CIRIA SuDS Manual 2015 PDF

C753 The SuDS This guidance covers the planning, design, construction and maintenance of Sustainable Drainage Systems (SuDS) to assist with their effective implementation wi...

C753 The SuDS This guidance covers the planning, design, construction and maintenance of Sustainable Drainage Systems (SuDS) to assist with their effective implementation within both new and existing developments. It looks at how to maximise amenity and biodiversity benefits, and deliver the key objectives of managing flood risk and water quality. There is also supporting information covering topics such as materials, landscape design, maintenance, community engagement and costs and benefits. Manual The information presented in this publication is a compendium of good practice, based on existing The SuDS Manual guidance and research both in the UK and internationally, and the practical experience of the authors, project steering group and industry. This guidance provides the framework for designing SuDS with confidence and to maximise benefits. Its contents are relevant for a wide-range of professions and roles and it highlights that through engagement and collaboration SuDS can be integrated into the design of urban areas, to create high quality places for future generations. The key message is that SuDS should be designed to maximise the opportunities and benefits that can be secured from surface water management. Project funders (see inside back cover) ACO Llywodraeth Cymru/Welsh Government Campbell Reith London Drainage Engineering Group Concrete Pipeline System Association National House Builders Council DARD Rivers Agency Northern Ireland Northern Ireland Environment Agency Department for Environment, Food and Rural Permavoid Affairs Polypipe Dŵr Cymru/Welsh Water Scottish Environment Protection Agency Environment Agency Stormwater Management Highways England WSP Parsons Brinckerhoff Hydro International XP Solutions CIRIA C753 9 780860 177593  Who we are Established in 1960, CIRIA is a highly regarded, industry-responsive, not for profit research and information association, which encompasses the construction and built environment industries. CIRIA operates across a range of market sectors and disciplines, providing a platform for collaborative projects and dissemination by enhancing industry performance, and sharing knowledge and innovation across the built environment. As an authoritative provider of good practice guidance, solutions and information, CIRIA operates as a knowledge- base for disseminating and delivering a comprehensive range of business improvement services and research products for public and private sector organisations, as well as academia. How to get involved CIRIA manage or actively participate in several topic-specific learning and business networks and clubs: zzCore membership zzProject funding Allows your employees to assist with the development of Project funders influence the direction of the research and access to good practice guidance, formal networks, and gain early access to the results. facilitation, conferences, workshops and training. zzLACL (Local Authority Contaminated Land zzAssociate membership Network) Allows your employees to access CIRIA’s services. LACL helps local authorities address responsibilities Members are able to access exclusive content via the under Part IIA of the Environmental Protection Act 1990. CIRIA website. zzEMSAGG (European Marine Sand and Gravel zzThe CIRIA Network Group) A member-based community where clients and CIRIA provides secretariat support to EMSAGG, including professionals meet, develop and share knowledge management of the Group’s conferences, workshops and about specific topics relevant to construction and the website and producing its newsletter. built environment. zzBRMF (Brownfield Risk Management Forum) zzCIRIA Books Club Promoting sustainable and good practice in brownfield Members can buy most CIRIA publications at half projects in the UK. price and can attend a range of CIRIA conferences at reduced rates. Where we are Discover how your organisation can benefit from CIRIA’s authoritative and practical guidance – contact us by: Post Griffin Court, 15 Long Lane, London, EC1A 9PN, UK Telephone +44 (0)20 7549 3300 Fax +44 (0)20 7549 3349 Email [email protected] Website www.ciria.org (for details of membership, networks, events, collaborative projects and to access CIRIA publications through the bookshop) CIRIA C753 London, 2015 The SuDS Manual B Woods Ballard HR Wallingford S Wilson The Environmental Protection Group H Udale-Clarke HR Wallingford S Illman Illman Young Landscape Design T Scott Grant Associates R Ashley Ecofutures/University of Sheffield R Kellagher HR Wallingford Griffin Court, 15 Long Lane, London, EC1A 9PN Tel: 020 7549 3300 Fax: 020 7549 3349 Email: [email protected] Website: www.ciria.org  CIRIA SuDS Manual 2015 The SuDS Manual Woods Ballard, B, Wilson, Udale-Clarke, H, Illman, S, Scott, T, Ashley, R, Kellagher, R CIRIA C753 © CIRIA 2015 RP992 ISBN: 978-0-86017-760-9 British Library Cataloguing in Publication Data A catalogue record is available for this book from the British Library Keywords Sustainable drainage, flood risk management, water quality, amenity, biodiversity, environmental good practice, sustainable construction, urban hydrogeology, rivers and waterways Reader interest Classification Sustainable drainage systems Availability Unrestricted (SuDS) are designed to Content Technical guidance maximise the opportunities and benefits we obtain from Status Committee-guided surface water management. User Developers, landscape architects, architects, consulting SuDS can deliver four main engineers, planners, local authorities, lead local benefits by improving the way flood authorities, highway authorities, environmental we manage water quantity, regulators, sewerage undertakers and other water quality, amenity and organisations involved in the provision and maintenance biodiversity of surface water drainage to new and existing developments Published by CIRIA, Griffin Court, 15 Long Lane, London, EC1A 9PN, UK This publication is designed to provide accurate and authoritative information on 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. 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. If you would like to reproduce any of the figures, text or technical information from this or any other CIRIA publication for use in other documents or publications, please contact the Publishing Department for more details on copyright terms and charges at: [email protected], Tel: 020 7549 3300. ii The SuDS Manual  CIRIA SuDS Manual 2015 Summary This guidance covers the planning, design, construction and maintenance of Sustainable Drainage Systems (SuDS) to assist with their effective implementation within both new and existing developments. It looks at how to maximise amenity and biodiversity benefits, and deliver the key objectives of managing flood risk and water quality. There is also supporting information covering topics such as materials, landscape design, maintenance, community engagement and costs and benefits. The information presented in this publication is a compendium of good practice, based on existing guidance and research both in the UK and internationally, and the practical experience of the authors, project steering group and industry. This guidance provides the framework for designing SuDS with confidence and to maximise benefits. Its contents are relevant for a wide-range of professions and roles and it highlights that through engagement and collaboration SuDS can be integrated into the design of urban areas, to create high quality places for future generations. The key message is that SuDS should be designed to maximise the opportunities and benefits that can be secured from surface water management. The SuDS Manual iii  CIRIA SuDS Manual 2015 Foreword When the first SuDS Manual was published in 2007, SuDS was still in its infancy in the UK. Technical advice on design and construction was sparse and spread across many separate publications. For the first time the original SuDS Manual placed this information in one place, making it a valuable resource for anyone engaged in SuDS delivery. Yet for guidance and examples we still had to rely a great deal on schemes from other countries where the implementation of SuDS was far more advanced. Since that time SuDS implementation has moved on a great deal in the UK. There are now plenty of examples from all the UK nations that demonstrate the benefits to be gained from SuDS and these offer reliable and detailed recommendations for their planning, design, construction, maintenance and operation. The world of SuDS has indeed moved on. So it is timely that a new edition of the SuDS Manual is now available. Not only does this new edition update the extensive technical information, it includes new guidance on SuDS components and the delivery of SuDS in a variety of situations. It should be clear from the engaging examples in this Manual that SuDS provide real benefits to society and to the environment, moving surface water from a problem to a valuable resource. For the first time the guidance includes how to plan for and manage extreme rain events so that communities can be more resilient to flooding. There are some excellent examples that demonstrate how good design can deliver far more appealing places in which to live and work, and this, in time, should lead to properties that have improved value and are easier to insure. Provided that drainage is considered early enough in the outline design of a new development then there is no reason why SuDS should not become the norm everywhere. The Manual is primarily aimed