held that the sewage
undertaker is not liable for sewage flooding of gardens etc but may be liable for damage caused
by sewage entering a house (see Appendix 5).
One solution for England and Wales could be that where a suitable sustainable drainage system
exists the right of connection for surface water drainage could be removed or made conditional on
the granting of planning permission
Problems with SUDS
There is still much to learn about SUDS, for example, how much land is needed for swales and
retention ponds and other SUDS features? What are the long-term maintenance costs and who
should pay for it?
Research is under way into some of these issues, and everyone concerned is learning all the
time.
In Scotland, there is a network of 19 Flood Liaison and Advice Groups from the Scottish Borders
to Shetland, where planning officials meet regularly with roads engineers, SEPA, Scottish Water,
and the author. While these groups are primarily established to discuss flooding issues, SUDS
problems are also regularly discussed, and this has enabled many of these problems to be
resolved. In particular, because the author is a member of all of these groups he can spread best
practice and information.
Initially, many planners in Scotland confused SUDS with flood alleviation schemes, and asked
developers to install SUDS to cope with a 100 or 200 year event. However the original intention of
SUDS was that the site should not increase run off to any more than the run off would be if the
site were left undeveloped. In other words that the development should have a neutral effect on
the flood risk downstream. For example the Dunfermline Expansion Scheme (DEX), the biggest
SUDS scheme in the UK, was the result of the council requirement that there would be no
development unless it could be shown that the site would not cause increased flooding
downstream.
There is now a growing realisation that there may be a need for SUDS to go beyond this neutral
effect to have a positive effect. In other words, to provide greater storage than if the site had been
left undeveloped. In effect this means that the SUDS scheme would also be a flood control
scheme. This is a prudent approach given that:
1. Climate Change projections indicate increased severe rainfall events.
2. As new developments mature, residents are likely to build conservatories, extensions, paved
patios and driveways etc, which will increase run off. This is often not allowed for in the
original design.
3. Downstream watercourses and drains may already be overloaded before the development
and positive SUDS may help to reduce this.
4. An upstream development of high-density social housing, or a road improvement scheme,
might result in an increase in run off which can be compensated for by positive SUDS
downstream in a form of “drainage trading”. (This is not official policy as yet.)
5. There have been cases where development near the Council Boundary needs some of the
SUDS features to be installed in an adjoining Council area. The adjoining council may require
positive SUDS in such cases, in order to be sure that the development will not impact on its
own flood risk.
(For more details, see Q11, and Appendix 4.)
Planning Advice Note 61 (PAN 61)
14
The Scottish Executive published this advice note 17 in July 2001 “to provide advice on good
practice and other relevant information.” This short note gives excellent guidance, and should
certainly be studied by all planners involved with such matters, not just those in Scotland. As with
the SUDS manuals, it explains many of the benefits of sustainable drainage, and there is no need
to repeat them here.
Drainage Impact Assessments
The North East Scotland Flood Liaison and Advice Group (NESFLAG) in conjunction with SEPA
and the North of Scotland Water Authority published a guideline for drainage impact assessments
(DIAs) in March 2002. This excellent, award winning publication, should be studied by all
planners and developers, and the author hopes that it will become part of the policies of all Local
Authorities, at least in Scotland. Copies are available from Aberdeenshire Council, and from
SEPA’s Website. It recommends that the DIA include sensitivity testing to assess the effects of a
200 year rainfall event, to ensure that if the drainage overflows onto the surface, it will not affect
land or property. (See also Q11 and Q25.) The Scottish SUDS working group, and Renfrewshire
Council have also prepared guidelines and these were published in May 2005. Again these are
available from the SEPA web site, and are in line with the NESFLAG guidelines.
Planning Advice Note 61 “Planning and Sustainable Urban Drainage Systems” Scottish Executive,
Edinburgh, July 2001. ISBN 0 7559 2097 X
17
15
Frequently asked questions about SUDS
Most Scottish local authorities now have Flood Liaison and Advice Groups set up under the
planning guideline NPPG 7, as replaced by planning guideline SPP7 in 2004. The issue of SUDS
has been a regular topic for discussion at all these groups, and many questions and problems
have been raised. Some of the key questions have been shown below, with suggested answers
where possible. Some of these answers are “unofficial” and in such cases this has been stated.
For specific cases, it is always sensible to check with the relevant environment agency.
Q1. When should one ask for SUDS?
developments, for example, gap sites?
Should SUDS be considered for very small
The SEPA position
It should be emphasised that SEPA policy states that
SUDS should be used for all development. SEPA
policy to use SUDS for all developments is now an
explicit requirement under the Water Environment
(Controlled Activities) Regulation 2005 (CAR), General
Binding Rule (GBR) 10 which came into force on the 1st
of April 2006. This applies to Discharge of surface
water run-off from a surface water drainage system to
the water environment from construction sites,
buildings roads, yards and any other built-up areas,
and states that “If the surface water run-off is from
areas constructed after 1 April 2006 or from a
construction site operated after 1 April 2006, these
sites must be drained by a Sustainable Urban Drainage
System (SUDS) or equivalent. The only exceptions are
(i) if the run-off is from a single dwelling and its
curtilage and
(ii) the discharge is to coastal water.
SEPA will be able to provide more accurate information
At its simplest SUDS for a single house could take the
form of a soakaway. The revised part M of the Scottish
Building Regulations also seeks to deal with surface
water in a sustainable manner. In other words, SEPA
would say that there should be a presumption to use
SUDS in every case whilst recognising that in
exceptional circumstances, SUDS will not be viable.
They would not support the idea of minimum
thresholds, even as a pragmatic approach.
Nevertheless at this early stage in the development of
SUDS some authorities are doing so. While the author
is a strong supporter of SUDS, he considers this
approach has some merit on a temporary basis as
authorities go up the learning curve, especially as
many local planning departments are understaffed.
There is always a danger that if an inflexible approach
is taken, the credibility of the SUDS concept could be
damaged.
A1. SEPA and the EA (and many
local authorities) would say it should
be considered for every development.
SEPA/EA do not need to be consulted
in every case, however, and initially
some authorities took a pragmatic
view and set a threshold of 5
properties or even 30 or 40 before
they would consider SUDS. As stated
above, this is not the policy of SEPA
or the EA, but given pressures on
local authority staff time, such
informal
thresholds,
are
understandable (see panel).
Meantime, there is no reason why
roof water butts and permeable drives
should not be used on even the
smallest development. Another option
is to store rainwater in a tank to use
for flushing toilets (see question 18).
There is nothing in the building
regulations to prevent this, and
indeed the Building (Scotland) Act,
2003 has a whole section on
sustainability which will enable
subsequent regulations to encourage
this practice.
Such
schemes
need
little
maintenance, what maintenance is
required should not be beyond the
householder's capabilities.
SUDS may be needed even for small
sites if the water authority is unable to
accept more surface water in its
drainage system, especially if there is
a combined sewage system, which
may overflow if it has to take
additional surface water.
Wherever possible, SUDS should be combined with habitat enhancement features. (This may
cause problems within the 15km consultation zone of an airport due to bird-strike fears.)
16
Even if there is a presumption in favour of SUDS for every development, there can be a number of
valid reasons why SUDS may not be entirely suitable for a particular site (see Q2.).
Q2. Why would a site not be suitable for SUDS?
A2. Really the only reasons why a site would not be suitable for SUDS are:
1. The site is on a floodplain or has a high flood hazard, say more frequent than one in 200
years, in which case there should not be any development there anyway (See Q. 11).
2. The site is close to the sea or a large area of standing water, which can readily take any
increase in surface water run off that the development creates. (This is not official policy,
simply the author’s view of a common sense solution. There seems little point in creating
a retention pond right next to the sea. In Scotland this policy, at least in relation to sites
close to the sea, is now supported by the CAR )
In some cases, the designers will have to pay specific attention to ground conditions, and not all
SUDS methods will be suitable. For example:
 Where the soil is impermeable - clay or heavily compacted soil will not be suitable for
soakaways and could just make the water run off the site. Retention ponds may be a solution
if the site is suitable. Infiltration systems can be effective in impermeable areas. Permeable
paving at sites that overlay clay, have shown benefits in terms of improved water quality and
reduced/delayed runoff. For example the car parks at the South Gyle retail park in Edinburgh
are all constructed with permeable surfaces on an impermeable lining. This has reduced
surface run off by 20%.
 There may be insufficient land for a soakaway (see Q31)
 Brown field sites where the soil is contaminated – SUDS could cause the contamination to
spread through the groundwater, (a particular concern for liability insurers) so again such sites
will not be suitable for soakaways and could just make the water run off the site. Again,
retention ponds or other SUDS designs may be a solution, provided they are lined to prevent
contamination entering watercourses. (See also Question 5 on contaminated sites.)
 Small or high-density developments, gap sites, or road widening projects, where there is not
enough land available for swales or ponds. In such cases underground storm cells under the
buildings may be one answer, although these “plastic boxes” are unpopular with SEPA.
Another may be “drainage trading” as part of a strategic approach (see Question 7).
 Where there are problems of access for maintenance purposes. This should be considered as
part of the design process, and low maintenance solutions considered. Such situations may
not be considered as “public SUDS” for the purposes of adoption by Scottish Water.
Sometimes the developers may argue that the capital and maintenance costs of SUDS are too
high to be justified for a particular site. Councils are increasingly taking the view that they want a
high quality environment, and if the developers are not prepared to pay the price, they will have to
go elsewhere. An exception to this may be for housing designed for low income families, where
again drainage trading might be a solution, in other words a shortfall in the SUDS design for low
income housing might be compensated by excess SUDS capacity upstream or downstream in a
high income development. For example, Aberdeenshire Council has introduced additional SUDS
storage upstream at Torphins to reduce the flood risk in a form of “SUDS Trading”.
(It should be emphasised that the concept of drainage trading suggested by the author is
an entirely pragmatic solution that has not been adopted officially.)
The developer should be asked to draw up a drainage strategy (see PAN 61, section 23), which
shows how he intends to implement SUDS, or if he believes SUDS is not suitable for the site, the
reasons. A model letter appears in Appendix 6. This drainage strategy should follow the model
published by NESFLAG, and should include a sensitivity test for the 200-year event (see Q11).
See also Appendix 4.
Q3. How should detention basins be used?
17
A3. Detention basins (see panel) can provide a solution where the soil is not sufficiently
permeable for soakaways, or where groundwater needs to be protected. They can also be used to
cater for severe rainfall events where the groundwater becomes so high that soakaways are no
longer effective. Often the detention basin will remain dry for much of the time and can be used
as a recreational area (Sewers for Scotland 2 will provide more details). On a sloping site, it
should obviously be located in the lowest part of the site.
There needs to be some consideration as to how the detention basin will be drained, and what will
happen if it overflows, in case this could cause flood damage to properties. Some form of positive
drainage will be required, and this may have to be manually controlled to prevent the overloading
of a swollen watercourse. It may even be necessary to have a pumping system installed if the
pond is lower than the nearest watercourse. This situation should be avoided if possible, because
