CIRIA C609
London, 2004
Sustainable drainage
systems
Hydraulic, structural and water
quality advice
S Wilson
Sustainable Drainage Associates
R Bray
Sustainable Drainage Associates
P Cooper
Sustainable Drainage Associates
Classic House, 174–180 Old Street, London EC1V 9BP, UK
TEL +44 (0)20 7549 3300 FAX +44 (0)20 7253 0523
EMAIL enquiries@ciria.org
WEBSITE www.ciria.org
Summary
This technical report summarises current knowledge on the appropriate approach to
the successful design and construction of sustainable drainage systems (SUDS).
The book provides an improved understanding of the hydrological, hydraulic,
structural, water quality and ecological issues of various SUDS features based on the
information currently available in the UK and overseas.
Sustainable drainage systems. Hydraulic, structural and water quality advice
Wilson, S; Bray, R; Cooper, P
CIRIA
CIRIA C609
© CIRIA 2004
RP663
ISBN 0-86017-609-6
This book constitutes Environment Agency R&D Report P2-261/20/TR
Keywords
Urban drainage, environmental good practice, pollution prevention, sustainable
construction, water quality, urban hydrogeology
Reader interest
Classification
Developers, landscape architects,
consulting engineers, local authorities,
architects, highway authorities,
environmental regulators, planners,
sewerage undertakers, contractors and
other organisations involved in the
provision or maintenance of surface
water drainage to new and existing
developments
AVAILABILITY
Unrestricted
CONTENT
Technical guidance
STATUS
Committee-guided
USER
Developers, architects,
engineers, regulators
Published by CIRIA, Classic House, 174–180 Old Street, London EC1V 9BP.
All rights reserved. No part of this publication may be reproduced or transmitted in any
form or by any means, including photocopying and recording, without the written
permission of the copyright-holder, application for which should be addressed to the
publisher. Such written permission must also be obtained before any part of this publication
is stored in a retrieval system of any nature.
This publication is designed to provide accurate and authoritative information in regard to
the subject matter covered. It is sold and/or distributed with the understanding that neither
the authors nor the publisher is thereby engaged in rendering a specific legal or any other
professional service. While every effort has been made to ensure the accuracy and
completeness of the publication, no warranty or fitness is provided or implied, and the
authors and publisher shall have neither liability nor responsibility to any person or entity
with respect to any loss or damage arising from its use.
2
CIRIA C609
Sustainable drainage systems (SUDS)
The SUDS concept is to mimic, as closely as possible, natural drainage of a site in order
to minimise the impact that urban development has on flooding and pollution of rivers,
streams and other water bodies. The use of a variety of techniques within the
management train allows the SUDS concept to be applied to all sites. The techniques
utilising vegetative features to treat pollution and slow down or reduce flows can
enhance the landscape and provide wildlife habitat.
CIRIA C609
3
4
CIRIA C609
Acknowledgements
Research contractor
This publication is the outcome of CIRIA Research Project 663. The publication was
prepared by Sustainable Drainage Associates.
Authors
Steve Wilson BEng MSc CEng MICE MCIWEM FGS
Technical director of Sustainable Drainage Associates, Steve has over 20 years’ practical
experience of geotechnical and environmental design and construction for building and
civil engineering projects. He is co-author of CIRIA C582 Source control using constructed
pervious surfaces. In addition to SUDS design work he has managed a number of SUDSrelated research projects including a study of silting in cellular drainage tanks and the
structural and pollutant removal performance of pervious pavements.
Bob Bray MLI BSc (Hons) DipLD
Director of Sustainable Drainage Associates, Bob has designed SUDS schemes since
1996, including two Environment Agency demonstration sites at Oxford Motorway
Service Area (M40) and Hopwood Park MSA (M42). Bob is currently designing SUDS
for schools, wildlife sites and housing.
Phil Cooper IEng MIHIE
Business development director of Sustainable Drainage Associates, Phil has extensive
experience in identifying and overcoming the issues relating to the large-scale uptake of
SUDS in the UK. He has been a steering group member on several of CIRIA’s SUDS
projects and has a particular interest in the independent technical validation of the
range of components utlised within SUDS solutions.
Steering group
Following CIRIA’s usual practice, the research project was guided by a steering group,
which comprised:
Chair
Mr Martin Osborne
Earth Tech Engineering Ltd
Attending members
Mr Alan Bamforth
ABG Geosynthetics Ltd
Mr Phil Chatfield
Environment Agency
CIRIA C609
Mr Nick Cooper
Atlantis Water Management Ltd
Mr Peter Forster
Southern Water Services (CIWEM Representative)
Mr John Hateley
Severn Trent Water
Mr Richard Kellagher
HR Wallingford Ltd
Mr Martin Lambley
A Proctor Group
Mr Jim Leat
WS Atkins (DTI Representative)
Mr Chris Mead
WSP Development Ltd
Mr Aidan Millerick
Micro Drainage Ltd
Mr Clive Onions
Arup (ICE Representative)
Mr Stan Redfearn
The BOC Foundation
Mr Andrew Shuttleworth
SEL Environmental
Mr Neil Smith
NHBC
Mr Tom Wild
SEPA
5
Corresponding
Mr Jim Conlin
Scottish Water
members
Mr Philip Day
Severn Trent Water Ltd
Mr Graham Fairhurst
Borough of Telford and Wrekin
Dr Chris Jefferies
University of Abertay
Mr Alex Middleton
The Greenbelt Group of Companies Ltd
Ms Nathalie Carter
The House Builders Federation
CIRIA manager
CIRIA’s research manager for the project was Paul Shaffer.
Project funders
The project was funded by:
The Department of Trade and Industry
The BOC Foundation
Environment Agency
Severn Trent Water
ABG Geosynthetics
Environmental Protection Group Ltd
Micro Drainage Ltd
NHBC
A Proctor Group
SEL Environmental
WSP Development Ltd
Contributors
6
CIRIA and the research contractors wish to acknowledge the following individuals who
provided help and information for the study and whose invaluable contributions have
been vital to the successful preparation of this report:
Caroline Aistrop
Stroud Valleys Project
Walter K Caldwell
Watershed Protection Division, Department of Health,
Government of the District of Columbia
Stewart R Comstock
Maryland Department of the Environment
Paul Culleton
Environmental Protection Group Limited
Alison Duffy
University of Abertay
Timothy J Karikari
Watershed Protection Division, Department of Health,
Government of the District of Columbia
Diane Leigh
Environmental Protection Group Limited
Richard Long
Ewan Associates
Dominic McBennett
University of Abertay
Kirsteen Macdonald
Ewan Associates
Gaye McKissock
Hyder Consulting
Alan Newman
Coventry University
Tom Schueler
Centre for Watershed Protection, Ellicott City, Maryland,
USA
Alun Tarr
Blackdown Horticultural Services Limited
Malcolm Wearing
CRM Associates Limited
Jennifer Zielinski
Centre for Watershed Protection, Ellicott City, Maryland,
USA
CIRIA C609
Contents
Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Sustainable drainage systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Acknowledgements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
List of figures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
List of tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
List of boxes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Abbreviations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Foreword . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
SUDS information guide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
SUDS design process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
PART 1 GENERAL ISSUES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27
1
2
3
4
CIRIA C609
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .28
1.1
What are sustainable drainage systems? . . . . . . . . . . . . . . . . . . . . . . . .28
1.2
Benefits of SUDS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .29
1.3
Background to project . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .30
1.4
Purpose and scope of this book . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31
1.5
Sources of information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31
1.6
Associated publications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .32
SUDS concepts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .33
2.1
Integration and planning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .33
2.2
The importance of the management train concept . . . . . . . . . . . . . . . .34
2.3
Quality, quantity and amenity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .37
2.4
Common SUDS techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .37
2.5
Retrofitting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .38
2.6
SUDS on brownfield sites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .39
2.7
SUDS and rainwater harvesting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40
Stormwater pollution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .41
3.1
Pollution and first flush concept . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .41
3.2
Pollution and water quality legislation . . . . . . . . . . . . . . . . . . . . . . . . . .51
3.3
Environmental risk assessment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .58
3.4
Pollutant removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .60
Rainfall and runoff . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .69
4.1
Urban hydrology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .69
4.2
Frequency of events . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .70