at UK applications, though it will be of interest to all engaged in drainage work globally. It recognises the need for better information and engagement for those involved in the development process, from planners, landscape architects, designers, engineers, architects and in some instances the community. It is structured in a way that allows easy access whether it be for high level appreciation of the concepts only, or for detailed design guidance. I am grateful to the members of the project steering group who reviewed and contributed to this important work, and to the energy and effectiveness of the project team. They have delivered a master-piece of technical guidance that will last for many years. I thoroughly recommend it to you. David Balmforth Chairman, project steering group iv The SuDS Manual  CIRIA SuDS Manual 2015 Acknowledgements This publication is the result of CIRIA Research Project (RP)992. Authors Bridget Woods Ballard MA MSc CEng MICE Bridget Woods Ballard is a principal engineer at HR Wallingford. She has more than 20 years’ experience in hydrology and sustainable flood risk management and has been a key contributor to research on SuDS costs, maintenance, performance and liabilities for regulators, the water industry and other private sector organisations. She was the principal author of the previous SuDS Manual (CIRIA C697) and since then has drafted BS 8582:2013, and has advised English and Welsh governments during the development of their national standards and associated guidance. Steve Wilson MSc BEng CEng MICE CEnv CSci CWEM MCIWEM FGS Steve is technical director of the Environmental Protection Group Limited. He is a UK registered ground engineering adviser and has had a wide ranging career in geotechnical and environmental engineering. Steve has demonstrated that SuDS can be used on any site in the UK to provide cost-effective surface water drainage systems. Steve also undertakes research and development work that helps to dispel a lot of the myths that surround the use of SuDS. Most recently Steve has been busy helping landscape architects successfully design retrofit schemes in a number of different locations. Helen Udale-Clarke BEng(Hons) MPhil Helen is a principal engineer at HR Wallingford. She has more than 20 years’ experience in drainage, flood and climate change risk assessments, with a particular interest in the development of guidance and working with stakeholders. Sue Illman BA DipLA GradDipCons(AA) PPLI Hon FSE Hon Fellow (UoG) Sue is managing director of Illman Young, a landscape architectural practice based in Cheltenham, and was president of the Landscape Institute from 2012–2014. Sue’s practice works across most planning and development sectors, but she is probably best known for her advocacy work promoting integrated water management and SuDS through inter-professional collaboration. The integration of grey, green and blue in urban landscapes has never been more relevant, and is a subject that Sue continues to promote. In addition to her current role, she is a champion for flood mitigation and resilience on behalf of the Construction Industry Council (CIC). Tamasine Scott MA (Hons) LArch CMLI Tamasine is a landscape architect and senior associate of Grant Associates. She has led a variety of large and small projects, from cooled conservatories and university campuses in Singapore to secondary schools in the UK and urban parks in Spain. SuDS has become second nature in her design process, integrating the functional requirements of water management within playful and thriving landscapes. Tamsine is fascinated by using SuDS in the design process to integrate landscape, architecture and engineering, thereby achieving diverse landscapes that ultimately enrich experience. Richard Ashley BSc MPhil CEng MICE Richard is a civil engineer with 50 years’ urban drainage experience in practice and as an academic. He is Emeritus professor of urban water, University of Sheffield, adjunct professor, Lulea Technical University The SuDS Manual v  CIRIA SuDS Manual 2015 and professor of flood resilience at UNESCO IHE, Delft. He was also recipient of the (IWA/IAHR) Joint Committee on Urban Drainage triennial career achievement award in 2014 and for research into sustainable water systems in 2008. Richard has worked on over 500 publications, advising governments and international institutions on urban water, flooding and water sensitive urban design. Richard Kellagher BEng MSc CEng MICE MCIWEM Richard Kellagher is a technical director at HR Wallingford. He has been involved in drainage and SuDS research and has produced a number of guidance documents on drainage-related issues for both CIRIA and HR Wallingford. Richard’s experience in drainage includes research projects for UKWIR, sewerage modelling, expert witness work on flooding incidents, master plans for cities overseas and leading or participating in a number of European research projects. Project steering group Following CIRIA’s usual practice, the project was guided by a project steering group (PSG) that comprised: Deonie Allen* Heriot Watt University David Balmforth (chair) MWH Global Andy Bailey Highways England Adam Baylis Environment Agency David Bliss Environment Agency Sally Boorer National House Building Council Simon Boots Campbell Reith Jo Bradley* Environment Agency Bob Bray Robert Bray Associates Simon Bunn Cambridgeshire City Council Bronwyn Buntine Kent County Council Phil Chatfield Llywodraeth Cymru Welsh Government Peter Close Northern Ireland Environment Agency Stuart Crisp Concrete Pipeline Systems Association Owen Davies Royal Borough Greenwich (formerly London Borough Lambeth)/London Drainage Engineering Group Paul Davies* Arup Peter Dawson Essex County Council Christopher Digman* MWH Global Alison Duffy* University of Abertay Martin Fairley ACO Grant Gahagan Department for Environment, Food and Rural Affairs Jonathan Glerum Anglian Water Rod Green Environmental Protection Group (formerly Polypipe) Andrew Hemingway* Scottish Environment Protection Agency Mike Henderson Aecom Ian Holt London Borough of Haringey Philip Hulme Environment Agency Jeremy Jones Atkins (formerly Dŵr Cymru Welsh Water) Andrew Leadbetter Peterborough City Council Lian Lundy* University of Middlesex Peter Martin Black & Veatch vi The SuDS Manual  CIRIA SuDS Manual 2015 Netsanet Mebrate XP Solutions Anthony McCloy McCloy Consulting Helen McHollan Illman Young Landscape Design Brian Morrow* Independent (formerly United Utilities) Stuart Nelmes BWB Consulting Roger Nowell Sheffield City Council Fola Ogunyoye Royal HaskoningDHV John Oldfield Bedford Group of Internal Drainage Boards Chris Patmore WSP Parsons Brinckerhoff Warren Peppard Lincolnshire County Council David Porter* DARD Rivers Agency Northern Ireland Judith Puckmayr Robert Bray Associates (formerly Illman Young Landscape Design) Neill Robinson-Welsh Stormwater Management Brian Smith Yorkshire Water Jason Shingleton Polypipe Amy Shoesmith Dŵr Cymru Welsh Water David Singleton DSA Environment & Design Alex Stephenson Hydro International Kevin Tidy Bracknell Forest Chryse Tinsley* Leicester City Council Zorica Todorovic* Atkins Phil Tomlinson Permavoid Michael Vout Telford and Wrekin Council David Watkins Cornwall County Council Les Watson Scottish Environment Protection Agency *corresponding members CIRIA Project managers Paul Shaffer Project director Suzanne Simmons Project manager Sirio D’Aleo Project assistant Paul Beverley Editor Clare Drake Publications manager Project funders ACO Llywodraeth Cymru Welsh Government Campbell Reith London Drainage Engineering Group Concrete Pipeline System Association NHBC Foundation DARD Rivers Agency Northern Ireland Northern Ireland Environment Agency Department for Environment, Food and Rural Permavoid Affairs Polypipe Dŵr Cymru Welsh Water Scottish Environment Protection Agency Environment Agency Stormwater Management Highways England WSP Parsons Brinckerhoff Hydro International XP Solutions The SuDS Manual vii  CIRIA SuDS Manual 2015 Other contributors As well as recognising the significant additional contributions from the project team of HR Wallingford, The Environmental Protection Group, Illman Young Landscape Design, Grant Associates and Ecofutures, CIRIA would like to recognise the contributions and support from: Bob Allen Aggregate Industries Julia Baker Parsons Brinckerhoff Alan Bamforth ABG Jessica Bastock London Borough of Lambeth (formerly London Borough of Tower Hamlets) Victoria Boorman London Borough of Hillingdon Victoria Brayshaw Dudleys Consulting Engineers (formerly Redrow) Tom Butterworth Natural England Brian D’Arcy University of Abertay Samantha Davenport Natural England Luke Engleback Studio Engleback Duncan Faulkener JBA Consulting Dusty Gedge Green Roof Consultancy Martina Girvan Arcadus (formerly Aecom) Gary Grant Green Roof Consultancy Keith Harvey Aggregate Industries Paul Hlinovsky BMT WBM Gordon Hunt Oxfordshire County Council Anne Jaluzot Trees and Design Action Group Sue James Trees and Design Action Group Kirsten Johnstone Environment Agency David Jones Llywodraeth Cymru Welsh Government Lian Lundy Middlesex University Gordon Mitchell University of Leeds Martin Moss Natural England Terry Nash UK Rainwater Management Association Keith Oldham ACO (formerly ABG) Helen O’Brien Leicester City Council Tim O’Hare Tim O’Hare Associates Martin Osborne Mouchel Kevin Reid Greater London Authority Mike Revitt University of Middlesex Santi Santhalingam Highways England Ruth Thorp Grant Associates Tony Weber BMT WBM Mike Whitehead Highways England Peter Worrall Penny Anderson Associates viii The SuDS Manual  CIRIA SuDS Manual 2015 Contents Summary...................................................................................... iii Foreword...................................................................................... iv Acknowledgements............................................................................. v Part A Introduction to the SuDS Manual.......................................................... 