of the increased maintenance costs, but may be necessary where the retention pond is part of a
flood alleviation system. A detention basin may also be used to detain water and prevent it from
entering a watercourse during a peak flow period, in order to mitigate flooding downstream.
If the detention basin requires embankments, the risk of failure must be considered.
Embankments should be properly constructed or maintained.
Retention Ponds and Detention Basins
A Retention Pond is an area of permanent standing water up to 4 times the Treatment Volume18.
A Detention Pond is pond designed to attenuate surface water runoff that has a permanent pool
volume which is at least equal to one times the Treatment Volume19.
A Detention Basin is an area which could temporarily contain water during a rainfall event, but
which is normally dry.
An Extended Detention Basin is normally dry, but with designed pools of water or marshy areas at
the bottom.
________________________________________________________________
Q4. Can SUDS be used outside urban areas?
A4. Yes. Indeed, it should be noted that while SUDS originally meant “Sustainable Urban
Drainage Systems” it now generally means “SUstainable Drainage Systems”, that is, that the word
“urban” is omitted, because it is intended for rural use as well.
However it should be remembered that in rural areas agricultural landowners may have the right
to carry out some excavation, engineering and land drainage work without the need for planning
approval, and this may affect the performance of a SUDS scheme (See Q36).
Changes in agricultural practices have resulted in more floods caused by surface water run off
from fields. For example, deforestation, and the ploughing up of grassland for winter cereals.
Such run off is usually very muddy, and can cause considerable damage. In Scotland the local
authority has powers to order the landowner to prevent this if a road is affected, but otherwise, the
planning authority has little power to prevent such flooding, other than building local defences and
drainage schemes. The time may well come when insurers consider lawsuits to recover claims
costs against such farmers under the rule in Rylands v Fletcher (1868) whereby land owners have
a strict liability not to allow water to escape from their land. However to do this they would have to
satisfy the court that the activities of the farmer constituted a non-natural use of the land.
SUDS in agricultural areas will also have to be designed to treat a different kind of pollution to that
in urban areas. Runoff from rural areas is likely to have very high bacteria concentration (such as
e.coli ) and be high in suspended sediments. Therefore SUDS will have to be designed to provide
18
A calculated volume of water (usually referring to the permanent pool volume in a pond) which provides
partial treatment to surface runoff. It is normally based on the site impermeable area and the local
hydrological characteristics
These are the definitions, agreed by SEPA, used in Scottish Water Technical Manual “Sewers
for Scotland” 2nd Edition which will set the design standards for public SUDS to be adopted by
Scottish Water
19
18
adequate water quality treatment before discharging into watercourses. (SEPA can provide more
information)
One solution used by a number of local authorities in Scotland is to invite representatives of land
owners to attend Flood Liaison and Advice Groups where the problems can be discussed and
solutions found. Such meetings give the author the opportunity to outline the insurance industry
position. The prospect of a civil action by insurers to recover the cost of flood claims directly from
the land owner could have more influence on their actions in the future.
Q5. Can SUDS be used on brownfield sites?
A5. Yes, but some special considerations may apply:
Brownfield land describes sites that have previously been developed or used for some purpose
which has ceased. (It does not include land which was previously used for agricultural or forestry
purposes and it excludes land previously used as private and public gardens, sports and
recreation grounds, woodlands and amenity open space.)
 The site may be contaminated, and excavation works could lead to pollution reaching
watercourses or groundwater
 There may be existing buildings or walls, which are acting as private flood defences. If
demolished, this could increase the flood risk. See also Q31.
 The soil may be heavily compacted or covered in impervious materials meaning that
soakaways may not be effective unless the soil is excavated and replaced with more
permeable material, or storage tanks. SEPA/EA will not usually insist on this if it means
breaking through an existing hardstanding in case there is polluted ground underneath the
hardstanding.
There are few occasions where SUDS cannot be used – they just have to be designed to take the
site conditions into account.
The EA have a “flagship site” on the M40 services at Wheatley, which is on contaminated land,
with an impermeable membrane under the porous surface car-park (see also Q13).
Liability insurance is becoming increasingly expensive and hard to obtain, and many small
companies have had to go out of business because they cannot afford the minimum cover
required by law. If a company is operating on land that has been contaminated, and SUDS have
been used without proper precautions to prevent escape of contamination, Environmental
Impairment Liability cover may be impossible to obtain. This in turn could cause problems when
legislation implementing the Environmental Liability Directive is introduced. In many cases the
only practical solution will be for the company to move to a Greenfield site.
At the time of writing SEPA is preparing a guidance note on contaminated land. It is not known if
this will take into account insurers’ concerns, although the author has been lobbying for this.
Of course the developer will have to take into account the financial implications of using SUDS on
contaminated land and would have to build this into the costs of the development. In England and
Wales, the developer will probably find it easier and cheaper to simply connect the surface water
drainage to the nearest sewer.
Q6. What powers do SEPA or EA have regarding SUDS?
A6. SEPA or EA can refuse a discharge consent on the grounds of water quality. Even if the only
water coming off the site is from roofs and roads etc they could issue a prohibition notice under
the Control of Pollution Act (COPA) 1974 for any discharge of surface water, which would
effectively make the discharge illegal, until a consent was applied for, and granted.
In Scotland, the CoPA regime has now been superseded by the Controlled Activities Regulations
(CAR) regime. Under this SUDS will not need a consent but will have be subject to General
Binding Rules (GBRs 10 and 11) General binding rules are intended for activities which represent
a small risk to the water environment. SEPA will not be contacted by operators acting under a
19
GBR and therefore SEPA will not know the location of such activities. Consequently, they are
appropriate for low risk activities which are unlikely to represent a cumulative impact.
These rules are intended to ensure the regulation of certain activities without the need for
registration or licensing. This minimises the regulatory burden on operators and the risk to the
water environment is still mitigated as it is possible for SEPA to require further controls if problems
become apparent.
Prior to CAR, SEPA could also serve a conditional prohibition notice under their “Policy 15”
stating that SUDS has to conform to the agreed design. In practice, SEPA Policy 15 states that
consent is not required, as long as the discharge is made via SUDS designed in accordance with
the manual. However they may still monitor water quality. If water quality is jeopardised, they can
issue prohibition notices. It is not clear whether policy 15 still applies.
SEPA also has powers with regard to it being a statutory consultee to the Planning Authority for
(almost all) new development.
The EA position is as yet undecided (as at November 2005.)
Q7. What if the development does not have enough land for SUDS?
A7. There is no doubt that some SUDS features can take up a lot of land. Much depends on how
flexible the local authority attitude is. Developers generally want to have the maximum possible
density on their sites and in England and Wales this is encouraged by ODPM guidelines. Thus in
Scotland, 25 dwellings per hectare is considered “high density” whereas in the South East of
England the standard rises to up to 35 dwellings per hectare. In the Thames Gateway there are
plans for 200 dwellings per hectare in some areas.
Scottish Water are proposing to use the concept of the “treatment train” (or “surface water
management train”) which would reduce the amount of land needed for a single SUDS solution
dealing with the runoff from a whole development. This involves the management of runoff in
stages as it drains the site, starting from using source control measures for individual premises
(such as water butts) to larger downstream site and regional control measures. The more runoff
can be dealt with at source, the smaller the downstream solutions will have to be.
In Scotland, around 10% of a housing site has to be open space, but it is up to the local authority
how much of this can be “wet”. If a small percentage of this is wet all the time and a bigger
percentage is wet during a rainstorm, it could be regarded as an amenity, and would not give
developers a problem.
Some local authorities estimate that SUDS require around 5% of the site’s land. If this is
interpreted as being in addition to the normal open space requirement, it can cause developers
problems. Local authorities in Scotland are also wary of allowing soakaways near the boundary of
a plot (see Q31)
It is not just the question of swales and retention ponds; there is also the issue of providing access
routes for maintenance vehicles. This can be a problem in brownfield sites or in high-density
housing developments. In some private housing developments, swales can be installed in front
gardens and this can help, but it can be a serious problem for other developments, especially for
road construction.
One (entirely unofficial) suggestion is to have some sort of “drainage trading” system so that lack
of adequate SUDS features in one development could be compensated for by additional SUDS
features elsewhere, for example additional swales and retention ponds in a less intensely
developed site nearby. This is not an officially recognised solution, but one that could be
considered for the future in certain cases, again as a pragmatic approach. For example a road
improvement scheme could create additional surface water run off into a water course, but
additional SUDS measures downstream could reduce run off into the same watercourse to
compensate. Fife Council has a strategic drainage plan with strategically placed treatment ponds
such as the Dunfermline Eastern Expansion (“DEX”) scheme, which is the largest SUDS
demonstration site in the UK.
20
Any drainage trading system would have to be very carefully designed and supervised, especially
where it crosses political boundaries, owing to the risk of creating floods.
Q8. Should SUDS apply to a flood management scheme as well?
A8. In principle, yes. Such schemes can require a large amount of land and can therefore affect
run off. Embankments can also lead to rising groundwater. There will also be issues of
maintenance and management of the scheme. Advice should be sought from the EA or SEPA, as
appropriate. In Scotland, Scottish Water should also be involved in the discussion to ensure an
integrated approach.
Q9. Who is responsible for maintenance of a SUDS scheme?
A9. In England this has still to be decided and it appears that legislation will be required.
Scotland is fortunate in that in the early days of SUDS it was agreed that the former three Scottish
water authorities companies (now merged into one, namely Scottish Water) will normally take
responsibility for below ground systems while local authorities would be responsible for above
ground systems. This was an informal arrangement and while a framework agreement was
worked out this was only adopted by one council. A copy appears in Appendix 1 for information.
This only applies to shared drainage systems, where the system takes water from a number of
sites or takes both curtilage and road water. SUDS on a private site are the responsibility of the
property owner, and SUDS dealing with road water alone are the responsibility of the roads
authority. The allocation of responsibilities has been formalised in Scotland following the Water
Environment and Water Services (Scotland) Act 2003, by making Scottish Water responsible for
the future maintenance and capital replacement of shared public SUDS and drainage systems.
The term “sewer” in Scotland has been redefined to include SUDS components and the Sewerage
(Scotland) Act 1968 was amended to provide for Scottish Ministers to make regulations dealing
with SUDS. These regulations will establish the construction standards and vesting conditions
that Scottish Water will apply to all SUDS for which it is to assume responsibility. The
amendments to the Sewerage (Scotland) Act will only be brought into force once the construction
standards and vesting conditions are in place. They are currently being drafted and it is expected
to undergo an public consultation exercise in Summer 2006.
In other words, Scottish Water will be made responsible for the future maintenance and capital
replacement of shared public SUDS. In particular, the following will be included in the design and
construction standards:

Detention ponds

Detention Basins

Underground storage
The takeover is conditional on such systems meeting design standards, which are to be set out in
the revised edition of Scottish Water’s technical manual “Sewers for Scotland”. The manual
defines the acceptable design and construction standards for Scottish Water’s sewerage
network20 and will be supported by the regulations. Scottish Water will receive additional funding
from the Scottish Executive for such maintenance costs. Once the legislation changes are
enacted, developers may wish to put forward existing SUDS for take over by SW. All SUDS
measures will be reviewed against the standards set out in the Regulations or the standards set
out in the consultation, if different, and if these are met the systems can be taken over by SW.
Systems which are not built to the standards can be taken over by SW, but only by agreement
and they may require modifications before this can take place
In the interim period SW has made the SUDS section to be included in the revised manual for the
consultation available on its website. All systems which are built to the draft standards set out in the
consultation can be taken over by SW
20
The SUDS section to be included in the revised manual can be found on SW website. This is still a work in
progress and may be amended once the public consultation has taken place.
21
Meantime, it is up to each individual local authority in Scotland to decide how to deal with adoption
and maintenance. Although only one council has formally adopted the framework agreement, the
author is not aware of any cases where a Scottish local authority has refused to adopt above
ground SUDS, or where Scottish Water has refused to adopt below ground systems. (If there are
any such cases, the author would be pleased to hear about them.)
In England and Wales, agreement has still to be reached between local authorities and water
companies, and although CIRIA have been working on this, it is unlikely that even a framework
agreement will be reached, and legislation may be required. Meantime, each case is considered
on a site by site basis. Meantime, the EA have taken on responsibility for some SUDS and there
is an Interim code of Practice which goes some way to developing maintenance schedules.
At present there is no legal obligation on the local authority to adopt a scheme in Scotland,
England or Wales, other than in connection with roads. If a scheme is not adopted either by the
water authority/company or the local authority, it is likely that it will not be maintained at all.
It can be argued that the council tax or water rate payer should pay for SUDS in the same way as
he does for sewers at present. As SUDS become more widespread, this view may become more
acceptable. In the meantime, Scottish Councils seem reluctant to accept additional burdens and
are looking for alternative solutions. No doubt the same applies in England and Wales. Councils’
prime target source of funding for maintenance seems to be the developer at the moment,
especially as developers are currently making significant profits due to the high demand for new
housing. Several Councils for example Aberdeen City are using the “planning gain” mechanism to
extract money from developers.
Aberdeenshire Council, unlike most other Scottish councils, seems to have no qualms about
writing SUDS into title deeds as is done in England and Wales. Aberdeenshire requires the deeds
to say that the system will be a flood storage area in perpetuity, and will require to be surveyed
every five years and re-contoured every 20 years.
In any event, it is important that responsibility for maintenance is resolved at the outset, not left as
an afterthought. Developers will not be at all happy at being presented with a bill for future
maintenance after the properties have been built and sold. If the issue is resolved at the start, the
developer can build the costs into his feasibility study to see if it is worth proceeding.
Solutions could include:
-
Asking the developer for a commuted sum of money to be held in trust to fund future
maintenance. This could form part of the “planning gain” negotiations, except that if this is
done, the commuted sum could end up in a general “pot” rather than being specifically
earmarked for SUDS maintenance. Another problem is estimating in advance how much the
maintenance costs will be; it can be difficult getting accurate estimates from designers and
landscape designers, especially as SUDS are relatively new in the UK. (Some features of
SUDS have been used in Canada for over 100 years.) In 2001, the UK water industry
identified the need for a comprehensive review of performance, risks and costs associated
with a SUDS approach to drainage. It was recognised that the United States had significant
experience in the implementation, operation and maintenance of such systems (know there as
Best Management Practices, or BMPs) so to facilitate effective knowledge sharing, a joint UK
Water Industry Research (UKWIR)/US Water Environment Research Foundation
(WERF)/American Waterworks Association Research Foundation (AwwaRF) research project
was initiated. The project resulted in the development of a whole life cost model of SUDS
systems by HR Wallingford, which allows calculation of the expected lifetime cost of a facility
based on design criteria, construction options, maintenance levels and operating regimes.
The Whole Life Cost model is available to be purchased form UKWIR.
-
Requiring the developer to pay an adjustable annual sum for actual maintenance costs
incurred. Often a developer will set up a separate limited company for each development,
and in this way could escape future obligations by liquidating that company. It is therefore
wise to insist that the developer take out an insurance bond to guarantee its solvency, rather
like the “Restoration Bonds” often used for open cast mining work. Unfortunately such
insurance bonds can rarely be issued for longer than 25 years.
22
-
-
Establishing a resident’s association, or applying a service agreement as part of the title
deeds for each property, requiring the residents to pay an annual maintenance fee. This
would apply in much the same way as residents in privately owned flats pay a service charge
for lifts, or maintenance of common parts such as stairs and roofs. In addition, special
insurance policies are available for the repair of common parts, they are called “Maisonette
Support Indemnity” policies, but can apply to any type of shared domestic property. In
practice there could be problems with this in that failure of SUDS could lead to public liability
claims and the residents’ association would have to be properly constituted and insured.
The Aberdeenshire Council solution, in which the title deeds apply obligations on the property
owner to have the systems regularly inspected and re-contoured at regular intervals.
Maintenance of “offsite” SUDS are even more problematic, for example retention ponds shared by
two or more developments, with different developers. It is important that the local authority has a
strategic drainage policy for such circumstances and takes a firm line with developers at the
outset as to the apportionment of maintenance costs.
In all cases, planners should ensure that the development allows for a right of access to SUDS
features for maintenance purposes. Residents may be tempted over the years to put up fences or
plant hedges, which might restrict access to shared SUDS systems on public ground. (The
maintenance of SUDS systems on their own land will be their own responsibility.) A right of
access may have to be written into the title deeds, along with covenants to prevent occupiers from
interfering with SUDS features on their own land, for example filling in swales to make grass
cutting easier or to allow car parking space. There are also maintenance access issues for
Scottish Councils in implementing their statutory duties for maintaining watercourses under the
Flood Prevention and Land Drainage (Scotland) Act 1997. Already, some Scottish Councils will
refuse to allow any development or garden ground within 5 metres of a watercourse, so that
maintenance vehicle access is not blocked.
In one recent case, a planning authority gave consent for a housing development near the
Council’s boundary, in which the SUDS installations were all in the area of the adjoining Council.
The adjoining Council was unaware of this development and had no power to stop it. Most Flood
Liaison and Advice Groups in Scotland now invite representatives from adjoining Councils, and
this should help to minimise this risk in the future, at least in Scotland. There is unfortunately no
similar mechanism in England or Wales.
Q10. One aspect of SUDS is that swales and detention basins may be needed to hold the
water until it can drain through a controlled outlet with infiltration or dry out naturally.
Elected council members have expressed reservations about such features and also about
retention ponds on the grounds of the possible risk of children falling in and drowning. Is
there a serious safety issue?
A10. These concerns are valid, but the law is more concerned about hidden dangers, or dangers
to very young children. Provided precautions are taken to stop very young children from straying
into watercourses or ponds, and provided the banks are not steeply sloping, the risks are obvious
and relatively low, certainly lower than the risk of crossing a road or having culverts. Retention
ponds should be surrounded by a low fence, say 300mm high, to stop toddlers getting in, and this
could be masked by shrubbery. (In the author’s own village there is a pond next to the primary
school and this is effectively protected in the summer by a profuse growth of nettles!). A ROSPA
(Royal Society for the Prevention of Accidents) assessment should be carried out at the design
stage to ensure all reasonable Heath and Safety precautions have been taken. In addition the
Water Industry has recently reviewed a “key liabilities report” which will be published in the next
few months. If there is any concern about the liability position, the Council should seek guidance
from their liability insurer or legal department. (Many busy public parks in London have ponds
protected only by a “toddler fence” some 300mm high.)
Q11. Should SUDS be to a 1 in 50, 1 in 100, or 1 in 200 design standard?
A11. EA and SEPA would say that the purposes of SUDS are to improve water quality. Scottish
Water and the water companies would say it is about source control.
23
The author would say that both are important, but the underlying principle of SUDS and the
feature which makes up the “sustainable” part of “sustainable drainage systems”, is something
else. Namely, that SUDS are intended to make the development site have a neutral impact on
rainfall run off, so that the rate of run off after development is the same as on a greenfield site.
Whatever the disagreements about what SUDS are, there is no disagreement about what they are
not. It is not primarily intended to alleviate flooding risk in a flood hazard area (although it should
have this effect), so the question of a design standard does not apply in the same way. In
Scotland there is nothing to prevent the local authority, as the body responsible for flood control,
applying a design standard to the risk of flooding downstream, or insisting that the scheme avoids
making the flood situation worse. In other words, it does have an important role in helping to
control the flood hazard downstream of the development, which might otherwise have been
increased by the existence of the development. Indeed, some activities could increase the flood
hazard upstream as well, for example if watercourse capacity is reduced by flooded retention
ponds.
It is important that planners do not have exaggerated expectations or requirements for SUDS.
SUDS can and should certainly reduce the flood hazard elsewhere arising from the development,
but if there is a flood hazard at the development site, then there should be a presumption against
consent for the development. If consent is to be given, then an appropriate flood management
scheme must be prepared and referred to SEPA or EA for guidance.
Some sort of design standard for SUDS should certainly be considered. It is often forgotten that
housing developments will change after residents have moved in. Many will want to build
extensions, paved patios and drives, carports, and conservatories, all of which will increase
surface water run off. Some allowance should be built in to cater for such increases, as well as an
allowance for climate change, to ensure that the development continues to have a neutral effect
on run off. The design should also take into account potential flood paths should the SUDS be no
longer able to cope with a heavy rainstorm. In Sewers for Scotland 2nd edition there is a
requirement to consider these issues at the design stage
.
Ideally there should be a 200 year return period for “sensitivity testing” as part of a “Drainage
Impact Assessment” (DIA) in accordance with the DIA Guidelines (NESFLAG, 2002). In other
words the designers should be asked to predict where the water would go it if exceeds the
capacity of the SUDS scheme, for example during a severe rainfall event. This “what if” exercise
can be useful in determining whether flooding is likely to be a problem on the site, or whether the
development of the site even with SUDS could make the flood problem worse elsewhere.
In some cases such as hilly ground, there may be clearly no danger of flooding of the site itself,
but there could be a problem for properties at a lower level.
There is no standard definition of a severe rainfall event, but sensitivity testing is usually carried
out to a 50-year or 100-year event. Many drainage systems can pass this test, even if the
pipework is designed for only a 2-year event. However, with climate change, if residents are to
avoid being flooded, or having flood insurance problems, councils would be well advised to
specify sensitivity testing for the 200 year event to see what effect this would have on flooding of
properties and key roads. For more information on this aspect see the DIA Guidelines
(NESFLAG, 2002).
This testing should take into account the possible impact of snowmelt, especially if the site is
liable to suffer from wind driven snowdrifts. The local authority should also specify that with a
200-year event, flooding should not come within 300 mm of floor levels or access routes, before
accepting a SUDS scheme. This is especially so in the light of the new requirements for level
access for the disabled.
Designers should also be asked to add a percentage (at least 10%) onto the
permeable/impermeable ratio to take into account changes in use (extensions, patios etc) and
changes in groundwater levels after a long period of rainfall.
If flooding is likely to be a problem, then a flood risk assessment should also be undertaken in
conjunction with the DIA. Positive drainage may be required, and in some cases a flood
alleviation scheme that takes into account the effects downstream and upstream.
24
It must be noted that if soakaways and other infiltration systems become waterlogged it could lead
to problems such as:


Damage to foundations, especially in freezing conditions (see Q31).
Rising groundwater in the development site, leading to localised flooding. It should be borne
in mind that rising groundwater is specifically excluded from household insurance policies.
 During an extreme event, the timing at which run off reaches the nearest watercourses can be
critical. If SUDS delay the run off into the watercourse, it could coincide with a peak flow due
to run off upstream, thus making the peak even higher and making downstream flooding
worse.
It should always be remembered that retention ponds can overflow or burst in a severe event, and
their existence might make matters worse than if the site had been left undeveloped.
SUDS are no reason to ignore the guidelines in the insurance template (see Appendix 2), nor
should it be used as an excuse to develop floodplains where the flood hazard exceeds a 200-year
return period. (See also PAN 61, and NPPG 7 in Scotland, or PPG 25 in England)
See also Appendix 4.
Q12. If SEPA approve a SUDS scheme, does that mean they consider the scheme will
have a neutral impact on run off?
A12. No. SEPA’s remit for SUDS is to consider water quality issues, not hydrology or flood risk.
SEPA approval of a SUDS scheme on water quality grounds should not be taken to imply that
they are saying that it would alleviate flood risk. However, SEPA or EA as appropriate can be
consulted on flood risks arising from a SUDS proposal. (Although SEPA do not have a remit on
flood control, their hydrologists are prepared to comment on flood risk assessments.)
Q13. Can SUDS lead to pollution?
A13. SUDS should be designed to reduce and treat pollution, but insurers are generally very
concerned about potential liabilities from the spread of pollution, and are not yet familiar with the
way SUDS works. The pollution risk is very dependent on the type of SUDS feature used, its
ability to treat pollutants and the flows and loads on the SUDS feature. Insurers are particularly
cautious about sites where the run off could contain oil or chemicals, and may insist on oil
interceptors for example, and the remainder of this answer deals with their biggest concern which
is oil.
In Scotland the General Binding Rules (GBRs) applying to surface water discharges under the
Controlled Activities Regulations (CAR) require that

The discharge shall not contain any trade effluent or sewage, shall not cause visual
impairment, destabilisation of stream bed or banks, or cause pollution.

The discharge shall not contain drainage from chemical, oil or other polluting matter from
loading/unloading/handling areas.