4.3
Design rainfall criteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .72
4.4
Modelling rainfall and runoff . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .84
4.5
Storage and flow estimation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .89
4.6
Sensitivity analysis for climate change . . . . . . . . . . . . . . . . . . . . . . . . . .89
7
5
6
7
8
General SUDS design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .91
5.1
Design information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .91
5.2
SUDS design teams and stakeholders . . . . . . . . . . . . . . . . . . . . . . . . . .93
5.3
Design standards and EA accreditation . . . . . . . . . . . . . . . . . . . . . . . . .94
5.4
Failure and risk management concepts . . . . . . . . . . . . . . . . . . . . . . . . .94
5.5
Guidance on selection of SUDS techniques . . . . . . . . . . . . . . . . . . . . . .96
5.6
Linking SUDS techniques together . . . . . . . . . . . . . . . . . . . . . . . . . . . .98
5.7
Wildlife, amenity and community involvement . . . . . . . . . . . . . . . . . . .99
5.8
Planting SUDS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .101
5.9
Silting and access for maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . .106
5.10
Health and safety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .107
5.11
Specification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .110
5.12
Geotextiles and geomembranes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .110
5.13
Geotechnical considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .112
5.14
Sustainable construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .112
5.15
Cold climates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .113
Construction of SUDS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .115
6.1
Education of site staff . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .115
6.2
Changes to construction practice . . . . . . . . . . . . . . . . . . . . . . . . . . . . .116
6.3
Erosion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .116
6.4
Prevention of damage and pollution during construction . . . . . . . . .116
6.5
Construction standards and tolerances . . . . . . . . . . . . . . . . . . . . . . . .117
6.6
Inspections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .117
Management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .119
7.1
Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .119
7.2
Operation and maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .120
7.3
Waste management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .121
7.4
Reliability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .123
7.5
Silting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .123
7.6
Wildlife . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .124
7.7
Adoption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .125
Economics of SUDS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .127
8.1
Construction costs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .127
8.2
Maintenance costs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .128
8.3
Whole-life cost comparisons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .129
PART 2 INFORMATION FOR INDIVIDUAL TECHNIQUES . . . . . . . . . . . . . . . . .131
9
8
Technical data for SUDS techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .133
9.1
Preventative measures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .133
9.2
Pervious pavements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .135
9.3
Green roofs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .152
9.4
Bioretention . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .162
9.5
Filtration techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .173
CIRIA C609
9.6
Grassed filter strips . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .185
9.7
Swales . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .191
9.8
Infiltration devices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .208
9.9
Infiltration basin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .218
9.10
Filter drains . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .223
9.11
Ponds and detention basins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .229
9.12
Constructed stormwater wetlands . . . . . . . . . . . . . . . . . . . . . . . . . . . .251
9.13
On-/off-line storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .260
9.14
Oil separators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .267
9.15
Innovative treatment systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .267
Appendices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .269
A1
Decision-making for SUDS techniques . . . . . . . . . . . . . . . . . . . . . . . .269
A2
Worked examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .275
A3
Design information checklist . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .286
A4
Case studies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .287
A5
Planting for SUDS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .299
A6
Design accreditation checklist . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .302
A7
Construction inspection checklist . . . . . . . . . . . . . . . . . . . . . . . . . . . . .303
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .305
CIRIA C609
9
Figures
10
1.1
SUDS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .28
2.1
Cost of environmental control versus point of implementation . . . . . . . . . . .33
2.2
The management train . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35
2.3
Common SUDS techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .37
2.4
Example installation of an infiltration system on a contaminated site . . . . . .40
3.1
Sub-surface pollutant transport . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .45
3.2
Effect of kerb height on particle loading of street surface . . . . . . . . . . . . . . . .48
3.3
Contribution of flow and pollution from urban surfaces . . . . . . . . . . . . . . . . .50
3.4
Example of a conceptual model for a SUDS scheme . . . . . . . . . . . . . . . . . . . .59
3.5
Risk assessment for SUDS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .60
4.1
Fate of rainfall on natural cover . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .70
4.2
Fate of rainfall on developed sites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .71
4.3
Relative volumes for each design criterion . . . . . . . . . . . . . . . . . . . . . . . . . . .73
4.4
Runoff–capture relationship . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .78
4.5
Effects of detention timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .81
4.6
Effects of increased volume and duration of runoff . . . . . . . . . . . . . . . . . . . .82
4.7
Illustrative schematic of a storage layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . .83
4.8
Runoff coefficients . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .87
4.9
Typical runoff hydrograph for an impermeable surface
4.10
Variation of calculated storage volume with storm duration . . . . . . . . . . . . . .89
5.1
Multidisciplinary SUDS design team and stakeholders . . . . . . . . . . . . . . . . . .93
5.2
SUDS designed to enhance local wildlife and amenity . . . . . . . . . . . . . . . . . .99
6.1
Geotextile silt fence to remove silt in runoff . . . . . . . . . . . . . . . . . . . . . . . . .117
9.2.1
Pervious pavement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .136
9.2.2
Example hydrograph from pervious surface . . . . . . . . . . . . . . . . . . . . . . . . .142
9.2.3
Comparison of rainfall with outflow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .143
9.2.4
Example hydrograph from outfall of pervious pavement at Wheatley MSA 144
9.2.5
Pervious pavement details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .149
9.3.1
Extensive green roof . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .153
9.3.2
Intensive green roof . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .153
9.3.3
Runoff hydrograph from a green roof . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .155
9.3.4
Runoff attenuation for trial roof in Philadelphia . . . . . . . . . . . . . . . . . . . . . .156
9.3.5
Example details of a green roof . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .158
9.3.6
Example detail of outlet from green roof . . . . . . . . . . . . . . . . . . . . . . . . . . . .160
9.4.1
Bioretention area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .163
9.4.2
Example detail of a bioretention area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .169
9.4.3
Diversion structures to bioretention areas . . . . . . . . . . . . . . . . . . . . . . . . . . .170
9.5.1
Types of filtration device . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .174
. . . . . . . . . . . . . . . .88
CIRIA C609
9.5.2
Variation of phosphorous removal efficiency with inlet concentration . . . . .178
9.5.3
TSS reduction and hydraulic conductivity . . . . . . . . . . . . . . . . . . . . . . . . . . .178
9.5.4
Flow rate versus cumulative TSS removed . . . . . . . . . . . . . . . . . . . . . . . . . .179
9.5.5
Example details for surface sand filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .182
9.5.6
Example details for underground sand filter . . . . . . . . . . . . . . . . . . . . . . . . .182
9.5.7
Example details for perimeter sand filter . . . . . . . . . . . . . . . . . . . . . . . . . . . .183
9.6.1
Grassed filter strip . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .185
9.6.2
Example details of a filter strip . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .189
9.7.1
Swale in a housing development, Scotland . . . . . . . . . . . . . . . . . . . . . . . . . .191
9.7.2
Types of swale . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .192
9.7.3