2 Executive summary.................................................................... 5 Introduction to the SuDS Manual........................................................ 11 Part B Philosophy and approach............................................................... 16 1 The philosophy of SuDS........................................................... 18 1.1 Delivering multiple benefits............................................... 19 1.2 Managing surface water runoff............................................ 21 1.3 Delivering resilience..................................................... 24 1.4 Making developments more sustainable.................................... 26 1.5 Complying with legislation and regulations.................................. 26 1.6 The SuDS design philosophy.............................................. 27 1.7 References............................................................ 30 2 Introducing the SuDS design approach.............................................. 32 2.1 The principle and objectives of SuDS design................................. 33 2.2 SuDS design criteria..................................................... 34 2.3 The role of the designer.................................................. 35 2.4 Assessing and approving SuDS schemes.................................... 35 3 Designing for water quantity....................................................... 36 3.1 Water quantity design objective........................................... 37 3.2 Water quantity design criteria............................................. 39 3.3 Water quantity design standards.......................................... 44 3.4 References............................................................ 48 4 Designing for water quality........................................................ 50 4.1 Water quality design objective............................................. 51 4.2 Water quality design criteria.............................................. 56 4.3 Water quality design standards............................................ 59 4.4 References............................................................ 64 5 Designing for amenity............................................................ 66 5.1 Amenity design objective................................................. 67 5.2 Amenity design criteria................................................... 70 5.3 References............................................................ 78 6 Designing for biodiversity......................................................... 80 6.1 Biodiversity design objective.............................................. 81 6.2 Biodiversity design criteria................................................ 83 6.3 SuDS design characteristics to support biodiversity........................... 89 6.4 References............................................................ 91 Part C Applying the approach.................................................................. 92 7 The SuDS design process......................................................... 94 7.1 Introduction............................................................ 95 7.2 SuDS and the planning system............................................ 96 7.3 SuDS design and stakeholder engagement.................................. 99 7.4 Stage 1: Setting strategic SWM objectives.................................. 99 7.5 Stage 2: Conceptual design.............................................. 100 7.6 Stage 3: Outline design................................................. 118 The SuDS Manual ix  CIRIA SuDS Manual 2015 7.7 Stage 4: Detailed design................................................ 123 7.8 References........................................................... 126 8 Designing for specific site conditions............................................... 126 8.1 Introduction........................................................... 129 8.2 Contaminated soils or groundwater below the site........................... 129 8.3 High groundwater levels below the site.................................... 132 8.4 Sloping sites.......................................................... 134 8.5 Very flat sites.......................................................... 137 8.6 Sites with potentially unstable subsurface rocks or soil workings............... 139 8.7 Sites with very deep backfill............................................. 139 8.8 SuDS on floodplains.................................................... 140 8.9 References........................................................... 141 9 Designing for roads and highways................................................. 142 9.1 Introduction........................................................... 143 9.2 Approval and adoption of SuDS in or adjacent to roads....................... 143 9.3 Interface with buried utility services....................................... 144 9.4 Connections between features below roads................................ 144 9.5 Application of SuDS for road drainage..................................... 144 9.6 Allowing water to infiltrate in close proximity to the road pavement............. 147 9.7 Filter drains for road drainage............................................ 148 9.8 Swales for road drainage................................................ 149 9.9 Roads for exceedance flow management................................... 151 9.10 Treating road runoff.................................................... 151 9.11 Designing safe SuDS adjacent to roads.................................... 152 9.12 Retrofitting SuDS for roads.............................................. 152 9.13 The maintenance of SuDS adjacent to roads................................ 153 9.14 Additional guidance relevant for SuDS draining roads........................ 153 9.15 References.................................................................... 154 10 Designing for urban areas........................................................ 156 10.1 Objectives for surface water management in the urban environment............ 157 10.2 Delivering the SuDS design criteria within urban areas....................... 165 10.3 Different urban development typologies................................... 174 10.4 Case studies.......................................................... 196 10.5 References........................................................... 202 Part D Technical detail....................................................................... 204 11 Rainwater harvesting............................................................ 206 11.1 General description.................................................... 207 11.2 Selection and siting of RWH systems...................................... 211 11.3 Hydraulic design....................................................... 212 11.4 Treatment design...................................................... 226 11.5 Amenity design........................................................ 227 11.6 Biodiversity design..................................................... 227 11.7 Physical specifications.................................................. 227 11.8 Materials............................................................. 227 11.9 Landscape design and planting.......................................... 228 11.10 Construction requirements.............................................. 228 11.11 Operation and maintenance requirements................................. 228 11.12 References........................................................... 230 12 Green roofs.................................................................... 232 12.1 General description.................................................... 233 12.2 General design considerations........................................... 236 12.3 Selection and siting of green roofs........................................ 237 12.4 Hydraulic design....................................................... 238 12.5 Treatment design...................................................... 240 12.6 Amenity design........................................................ 241 12.7 Biodiversity design..................................................... 242 x The SuDS Manual  CIRIA SuDS Manual 2015 12.8 Physical specifications.................................................. 245 12.9 Materials............................................................. 247 12.10 Landscape design and planting.......................................... 249 12.11 Construction requirements.............................................. 250 12.12 Operation and maintenance requirements................................. 251 12.13 References........................................................... 253 13 Infiltration systems.............................................................. 256 13.1 General description.................................................... 257 13.2 General design considerations........................................... 260 13.3 Selection and siting of infiltration components.............................. 261 13.4 Hydraulic design....................................................... 262 13.5 Treatment design...................................................... 263 13.6 Amenity design........................................................ 