Don’t dispose of oil, paint or paint thinners, pesticides, detergents, disinfectants or other
pollutants into a surface drainage system, or allow any material that might impair its
performance and function to enter a surface water drainage system
Further information can be obtained from SEPA
SEPA and EA policy is that oil interceptors will not be required in most cases for car parking areas
where SUDS are used. This is partly because maintenance may not be adequate, and partly
because the small quantities of oil lost from cars in car parks will be broken down in appropriately
designed SUDS schemes, such as permeable surface systems. However, from an insurance
point of view, where there are large, frequently used car parks, for example next to retail parks,
supermarkets, or motorway service areas, the underwriter could well fear a severe pollution
liability and may require oil interceptors. In such cases the owner of the car park should be
responsible for maintenance. Obviously, high risk areas such as filling station forecourts will need
25
special consideration. Spill catch pit areas can provide a solution and should be designed into a
SUDS system wherever there is a risk of pollution. They can be pumped out in the same way as
an interceptor can.
There could be problems if agricultural land is used for run off or storage and becomes polluted.
There are already serious problems in some areas due to pollution from diesel tanks, phosphates,
nitrates and septic tanks in agricultural land. Watercourses and standing water can easily be
polluted in this way, leading to a reduction in environmental quality status under the Water
Framework Directive. More important from an insurer’s point of view perhaps is that farmers can
be sued for damaging riparian rights, and such claims can be surprisingly expensive. As it is,
most insurers will no longer accept farming risks without a survey to assess the pollution potential.
There can also be serious potential insurance losses from cryptosporidium or e-coli washed into
standing water which might be used for the drinking water supply. As a result, organic farms are a
particularly high risk for insurers.
In Scotland, Part M of the Building Regulations will permit “grey water” to be disposed of into
SUDS. This could also become a concern for insurers.
SEPA data show that 500km of polluted watercourses in Scotland are due to diffuse pollution from
urban areas (PAN 61). SUDS should be designed to avoid any increase in the scale of this
problem.
The Scottish WEWS legislation under the Water Framework Directive will introduce tighter
controls on diffuse pollution in the future. The Scottish Executive has recently carried out a
consultation on how to deal with diffuse pollution from rural land use (Diffuse Water Pollution from
Rural Land Use Paper 2005/35) in which the Executive proposes to develop General Binding
Ruiles (GBRs), both national and targeted, for farming and other rural land use activities, for
consultation with farming and other interested parties over the course of 2006 and 2007. At the
same time, through Land Management Contracts, the Executive will be making available
incentives to promote good practice aimed at environmental goals
Precautions should be taken to prevent pollution or litter reaching a watercourse.
particular hazard during the construction stage.
This is a
Construction Industry
There is specific and detailed EA/SEPA guidance on protecting watercourses during construction.
A few councils in Scotland are now insisting on buffer zones between the site and watercourses.
These have two additional benefits, firstly they can subsequently become wildlife corridors, and
secondly they allow access by maintenance vehicles for maintaining the watercourses. For
example, Perth and Kinross Council will not allow any construction within 5 metres of a
watercourse.
Q14. What is the position regarding culverts?
A14. Culverted watercourses can cause localised flooding, and can easily be blocked. “Wheelie
Bins” are an ideal size for making unwanted “plugs” in culverts, with supermarket trolleys running
a close second. In rural areas, round hay bales also make ideal plugs. The Flood Prevention and
Land Drainage (Scotland) Act 1997 contains provisions for regular assessments and maintenance
of urban watercourses (there is no similar legislation in England or Wales). Both SEPA and the
EA strongly discourage new culverts if they can be avoided.
Insurers would agree that wherever possible, culverts should be avoided. They are hard to
maintain, easily blocked or polluted, and can make flooding problems much more severe. They
encourage brown rats, and discourage other wildlife, and they can be dangerous for children or
maintenance workers. It is better to have an open, natural, watercourse, with gently sloping sides,
and areas on each side that can be allowed to flood during extreme events.
Wherever possible, existing culverts should be opened up, and the watercourse reinstated.
If culverts have to be installed, they should be straight, and should include raised platforms in the
cross section so that wildlife can travel through them without getting wet except during extreme
events.
Debris traps on culverts should be regularly cleared, and culverts should be regularly inspected
using closed circuit television, or physical inspection.
26
One of the biggest causes of subsidence insurance claims for buildings is the spread of tree roots.
Climate change will lead to warmer, drier summers, which could lead to tree roots spreading
wider, in order to seek water. This could result in an increase in damage to sewers, drains and
culverts from this source. SUDS could lead to reduced flows in downstream watercourse in dry
conditions and this could lead to subsidence.
SUDS are meant to remove the need for large surface water drains and culverts, but even without
SUDS, wherever possible existing drainage culverts should be opened up or “day-lighted” so that
any potential blockages can be spotted and easily removed.
Watercourses should be restored to their natural state wherever possible with adequate space to
allow for flooding following severe rainfall or snowmelt events, or failing that, that housing is not
permitted in areas at risk should the systems overflow.
Q15. How do Building Regulations and Building Control fit in with SUDS?
A15. Building Regulations do not stop people from building in flood hazard areas, but if the area
is liable to flood the site must be properly drained. The Regulations are not intended to deal with
river flood, only rainfall ponding, and even then, if the drains comply with British Standards, this
will satisfy the regulations.
Note that the new Part M of the Scottish Building Regulations, which came into force in 2002,
strongly promotes SUDS for surface water run off from buildings and hard surfaces, such as roofs,
roads, and car parks. It also allows disposal of grey water from sinks and washing machines to
ground, provided suitable infiltration is used (see Appendix 3).
There are two major issues with Greywater:
 Greywater comes from water originally imported onto the site by the mains water supply,
therefore disposal of greywater through SUDS means that SUDS have to cope with more
water than would fall on the site naturally from rainwater.
 Potential pollution problems from disposal of detergent, bleach etc. even if the infiltration
systems are properly maintained.
These could cause concerns within the insurance industry, and councils would be well advised to
restrict this measure to rural areas or areas where there are large enough gardens to avoid the
risk of spread of pollution into adjoining land or watercourses.
This is a very complex subject and for more detailed guidance see the relevant planning and
building control policies and guidance notes.
Q16. If the water authority/company take on responsibility for a SUDS scheme, will they
provide the engineering expertise?
A16. In Scotland, Scottish Water will have to approve the scheme before they will take on
responsibility for it, but will not necessarily have to provide expertise at the design stage. Scottish
Water will audit the SUDS against the design and construction standards which will be set in the
technical manual and regulations but, by and large, will not provide engineering expertise. (In
Scotland these changes are the result of the Water Environment and Water Services (Scotland)
Act, 2003.)
Q17. It takes a long time for the water authority/company to approve a SUDS scheme. If
the designer is a qualified engineer, is it not possible for the engineer to certify it as
meeting the requirements?
A17. It is appreciated that this can be done for some engineering solutions, but the pressure to
use SUDS in the UK is relatively new, and few engineers have enough experience yet. Also
many engineers may be tempted to go for “hard” solutions, such as tanks and concrete when a
more natural system may be better and more sustainable.
27
Neither EA nor SEPA are able to act as engineering consultants in this matter, and they would
encourage local authorities to seek guidance from experienced consultants.
It should be noted that the CIRIA manuals on SUDS are not engineering manuals.
The developer is responsible for the design, and without an independent check then the following
could occur:
 Natural solutions may not be considered sufficiently. There is a perception that these take up
a lot of space on the site that could be used for housing etc. “Hard” solutions take up less
space. Some developers for example, tend to go for features such as underground storm
cells, often built underneath garages. These are not considered as SUDS by SEPA.
 A design that is cheaper to install initially may end up as more costly to maintain. For example
small diameter (25mm or less) orifices into soakaways.
 The design may not address water quality issues properly. This could result in SEPA or the
EA refusing to approve the scheme.
At the end of the day, final approval has to come from the planners who have to respond within a
timescale laid down by statute. Some planning authorities now employ their own engineers on a
consultancy basis to approve SUDS schemes.
Scottish Water is currently updating their Technical Manual "Sewers for Scotland" to include a
SUDS section. The manual defines the acceptable design and construction standards for SW’s
sewerage network and public SUDS designed to the specifications outlined in the manual will be
taken over by SW.
Q18. Can rainwater be recycled?
A18. Rainwater could and should be recycled, for example, it could be used for flushing toilets,
especially in large retail premises with a big expanse of roof. (For example the B&Q Warehouse in
Sutton in Ashfield, Nottinghamshire, which was opened in October 2002, has “rainwater
harvesting” on its roof to use for flushing toilets.) This would relieve the pressure on the SUDS
scheme by diverting some rainwater into the foul sewer, after it has been used for toilet flushing. It
would also reduce the amount of mains water brought onto the site.
There may be some problems with algae in tanks however, if the water is stored for long periods,
and the property owner would need to accept responsibility for cleaning them. For more details,
see CIRIA Report C539.
Q19. What issues arise with phased developments?
A19 A phased development is likely to result in piecemeal SUDS development, which is likely to
be unsatisfactory. Developers generally should be asked to produce a drainage impact
assessment (DIA) before planning permission can be considered. Insurers would like to see all
DIAs using a 200 year return period as recommended by the DIA guidelines mentioned in answer
to Question 11 (NESFLAG, 2002). They should use the 200 year return period for sensitivity
testing and should design the overall SUDS installation first, taking topography into account, and
using soft solutions where possible. See Appendix 6.
This should be followed by a strategic development plan covering all planned phases at the
outset, containing the layout of roads and SUDS measures. Planners in some Councils are
proposing to make it clear to developers that if they do not, subsequent developments may have
the number of house plots reduced in order to accommodate SUDS.
It is also important to ensure that the impact of runoff on SUDS during the construction phase is
limited. Studies have shown that the majority of sediments deposited in, for example, ponds,
come as a result of construction activities. Sediments can block inflow and outflow pipes, and
reduce the capacity of the system or, in the case of filter trenches, reduce the permeability of the
drainage area increasing maintenance requirements and reducing the efficiency of the system. In
many occasions sacrificial SUDS are used during the construction phase which are then filled in
once the development has been completed.
Q20. In places like Singapore, Los Angeles, and Madeira, they have large storm drainage
channels to take surface water away. Could this not be tried in the UK?
28
A20. Yes it could, but these will only work if you can be sure the water can get away quickly, for
example to the sea, or to a large lake or loch. If disposal is to the sea and the land is low lying,
there is a danger of the sea filling the channels during a storm surge or high tide, leading to salt
water intrusion and flooding. The official view is that current rainfall concentrations in the UK are
unlikely to justify such extreme measures, which would not be deemed to be SUDS. This view
seems to ignore such disastrous floods as in Lynmouth in 1952, or Llandudno in 1993, or
Boscastle in 2004. Such events will become more common with climate change and this may
ultimately force a change of view on this point.
Q21. One developer has been told by SEPA that they don’t need SUDS because only roof
water is involved so there are no water quality issues.
A21. There must be a misunderstanding here. SEPA’s policy is a presumption in favour of SUDS
for every development. SEPA are more likely to have said that only minimal SUDS would be
required in such a case. The confusion may arise from the fact that SEPA’s enforcement powers
are limited to water quality issues, but even rainwater can be contaminated. Another possibility is
that the roofwater is to be directed straight into the sea, in which case it would not be logical to
insist on SUDS.
Q22. Who can enforce remedies for a breach of a SUDS design?
A22. Planning Departments can serve a “Breach of Conditions” notice, provided the planning
consent has been made subject to compliance with the SUDS plans. However, it should be
remembered that unexpected site conditions could dictate changes to the original plans, for
example if much deeper swales are needed to reach down to permeable ground.
Also, Building Control could refuse a completion certificate, as they are required to assess
porosity tests and the design of soakaways (see also Q31). If the problem resulted in water quality
problems, then SEPA or the EA could enforce a remedy under COPA 74, now superceded in
Scotland by the Controlled Activities Regulations.
Q23. Some householders are complaining that their gardens are always waterlogged and
they want them to be drained.
A23. This can be a big problem for householders and may indicate poor design. It can also be
dangerous for families with very young children who can drown in only two inches of water. There
are also disease risks in warmer weather. As a minimum, SUDS should be designed to ensure
that access to the house is not waterlogged. Some local authorities make an allowance for
garden drainage, but not all. It is essential that developers and house builders are involved at an
early stage in discussions with planners. Ideally, SUDS should be designed in such a way as to
avoid making garden ground more waterlogged than it would have been before the development.
In any case, gardens should be designed to slope away from the property, and there should be
sufficient depth of topsoil supplied to provide some drainage. However, the householder may
simply have to become used to having a wet area at the foot of the garden and that this may
make the property harder to sell or insure in the future.
Q24. What about roads issues?
A24 a. The construction of roads will have a major impact on surface water drainage. This is a
particular problem for roads which are not adopted or adequately maintained and as a result
cause flooding. Road building or widening schemes are subject to SUDS. This can cause
problems if there is not enough land available for SUDS, and this situation can easily arise with
road widening programmes.
b. In addition, any SUDS scheme, drainage scheme, or flood alleviation scheme should
consider the impact on roads. In particular, a sensitivity analysis should be carried out on the 200year return period flood, taking into account the combined sewer overflow potential.
There are several aspects to consider:
 Highway drainage systems may not cope with heavy rainfall and the road may become a
“river” transporting floodwaters to other properties, including areas that may never have
flooded before.
29