Effect of water depth and swale length on TSS removal efficiency . . . . . . . .196
9.7.4
Example details for a dry swale . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .203
9.7.5
Example details for a wet swale . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .203
9.7.6
Reinforcing the road edge in Holland . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .203
9.7.7
Check dams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .204
9.7.8
Swale integrated into landscape and retention pond . . . . . . . . . . . . . . . . . .205
9.7.9
Planting zones for swales . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .206
9.8.1
Infiltration trench . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .208
9.8.2
Example soakaway construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .209
9.8.3
Contamination below base of 30-year-old soakaway. . . . . . . . . . . . . . . . . . . .211
9.8.4
Response of soakaway to rainfall events. . . . . . . . . . . . . . . . . . . . . . . . . . . . .212
9.8.5
Example infiltration device details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .217
9.9.1
Infiltration basin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .218
9.9.2
Example details of an infiltration basin . . . . . . . . . . . . . . . . . . . . . . . . . . . . .221
9.10.1
Filter drain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .224
9.10.2
Rainfall compared to outfall from a filter drain . . . . . . . . . . . . . . . . . . . . . . .226
9.10.3
Example details of a filter drain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .227
9.11.1
Wet pond . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .229
9.11.2
Removal rate versus detention time for wetlands . . . . . . . . . . . . . . . . . . . . .233
9.11.3
Sediment depth, Linburn Pond, Scotland, 1999 . . . . . . . . . . . . . . . . . . . . . .233
9.11.4
Peak flow attenuation at Claylands Pond, Scotland . . . . . . . . . . . . . . . . . . . .235
9.11.5
Mixed pond vegetation zones . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .238
9.11.6
Example details of a wet pond . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .241
9.11.7
Pond geometry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .242
9.11.8
Example outlet detail for ponds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .243
9.11.9
Landscaping zones in a wet pond . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .243
9.11.10 Extended detention basin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .245
9.11.11 Example details of an extended detention basin . . . . . . . . . . . . . . . . . . . . . .249
CIRIA C609
9.12.1
Constructed wetland, Dumfries, Scotland . . . . . . . . . . . . . . . . . . . . . . . . . . .251
9.12.2
Example details of a wetland for stormwater treatment . . . . . . . . . . . . . . . .258
9.13.1
Plastic modular storage tank below a trial car park at Coventry University 261
9.13.2
Compression test configurations on plastic cellular structures . . . . . . . . . . .263
9.13.3
Example stress–strain curve for compression tests . . . . . . . . . . . . . . . . . . . .264
9.13.4
Bending in box structure with an internal void . . . . . . . . . . . . . . . . . . . . . . .264
11
12
9.13.5
Example creep test results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .265
9.13.6
Spread of load below a wheel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .266
9.13.7
Testing of a full-scale pavement incorporating a plastic cellular sub-base
replacement system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .266
A2.1
Site plan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .277
A2.2
Site layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .280
A2.3
Section of bioretention area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .280
A2.4
Preliminary layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .282
A4.1
Plan of drainage system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .288
A4.2
View of the ponds at Aztec West . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .288
A4.3
Schematic of Linburn Pond catchment . . . . . . . . . . . . . . . . . . . . . . . . . . . . .290
A4.4
Linburn Pond . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .290
A4.5
Outflow hydrograph for a typical rainfall event . . . . . . . . . . . . . . . . . . . . . .291
A4.6
Sediment depth in pond in July 1999 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .292
A4.7
Change in mean sediment depth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .293
A4.8
Plan of drainage system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .295
A4.9
Swale and pervious pavement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .298
CIRIA C609
Tables
CIRIA C609
3.1
Sources of pollution on impermeable surfaces . . . . . . . . . . . . . . . . . . . . . . . . .42
3.2
Effects, transport and fate of pollutants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .43
3.3
Recommended mean EMC values for North European screening
applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .46
3.4
Typical pollutant build-up rates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .47
3.5
Concentrations of selected pollutants for various land uses . . . . . . . . . . . . . .49
3.6
Heavy metal fractions in runoff . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .49
3.7
Estimates of pollutant removal capability for assessment of SUDS
management train . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .64
3.8
Median pollutant concentrations for stormwater treatment practices . . . . . .65
3.9
Design robustness for SUDS techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .67
4.1
Probability of a storm occurring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .72
4.2
Greenfield runoff calculation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .77
4.3
Recommended criteria for determining the water quality volume . . . . . . . . .78
4.4
Design flood return periods for site level of service . . . . . . . . . . . . . . . . . . . .80
4.5
Recommended criteria for storage volume design . . . . . . . . . . . . . . . . . . . . .83
5.1
Example of a safety audit for a SUDS pond . . . . . . . . . . . . . . . . . . . . . . . . . .109
7.1
Sediment removal frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .122
8.1
Maintenance costs for SUDS schemes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .128
8.2
Estimated remedial maintenance costs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .129
9.2.1
Advantages and disadvantages of pervious surfaces . . . . . . . . . . . . . . . . . . .137
9.2.2
Water quality result for general quality parameters . . . . . . . . . . . . . . . . . . .139
9.2.3
Water quality results for hydrocarbons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .139
9.2.4
Results from heavy metals analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .139
9.2.5
Retention of pollutant within pavement structure . . . . . . . . . . . . . . . . . . . .140
9.2.6
Nutrient concentrations in flow from laboratory pavement . . . . . . . . . . . . .141
9.2.7
Various quoted pollutant removal efficiencies for constructed pervious
surfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .142
9.2.8
Mean percentage runoff from pavement surface . . . . . . . . . . . . . . . . . . . . . .144
9.2.9
Surface infiltration rates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .145
9.2.10
Material conversion factors from BS 7533-1:2000 and Knapton, 1989 . . . .148
9.2.11
Recommended grading requirements from BS 882:1992 . . . . . . . . . . . . . . .149
9.2.12
Maintenance requirements for pervious pavements . . . . . . . . . . . . . . . . . . .151
9.3.1
Advantages and disadvantages of green roofs . . . . . . . . . . . . . . . . . . . . . . . .154
9.3.2
Specification of soil cover for extensive roof . . . . . . . . . . . . . . . . . . . . . . . . .159
9.3.3
Planting for green roofs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .161
9.3.4
Maintenance requirements for green roofs . . . . . . . . . . . . . . . . . . . . . . . . . .162
9.4.1
Advantages and disadvantages of bioretention areas . . . . . . . . . . . . . . . . . .164
9.4.2
Variation in pollutant removal with depth for bioretention areas . . . . . . . .165
13
14
9.4.3
Pollutant removal efficiencies for bioretention areas . . . . . . . . . . . . . . . . . . .165
9.4.4
Soil specification for bioretention areas . . . . . . . . . . . . . . . . . . . . . . . . . . . . .168
9.4.5
Design criteria for bioretention areas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .169
9.4.6
Maintenance requirements for bioretention areas . . . . . . . . . . . . . . . . . . . . .172
9.5.1
Advantages and disadvantages of filters . . . . . . . . . . . . . . . . . . . . . . . . . . . . .176
9.5.2
Pollutant removal efficiencies for filters . . . . . . . . . . . . . . . . . . . . . . . . . . . . .177
9.5.3
Irreducible pollutant concentrations for sand and organic filters . . . . . . . . .177
9.5.4
Specification of sand for sand filters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .183
9.5.5
Maintenance requirements for filters
9.6.1
Advantages and disadvantages of grassed filter strips . . . . . . . . . . . . . . . . . .186
9.6.2
Annual loading rate of metals in filter strips . . . . . . . . . . . . . . . . . . . . . . . . .187
9.6.3
Pollutant removal efficiencies for grassed filter strips . . . . . . . . . . . . . . . . . .187
9.6.4
Maximum drainage length possible to maintain sheet flow . . . . . . . . . . . . .188
9.6.5
Maintenance requirements for grassed filter strips . . . . . . . . . . . . . . . . . . . .190
9.7.1
Advantages and disadvantages of swales . . . . . . . . . . . . . . . . . . . . . . . . . . . .194
9.7.2
Pollutant removal of 30 m and 60 m swales . . . . . . . . . . . . . . . . . . . . . . . . . .195
9.7.3