263 13.7 Biodiversity design..................................................... 263 13.8 Physical specifications.................................................. 264 13.9 Materials............................................................. 264 13.10 Landscape design and planting.......................................... 265 13.11 Construction requirements.............................................. 265 13.12 Operation and maintenance requirements................................. 266 13.13 References........................................................... 269 14 Proprietary treatment systems.................................................... 270 14.1 General description.................................................... 271 14.2 General design considerations........................................... 271 14.3 Selection and siting of proprietary treatment systems........................ 281 14.4 Hydraulic design....................................................... 282 14.5 Treatment design...................................................... 282 14.6 Amenity design........................................................ 284 14.7 Biodiversity design..................................................... 284 14.8 Physical specifications.................................................. 284 14.9 Materials............................................................. 285 14.10 Landscape design and planting.......................................... 285 14.11 Construction requirements.............................................. 285 14.12 Operation and maintenance requirements................................. 286 14.13 References........................................................... 288 15 Filter strips.................................................................... 290 15.1 General description.................................................... 291 15.2 General design considerations........................................... 292 15.3 Selection and siting of filter strips......................................... 293 15.4 Hydraulic design....................................................... 293 15.5 Treatment design...................................................... 294 15.6 Amenity design........................................................ 295 15.7 Biodiversity design..................................................... 295 15.8 Physical specifications.................................................. 296 15.9 Materials............................................................. 296 15.10 Landscape design and planting.......................................... 296 15.11 Construction requirements.............................................. 297 15.12 Operation and maintenance requirements................................. 298 15.13 References........................................................... 300 16 Filter drains.................................................................... 302 16.1 General description.................................................... 303 16.2 General design considerations........................................... 304 16.3 Selection and siting of filter drains........................................ 305 16.4 Hydraulic design....................................................... 306 16.5 Treatment design...................................................... 307 16.6 Amenity design........................................................ 308 16.7 Biodiversity design..................................................... 308 16.8 Physical specifications.................................................. 308 The SuDS Manual xi  CIRIA SuDS Manual 2015 16.9 Materials............................................................. 308 16.10 Landscape design and planting.......................................... 308 16.11 Construction requirements.............................................. 309 16.12 Operation and maintenance requirements................................. 309 16.13 References........................................................... 311 17 Swales........................................................................ 312 17.1 General description.................................................... 313 17.2 General design considerations........................................... 316 17.3 Selection and siting of swales............................................ 317 17.4 Hydraulic design....................................................... 318 17.5 Treatment design...................................................... 321 17.6 Amenity design........................................................ 322 17.7 Biodiversity design..................................................... 323 17.8 Physical specifications.................................................. 323 17.9 Materials............................................................. 324 17.10 Landscape design and planting.......................................... 326 17.11 Construction requirements.............................................. 326 17.12 Operation and maintenance requirements................................. 327 17.13 References........................................................... 330 18 Bioretention systems............................................................ 332 18.1 General description.................................................... 333 18.2 General design considerations........................................... 339 18.3 Selection and siting of bioretention systems................................ 340 18.4 Hydraulic design....................................................... 341 18.5 Treatment design...................................................... 343 18.6 Amenity design........................................................ 345 18.7 Biodiversity design..................................................... 345 18.8 Physical specifications.................................................. 345 18.9 Materials............................................................. 350 18.10 Landscape design and planting.......................................... 352 18.11 Construction requirements.............................................. 354 18.12 Operation and maintenance requirements................................. 355 18.13 References........................................................... 357 19 Trees......................................................................... 360 19.1 General description.................................................... 361 19.2 General design considerations........................................... 364 19.3 Selection and siting of trees............................................. 369 19.4 Hydraulic design....................................................... 370 19.5 Treatment design...................................................... 372 19.6 Amenity design........................................................ 373 19.7 Biodiversity design..................................................... 374 19.8 Physical specifications.................................................. 374 19.9 Materials............................................................. 376 19.10 Landscape design and planting.......................................... 380 19.11 Construction requirements.............................................. 381 19.12 Operation and maintenance requirements................................. 382 19.13 References........................................................... 383 20 Pervious pavements............................................................. 386 20.1 General description.................................................... 387 20.2 General design considerations........................................... 393 20.3 Selection and siting of pervious pavements................................ 395 20.4 Overall design requirements............................................. 397 20.5 Hydraulic design....................................................... 400 20.6 Treatment design...................................................... 406 20.7 Amenity design........................................................ 407 20.8 Biodiversity design..................................................... 407 20.9 Structural design (pavement engineering).................................. 408 xii The SuDS Manual  CIRIA SuDS Manual 2015 20.10 Physical specifications.................................................. 420 20.11 Materials............................................................. 422 20.12 Landscape design and planting.......................................... 425 20.13 Construction requirements.............................................. 426 20.14 Operation and maintenance requirements................................. 429 20.15 References........................................................... 431 21 Attenuation storage tanks........................................................ 436 21.1 General description.................................................... 437 21.2 Selection and siting of attenuation tank systems............................ 446 21.3 General design considerations........................................... 447 21.4 Structural design.......................................................447 21.5 Hydraulic design....................................................... 457 21.6 Treatment design...................................................... 459 21.7 Amenity design........................................................ 459 21.8 Biodiversity design..................................................... 459 21.9 Physical specifications.................................................. 460 21.10 Materials............................................................. 