While CSOs are designed to only spill into receiving waters (rivers, sea etc.) During extreme
rainfall events manholes may flood if the sewerage system is unable to cope with the increased inflow.
In these cases sewage may be spilled onto the road and it may be worth carrying out a sensitivity
analysis The sensitivity analysis should attempt to work out where the sewage will end up. If
necessary kerbs may have to be raised to keep the overflow away from housing.
If roads become impassable, a site may become cut off by floodwaters, leading to possible
problems should an emergency medical problem arise.
If flooding of roads is widespread, there could be longer-term business interruption problems
for example if employees cannot get to work or if raw materials cannot be transported to the
premises.
 In Scotland, the Roads (Scotland) Act 1984 gives Councils the power to issue an Order to
the landowner or occupier requiring measures to be taken to prevent surface run off from
flooding an adjoining road. There is no corresponding legislation in England. (Section 99
(1) of this Act states: “The owner and the occupier of any land, whether or not that land is
such as constitutes a structure over or across a road, shall prevent any flow of water or of
filth, dirt or other offensive matter from, or any percolation of water through, the land onto
the road.” )
Q 25. If someone’s property is damaged by flood or drainage surcharge, can they sue the
local authority or the water company?
A 25 As regards local authorities, the answer is not yet known. A test case is being considered
in Edinburgh by a consortium of insurers to recover flood claims payments from Edinburgh City
Council. There may well be a civil liability on Scottish Councils under the Flood Prevention and
Land Drainage (Scotland) Act 1997. (There is no equivalent legislation in England or Wales.)
Flood victims, following the precedent of Hedley Byrne v Heller (1964), may also be able to sue
planners on the grounds of professional negligence in allowing their house to be built in a
hazardous area.
As regards water companies, in England there was a recent action against Thames Water (See
Appendix 5). The court determined that Thames Water had potentially violated human rights as a
result of allowing a sewer to flood a garden many times over a period of nine years (Venters, R.,
2002); Thames Water estimated that it would cost £1bn to rectify all such problems (ICE, 2001).
However, Thames Water won their subsequent appeal to the House of Lords.
Q26 What are insurers’ concerns about SUDS?
A 26 At the time of writing, most insurers have little awareness of SUDS or its implications. So
far there has been no consultation with insurers other than with the author (who represented the
Association of British Insurers on the UK Steering Committee for the CIRIA manuals). This is likely
to result in a cautious approach to SUDS problems by individual insurance companies due to a
lack of understanding of the issues.
In May 2005, the author sent a questionnaire to all the biggest insurance companies to ask about
their views on SUDS. There was an excellent response. The main areas of concern for insurers
are flooding, subsidence, and liability for pollution. For more details see Appendix 7.
Flooding:
- Many drainage systems are designed to cope only with high frequency, low severity flood
conditions, such as might be found every 2 or 3 years or so. New research on flood frequency
estimation techniques and on climate change impacts indicates that existing drainage designs
will increasingly result in surcharges and spills (see Appendix 4).
- The “level access” wheelchair requirements recently introduced into the building regulations is
resulting in lowered ground floor levels and more frequent surface water flooding. This could
raise justified fears that if SUDS systems are not designed to cope with surface water in
extreme events, flood claims will increase.
- Backup into buildings, for example through toilets and baths directly into houses, produces
particularly unpleasant and costly damage. Recent changes in building regulations now
require new houses to have ground floor toilets.
30
-
Culverts can be blocked very easily, especially during a flood. Such blockages will lead very
quickly to local flooding, often in unexpected places.
Subsidence and heave
During droughts, SUDS ponds and detention basins can reduce flows in downstream
watercourses, leading to spread of tree roots and subsidence. It can also lead to rising
groundwater upstream, resulting in heave.
Environmental Liability for Pollution
SUDS on contaminated land can result in increased groundwater and watercourse contamination.
Standards can and are drawn up to deal with these issues to minimise risks. There are a number
of different systems that can be used which would not impact on groundwater. SEPA or the EA
can give guidance as to the most appropriate systems and they should always be consulted when
SUDS are built on contaminated land. Legislation to transpose the EU Environmental Liability
Directive could give insurers additional causes of action against the local authority or water
company.
Guaranteed availability of household flood insurance ceased at the end of 2002, and was
replaced by the “ABI Statement of Principles”, revised in November 2005. For details see
www.abi.org .
This provided a limited guarantee of cover in certain circumstances, and from January 2006
insurers have more freedom to decline to renew policies in flood hazard areas. While most will try
to maintain cover, the ABI estimate that more than 350,000 homes will become uninsurable in
Britain due to the flood hazard.
Q 27 Some insurers are now refusing to cover houses within 50 metres of a river or
pond. Will this be a problem?
A27
It will be a problem, because of the lack of awareness of insurers about SUDS
(see Q26). Unless this is addressed urgently, the problem is likely to grow. In the meantime, the
only solution would seem to be to “shop around”.
If cover is offered, it is possible that some insurers will exclude cover for liability arising from
SUDS features in gardens, escape of surface water from gardens, or contaminated groundwater
from brownfield sites.
Q 28
What are the implications of Marcic v Thames Water for insurers?
A 28
For details of this case see Q25 and Appendix 5. Insurers were all set to start suing water
companies and Scottish Water if Marcic had won his case in the House of Lords in October 2003.
They would have been able to seek recovery of claims costs arising from flooding caused by
sewage overflows. In the event, the Lords decision went against Marcic 21. It is too early to
comment on the implications, because part of the case rested on the EU Human Rights Directive
and he may wish to appeal to the European courts.
Q 29
Will SUDS make it harder to obtain a mortgage?
A 29
Potentially, “yes”. Building Societies and property valuation surveyors have not been
consulted any more than insurers about SUDS. They are likely to have the same concerns as
insurers (see Q26), and the Council of Mortgage Lenders has stated clearly that if insurance is not
available on property used as collateral (see Q 27) that a mortgage will not be available.
In addition, there is the issue of groundwater flooding. This is not insured under a standard
household policy. Groundwater is already rising quickly in some areas due to reduced abstraction,
21
Marcic v Thames Water [2003] UKHL 66; [2004] 2 AC 42; [2003] 3 WLR 1603; [2004] 1 All ER 135; [2004] BLR 1; 91 Con LR 1; [2004]
Env LR 25; [2004] HRLR 10; [2004] UKHRR 253; [2003] 50 EGCS 95; (2004) 101(4) LSG 32; (2003) 153 NLJ 1869; (2003) 147 SJLB 1429;
[2003] NPC 150.
31
or the ceasing of pumping from underground mining works. This is a big problem in London,
Liverpool and Fife. SUDS could well accelerate groundwater rise in these and other areas.
At the moment, insurance availability is not unduly affected by SUDS, but insurers are
increasingly refusing to cover any properties in a development which proceeds against the advice
of the EA on the grounds of flood hazard. If a developer finds that houses are not selling because
of mortgage problems he may be forced to abort the development, leaving SUDS uncompleted.
Q 30 The public has perceptions of how a pond should look based on experience of
ponds in parks and the grounds of stately homes. Will the public demand aggressive
management of ponds (dredging, weed removal etc) rather than leaving them to stabilise
naturally?
A30
This is quite likely and understandable. Clearly it will increase maintenance costs, and if
there is such a demand this should be taken into account if those living near such ponds cannot
be persuaded to accept the “natural look”.
Educating the public about what SUDS do, how they work, and why they are maintained in a
certain way may ease residents’ expectations.
The EA and SEPA both have a policy of minimal management of SUDS to enable habitat
development.
Q31 Can soakaways be positioned near to the boundary of the curtilage?
A31
In Scotland, prior to 2005, Building Regulations did not allow a soakaway within 5m of a
property. It was not clear whether this just applied to buildings or to boundaries as well. Some
councils were applying this to boundaries, others, such as Highland and Aberdeenshire were not.
The Scottish Building Regulations were changed in 2005 and the relevant section now reads:
Building (Scotland) Regulations 2005
3.6.3 Location of soakaway –
“To prevent such damage therefore, every part of a soakaway should be located at least 5m from
a building and from a boundary in order that an adjoining plot is not inhibited from its full
development potential. However the volume of surface water run-off, ground strata or
permeability of the soil may influence this dimension and it may be reduced, or indeed may need
to be increased, to preserve the structural integrity of the building.”
In Aberdeenshire this has been interpreted as meaning that the 5m rule between the soakaway
and a building cannot be relaxed due to the need to protect the building’s foundations (e.g. from
ice in winter conditions, which may crack the brickwork). However the 5m rule between the
soakaway and the boundary could be reduced providing the porosity of the ground allowed for
this. For example using a ‘strip soakaway’ down the middle of a garden.
General points/issues:
 Housing plots are becoming narrower (less than 10m wide) as a result of integral rather than
separate garages.
 Developers are not considering the drainage of surface water and the siting of soakaways
(e.g. carrying out porosity tests) until after planning permission has been granted, and often
fail building control ‘tests’ for a warrant. Developers should be identifying the location and
types of soakaways (depending on the soil porosity) prior to siting housing in a proposed
development.
 The pros and cons of different soakaways /systems need to be considered, e.g., strip
soakaways, rubble soakaways, mounds (for very bad ground conditions), and reed beds.
 The recycling of rainwater (and tie it with a grey water system).
 The impacts of climate change - can existing systems cope with heavy or persistent rainfall?
32