Pollutant removal efficiencies for swales . . . . . . . . . . . . . . . . . . . . . . . . . . . . .197
9.7.4
Irreducible concentrations for swales . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .197
9.7.5
Required swale length for TSS removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . .197
9.7.6
Roughness coefficient, n, for grass swales . . . . . . . . . . . . . . . . . . . . . . . . . . .199
9.7.7
Maximum allowable flow velocities based on soil type . . . . . . . . . . . . . . . . .201
9.7.8
Limits on channel slopes in swales . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .202
9.7.9
Maintenance requirements for swales . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .207
9.8.1
Advantages and disadvantages of infiltration devices . . . . . . . . . . . . . . . . . .210
9.8.2
Pollutant removal efficiencies for infiltration devices . . . . . . . . . . . . . . . . . . .210
9.8.3
Percentage retention of pollutants in soils and sludge at base of soakaways .211
9.8.4
Factors of safety for infiltration design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .214
9.8.5
Maintenance requirements for infiltration devices . . . . . . . . . . . . . . . . . . . .217
9.9.1
Advantages and disadvantages of infiltration basins . . . . . . . . . . . . . . . . . . .219
9.9.2
Pollutant removal efficiencies for infiltration basins . . . . . . . . . . . . . . . . . . .220
9.9.3
Maintenance requirements for infiltration basins . . . . . . . . . . . . . . . . . . . . .223
9.10.1
Advantages and disadvantages of filter drains . . . . . . . . . . . . . . . . . . . . . . . .224
9.10.2
Pollutant concentrations in outflow from a filter drain . . . . . . . . . . . . . . . . .225
9.10.3
Mean annual removal efficiencies for filter drains . . . . . . . . . . . . . . . . . . . . .225
9.10.4
Maintenance requirements for filter drain . . . . . . . . . . . . . . . . . . . . . . . . . .228
9.11.1
Advantages and disadvantages of wet ponds . . . . . . . . . . . . . . . . . . . . . . . . .230
9.11.2
Effect of pond dimensions on pollutant removal . . . . . . . . . . . . . . . . . . . . . .231
9.11.3
Pollutant removal efficiencies for wet ponds . . . . . . . . . . . . . . . . . . . . . . . . .232
9.11.4
Pollutant concentrations in pond sediment . . . . . . . . . . . . . . . . . . . . . . . . . .234
9.11.5
Pollutant removal design criteria for ponds . . . . . . . . . . . . . . . . . . . . . . . . . .240
9.11.6
Maintenance requirements for wet ponds . . . . . . . . . . . . . . . . . . . . . . . . . . .244
9.11.7
Advantages and disadvantages of extended detention basins . . . . . . . . . . . .246
9.11.8
Pollutant removal efficiencies for extended detention basins . . . . . . . . . . . .247
9.11.9
Maintenance requirements for extended detention basins
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .184
. . . . . . . . . . . . .250
CIRIA C609
CIRIA C609
9.12.1
Advantages and disadvantages of wetlands . . . . . . . . . . . . . . . . . . . . . . . . . .252
9.12.2
Pollutant removal of a wetland during large and small storms . . . . . . . . . . .253
9.12.3
Pollutant removal efficiencies for a constructed wetland . . . . . . . . . . . . . . . .254
9.12.4
Design criteria for wetlands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .257
9.12.5
Allocation of treatment volumes and surface area in a wetland . . . . . . . . . .257
9.12.6
Maintenance requirements for wetlands . . . . . . . . . . . . . . . . . . . . . . . . . . . .259
9.13.1
Advantages and disadvantages of on-line or off-line storage systems . . . . . .260
9.13.2
Partial load factors from BS 8110, Part 1:1997 . . . . . . . . . . . . . . . . . . . . . . .262
9.13.3
Maintenance requirements for storage tanks . . . . . . . . . . . . . . . . . . . . . . . .267
A1.1
Decision criteria for selecting SUDS techniques . . . . . . . . . . . . . . . . . . . . . .271
A1.2b
Selection matrix for SUDS techniques – hydrological and land use . . . . . . .272
A1.2b
Selection matrix for SUDS techniques – physical site features . . . . . . . . . . .273
A1.2c
Selection matrix for SUDS techniques – economics, maintenance,
community and environment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .274
A2.1
Filter strip connected to a wetland (missing the silt trap or forebay) to
an infiltration basin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .278
A2.2
Filter drain connected to a wetland (via silt trap or forebay) to an
infiltration basin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .279
A2.3
Estimation of pollutant removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .279
A4.1
Pollutant levels continuously monitored at outlet to Linburn Pond . . . . . . .291
A4.2
Pollutant levels at inlet and outlet to Linburn Pond . . . . . . . . . . . . . . . . . . .292
A4.3
Sediment quality in 1999 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .293
A4.4
Cost comparison . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .296
15
Boxes
16
3.1
Summary of environmental legislation applicable to SUDS . . . . . . . . . . . . . . 53
3.2
Stormwater hotspots . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
3.3
Groundwater source protection zones . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
3.4
EA criteria on use of infiltration techniques in England and Wales . . . . . . . . 57
3.5
Assessment of accidental spillages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
3.6
Pollutant removal mechanisms in SUDS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
3.7
Methods of estimating pollutant removal. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
4.1
Estimation of greenfield runoff rates and volumes . . . . . . . . . . . . . . . . . . . . . 76
4.2
Water quality criteria from various sources . . . . . . . . . . . . . . . . . . . . . . . . . . . 79
5.1
Recommended geotextile filter criteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111
6.1
Example information checklist for site staff . . . . . . . . . . . . . . . . . . . . . . . . . . 115
7.1
Waste disposal of sediments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122
7.2
Wildlife piles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125
8.1
Example bill of quantities for a SUDS scheme . . . . . . . . . . . . . . . . . . . . . . . . 128
9.2.1
Key considerations for pervious pavement design. . . . . . . . . . . . . . . . . . . . . 135
9.2.2
Locations for use of constructed pervious surfaces . . . . . . . . . . . . . . . . . . . . 136
9.2.3
Recommended specification of aggregate for strength and durability . . . . . 150
9.3.1
Key considerations for green roof design . . . . . . . . . . . . . . . . . . . . . . . . . . . 152
9.4.1
Key considerations for bioretention design . . . . . . . . . . . . . . . . . . . . . . . . . . 162
9.5.1
Key considerations for filter design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173
9.6.1
Key considerations for grass filter strip design . . . . . . . . . . . . . . . . . . . . . . . 185
9.7.1
Key considerations for swale design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 191
9.8.1
Key considerations for design of infiltration devices . . . . . . . . . . . . . . . . . . . 208
9.8.2
Infiltration design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215
9.9.1
Key considerations for infiltration basin design . . . . . . . . . . . . . . . . . . . . . . . 218
9.10.1
Key considerations for filter drain design . . . . . . . . . . . . . . . . . . . . . . . . . . . 223
9.11.1
Key considerations for wet pond design . . . . . . . . . . . . . . . . . . . . . . . . . . . . 229
9.11.2
Ways to maximise the nature conservation value of SUDS ponds . . . . . . . . 237
9.11.3
Key considerations for extended detention basin design . . . . . . . . . . . . . . . 245
9.12.1
Key considerations for constructed wetland design. . . . . . . . . . . . . . . . . . . . 251
9.13.1
Key considerations for on-/off-line storage. . . . . . . . . . . . . . . . . . . . . . . . . . . 260
9.13.2
Limit state design of geocellular structures . . . . . . . . . . . . . . . . . . . . . . . . . . 262
CIRIA C609
Glossary
Adsorption – The adherence of gas, vapour or dissolved matter to the surface of solids.
Aquifer – Layer of rock or soil that holds or transmits water.
Asphalt – European standard description of all mixtures of mineral aggregates bound with
bituminous materials used in the construction and maintenance of paved surfaces.
Asphalt concrete – New European standard description of materials previously known as
macadams and Marshall asphalt.
Attenuation – Reduction of peak flow and increase of the duration of a flow event.
Balancing pond – A pond designed to attenuate flows by storing runoff during the peak flow and
releasing it at a controlled rate during and after the storm. The pond always contains water. Also
known as wet detention pond.
Base – European standard description of the lowest bound layer of an asphalt pavement; known
in UK as roadbase.
Base flow – The sustained flow in a channel or system because of subsurface infiltration.
Basin – A ground depression acting as a flow control or water treatment structure that is normally
dry and has a proper outfall, but designed to detain stormwater temporarily (see Detention basin).
Binder course – European standard description of an asphalt pavement’s second layer; known in
UK as basecourse.
Biodegradation – Decomposition of organic matter by micro-organisms and other living things.
Bioretention area – A depressed landscaping area that is allowed to collect runoff so it percolates
through the soil below the area into an underdrain, thus promoting pollutant removal.
Bitumen – A hydrocarbon binder. A virtually involatile adhesive material derived from crude
petroleum that is used to coat mineral aggregate for use in construction and maintenance of
paved surfaces.