463 21.11 Landscape design and planting.......................................... 464 21.12 Construction requirements.............................................. 464 21.13 Operation and maintenance requirements................................. 467 21.14 References........................................................... 468 22 Detention basins............................................................... 472 22.1 General description.................................................... 473 22.2 General design considerations........................................... 474 22.3 Selection and siting of detention basins................................... 475 22.4 Hydraulic design....................................................... 476 22.5 Treatment design...................................................... 477 22.6 Amenity design........................................................ 478 22.7 Biodiversity design..................................................... 479 22.8 Physical specifications.................................................. 479 22.9 Materials............................................................. 480 22.10 Landscape design and planting.......................................... 480 22.11 Construction requirements.............................................. 481 22.12 Operation and maintenance requirements................................. 481 22.13 Reference............................................................ 483 23 Ponds and wetlands............................................................. 484 23.1 General description.................................................... 485 23.2 General design considerations........................................... 489 23.3 Selection and siting of ponds or wetlands.................................. 490 23.4 Hydraulic design....................................................... 491 23.5 Treatment design...................................................... 492 23.6 Amenity design........................................................ 493 23.7 Biodiversity design..................................................... 494 23.8 Physical specifications.................................................. 495 23.9 Materials............................................................. 497 23.10 Landscape design and planting.......................................... 498 23.11 Construction requirements.............................................. 500 23.12 Operation and maintenance requirements................................. 500 23.13 References........................................................... 503 Part E Supporting guidance.................................................................. 504 24 Hydrology and hydraulics: design methods and calculations............................ 506 24.1 Introduction........................................................... 507 24.2 Runoff estimation methods.............................................. 508 24.3 Greenfield sites: peak runoff rate estimation............................... 510 24.4 Greenfield sites: runoff volume estimation................................. 516 24.5 Previously developed sites: peak runoff rate and runoff volume estimation...... 518 The SuDS Manual xiii  CIRIA SuDS Manual 2015 24.6 The proposed development site: peak runoff rate and runoff volume estimation... 519 24.7 Climate change and urban creep allowances................................526 24.8 Designing for Interception............................................... 527 24.9 Designing for attenuation storage......................................... 530 24.10 Designing for long-term storage.......................................... 533 24.11 Conveyance design..................................................... 537 24.12 Exceedance design..................................................... 538 24.13 Surface water pumping station design..................................... 539 24.14 References........................................................... 539 25 Infiltration: design methods....................................................... 542 25.1 General concepts...................................................... 543 25.2 Evaluating potential constraints to the use of infiltration...................... 544 25.3 Infiltration testing methods.............................................. 549 25.4 The impacts of siltation on infiltration system performance................... 550 25.5 Reuse of existing soakaways............................................. 551 25.6 Infiltration system hydraulic design........................................ 551 25.7 Emptying time checks.................................................. 557 25.8 References........................................................... 558 26 Water quality management: design methods........................................ 560 26.1 Introduction........................................................... 561 26.2 Protecting surface waters............................................... 561 26.3 Protecting groundwater................................................. 562 26.4 The level of pollution in surface water runoff................................ 563 26.5 Treatment processes within SuDS........................................ 563 26.6 Evidence relating to managing water quality risks............................ 563 26.7 Methods for managing pollution risks..................................... 565 26.8 Designing a treatment system using a SuDS Management Train............... 574 26.9 References........................................................... 576 Annex 1 Contaminants in urban runoff and their potential toxicity..................... 579 Annex 2 Types of pollutant removal mechanisms in SuDS............................ 585 Annex 3 SuDS performance data................................................. 587 Annex 4 Groundwater protection evidence......................................... 589 Annex 5 Ellis et al, 2012........................................................ 591 27 Pollution prevention strategies.................................................... 596 27.1 General description.................................................... 597 27.2 Avoid polluting materials and activities.................................... 598 27.3 Minimise polluting materials or activities................................... 598 27.4 Prevent pollutants mixing with rainfall..................................... 599 27.5 Provide education and training........................................... 600 27.6 References........................................................... 602 28 Inlets, outlets and flow control systems............................................. 604 28.1 Introduction........................................................... 605 28.2 General design considerations........................................... 606 28.3 Inlet and outlet layout................................................... 607 28.4 Inlet systems.......................................................... 608 28.5 Outlet structure (outlets and flow control systems)........................... 616 28.6 Flow measurement..................................................... 628 28.7 References........................................................... 629 29 Landscape..................................................................... 630 29.1 Introduction........................................................... 631 29.2 Landscape character................................................... 633 29.3 Site considerations..................................................... 634 29.4 Bioengineering........................................................ 637 29.5 Topsoils, ameliorants and mulches........................................ 639 29.6 Choosing the right plants................................................ 642 29.7 Grass................................................................ 647 29.8 Designing for maintenance.............................................. 650 xiv The SuDS Manual  CIRIA SuDS Manual 2015 29.9 References........................................................... 652 30 Materials...................................................................... 654 30.1 Introduction........................................................... 655 30.2 Standards and certification schemes...................................... 656 30.3 Generic approaches to materials specification.............................. 657 30.4 Soils and aggregates................................................... 658 30.5 Geosynthetics......................................................... 660 30.6 References........................................................... 670 31 Construction................................................................... 674 31.1 Construction best practice for SuDS....................................... 675 31.2 Construction programming for SuDS...................................... 677 31.3 Construction method statements......................................... 679 31.4 Erosion control........................................................ 681 31.5 Sediment control....................................................... 683 31.6 Pollution control....................................................... 684 31.7 SuDS construction inspections........................................... 686 31.8 Summary............................................................. 687 31.9 References........................................................... 688 32 Operation and maintenance...................................................... 690 32.1 Introduction........................................................... 691 32.2 Operation and maintenance manual...................................... 