A Building Warrant may not always be required for minor works. Therefore these small works
would possibly not require a new soakaway. The regulations state that gutters and down
pipes are not required from a roof with an area of 8m 2 .
Supplementary Planning Guidance on SUDS could mention the need for developers to
consult the Building Control Service at the pre-planning application stage (although this incurs
a fee - therefore developers should read the appropriate manual on SUDS/soakaways).
Comments
The topic reminds the author of a friend in Canada who was sued by his next door neighbour
because his soakaway was too close to the boundary and his neighbour's basement was flooded
as a result. There are not so many basements in the UK, but it is something to bear in mind,
especially when the basement has a window at ground level or below.
From an insurance point of view, there is the issue of potential liability for allowing water to escape
across the boundary; there may even be a case under Rylands v Fletcher as the soakaway is an
artificial feature, in which case strict liability could apply in England (not in Scotland). In Scotland,
there could be subrogation against the council under the Law Reform (Miscellaneous Provisions)
(Scotland) Act 1985.
Householders may not realise the need to maintain the condition of soakaways within their
cartilage, and as the years pass are even less likely to do so. Such soakaways could fail to
operate, leading to flooding.
The author recently conducted a survey of all the major insurers about their attitudes to SUDS and
the reaction was interesting: some of the majors stated that they were concerned that many
SUDS, especially in England, were poorly designed, and the approach they were adopting was to
continue to provide cover to individuals but to be much more prepared to seek recovery of flood
losses from the council officials or professional advisers involved.
The whole issue becomes even more important with climate change and the increase in the
frequency of extreme events. Adding the greywater dimension is also a concern, especially as
housing plots seem to be getting smaller and density above the 25 dwellings per hectare level is
becoming common.
Q32
How much will Scottish Water charge for maintenance?
A32
SW is planning to charge a capitalised maintenance cost based on 28 years maintenance
until they have more experience of how much maintenance will cost. It may eventually come
down to 10 years. It is not yet clear how SW plan to deal with asset depreciation issues, although
they did announce some preliminary results at the 2005 annual SUDS conference in Coventry.
They omitted to mention however, how they planned to deal with liability from professional
negligence actions brought by insurers following flooding due to inadequate maintenance and this
does not seem to have figured in their calculations.
SW has used a Whole Life Cost model and the future development proposals to estimate the
future costs of taking over public SUDS systems. This estimation was used to inform the Water
Industry Commission of the necessary funding required to comply with the new regulations. The
contribution that SW will give to developers when SUDS have been vested in SW is determined
by the Provision of Water and Sewerage Services (Reasonable Cost) (Scotland) Regulations
2006. (a guide to how this works can be found on SW website (“Guide for obtaining new water
and waste water services”).
SW will does not intend to maintain any SUDS, which are not vested in them
Q33 What are CSOs?
A33 CSOs are “Combined Sewer Overflows”.
Historically drainage systems were designed to carry rainwater runoff only. Disposing of human
waste through pipes and trenches this way was an added bonus. Once the Victorians established
33
a link between human waste and illness, sewerage systems as we know them today were built.
To ensure pipes were kept clear of blockages a certain amount of surface water has to be
conveyed to flush the system and that is why the system was a combined one. At the time of the
Victorians the impact on the environment from CSOs and highly diluted sewerage was considered
to be negligible. Nowadays it is considered better to have two separate systems, so current
practice for new urban wastewater collection systems normally involve the design of separate
systems for wastewater and storm water. One Scottish local authority is now contemplating
adding a third system at its own expense purely for storm water from extreme rainfall events to
prevent flooding. However, most of the UK systems are still combined systems.
Wastewater is the foul water or effluent from toilets combined with “grey water”. (Grey water is
the term given to waste water from baths, sinks, washing machines etc but not toilets or bidets).
Storm water is rainfall derived water runoff from roofs and impermeable surfaces.
Typically these pipes are designed to cope only with the two to five year return period event, (see
table 1 below). In more extreme events they will “surcharge” when the sewer pipes cannot cope
with the flow and the water rises up inside manholes. In an event greater than the 30-year return
period, the water can fill the manholes, and the surcharge becomes an overflow.
CSOs exist as relief valves to limit the maximum inflow to sewers and treatment works. In this
way, by deliberately designing the system to drain sewage into watercourses, they limit not only
the risk of damage during storm events but also reduce the design specification required for these
facilities (and hence the cost of construction).
CSO valves are therefore intended to limit the cost of drainage infrastructure and to manage the
risk to the aquatic ecology by only permitting direct discharges during periods when dilution is
maximised, for example during storms.
The current CSO approach has some similarities with the “Ford Pinto” argument. In the USA, the
Ford Pinto was known to be vulnerable to catching fire if it suffered a rear end collision. Ford
carried out a cost benefit appraisal which concluded that they could save $50m by paying product
liability claims rather than by re-engineering the car to make it safer. The courts took a dim view
of this and imposed punitive damages of $50m in a case where a family had burned to death.
This was to punish Ford for their decision, and to force them to modify the car. The same
argument might one day be used in UK courts against water companies which say it is cheaper to
flood homes than to build adequate drainage systems.
During 2005, Scottish Water started to ask local authorities to provide them with an indemnity
against liability arising from pollution of watercourses by CSOs as a condition of accepting new
sewer connections. So far, Scottish local authorities have refused and there is a stalemate
situation. One proposal being tried by nine local authorities in Scotland is to release capacity in
existing combined sewers by disconnecting them from storm water drainage (which goes to retro
fitted SUDS) so the sewers carry only sewage and greywater, allowing more new connections to
the old sewer systems. This will of course increase the concentration of sewage in CSOs if they
should overflow and increase pollution from existing CSOs. The author is working with these
authorities and has warned them of the increased legal liability risks.
In recent times overflows have become a major problem because:
 Historic lack of maintenance is leading to leakage and collapse of drains or sewers.
 Many surface and groundwater inputs are unknown or unauthorised.
 Urbanisation has increased inputs of both effluent and run off.
 Screening facilities were not designed for modern day objects such as sanitary products (EA,
2002).
 There have been a number of extremely severe rainfall events, consistent with climate change
projections.
 The number of CSOs has increased so reducing the diluting capacity of storm runoff.
 The capacities of many urban watercourses to convey runoff from CSOs have been reduced
or limited as a result of culverting.
CSO valves can include non return devices that close the valve when sea level is high or the
watercourse is flooded. The aim is to prevent flood water from entering the sewer system, but
because sewage and surface water can no longer drain away, it also leads to backup within the
34
combined sewer system. Thus even with good river or coastal flood defences, sewage flooding
can still take place, as happened in Carlisle in January 2005.
Of course, combined sewer overflows can occur in other ways than through CSO valves, for
example,
 escape from manholes
 backup through ground floor toilets, baths and domestic appliances
 backup through surface water drainage gullies and gratings
In Scotland, measures are often taken so that combined sewer overflows from manholes and
gullies are directed away from buildings using kerbing and banking.
The European Commission’s new EN-standard (EN 752) for sewer and drainage networks will
become increasingly relevant for insurers. The dimensioning rain return periods are shown in
table 1. This EN-standard, as virtually all EN-standards, is adopted throughout Europe, but as
stated in EN-752 the relevant authority in each case may decide that another standard should
apply22. An important result of the EN-752 is that the drainage system must cope with a return
period expressed in terms of the flood hazard rather than rainfall intensity. Whether the standards
shown in EN 752 are sufficiently high is debatable, and have indeed been the subject of
challenges in the courts in Norway. The sewage undertaker had sought to show that compliance
with EN 752 was sufficient to avoid liability for flooding, but the courts held otherwise, saying that
this was only a defence where the flooding was more extreme than the 100 year return period.
Table 1. The return periods given in the EN-standard EN-752.
Design storm
frequency*
(1 in "n" years)
1 in 1
1 in 2
Location
Design flooding
frequency**
(1 in "n" years)
1 in 10
1 in 20
Rural areas
Residential areas
City centres / industrial / commercial
1 in 2
-with flooding check
1 in 30
1 in 5
-without flooding check
1 in 10
Underground railway / underpasses
1 in 50
*For these design storms the pipes must only be filled to the top of the pipes and no surcharge shall occur
** Flooding allowed to the level of the basement floors, usually 90 cm above the top of the pipes
In 1998, the Construction Industry Research and Information Association published a very useful
manual called “Low Cost options for prevention of flooding from sewers” (CIRIA publication C506).
Solutions include:
 Increase flows by pumping.
 Increase capacity by increasing the size of the sewer pipes or building retention tanks.
 Fitting screens on CSOs to trap solid effluent.
 Source control
For more details, see Appendix 4.
A recent development is to change the function of combined sewers by diverting storm water and
even grey water into SUDS so that the sewer is used only for foul water. This means that if the
sewer overflows, the discharge will be almost all from toilets, leading to a much more unpleasant
flood.
22
Lindholm, O.G., Schilling, W., Crichton, D., in press “Urban Water Management before the Court- A Flooding Event in
Fredrikstad / Norway”
35
A problem for insurers is that maps of the locations of CSOs are not readily available and the
water companies seem reluctant to publish them. Insurers therefore assume that a CSO flood
could happen anywhere and charge premium accordingly.
Q34 What is source control?
A34 The favoured solution to reducing the load on sewers is source control to reduce rainfall
derived storm-water flows. SEPA and the EA are actively promoting source control techniques.
(The EA regard these as “Best Management Practices” (BMP). For SEPA, “BMP” was the term
used for sustainable drainage systems before “SUDS” was coined. SEPA does not use this term
now.)
Source control includes:

Increasing the permeability of the area in developments and car parks

Preventing surface run off from entering combined sewers

Stricter enforcement of building standards

Land use management

Sustainable Drainage Systems (SUDS)
Q35 Is groundwater a problem?
A35 Rising groundwater is a common cause of flooding and it is interesting to note that, following
the case of Young v Sun Alliance (1976), which held that flood does not include seepage of water
from an underground watercourse, UK householders’ insurance policies specifically exclude flood
from this source. In practice, rising groundwater claims would probably not be turned down if they
occur during an event where several properties are flooded from surface water.
Flood alleviation schemes involving embankments can lead to rising groundwater on the defended
side of the embankment. Installing sheet steel piling during the construction process can alleviate
this, but this will deteriorate over time and will need to be replaced.
Sometimes a site will be “uplifted” by bringing in landfill material to reduce flooding risks. Apart
from the fact that this reduces flood storage, it impedes the flow of floodwater and can cause
rising groundwater problems in adjoining sites.
Sustainable drainage solutions may also lead to raised groundwater.
Q36 Is planning permission needed to build a pond?
A36 Normally, yes, and of course this would form part of the overall planning permission for the
development.
The position may be different on agricultural land. Farmers who are proposing to build a pond on
their farm may be obliged to seek planning permission. However in most instances, planning
permission will not be required because the site qualifies for “permitted development” status. The
dividing line between the two situations is not always clear, so clarification should be sought by
advising the local authority’s planning department of the intention to excavate a pond. The
following advice is from a National Farmers’ Union circular issued in 2005:
 Before building a pond, tell the local authority. It is their responsibility to check whether
planning permission is required.
 If it is not required, formal notice of the intention may still be necessary. Then, works should
not proceed until the position has been acknowledged or 28 days has elapsed.
The legislation governing permitted development says that "agricultural land" means land which,
before development permitted under this order is carried out, is land in use for agriculture. If the
pond is to be built/excavated on a qualifying site, permitted development status means that
planning permission is not required.
In Scotland, a qualifying site must satisfy the following criteria:

not be within 25 metres of the edge of the road surface of a trunk road or classified road;