Block paving – Pre-cast concrete or clay brick sized flexible modular paving system.
Capping layer – Layer of unbound aggregate of lower quality than sub-base, used to improve
performance of foundation soils before laying the sub-base and to protect subgrade from damage
by construction traffic.
Carriageway – The part of the road used to carry vehicular traffic.
Catchment – The area contributing surface water flow to a point on a drainage or river system.
Can be divided into sub-catchments.
CBR value – California Bearing Ratio. An empirical measure of the stiffness and strength of soils,
used in road pavement design.
Construction Quality Assurance (CQA) – A documented management system designed to provide
adequate confidence that items or services meet contractual requirements and will perform
adequately in service. CQA usually includes inspection and testing of installed components and it
records the results.
Continuously graded – A soil or aggregate with a balanced range of particle sizes with significant
proportions of all fractions from the maximum nominal size down.
Control structure – Structure to control the volume or rate of flow of water through or over it.
Controlled waters – Waters defined and protected under the Water Resources Act 1991. Any
relevant territorial waters that extend seaward for three miles from the baselines, any coastal
waters that extend inland from those baselines to the limit of the highest tide or the freshwater
limit of any river or watercourse, any enclosed dock that adjoins coastal waters, inland freshwaters,
including rivers, watercourses, and ponds and lakes with discharges and ground waters (waters
contained in underground strata). For the full definition refer to the Water Resources Act 1991.
Conveyance – Movement of water from one location to another.
Denitrification – A microbial process that reduces nitrate to nitrite and nitrite to nitrogen gas.
Design criteria – A set of standards agreed by the developer, planners and regulators that the
proposed system should satisfy.
Detention basin – A vegetated depression that is normally dry except following storm events
constructed to store water temporarily to attenuate flows. May allow infiltration of water to the
ground.
Diffuse pollution – Pollution arising from land-use activities (urban and rural) that are dispersed
across a catchment or sub-catchment and which do not arise as a process effluent, municipal
sewage effluent or an effluent discharge from farm buildings.
Elastic modulus – Also known as Young’s Modulus or stiffness modulus; the ratio of stress divided
by strain for a particular material.
CIRIA C609
17
Eutrophication – Water pollution caused by excessive plant nutrients that results in reduced
oxygen levels. The nutrients are powerful stimulants to algal growth which in turn use up oxygen
in water. The excessive growth, or “blooms”, of algae promoted by these phosphates change the
water quality in lakes and ponds, and can kill fish.
Evapotranspiration – The process by which the Earth’s surface or soil loses moisture by
evaporation of water and its uptake and then transpiration from plants.
Extended detention basin – A detention basin where the runoff is stored beyond the time
normally required for attenuation. This provides extra time for natural processes to remove some
of the pollutants in the water.
Filter drain – A linear drain consisting of a trench filled with a permeable material, often with a
perforated pipe in the trench’s base to assist drainage and store and conduct water, but it may also
be designed to permit infiltration.
Filter strip – A vegetated area of gently sloping ground designed to drain water evenly off
impermeable areas and filter out silt and other particulates.
Filtration – The act of removing sediment or other particles from a fluid by passing it through a
filter.
Fines – Small soil particles less than 63 micron in size.
First flush – The initial runoff from a site/catchment following the start of a rainfall event. As
runoff travels over a catchment it will collect or dissolve pollutants and the “first flush” portion of
the flow may be the most contaminated as a result. This is especially true for intense storms and in
small or more uniform catchments. In larger or more complex catchments, pollution wash-off may
contaminate runoff throughout a rainfall event.
Floodplain – Land adjacent to a watercourse that would be subject to repeated flooding under
natural conditions. See the Environment Agency’s Policy and practice for the protection of groundwater
(EA, 1998b) for a fuller definition.
Flow control device – A device used to manage the movement of surface water into and out of an
attenuation facility, for example weirs.
Footway – Areas for pedestrians at the side of the carriageway.
Geocellular structure – A plastic box structure used in the ground often to attenuate runoff.
Geogrid – Plastic grid structure used to increase strength of soils or aggregates.
Geomembrane – An impermeable plastic sheet, typically manufactured from polypropylene, highdensity polyethylene or other geosynthetic material.
Geotextile – A plastic fabric that is permeable.
Green roof – A roof on whose surface plants can grow. The vegetated surface provides a degree of
retention, attenuation and treatment of rainwater, and promotes evapotranspiration.
Groundwater – Water that has percolated into the ground; it includes water in both the
unsaturated zone and the water table.
Groundwater protection zone (source protection zone) – Areas that influence water supply
boreholes where groundwater must be protected from pollution. These are defined by reference
to travel times of pollutants within the groundwater. See the Environment Agency’s Policy and
practice for the protection of groundwater (EA, 1998b) for specific details.
Gully – Opening in the road pavement, usually covered by metal grates, which allows water to
enter conventional drainage systems.
Highway drain – A conduit draining the highway. For highways maintainable at the public
expense it is vested in the highway authority.
Hydrograph – A graph illustrating changes in the rate of flow from a catchment over time.
Hydrology – The study of the waters of the Earth, their occurrence, circulation and distribution,
their chemical and physical properties and their reaction with the environment including their
relation to living things.
Impermeable – Does not allow water to pass through it.
Impermeable surface – An artificial non-porous surface that generates a surface water runoff after
rainfall.
Infiltration (to a sewer) – The entry of groundwater to a sewer.
Infiltration (to the ground) – The passage of surface water into the ground.
Infiltration basin – A dry basin designed to promote infiltration of surface water to the ground.
Infiltration device – A device designed to aid infiltration of surface water into the ground.
Infiltration trench – A trench, usually filled with permeable granular material, designed to
promote infiltration of surface water to the ground.
Integrated management practice – The concept of integrating SUDS into the design of a
development from the feasibility stage so that the development is designed to achieve the best
SUDS layout.
Interflow – Shallow infiltration to the soil, from where it may infiltrate vertically to an aquifer,
move horizontally to a watercourse or be stored and subsequently evaporated.
18
CIRIA C609
Initial rainfall loss – The amount of rain that falls on a surface before water begins to flow off the
surface.
Lagoon – A pond designed for the settlement of suspended solids.
Pathogen – An organism that causes disease.
Micropool – Pool at the outlet to a pond or wetland that is permanently wet and improves the
pollutant removal of the system.
Pavement – Technical name for the road or car park surface and underlying structure, usually
asphalt, concrete or blockpaving. Note that the path next to the road for pedestrians (colloquially
known as “pavement”) is formally called the footway.
Percentage runoff – The proportion of rainfall that runs off a surface. See also Runoff.
Permeability – A measure of the ease with which a fluid can flow through a porous medium. It
depends on the physical properties of the medium, for example grain size, porosity and pore
shape.
Permeable surface – A surface formed of material that is itself impervious to water but, by virtue
of voids formed through the surface, allows infiltration of water to the sub-base through the
pattern of voids, for example concrete block paving.
Pervious surface – A surface that allows inflow of rainwater into the underlying construction or
soil.
Piped system – Conduits generally located below ground to conduct water to a suitable location
for treatment and/or disposal.
Pollution – A change in the physical, chemical, radiological or biological quality of a resource (air,
water or land) caused by man or man’s activities that is injurious to existing, intended or potential
uses of the resource.
Pond – Permanently wet basin designed to retain stormwater and permit settlement of suspended
solids and biological removal of pollutants.
Porosity – The percentage of the bulk volume of a rock or soil occupied by voids, whether isolated
or connected.
Porous asphalt – An asphalt material used to make pavement layers pervious, with open voids to
allow water to pass through (previously known as pervious macadam).
Porous surface – A surface that infiltrates water to the sub-base across the entire surface of the
material forming the surface, for example grass and gravel surfaces, porous concrete and porous
asphalt.
Prevention – Site design and management to stop or reduce the pollution of impermeable
surfaces and reduce the volume of runoff by reducing impermeable areas.
Proper outfall – An outfall to a watercourse, public sewer and in some instances an adopted
highway drain. Under current legislation and case law, having a proper outfall is a prerequisite for
defining a sewer.