692 32.3 Level of operation and maintenance...................................... 693 32.4 Operation and maintenance activity categories............................. 694 32.5 Health and safety...................................................... 695 32.6 Regular maintenance................................................... 696 32.7 Occasional maintenance................................................ 699 32.8 Remedial maintenance................................................. 703 32.9 Frequency of maintenance tasks......................................... 704 32.10 Applying the principles of landscape management........................... 705 32.11 References........................................................... 706 33 Waste management............................................................. 708 33.1 Introduction........................................................... 709 33.2 Waste management requirements........................................ 709 33.3 Sediment characterisation and disposal................................... 712 33.4 References........................................................... 714 34 Community engagement......................................................... 716 34.1 Introduction – what is Community Engagement?............................ 717 34.2 The benefits of successful engagement.................................... 718 34.3 Developing an engagement plan.......................................... 719 34.4 Delivering engagement.................................................. 722 34.5 References........................................................... 732 35 Costs and benefits.............................................................. 734 35.1 Introduction........................................................... 735 35.2 Key concepts for assessing costs and benefits.............................. 738 35.3 Estimating costs....................................................... 741 35.4 Assessing benefits..................................................... 748 35.5 Comparing costs and benefits............................................ 751 35.6 References........................................................... 756 36 Health and safety............................................................... 758 36.1 Introduction........................................................... 759 36.2 SuDS health and safety: the context....................................... 760 36.3 Effective health and safety risk management............................... 761 36.4 Health and safety risk assessment requirements............................ 769 36.5 Health and safety legislation............................................. 772 36.6 References........................................................... 773 Appendices.................................................................................. 776 A Glossary and abbreviations....................................................... 778 The SuDS Manual xv  CIRIA SuDS Manual 2015 Glossary..................................................................... 779 Abbreviations.................................................................. 794 B Checklists..................................................................... 802 B.1 SuDS design and land use planning submissions............................ 803 B.2 Scheme design checklist................................................ 811 B.3 SuDS health and safety risk assessment checklist........................... 816 B.4 Infiltration assessment.................................................. 822 B.5 SuDS component design checklists....................................... 826 B.6 Construction method statements and assessment checklists................. 854 B.7 Construction specification............................................... 859 B.8 Maintenance Plan and checklist.......................................... 865 B.9 Adoption handover checklist............................................. 883 B.10 References........................................................... 885 C Design example................................................................ 888 C.1 Site description........................................................ 889 C.2 Stage 1: Strategic surface water management objectives..................... 889 C.3 Stage 2: Conceptual design.............................................. 890 C.4 Stage 3: Outline design................................................. 903 C.5 Stage 4: Detailed design................................................ 908 C.6 References........................................................... 937 Boxes Box 1.1 Benefits of SuDS........................................................................ 20 Box 1.2 The SuDS approach to managing surface water runoff......................................... 21 Box 1.3 Functions of SuDS components............................................................ 28 Box 3.1 Return periods, probability of occurrence and critical durations................................. 44 Box 4.1 Factors influencing pollution levels in urban runoff............................................ 52 Box 4.2 Pollutant concentrations and loads......................................................... 54 Box 4.3 Good practice for SuDS treatment design................................................... 58 Box 4.4 UK regulations for discharges to groundwaters............................................... 62 Box 5.1 Amenity, place-making and liveability....................................................... 67 Box 6.1 Useful definitions........................................................................ 82 Box 6.2 The importance of grasslands............................................................. 90 Box 11.1 Rainwater harvesting for schools, Essex................................................... 209 Box 11.2 Runoff yield calculation (intermediate method: water supply only).............................. 219 Box 11.3 Non-potable water demand calculation (intermediate method: water supply only)................. 220 Box 11.4 Tank storage volume calculation: simple method, water conservation + surface water management, passive control............................................................ 221 Box 11.5 Tank storage volume calculation: intermediate method, water conservation + surface water management, passive control............................................................ 222 Box 11.6 Tank storage volume calculation: detailed method, water conservation + surface water management, passive control............................................................ 223 Box 12.1 Reported evidence of Interception delivered by green roofs................................... 239 Box 18.1 Example specification for a bioretention filter medium........................................ 350 Box 19.1 Trees and runoff volume reduction........................................................ 363 Box 19.2 Performance of trees in removing phosphorous and nitrogen.................................. 373 Box 19.3 Example specification for soil to provide rooting environment in modular structures and rafts....... 377 Box 19.4 Example specification for structural soil.................................................... 379 Box 19.5 Testing and approval of tree soils and structural soils........................................ 381 Box 20.1 Units used for infiltration................................................................ 397 Box 21.1 The use of BBA and other certification schemes............................................. 460 Box 24.1 A summary of the approach to modelling paved surfaces using the UKWIR UK runoff model........ 525 Box 24.2 A summary of the approach to modelling pervious surfaces using the UKWIR runoff model......... 526 Box 24.3 Simple approaches to Interception delivery and compliance assessment........................ 528 Box 26.1 Generic findings regarding the removal of TSS and metals.................................... 564 Box 26.2 Steps of the simple index approach....................................................... 567 Box 28.1 Structural trash screen design criteria..................................................... 628 Box 30.1 Geomembranes and construction......................................................... 665 Box 30.2 Independent verification................................................................. 667 Box 31.1 General construction issues relating to SuDS............................................... 675 Box 35.1 Examples of methods for quantifying benefits............................................... 749 xvi The SuDS Manual  CIRIA SuDS Manual 2015 Box B.1 An example SuDS specification........................................................... 862 Box B.2 Example SuDS Maintenance Plan for Robinswood Primary School.............................. 873 Case studies Case study 1.1 The Circle, Uptown Normal, Illinois......................................................... 20 Case study 1.2 Fair Street vertical rain garden, London..................................................... 25 Case study 5.1 The Triangle, Swindon.................................................................... 69 Case study 6.1 Manor Park, Sheffield.................................................................... 83 Case study 6.2 Green roof at Horniman Museum, London................................................... 84 Case study 6.3 Gosforth Valley wetlands, Dronfield......................................................... 86 Case study 6.4 Watercolour, Redhill, Surrey............................................................... 