be on agricultural land of at least 0.4 per cent of a hectare, i.e. 4,000 sq. m., in size; (In
some local authority areas, the area of 0.4 hectares may be calculated by adding together
the areas of separate parcels of land.)
 be for the purposes of agriculture;
36
 if used for storage of slurry, not be within 400 metres of a protected building.
In any case it is safer to advise the local planning authority at least a month before construction.
Rural Stewardship Scheme Ponds
The position on agri-environment scheme ponds is that applicants must obtain any permission
that may be required. Participation in an agri-environment scheme does not give a farmer any
new or additional rights in relation to statutory approvals that may be required. It is for individual
planning authorities to determine whether an activity such as pond creation should be subject to
the planning process.
Q37 Are there any guidelines for planting SUDS areas?
A37. Not at present, however a Working Group has been established in Scotland to produce such
guidelines. There is also a Scottish Working Group establishing guidelines for public open
spaces. These guidelines should be available in 2006.
The following questions arising in FLAGS relate specifically to Scottish Water issues and
the answers have been supplied directly by Scottish Water
Q 38 Will Scottish Water try to discourage SUDS schemes that have a high maintenance
cost in the future? (There is anecdotal evidence that individuals in SW are already encouraging
developers to put surface water into watercourses, 100-year-old land drains, combined sewers,
and private gardens, anywhere rather than public SUDS solutions, which SW would have to
adopt. Is this SW policy?. If so will it lead to more flooding events from watercourses, rising
groundwater and CSOs? Watercourses are already likely to become overloaded due to climate
change and adding more surface water to them could well lead to problems.)
A 38 The policy to promote Sustainable Urban Drainage Systems (SUDS) was originally
introduced to the East of Scotland by the Forth River Purification Board in 1995. After the Scottish
local government reorganisation of 1996 and the formation of the Scottish Environment Protection
Agency (SEPA) this policy was adopted and extended to the whole of Scotland. Scottish water
policy is still one of encouraging SUDS systems. Although only certain types will be eligible for
take over (detention ponds, detention basins and underground storage) if designed to specified
standards, SW will not discourage the use of other types of SUDS where and when they are
beneficial to the overall drainage system design. These systems are not necessarily precluded
from being vested where they are appropriate. Discussions with Scottish Water on their suitability
should be held at an early stage in the design.
Q 39 Scottish Water is less concerned about habitat than SEPA. Will they seek hard
engineering solutions rather than soft solutions? For example they will now accept hydro
cells in some areas. Are we going to end up with plastic boxes everywhere?
A. 39 The SUDS section in the Sewers for Scotland Manual outlines the philosophy of using SUD
systems as one to provide a drainage system that minimises the impact of the diffuse pollution in
urban runoff, reduces runoff and maximises the environmental and social benefits which
includes improvements in habitats and biodiversity. Developers are encouraged to design the
drainage system holistically for the site using appropriate systems and control structures in order
to maximise operational advantages, water treatment and other social and environmental
benefits within the framework of the requirements of this document. The preferred hierarchy for
providing appropriate drainage and attenuation using the SUDS specified in the technical manual
is:
1. detention ponds;
2. detention basins;
3. underground storage.
37
This clearly indicates that although Scottish Water’s primary duty is that of drainage provider the
whole SUDS philosophy adopted by Scottish Water is one of encouraging environmental benefits
alongside providing appropriate drainage solutions.
Q 40 When “SUDS for Scotland” is agreed, will SW take on the responsibilities for
monitoring surface water quality currently held by SEPA? Will SW have responsibilities for
preventing diffuse pollution under the WFD/WEWS?
A 40 No, SEPA will still be responsible for monitoring surface water quality. As a responsible
Authority SW has a duty to exercise their designated functions so as to secure compliance with
the requirements of the WFD directive (including preventing the deterioration of water bodies
through diffuse pollution) in partnership with all other stakeholders. This can only be done within
the context of Scottish Water’s remit to provide water and wastewater services
Q 41 There seems to be conflict already within SEPA between those responsible for WFD,
and those concerned about flood protection, despite the fact that WEWS emphasises the
over riding importance of liaison between all the agencies concerned to ensure sustainable
flood management. (It must be emphasised that in Scotland, WFD has not been
transposed without modification as it has in other countries). What is SW policy on this?
WFD or sustainable flood management?
A 41 As a responsible Authority SW has a duty to exercise their designated functions so as to
secure compliance with the requirements of the WFD directive as transposed by the WEWS Act.
In terms of flooding all responsible authorities have a duty to comply with advice issued on
Sustainable Flood Management (SFM) and this duty serves to endorse the Water Framework
Directive principle of integrated management for all water bodies. In addition SW is a member of
the Scottish Executive’s Flood Issues Advisory Committee (FIAC), which was set up to provide
guidance on flood management, including the promotion of sustainable flood management.
Guidance produced by FIAC will be used in the National Advisory Group and Area Advisory
Groups. SW currently chairs the Flood Issues Advisory sub-committee on Avoidance which has 3
main workstreams:
 Promote sustainable flood management, covering all types of flooding,
 identify, gather and share sustainable flood management best practice examples,
 Link catchment flood management plans (CFMP) to river basin management planning
(RBMP)
Q 42 Will SW take into account the issue of insurability in their new construction
standards and vesting conditions? Have they consulted the insurance industry about
insurers’ concerns? Will this also apply to design standards? For example a common
problem is waterlogged gardens because of inadequate drainage. Also as new
developments mature, residents are likely to build conservatories, extensions, paved
patios and driveways etc, which will increase run off. This is often not allowed for in the
original design.
A 42 Scottish Water has set technical and design standards based on risk factors including, for
example, risk of flooding of nearby buildings, however the issue of insurability was not directly
examined. The new standards and vesting conditions and technical manual will be subject to
public consultation and we will be happy to consider the insurance industry view. The design
requirements also consider an increase in hard standing and, consequently, runoff through a 10%
allowance in the design of the system
Q 43 What allowance is made for climate change?
A. 43 The design standards requires a 10% allowance in the design of the system for climate
change and changes in the development (i.e, extensions, patios etc.)
Q 44 Will SW say that the capital and maintenance costs of SUDS are too high to be
justified for a particular site? Can Councils argue when they need affordable housing for
38
low-income families? As SW has no legal obligation to accept surface water drainage into
their systems, presumably this would prevent the development from proceeding?
A. 44 Scottish Water will have a legal duty to take over SUDS which are built to the
specifications in the technical manual (independently from the maintenance costs). SW has a
legal duty to accept drainage from the curtilage of buildings (roofs, hard-standing areas etc..) The
duty does not extend to land drainage, ground water or road drainage, however section 7 of the
Sewerage (Scotland) Act 1968 gives SW the possibility of enter into agreement with the roads
authorities to provide road drainage (and there always is a presumption that we will do so). The
only instances where a problem exists is when the sewerage system is at full capacity placing a
constraint on the development. SW is currently working with Local Authorities to eliminate these
constraints and one way to do so is to encourage the separation of surface water and foul water
by using separate systems (as opposed to combined systems) and SUDS thus dramatically
reducing the amount of surface water entering the sewerage system, alleviating capacity issues
and reducing the chance of these development constraints reoccurring in the future.
Miscellaneous questions for debate
1. Will airport operators seek to prevent SUDS within the 15km “consultation zone” of airports
due to the bird-strike risk from habitat enhancement?
2. Are SEPA’s Drainage Impact Assessment (DIA) guidelines suitable nationally? One council
has already rejected them as not going far enough for local conditions.
3. Property values are escalating so much that it has been estimated that one particular SUDS
pond would now be worth over £1.5m as building land. Can this be sustained?
4. Climate Change projections indicate increased winter rainfall, up to 30% in some areas and
existing SUDS designs do not take this into account adequately. Are there any plans to
change SUDS designs?
5. SEPA have now received funding from the Scottish Executive to produce a comprehensive
set of flood maps for river and coastal flood. They also have been given a copy of the digital
terrain model funded by Norwich Union insurance company. Ultimately the plan is to map and
take into account the effects of flood defences. Should there be plans to map and take into
account CSOs and SUDS schemes?
Clearly SUDS raise a number of complex issues and new questions will continue to arise.
David Crichton
May 2006.
David@crichton.sol.co.uk
39
Appendix 1 Extract from the CIRIA Maintenance Framework Agreement for Scotland
“In any case where SUDS are required by SEPA as part of the shared surface water drainage
system, the allocation of maintenance responsibility shall be as follows:
Above-ground works such as grass swales, retention ponds, detention ponds, etc shall be taken
over and maintained by the Local Authority
Below-ground structures, such as piped systems (including perforated pipes and surrounding
material), soak ways, catch pits, filter drains etc will be owned and maintained by the Water
Authority.
The Water Authority will also be responsible for the discharge into watercourses where applicable.
The Water Authority reserves the right to require a Site Specific Agreement involving third parties
where a development requires major SUDS and/or flood attenuation measures.”
Source: CIRIA Manual Reference C521.
Appendix 2: Extract from the residential property section of the ‘insurance template’
The insurance template is meant to guide planners as to what levels of risk will be acceptable to
insurers at normal terms after the expiry of the insurance guarantee. It is the only national
standard of acceptable risk levels, and as such has been incorporated into many local authorities’
Structure Plans in Scotland. For a full copy of the template, including guidance on property other
than housing, see the author’s guidelines for local authorities.
Type of housing
Standard of protection
Return period
Sheltered housing, and homes for the
disabled and elderly
Children’s homes, boarding schools,
hotels, hostels
Basement flats
Bungalows without escape skylights
Ground floor flats
‘Flashy’ catchments
(little or no flood warning available)
Bungalows with escape skylights
Caravans for seasonal occupancy only,
provided adequate warning notices and
evacuation systems are in place
50 years
All other residential property
200 years
1,000 years
750 years
750 years
500 years
500 years
500 years
300 years
Return period up to the year 2050 in each case, taking climate change into account
© D. Crichton, 1998
Appendix 3: Greywater
A recent development in Scotland is the change to Part M of the Scottish Building Regulations to
allow greywater to be disposed of to ground rather than to the drainage system. “Greywater” is
water from sinks and washing machines, often containing detergent or cooking oil. This is an
extension of SUDS, but is intended only to apply where suitable infiltration measures are taken.
The Scottish Executive and SEPA (and the insurance industry) will carefully monitor the
implementation of these regulations in case there are pollution problems.
For more guidance on greywater, see CIRIA Report C539.
Appendix 4: Design of Drains and Sewers
Since 1975, engineers have designed sewers and drains based on storm and rainfall estimation
methods outlined in the “Flood Studies Report” (FSR). The publication of the Flood Estimation
40
Handbook (FEH) in March 2000 introduced a number of new data sets and approaches to the
estimation of flood related issues.
The FEH includes changes in design flood estimation that caused some hydrologists to express
concern over impacts on dam spillway design. However, an important paper by Futter and Lang,
outlined at a conference in 2001, but not yet published, indicates that the FEH may also have a
potentially significant impact on sewerage modelling, design and operation. These are principally
changes to the method used to derive rainfall depth-duration-frequency (DDF) relationships for
catchments of interest.
The FEH includes the use of an updated and revised approach to rainfall frequency estimation.
The approach developed in the FEH is based on annual maximum rainfalls, and it adopts as the
index value the median of the annual maximum rainfalls at a site, called “RMED”. According to
Futter and Lang, the new results may be much larger over upland areas, by as much as 40 %.
They demonstrate that an increase of 20-30 % corresponds to a decrease of around half in
estimated return period events i.e. storms with an estimated return period of 100 years should
now be allocated a return period of 50 years.
The subject is complex, but the message is simple: the new FEH uses different data and
methodology from the old FSR on which many of our old drainage systems are based. FEH
seems to indicate that severe rainfall events may be more frequent than are indicated by FSR.
Therefore older drains may not be designed to the appropriate standard. It is important that