Public sewer – A sewer that is vested and maintained by the sewerage undertaker.
Rainfall event – A single occurrence of rainfall before and after which there is a dry period that is
sufficient to allow its effect on the drainage system to be defined.
Rainwater use system – A system that collects rainwater from where it falls rather than allowing it
to drain away, and includes water that is collected within the boundaries of a property, from roofs
and surrounding surfaces.
Retention pond – A pond where runoff is detained for a sufficient time to allow settlement and
possibly biological treatment of some pollutants.
Return period – The occurance frequency of an event. A 100-year storm refers to the storm that
occurs on average once every 100 years. In other words, its annual probability of exceedance is 1
per cent (1/100). A 500-year storm is the storm expected to occur once every 500 years, or has an
annual probability of exceedance equal to 0.2 per cent (1/500).
Road pavement – The load-bearing structure of a road (note that the path at the side of a road,
commonly referred to as a “pavement”, is properly called the footway).
Runoff – Water flow over the ground surface to the drainage system. This occurs if the ground is
impermeable or saturated, or if rainfall is particularly intense.
Runoff coefficient – A measure of the amount of rainfall converted to runoff.
Sewer – A pipe or channel with a proper outfall that takes domestic foul and/or surface water from
buildings and associated paths and hardstandings from two or more curtilages.
Sewerage undertaker – An organisation with the legal duty to provide sewerage services in an
area, including disposal of surface water from roofs and yards of premises. In England and Wales
these services are provided by water companies, in Scotland by water authorities and in Northern
Ireland by the Water Service of the Department of the Environment, NI.
Sewers for adoption – A guide agreed between sewerage undertakers and developers (through the
House Builders Federation) specifying the standards to which private sewers need to be
constructed to facilitate adoption.
Sewers for Scotland – Technically the same as Sewers for adoption, but varying in legal detail.
CIRIA C609
19
Single-size grading (single-size material) – The majority of the soil or aggregate particles are of one
nominal size, although there may be small proportions of other sizes.
Soakaway – A subsurface structure into which surface water is conveyed to allow infiltration into
the ground.
Source control – The control of runoff at or near its source.
Storm – An occurrence of rainfall, snow or hail.
Stormwater hotspot – Stormwater hotspots are defined in the USA as areas where land use or
activities may generate highly contaminated runoff, or where groundwater is an important
resource for drinking water abstraction.
Sub-base – The unbound layer of aggregate used immediately below the bound layers. It is laid on
the soil (or capping layer) to provide a stable foundation for construction of the road pavement.
Sub-catchment – A division of a catchment, allowing runoff management as near to the source as
is reasonable.
Subgrade – The soils onto which the road pavement is constructed.
SUDS – Sustainable drainage systems or sustainable (urban) drainage systems. A sequence of
management practices and control structures designed to drain surface water in a more
sustainable fashion than some conventional techniques (may also be referred to as SuDS).
Surface course – European standard description of the top layer of an asphalt pavement currently
known in UK as wearing course.
Surface water management train – The management of runoff in stages as it drains from a site.
Suspended solids – Undissolved particles in a liquid.
Swale – A shallow vegetated channel designed to conduct and retain water, but may also permit
infiltration; the vegetation filters particulate matter.
Time of entry – Time taken for rainwater to reach an inlet into the drainage system after hitting
the ground.
Treatment – Improvement of the quality of water by physical, chemical and/or biological means.
Treatment volume – The proportion of total runoff from impermeable areas captured and treated
to remove pollutants.
Turbidity - Reduced transparency of a liquid caused by the presence of undissolved matter.
Type 1 sub-base – Specification for the most commonly used sub-base material in conventional
pavements, from the Specification for highway works (Highways Agency et al, 1998a).
Void ratio – The ratio of open air space to solid particles in a soil or aggregate.
Watercourse – Any natural or artificial channel that conveys surface and/or ground water.
Weep garden – Bioretention system built into a terrace on a sloping site, where the water is
allowed to seep out of the face of the retaining wall that forms the terrace.
Wetland – A pond that has a high proportion of emergent vegetation in relation to open water.
20
CIRIA C609
Abbreviations
CIRIA C609
Ad
total area to be drained, including any adjacent impermeable area
Ab
base area of infiltration system below pervious pavement
AI
area of adjacent impermeable surface draining on to pervious surface
Ap
area of pervious pavement
AADT
annual average daily traffic
AASHTO
American Association of State Highway and Transportation Officials
ADAS
Agricultural Development and Advisory Service
AGS
Association of Geotechnical and Geo-environmental Specialists
AOS
apparent opening size
ASTM
American Society for Testing of Materials
BAP
biodiversity action plan
BMP
best management practice
BOD
biochemical oxygen demand
BSI
British Standards Institution
BRE
Building Research Establishment
C
shape factor
CBM
cement-bound material
CBR
Californian Bearing Ratio
CDM
Construction (Design and Management) Regulations 1984
CEN
Comité Européen de Normalisation (European Committee for Standardisation)
CESMM3
Civil Engineering Standard Method of Measurement, third edition
CIWEM
Chartered Institution for Water and Environmental Management
CMA
calcium magnesium acetate
COD
chemical oxygen demand
COPA
Control of Pollution Act 1974
CQA
construction quality assurance
CSO
combined sewer overflow
D
rainstorm duration
DBM
dense bitumen macadam
DEFRA
Department of the Environment, Food and Rural Affairs (UK)
DMRB
Design manual for roads and bridges (the Highways Agency, Scottish Executive
Development Department, the National Assembly for Wales and the Department for
Regional Development Northern Ireland)
DNAPL
dense non-aqueous-phase liquid
DTLR
Department for Transport, Local Government and the Regions (UK)
Ds
effective particle size diameter
D10
soil particle size such that 10 per cent of the sample consists of particles having a
smaller nominal diameter
D15
soil particle size such that 15 per cent of the sample consists of particles having a
smaller nominal diameter
D50
soil particle size such that 50 per cent of the sample consists of particles having a
smaller nominal diameter
D85
soil particle size such that 85 per cent of the sample consists of particles having a
smaller nominal diameter
e
void ratio of aggregate
E
Young’s Modulus
EA
Environment Agency (England and Wales)
EMC
event mean concentration
EPA
Environmental Protection Agency (USA)
EQS
environmental quality standard
21
22
FEH
Flood estimation handbook, produced by Institute of Hydrology
FHWA
Federal Highway Administration
FLL
Forschungsgesellschaft Landschaftsentwicklung Landschaftsbau e.V.
Gs
specific gravity of soil or aggregate particles
h
Thickness of aggregate or other storage medium below pervious pavement
hmax
maximum depth of water that will occur in the storage medium
i
rainfall intensity
IMP
integrated management practice
IOH
Institute of Hydrology (now Centre for Ecology and Hydrology)
IRL
initial runoff loss
k
coefficient of permeability
LNAPL
light non-aqueous-phase liquids
MSA
motorway service area
MTBE
methyl tert butyl ether
NSWG
National SUDS Working Group
n
porosity of soil or aggregate
O95
apparent opening size
PAH
polycyclic aromatic hydrocarbons
PPG 3
Planning Policy Guidance 3 Housing
PPG 25
Planning Policy Guidance 25 Development and flood risk
Q
flow through outlet from storage below pavement
q
infiltration coefficient
r
rainfall ratio
SEPA
Scottish Environment Protection Agency
SNIFFER
Scotland and Northern Ireland Forum for Environmental Research
SSSI
site of special scientific interest
SUDS
sustainable drainage systems
T
return period for storm event
TON
total oxidised nitrogen
TPH
total petroleum hydrocarbons
TRL
Transport Research Laboratory (formerly Transport and Road Research
Laboratory,TRRL, and Road Research Laboratory, RRL)
TSS
total suspended solids
USEPA
United States Environmental Protection Agency
V
maximum storage volume for water below pervious pavement
Vt
treatment volume
VOC
volatile organic compound
γd
dry unit weight of soil or aggregate
γw
unit weight of water
µ
viscosity
ν
Poisson’s ratio
WQO
water quality objective
WQS
water quality standard
CIRIA C609
Foreword
This publication is intended for use by clients, landscape architects, consulting
engineers, local authorities, architects, highway authorities, environmental regulators,
planners, sewerage undertakers, contractors, developers and other organisations
involved in the provision or maintenance of surface water drainage to new and existing
developments. It discusses the critical issues that must be considered when designing,
constructing and maintaining SUDS schemes to effectively manage rainwater runoff
from development sites.