88 Case study 7.1 Singleton Hill, Ashford, Kent.............................................................. 103 Case study 10.1 Hunter Avenue, Kent.................................................................... 159 Case study 10.2 Bristol Harbourside..................................................................... 196 Case study 10.3 Derbyshire Street....................................................................... 197 Case study 10.4 Rathbone Market....................................................................... 198 Case study 10.5 Tanner Springs Park.................................................................... 199 Case study 10.6 Augustenborg.......................................................................... 200 Case study 10.7 Benthemplein Water Square............................................................. 201 Case study 12.1 Kanes Food, Evesham................................................................... 241 Case study 12.2 Abbey Hive, Camden, London............................................................. 244 Case study 12.3 Sharrow School, Sheffield................................................................ 244 Case study 34.1 Upton – large-scale housing estate........................................................ 725 Case study 34.2 Priors Farm, Oakley – small-scale retrofit demonstration project............................... 728 Case study 35.1 Herne Hill and Dulwich flood alleviation scheme............................................. 736 Case study 35.2 Application of the BeST tool to compare the benefits of different drainage options................ 752 Equations Equation 15.1 Manning’s equation for filter strip design................................................... 295 Equation 18.1 Calculating required bioretention surface area.............................................. 342 Equation 18.2 Forebay design........................................................................ 347 Equation 20.1 Equation to estimate outfall pipe spacing.................................................. 404 Equation 20.2 Darcy’s law to calculate sub-base flow..................................................... 404 Equation 23.1 Water quality treatment volume calculation using variable rainfall depths (for Scotland)........... 492 Equation 24.1 Estimating the flow frequency curve using the FEH statistical method........................... 511 Equation 24.2 FEH statistical method: catchment descriptor equation....................................... 512 Equation 24.3 IH124: Catchment descriptor equation..................................................... 513 Equation 24.4 Fixed percentage runoff model........................................................... 517 Equation 24.5 Modified rational method equation to determine peak flow rates............................... 520 Equation 24.6 Fixed UK runoff model.................................................................. 521 Equation 24.7 Variable UK runoff model................................................................ 522 Equation 24.8 The UKWIR UK runoff model............................................................. 523 Equation 24.9 Integration of storage volume from depth/area relationship................................... 532 Equation 24.10 Estimating the extra runoff volume from a development site compared to the greenfield equivalent. 534 Equation 24.11 Estimating the extra runoff volume from a proposed development site compared to the previously developed site......................................................................... 536 Equation 24.12 Manning’s conveyance equation.......................................................... 537 Equation 25.1 Determination of maximum depth of water for plane infiltration systems........................ 553 Equation 25.2 Procedure for design of plane infiltration systems........................................... 554 Equation 25.3 Procedure to determine the base area required for a given maximum depth..................... 555 Equation 25.4 Determination of maximum depth of water for 3D infiltration systems........................... 555 Equation 25.5 Procedure for design of 3D infiltration systems.............................................. 556 Equation 25.6 Equations to calculate the time to empty an infiltration system................................ 558 Equation 28.1 Standard orifice equation................................................................ 618 Equation 28.2 Total flow capacity of a perforated riser.................................................... 619 Equation 35.1 Calculating present value and net present value............................................. 740 Figures Figure 1.1 The Circle in Uptown Normal, Illinois, USA................................................... 20 Figure 1.2 Impacts of urbanisation on a catchment.................................................... 22 Figure 1.3 SuDS using natural processes............................................................. 23 Figure 1.4 SuDS providing urban cooling............................................................. 25 Figure 1.5 Fair Street vertical rain garden............................................................ 25 Figure 1.6 Examples of commonly used SuDS for different development types............................. 30 The SuDS Manual xvii  CIRIA SuDS Manual 2015 Figure 2.1 The four pillars of SuDS design............................................................ 33 Figure 3.1 Example of a runoff hydrograph............................................................ 38 Figure 3.2 Controlling runoff rates using attenuation storage............................................ 38 Figure 3.3 Example of the combined effect of multiple attenuation systems................................ 39 Figure 4.1 Example of flow, pollutant concentration and pollutant load build-up during a rainfall event......... 54 Figure 5.1 The green.............................................................................. 69 Figure 5.2 Play pump (a) and hand pump (b) in the kitchen garden........................................ 69 Figure 5.3 Orange Park, London..................................................................... 71 Figure 5.4 Examples of bioretention systems providing traffic calming measures, Llanelli.................... 72 Figure 5.5 Rain garden, Ribblesdale Road, Nottingham................................................. 72 Figure 5.7 Greenwich University vegetable growing plot................................................. 73 Figure 5.8 Portland City Council edible garden........................................................ 73 Figure 5.9 Canalside living, Redhill, Surrey............................................................ 73 Figure 5.10 SuDS and play.......................................................................... 74 Figure 5.11 Alcester Primary Care Centre.............................................................. 75 Figure 5.12 Planted canal, Stamford.................................................................. 75 Figure 5.13 Inlet, Heriot Watt Science Park............................................................ 75 Figure 5.14 Signage and todder-proof fencing at a supermarket site....................................... 76 Figure 5.15 Pond dipping........................................................................... 77 Figure 5.16 Shared learning at Stebonheath........................................................... 77 Figure 5.17 SuDS outreach project, Portland........................................................... 78 Figure 5.18 Planting at Coppetts Wood Primary School.................................................. 78 Figure 6.1 View over the park showing the SuDS working as predicted following heavy rain in 2007............ 83 Figure 6.2 Pond dipping as part of an educational programme for schools................................. 83 Figure 6.3 Green roof at Horniman Museum, London................................................... 84 Figure 6.4 The wetlands and example of activities by the volunteers...................................... 86 Figure 6.5 Green corridors......................................................................... 87 Figure 6.6 Watercolour, Redhill..................................................................... 88 Figure 6.7 Pond and grassland habitat mosaic, Moreton-In-Marsh Community Hospital, Gloucestershire....... 89 Figure 6.8 Infiltration basin with wildflower turf and grass seeding, Victoria Park Health Centre, Leicester....... 91 Figure 6.9 Wetland with marginal aquatics, grasses, sedges, rushes and wildflower grass seed mix, Kington, Herefordshire........................................................................... 91 Figure 7.1 The four stages of SuDS design............................................................ 95 Figure 7.2 The drainage system design process: links with land use planning............................... 97 Figure 7.3 The conceptual design process........................................................... 101 Figure 7.4 Characterising flow routes and discharge points............................................. 103 Figure 7.5 Singleton Hill.......................................................................... 103 Figure 7.6 Defining surface water sub-catchments.................................................... 110 Figure 7.7 Defining parks, open spaces and corridors................................................. 111 Figure 7.8 Defining the road network............................................................... 112 Figure 7.9 SuDS component selection process....................................................... 