hydrologists and engineers should be aware of this problem and the need to keep up to date in
the research in this area.
The general conclusion about the new depth, duration and frequency model (DDF) as quoted in
the FEH is:
“The rainfall growth factors in the FSR appear to be over-general, masking important local and
regional variations in rainfall. The FEH procedure takes more account of local data, both in
constructing the focussed growth curves, and in mapping the standardised variable, RMED”.
Futter and Lang (2001) point out that in addition to the new methodology, if projected climate
change is taken into account, based on the latest projections for Scotland (Hulme et al, 2001),
“the implications on sewerage systems are potentially large”. This is not only for extreme events
where combined sewer overflows (CSO) and storage tanks could spill, but also for less extreme
events which may become more frequent. As an example, they warn that a CSO designed to spill
nine times a year could, by 2020 be spilling more than 20 times a year.
They go on to point out that their analysis of the FEH rainfall model has also indicated potential
under-estimates of rainfall for design purposes compared with FSR estimates. For instance, the
projected potential increase in a 2 year 24 hour duration rainfall event in Edinburgh from FSR to
FEH plus climate change is up to 10% in 2020 and 20% in 2080. It is likely to be potentially larger
in other areas, particularly areas like Fort William, where the projected increases are estimated to
be around 17% in 2020 to 45% in 2080.
Futter and Lang (2001) conclude that additional CSO spills and increased flooding incidents are
major risks, and that the water industry should develop sustainable drainage systems and other
approaches to deal with climate change. They also refer to a new UKWIR research project
“Climate Change and the Design of Sewerage Systems” which will seek to address these issues.
In the meantime, it is important not to place too much emphasis on the findings of a single paper,
at least pending comments from peer review and the authors of the FEH. However in the author’s
opinion they build a convincing case as to yet another reason why the problems of sewage
overflows in urban areas are likely to increase. Namely the data and tools in the FEH may indicate
that previous designs using FSR are inadequate to cope with existing levels of rainfall, let alone
climate change.
In Scotland, research published in 2001 indicated that climate change will have a significant
impact on flood defences (Price and McInally, 2001). The researchers recommended that future
41
flood alleviation schemes be designed for the 200 year event and to have the capability of being
modified to cater for even more extreme events.
In view of all these factors, the message would seem to be clear, as insurers and the public
become increasingly concerned over the incidence of flood damage from drains and sewers, the
practice of designing surface water drains to cope with only a two or five-year event should be
reviewed. At the very least, drainage impact assessments should be carried out using a 200-year
return period and an element of freeboard, to ensure that sewage overflows will not result in
damage to property.
The FEH is not a code of practice, simply a set of methods and tools available to hydrologists and
consulting engineers. They have the freedom, as they did with FSR, to review its methods and to
balance them against local information and required design standards. At the end of the day,
however, local authorities, Scottish Water, and water companies have a duty to the public to
ensure that public health and safety is protected.
Appendix 5: Marcic v Thames Water Utilities
Peter Marcic owns a house in Stanmore. When there is heavy rainfall his garden is flooded with
sewage back up, although the house itself is not flooded.
The Director General of Water Services has imposed a price cap on Thames Water, which takes
into account construction work to reduce the number of houses subject to internal sewage
flooding, but he has not made any allowance for properties subject to external flooding.
Mr Marcic brought legal proceedings against Thames Water for
 Breach of statutory duty
 Negligence
 Nuisance
 Breach of the European Convention of Human Rights
The judge dismissed all of these except for claims based on the European Convention. The case
then went to the Court of Appeal which upheld the original judgement but also found for Mr Marcic
on the basis of private nuisance. It had been the position that a sewerage undertaker could only
be held liable in nuisance when it was guilty of misfeasance, where its actions had contributed to
the nuisance. It could not be held guilty of non-feasance, where it had not taken any action. The
Court of Appeal held that even though Thames Water was not guilty of misfeasance, they were
still guilty of nuisance because they had failed to take all reasonable steps to prevent the flooding.
The case went to the House of Lords in October 2004. To the surprise of many, the Lords
overturned the decision in the Court of Appeal23 and drew back from making what would have
been a significant change in the law of nuisance as it applies to sewage undertakers, and possibly
other privatised utilities.
Source: Venters, R., (2002) “Marcic v Thames Water: a change in the law” Water UK, 19 June
2002, Number 151, p7.
23
Marcic v Thames Water [2003] UKHL 66; [2004] 2 AC 42; [2003] 3 WLR 1603; [2004] 1 All ER 135; [2004] BLR 1; 91 Con LR 1; [2004]
Env LR 25; [2004] HRLR 10; [2004] UKHRR 253; [2003] 50 EGCS 95; (2004) 101(4) LSG 32; (2003) 153 NLJ 1869; (2003) 147 SJLB 1429;
[2003] NPC 150
42
Appendix 6: Model letter to developer
(Courtesy of Aberdeenshire Council)
Having studied the proposals I would request that the Developer forward details of the following:
1. A Drainage Impact Assessment prepared in accordance with the Council guidelines,
2. A full SUDS design prepared to meet with the requirements of the CIRIA manual C521:
a) The design should show the effects of a 1 in 200 year storm and run-off and include an
allowance of 20% for climate change,
b) The design should show the effects of differing storm intensities over and above the 10
year return period,
c) The design should show the extents of the differing flood conditions on a site plan to
ensure no water enters buildings or restricts movement of emergency vehicles,
d) The design should give consideration to the capacity of existing water courses and the
effects on any downstream properties,
e) Details will be required of the outlet to the receiving watercourse.
3. If it is proposed to discharge surface water to an existing sewer, confirmation from Scottish
Water that this is acceptable and what rate of discharge will be permitted.
4. A strategy for dealing with any field drainage affected by the works, and
5. A maintenance regime for surface water drainage measures.
43
Appendix 7: Survey of insurers’ attitudes to SUDS
This survey was carried out by David Crichton in May and June 2005, with the assistance of the
Association of British Insurers and the Council of Mortgage Lenders. The results have not been
fully analysed as yet. The response was excellent and comments were received from insurers
responsible for by far the majority of the household insurance market.
It was very clear that awareness of SUDS amongst insurers was very low: most had never heard
of it. Here are some of the comments received:
•
•
•
•
•
•
•
•
•
•
•
•
•
Have you heard of SUDS?
– Yes, however, the awareness of SUDS is low. I did try to obtain the video from
the EA but without success.
– No, nor have my colleagues.
Do you ask a question such as: “Is your property within 100metres of a pond or
watercourse?”
– Yes, but our question says ¼ mile.
– This along with other new questions will be introduced in the near future.
Have you heard of FLAGs?
– We were aware of FLAGs and do discriminate in favour of Scotland.
Are you concerned about grey water being drained into SUDs?
– We were not aware of this one, and this does cause us some concern.
– We would exclude claims.
Would you be concerned about oil contamination of groundwater from roads?
– Yes.
– We would exclude
Are maintenance arrangements something you would wish to take into account in
underwriting the risk?
– Yes if possible, but if not it will be the individual customers who could have
restricted cover following a claim due to this.
– Maintenance of SUDs is a concern
Many councils regard SUDS as a cheap alternative to flood defences, but SUDS can
actually increase the flood hazard for properties built on floodplains.
– I was not aware of this. It will now be a matter for us to consider further.
SUDs can have the effect in some areas of starving watercourses of water and causing
them to dry up during drought conditions. This could lead to the spread of tree roots and
possible subsidence in shrinkable clay areas.
– I was not aware of this and would regard this as a relevant factor in underwriting
Do you consider SUDS should be of concern to the insurance industry?
– Yes.
– Definitely – I see localised drain\sewer capacity problems as the biggest and most
costly issue after coastal\river floods – incident cost is much lower but frequency
is alarmingly high in some smaller drainage problem areas.
What are your biggest concerns?
– … the SUDs must be properly controlled and planned if it is to be successful –
maintenance may be the major problem – developers may adopt the ideas but if
private tenants are left to cope unaided with maintenance the whole thing may
simply degenerate into chaos.
Liability issues
– if we have a flooded property where we can successfully recover costs from a
responsible authority, we would have no reason to apply terms to that property for
the future flood risk.
–
The liability would probably rest with those who designed a system…
Other concerns
– Disability Discrimination Act - level access and ground floor toilets are increasing
the risk of flooding.
– Householders are filling in SUDs ponds to make grass cutting easier, or to
provide parking space.
Finally
44
–
clearly we all have a lot to learn in this area and we expect the relevant authorities
to develop use of SUDS cautiously.
The main lessons to be learned are:
1.
2.
3.
4.
Insurers are concerned when they find out about SUDS.
If they have heard about SUDS they are not aware how widespread these have become.
Many are likely to refuse insurance for properties near to SUDS ponds.
Where cover is given and flooding or subsidence arises from a SUDS installation they will
consider legal action against the designers of the installation.
In other words availability of insurance can not be taken for granted; insurers must be taken into
account because if insurance is withdrawn, mortgage blight will follow. Those involved in
installing SUDS should make sure that they have adequate Professional Indemnity insurance.
45
References
CIRIA Report C506
“Low cost options for prevention of flooding from sewers.” London, 1998. ISBN 0-86017-506-5
CIRIA Report C521
“Sustainable urban drainage systems. Design manual for Scotland and Northern Ireland”, London
2000.
CIRIA Report C522
“Sustainable urban drainage systems. Design manual for England and Wales”, London 2000.
ISBN 0 86017 522 7
CIRIA Report C523
“Sustainable urban drainage systems – best practice manual”, London, 2001.
CIRIA Report C539
“Rainwater and greywater recycling in buildings – best practice guidance”, London, 2001.
Crichton, 2003
Crichton, D., 2003 “Flood risk and insurance in England and Wales: are there lessons to be learnt
from Scotland?” Technical Paper Number 1, Benfield Hazard Research Centre, University
College London. Available for free downloading from
www.benfieldhrc.org/SiteRoot/activities/tech_papers/flood_report.pdf
D’Arcy, 2002
D’Arcy, B.J., Ellis, J.B., Ferrier, R.C., Jenkins, A., and Dils, R., 2002. “Diffuse Pollution Impacts:
The environmental and economic impacts of diffuse pollution in the UK.” Chartered Institution of
Water and Environmental Management (funded by EA, SEPA and SNIFFER)
EA, 2001
“Lessons Learned. Autumn 2000 floods” Environment Agency, Bristol, 2001. ISBN 1857055063
EA Wales, 2001
“Flooding in Wales. October – November 2000.” Environment Agency, Cardiff, 2001.
EA 2002
“Combined Sewer Overflows (CSOs)” Chris Chubb, Point Source Manager, EA, Bristol, 2002.
Futter and Lang, 2001.
Mark Futter and Ian Lang of Messrs. Montgomery Watson “Implications for Scotland of Recent
Developments in Design Rainfall Estimation and Climate Change” WaPUG Meeting 12th June
2001, Dunblane, 2001.
Hulme et al, 2001.
M Hulme, J Crossley and X. Lu (2001) “An Exploration of Regional Climate Change Scenarios For
Scotland.” Report prepared on behalf of the Scottish Executive Central Research Unit. HMSO
Edinburgh.
ICE, 2001
Institution of Civil Engineers Presidential Commission (2001) “Living with Rivers”. ICE, London
NESFAG, 2002
North East Scotland Flood Appraisal Group (2002) “Drainage Impact Assessment: Guidance for
Developers and Regulators.” Aberdeenshire Council, Stonehaven, 2002.
NPPG 7, 1995
National Planning Policy Guideline Number 7 “Planning and Flooding”.
Edinburgh, 1995. ISBN 0 7480 2961 3.
Scottish Executive,
46
Ofwat, 2002.
Ofwat Report 18/02, (2002) “Flooding from sewers, a way forward: consultation.”
PAN 44
Planning Advice Note 44 “Fitting new Housing Development into the landscape” Scottish Office,
Edinburgh, March 1994. ISBN 0 7480 0875 6
PAN 61
Planning Advice Note 61 “Planning and Sustainable Urban Drainage Systems” Scottish Executive,
Edinburgh, July 2001. ISBN 0 7559 2097 X.
Price and McInally, 2001
D.J. Price and G. McInally: Climate Change: Review of Levels of Protection Offered by Flood
Prevention Schemes. Scottish Executive Central Research Unit. Edinburgh, May 2001
Scottish Executive, 2001
Scottish Executive, Convention of Scottish Local Authorities, and The Society of Local Authority
Chief Executives and Senior Managers (SOLACE), “Climate change Guidance for Chief
Executives” Scottish Executive, Edinburgh, September 2001.
Venters, 2002
Venters, R., (2002) “Marcic v Thames Water: a change in the law” Water UK, 19 June 2002,
Number 151, p7.
Werritty et al, 2002
Werritty, A., Black, A., Duck, R., Finlinson, W., Shackley, S., Crichton, D., “Climate Change, Flood
Occurrences Review.” Scottish Executive Environment Group Research Programme Research
Findings No. 19. Scottish Executive, Edinburgh. Available from www.scotland.gov.uk/cru/resfinds
Video on SUDS
Shot in the Dark Centre for Environmental Communications (2002) “Designs that hold water:
Sustainable Urban Drainage Systems Explained” Video production (25 minutes) sponsored by
SEPA, The Environment Agency, and the Institution of Civil Engineers.