The first part of the book includes general information relevant to all SUDS
techniques. The second part contains detailed discussions about the design and
performance of each technique.
To help the reader navigate the book, two flow charts are provided on the following
pages (the SUDS information guide and the SUDS design process). The first identifies
where information is located within the document, based on typical questions that a
reader may want answered. The second identifies those sections of the book that are
relevant to the various stages of the SUDS design process.
Part 1
Chapter 1 (Introduction) introduces the concepts of SUDS and discusses the background
to the development of a concept that deals with the management of surface water
runoff. It identifies the relationship between this book and publications from CIRIA
and other organisations.
Chapter 2 (SUDS concepts) identifies the management train concept, discusses how to
integrate SUDS into site design and introduces the different techniques available. It
gives information on the use of SUDS on brownfield sites (or sites where natural
contamination is present). It also looks at the use of SUDS in conjunction with
rainwater harvesting schemes.
Chapter 3 (Stormwater pollution) deals with stormwater pollutants that are either
discharged to watercourses and sewers or infiltrated into the ground from SUDS
schemes. It looks at the mechanisms and processes that occur within SUDS to improve
water quality. This section also identifies applicable legislation and the issues that must
be addressed to avoid causing pollution of either surface or groundwater. It describes
how different combinations of techniques can be assessed to give the optimum
efficiency for the management train.
Chapter 4 (Rainfall and runoff) is concerned with the assessment of greenfield runoff
rates and runoff from developed sites. It identifies the criteria that should be
considered when designing SUDS. This approach requires consideration of runoff from
events with a range of annual probabilities (or return periods) and also requires careful
consideration of overland flow routes during events that exceed the design criteria of
the system (also known as flood routeing).
Chapter 5 (General SUDS design) discusses the general design issues that relate to all
SUDS features, including the make-up of design teams, guidance on the choice of
techniques to meet site-specific constraints and design information. It also explains how
SUDS may be designed to maximise environmental benefits and to meet the required
health and safety standards.
CIRIA C609
23
Chapter 6 (Construction of SUDS) includes information on the education of site staff and
how the construction programme may need to be changed to allow for the SUDS. It
recommends an independent inspection regime during construction.
Chapter 7 (Management) provides information on the maintenance regimes required.
Chapter 8 (Economics of SUDS) discusses the factors that should be included in any cost
analysis of SUDS.
Part 2
Chapter 9 (Technical data for SUDS techniques) offers an in-depth discussion of the
performance for each individual SUDS technique and provides best practice guidance
for the design, construction and operation of SUDS.
Appendix 1 includes a decision matrix and flow chart to assist in selecting SUDS
techniques.
Appendix 2 provides design examples.
Appendix 3 is a design information checklist.
Appendix 4 provides case studies (for further case studies see the CIRIA website,
<www.ciria.org>).
Appendix 5 discusses the planting for SUDS.
Appendix 6 gives a design accreditation checklist.
Appendix 7 gives a construction inspection checklist.
24
CIRIA C609
SUDS information guide
CIRIA C609
25
26
CIRIA C609
Part 1
1
General issues
2
What does this part include?
General introduction to the concept of sustainable drainage systems (SUDS) and a
description of the techniques available (Chapter 1).
A discussion of how SUDS might be used on brownfield sites (Section 2.6).
3
General information on pollutant removal and the different mechanisms that occur with
SUDS techniques (Chapter 3).
A discussion of the environmental legislation that affects SUDS designers, builders,
operators and owners (Section 3.2).
4
General information on the assessment and modelling of rainfall and runoff for SUDS
techniques (Chapter 4).
Description of how site-specific constraints affect the choice of techniques (Section 5.2).
A discussion of the design information required for SUDS (Section 5.4).
5
Information on how to maximise the wildlife benefits of SUDS (Section 5.6).
General issues relating to the construction of SUDS (Chapter 6).
General issues relating to the maintenance of SUDS (Chapter 7).
Information on the costs associated with SUDS schemes (Chapter 8).
6
7
8
CIRIA C609
27
1
Introduction
This chapter provides information for all readers of this technical report.
It describes the purpose and scope of the book and, for those readers not familiar with
sustainable drainage systems (SUDS), gives a general introduction.The chapter also
describes the important concepts and benefits that may be gained by using the techniques.
It provides other sources of information on SUDS techniques.
1.1
WHAT ARE SUSTAINABLE DRAINAGE SYSTEMS?
Sustainable drainage systems (SUDS) are increasingly being used to mitigate the flows
and pollution from runoff. The philosophy of SUDS is to replicate as closely as possible
the natural drainage from a site before development and to treat runoff to remove
pollutants, so reducing the impact on receiving watercourses. This requires a reduction
in the rate and volume of runoff from developments, combined with treatment to
remove pollutants as close to the source as possible. They can also provide other
environmental benefits such as wildlife habitat, improved aesthetics or community
resource (Figure 1.1).
Figure 1.1
SUDS
SUDS permit a very flexible approach to be taken to drainage, and the techniques
available range from soakaways to large-scale detention basins. The individual
techniques are used in series in a management train designed to meet the site-specific
constraints (Section 2.1). The techniques are not new, and many have been successfully
used both in the UK and worldwide for at least 20 years, especially in the USA where
they are known as best management practices (BMPs). A wealth of knowledge about
their performance has been developed, particularly in the USA and mainland Europe.
Over the past five years, a comprehensive SUDS research and monitoring programme
has been undertaken in the UK, in Scotland in particular, which is beginning to yield a
lot of performance data on systems in the UK climate.
28
CIRIA C609
Some common misconceptions about SUDS and what they comprise include:
z
SUDS is the use of soakaways
z
SUDS cannot be used on clay soils
z
SUDS is the use of ponds and wetlands
z
SUDS is storing rainwater on site and allowing it to flow out at a restricted rate
z
SUDS does not include pipes.
1
None of these statements is entirely correct. The SUDS approach to drainage involves
controlling the runoff from development sites so that it mimics greenfield runoff and
maintains the natural drainage patterns, as far as possible. SUDS should also enhance
the local environment.
To achieve this, a treatment or management train is required (Section 2.2) that
comprises one or more techniques. These may or may not include soakaways, ponds
and wetlands or pipes. The management train may also include techniques such as
good site management to prevent pollution. Several SUDS techniques will be needed to
reduce the volume of runoff and treat pollution.
A drainage set-up that does not provide a management train to meet all three criteria
of quality, quantity and amenity may not be a sustainable drainage system in the
strictest sense, although on some sites specific factors it may be that one criterion is
more prominent than the others. A SUDS approach to drainage can and should be
applied to all sites, although site constraints may limit the potential for a truly
sustainable solution (Section 5.5).
Sustainable drainage systems may also incorporate storage for water reuse. (The
permanent storage volume will generally be additional to any storage volume required
to control runoff rates, unless a continuous rate of use can be guaranteed.) Further
information on the design of systems for rainwater reuse can be found in CIRIA
publication C539 (Leggett et al, 2001).
1.2
BENEFITS OF SUDS
It is widely accepted that the use of SUDS, as opposed to conventional drainage
systems, generates several benefits (Martin et al, 2000a, 2000b and 2001). Appropriately
designed, constructed and maintained SUDS can mitigate many of the adverse effects
of urban stormwater runoff on the environment.
CIRIA C609
1
Lowering peak flows to watercourses or sewers, thereby reducing the risk of
flooding downstream.
2
Reducing volumes and frequency of water flowing directly from developed sites to
watercourses or sewers, to replicate natural land drainage and reduce flood risk.