114 Figure 7.10 Defining exceedance routes.............................................................. 117 Figure 7.11 The outline design process.............................................................. 119 Figure 7.12 Site and sub-catchment scale component sizing for outline design............................. 121 Figure 7.13 The detailed design process............................................................. 123 Figure 8.1 Contaminated land and SuDS: typical capping layers......................................... 131 Figure 8.2 Unlined permeable pavement on a contaminated site, Stamford, Lincolnshire.................... 131 Figure 8.3 Locating infiltration systems beneath layers of contamination and/or removal of contaminated soils from around soakaways................................................................. 132 Figure 8.4 Lined permeable pavement constructed over a former landfill site, Portsmouth.................. 132 Figure 8.5 Shallow swale on a site with shallow groundwater, Witney, Oxfordshire.......................... 133 Figure 8.6 Cross-section showing example SuDS on a sloping site....................................... 135 Figure 8.7 Retaining wall and waterfall (a) and planted pool with overflow to play basin (b), Springhill Co-housing, Stroud..................................................................... 135 Figure 8.8a Check dams in a swale, Oxfordshire....................................................... 136 Figure 8.8b Check dam in a swale during construction, Lincoln........................................... 136 Figure 8.8c Check dams can be combined with road/pedestrian crossings, Upton, Northamptonshire.......... 136 Figure 8.9 Impact of geology on water flows from infiltration drainage on sloping sites...................... 136 Figure 8.10 Example comparison of piped drainage system to a SuDS scheme............................. 138 Figure 9.1 Concrete block permeable paving used for a residential road, Cambridge....................... 145 Figure 9.2 Concrete grid grass reinforcement along tramlines, Switzerland............................... 145 Figure 9.3 Swale and wetland systems with reinforced grass used in less trafficked areas such as laybys and field access points, A16, Lincolnshire.................................................. 145 xviii The SuDS Manual  CIRIA SuDS Manual 2015 Figure 9.4 Swale on a steeply sloping road, Oxfordshire................................................ 146 Figure 9.5 Swale and wetland system, A16, Lincolnshire............................................... 146 Figure 9.6 Filter drain, A7, Dumfries and Galloway..................................................... 146 Figure 9.7 Detention basin draining a rural road, Oxfordshire........................................... 146 Figure 9.8 Wetland draining a complex traffic island, M4 junction 11, Reading............................. 147 Figure 9.9 Bioretention system, inner ring road around Ashford town centre............................... 147 Figure 9.10 Installation of vortex separator, M25...................................................... 147 Figure 9.11 Geocellular storage below roundabout, A595 Parton to Lillyhall................................ 147 Figure 9.12 Detail of a bioretention system designed to prevent water ingress into adjacent sub-base.......... 148 Figure 9.13 Water flows from shallow swales acting as edge drains for the road sub-base.................... 148 Figure 9.14 Filter drain details for cuttings – combined surface water and groundwater drainage.............. 149 Figure 9.15 Swale detail........................................................................... 150 Figure 9.16 Kerb drains and channel connected to swale............................................... 150 Figure 9.17 Outlet from kerb drain into swale.......................................................... 150 Figure 9.18 Swale set back from road, Elvetham Heath................................................. 150 Figure 9.19 Highway acting as a flood pathway in an exceedance event.................................... 151 Figure 10.1 Hunter Avenue......................................................................... 159 Figure 10.2 Pervious surfaces...................................................................... 161 Figure 10.3 Kerb drainage, rills and channels......................................................... 161 Figure 10.4 Planted channels....................................................................... 161 Figure 10.5 Bioretention systems and rain gardens.................................................... 162 Figure 10.6 Swales and linear wetlands.............................................................. 162 Figure 10.7 On-plot SuDS.......................................................................... 162 Figure 10.8 Green roofs........................................................................... 163 Figure 10.9 Public spaces.......................................................................... 163 Figure 10.10 Playful and informative elements......................................................... 163 Figure 10.11 Example of a bioretention system upstream of an existing gully................................ 165 Figure 10.12 Communal space using runoff as a resource................................................ 167 Figure 10.13 Rain garden with weirs to control flows on sloping site in Ashford, Kent.......................... 168 Figure 10.14 Multi-functional civic space.............................................................. 169 Figure 10.15 Benthemplein Water Square, Rotterdam................................................... 170 Figure 10.16 Multi-functional streetscape............................................................. 171 Figure 10.17 Multi-functional use of elevated spaces.................................................... 172 Figure 10.18 Roadside rills, Cambridge................................................................ 172 Figure 10.19 Typologies within the urban landscape..................................................... 175 Figure 10.20 Typology 1 – Small residential infill........................................................ 179 Figure 10.21 Typology 2 – Medium residential infill...................................................... 181 Figure 10.22 Typology 3 – Mixed use.................................................................. 183 Figure 10.23 Typology 4 – Destination public realm..................................................... 185 Figure 10.24 Typology 5 – Transitional public realm..................................................... 187 Figure 10.25 Typology 6 – Elevated spaces............................................................ 189 Figure 10.26 Typology 7 – Neighbourhood street........................................................ 191 Figure 10.27 Typology 8 – Civic street................................................................. 193 Figure 10.28 Typology 9 – Greenway.................................................................. 195 Figure 11.1 Rainwater harvesting storage tanks for domestic and commercial application.................... 207 Figure 11.2 Columbus School and College............................................................ 209 Figure 11.3 A conceptual gravity-fed RWH system...................................................... 210 Figure 11.4 A conceptual pumped rainwater harvesting system.......................................... 211 Figure 11.5 1 in 100 year, 6-hour rainfall depths for the UK.............................................. 214 Figure 11.6 Average annual rainfall for the UK......................................................... 215 Figure 11.7 The simple method for sizing RWH tanks – for water conservation only.......................... 218 Figure 11.8 The simple look-up approach for sizing RWH tanks – aggregated for various occupancy rates....... 219 Figure 11.9 Additional storage volume VSC required for surface water management, over and above the storage needed for water conservation, simple approach..................................... 222 Figure 11.10 Rainwater harvesting tanks with active control for surface water management................... 225 Figure 11.11 Rainwater harvesting storage tanks during construction...................................... 228 Figure 12.1 Section showing typical extensive green roof components.................................... 234 Figure 12.2 The Savill Garden extensive green roof..................................................... 235 Figure 12.3 British Horse Society sedum blanket...................................................... 235 Figure 12.4 Examples of accessible green roof with intensive and extensive planting, Bishops Square, London.. 235 Figure 12.5 Domestic green roofing, Swansea......................................................... 237 Figure 12.6 Distribution of runoff response (0% imperviousness means no runoff).......................... 239 The SuDS Manual xix  CIRIA SuDS Manual 2015 Figure 12.7 Green roof bus stop, Dundee City Centre................................................... 241 Figure 12.8 Green roof bike shelter at Six Acres Estate, Islington, London.................................. 241 Figure 12.9 Kanes Food wildflower green roof......................................................... 241 Figure 12.10 Biodiverse green roof with varied substrate depths.......................................... 243 Figure 12.11 Biodiverse green roof, Unicorn Grocery, Manchester......................................... 243 Figure 12.12 Abbey Hive biodiverse roof.........................................................