3
Improving water quality over conventional surface water sewers by removing
pollutants from sources such as cleaning activities (vehicles, windows), wear from
tyres, oil leaks from vehicles or atmospheric fallout from combustion (in rural areas
this can include runoff from fields where fertilisers and biocides are used).
4
Improving amenity through the provision of features such as wildlife habitat.
5
Reducing the number of times that combined sewer overflows (CSOs) operate and
discharge polluted water to watercourses.
6
Replicating natural drainage patterns so that changes to base flows are minimised.
7
Finally, by increasing base flow to watercourses (through slow release of water).
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3
4
5
6
7
8
The UK Government has recognised the benefits in relation to flooding, in PPG 25,
Development and flood risk (DTLR, 2001).
Imaginative site design allows SUDS to be incorporated into almost any development,
provided the risk of watercourse or groundwater contamination can be managed to
acceptable levels. There is no reason why SUDS cannot be incorporated into urban
developments where space is restricted. To achieve this, the SUDS design should be
integrated into the site layout at the feasibility stage (Goransson, 1997 and Piel et al,
1999). Allocating space for SUDS was not a problem on Scottish developments owing to
the production of innovative solutions for cramped sites (Jefferies, 2000). In these
situations it is helpful to use SUDS features such as proprietary modular treatment
systems and green roofs, or to implement rainwater harvesting. It should be
remembered that public open space can be used for storing runoff in extreme storm
events.
One aspect of SUDS that has received little attention in the UK is the “pond premium”
(USEPA, 1995 and Schueler, 2000m). Evidence from the USA has shown there is a
price premium on waterfront properties where SUDS ponds are incorporated into new
developments. The premium in the USA is greatest for houses, flats or offices
overlooking a well-designed and well-maintained pond or wetland with an area greater
than 0.4 ha. This effect was also observed at a development in Scotland (McKissock et
al, 1999) although the economic benefits experienced in the US were greater. There
are other economic benefits from integrating SUDS into the overall site design, such as
reduced construction costs (New Jersey Department of Environmental Protection,
2000), especially where impervious areas are reduced.
In the broader planning of the urban landscape, the use of SUDS for water storage for
reuse may help with the maintenance of plants, trees and shrubs. The use of stored
rainwater, which is often less acidic (and cheaper) than treated mains water, is another
benefit available through the appropriate use of SUDS, with the potential to reduce
demand for potable water.
Maintenance requirements for SUDS are no more onerous (and often less so) than
those for conventional drainage, but they are different (Section 7.2). This should not
prevent the selection of SUDS, as the other advantages in flood control, water reuse
and groundwater recharge may have greater benefits, both locally and more widely in
the environment.
1.3
BACKGROUND TO PROJECT
Organisations including DEFRA, Environment Agency, SEPA and Environment
Heritage Services (Northern Ireland) widely promote SUDS as a more sustainable
alternative to traditional drainage schemes. There has been a growth in the number of
SUDS schemes implemented since 1995, especially in Scotland, where nearly 4000
systems have been installed. Nonetheless, for many involved in site development there
is scope for increased knowledge about the technical detail of SUDS, including the
available techniques and, in particular, the hydraulic, structural and water quality issues
that need to be considered during their design life (including the life-span itself). To
date there has been no wide-scale implementation of the management train, one of the
key concepts of SUDS, so the valuable amenity benefits SUDS could deliver have not
been fully realised.
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CIRIA C609
CIRIA and other organisations in the UK have produced general design guidance for
SUDS systems, but consultation with a wide range of stakeholders, including clients,
designers and contractors, has identified the need for more detailed design guidance.
This book and its associated research project address this by providing more detailed
information than has been previously available for the individual SUDS techniques,
drawn from UK and international sources. This should encourage even wider uptake
of SUDS and ensure greater consistency in design in the UK as a whole.
1.4
PURPOSE AND SCOPE OF THIS BOOK
This technical guide informs readers about the appropriate approach to take for the
successful design and construction of SUDS. Using the best available information, it also
aims to improve readers’ understanding of the hydraulic, structural and water quality
performance issues of SUDS techniques and components. The current level of knowledge
relating to some of the design and performance issues varies, and in some cases
rigorous analysis is not possible. This is true in other areas of engineering and should
not be a barrier to the use of SUDS. Where necessary, conservative assumptions and
judgement based on observed performance can be used to produce a successful design.
The book provides sufficient design information to enable both specifiers and
constructors of SUDS to adopt a more scientifically-based approach to the design of a
stormwater treatment or management train. SUDS management trains designed in
accordance with this publication should:
z
deal with stormwater by helping to maintain runoff rates and volumes from
developments at or close to pre-development levels
z
minimise the risk of pollution to controlled waters
z
provide improved public amenity
z
be appropriate for the site.
The book does not cover the design of sustainable drainage schemes for major
highways under the control of the Highways Agency. The Highways Agency in England
and Wales does not recognise the term “sustainable drainage system” and refers to a
range of sustainable highways drainage practices, including vegetative treatment. It
does not allow the use of pervious pavements for source control on major roads (Pratt
et al, 2002). Readers should refer to the Design manual for roads and bridges (Highways
Agency et al, 2001) for design advice for SUDS for major roads controlled by the
Highways Agency. This does not preclude the use of SUDS on other highways.
In Scotland the use of SUDS on highways is an accepted drainage technique.
3
5
6
7
SOURCES OF INFORMATION
The book has been compiled from information gained from a worldwide literature
review covering all aspects of SUDS. Where possible, UK data has been used, in
particular drawing on the wealth of monitoring that has been undertaken in Scotland.
The literature search revealed a strong weighting towards the USA, where monitoring
and assessment of SUDS techniques has been carried out for more than 15 years.
CIRIA C609
2
4
This book is not intended be a detailed guide to the hydraulic or structural design of
drainage systems. Only those aspects of hydraulic and structural design directly affected
by the use of SUDS are discussed. Where necessary, reference is made to other
publications describing design methods that can be applied to SUDS.
1.5
1
31
8
To obtain the widest possible range of opinions, views have been sought from a diverse
range of consultants, contractors and manufacturers/distributors.
The research has been reviewed and agreed by a dedicated steering group comprising
experienced individuals from a diverse range of disciplines.
1.6
ASSOCIATED PUBLICATIONS
This book provides independent best practice guidance on the development of a more
scientific approach to the design, construction and maintenance of SUDS techniques
and components. It forms part of a suite of CIRIA publications relating to the design
and construction of SUDS. Published titles are listed below, by date of publication.
z
Design of flood storage reservoirs, Book 14 (Hall et al, 1993). A design guide that can
be applied to SUDS ponds.
z
Control of pollution from highway drainage discharges, Report 142 (Luker and
Montague, 1994). Information on the water quality of highway runoff.
z
Infiltration drainage, manual of good practice, Report 156 (Bettess, 1996). Provides a
method of rainfall estimation and a design method for infiltration below pervious
pavements.
z
Review of the design and management of constructed wetlands, Report 180 (Nuttall et al,
1997). Design information for wetlands for water treatment.
z
Sustainable urban drainage systems – design manual for Scotland and Northern Ireland,
publication C521 (Martin et al, 2000a). Background information on design of
pervious surfaces, as one element of a sustainable urban drainage system.
z
Sustainable urban drainage systems – design manual for England and Wales, publication
C522 (Martin et al, 2000b). Background information on design of pervious
surfaces, as one element of a sustainable urban drainage system.
z
Sustainable urban drainage systems – best practice manual, publication C523 (Martin et
al, 2001c). Background information on pervious surfaces, as one element of a
sustainable urban drainage system.
z
Source control using constructed pervious surfaces, publication C582 (Pratt et al, 2002).
Technical review of existing information on pervious surfaces, which discusses the
hydraulic, structural and water quality issues.
z
Model agreements for sustainable water management systems. Model agreements for SUDS,
publication C625 (Shaffer et al, 2004). Basic advice on the use and development of
model operation and maintenance agreements for SUDS alongside simple
guidance on their incorporation in developments.
Further information on the publications and general information about SUDS is
provided on the CIRIA website, <www.ciria.org>, together with additional case studies.
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CIRIA C609