cover_zevenbergen3.qxd 03-09-2010 10:05 Pagina 1 URBAN M U A R N B FLOOD A A G N E F M L M A N AG E M E N T E O N O T D ZEVENBERGEN, CASHMAN, C.ZEVENBERGEN,A.CASHMAN, N. EVELPIDOU, EVELPIDOU, E. PASCHE, S. GARVIN & R.ASHLEY PASCHE, GARVIN & ASHLEY Along with windstorms,floods are the most common and widespread of all natural disasters.Although they can often be predicted,they cause loss of life,damage and destruction,as many urban communities are located near coasts and rivers.In terms of victims,floods are responsible for more than half the deaths caused by natural catastrophes.As flood events appear to be rapidly increasing worldwide,an advanced and universal approach is needed to manage urban Floods and reduce their impact. Urban Flood Management presents a comprehensive and multi-disciplinary introduction to urban Floods for a global audience.It uniquely integrates the expertise from disciplines such as hydrology, sociology, architecture, urban design, construction and water resources engineering.The subject is approached from an international perspective and multiple case studies,exercises,expert advises and literature recommendations are included to support the theory and illustrations. Developed by a team of specialists,this textbook is intended for urban flood management education of hydrology, geography, civil and environmental engineering and management students at university level. Moreover, researchers and professionals will find this book useful as a reference.A supporting website can be addressed for current information. COST stands for European Co-operation in the field of Scientific and Technical Research, an intergovernmental framework for the co-ordination of nationally-funded research at a European level.COST Action C22,a European research platform on Urban Flood Management,was establishedin 2005. an informabusiness Urban Flood ManageMent Zevenberg_Book.indb 1 9/3/2010 2:30:36 PM Zevenberg_Book.indb 2 9/3/2010 2:30:36 PM Urban Flood ManageMent Chris Zevenbergen UNESCO-IHE/Delft University of T echnology, Delft, The Netherlands Dura Vermeer Group, Hoofddorp,The Netherlands adrian CashMan CERMES – University of the West Indies, Barbados niki evelpidoU University of Athens, Greece erik pasChe Hamburg University of Technology, Germany stephen garvin BRE Scotland, Glasgow, UK riChard ashley Pennine Water Group, Sheffield, UK Zevenberg_Book.indb 3 9/3/2010 2:30:36 PM CRC Press Taylor & Francis Group 6000 Broken Sound Parkway NW, Suite 300 Boca Raton, FL 33487-2742 © 2010 by Taylor & Francis Group, LLC CRC Press is an imprint of Taylor & Francis Group, an Informa business No claim to original U.S. Government works Version Date: 20140602 International Standard Book Number-13: 978-1-4398-9433-0 (eBook - PDF) This book contains information obtained from authentic and highly regarded sources. Reasonable efforts have been made to publish reliable data and information, but the author and publisher cannot assume responsibility for the validity of all materials or the consequences of their use. The authors and publishers have attempted to trace the copyright holders of all material reproduced in this publication and apologize to copyright holders if permission to publish in this form has not been obtained. If any copyright material has not been acknowledged please write and let us know so we may rectify in any future reprint. Except as permitted under U.S. Copyright Law, no part of this book may be reprinted, reproduced, transmitted, or utilized in any form by any electronic, mechanical, or other means, now known or hereafter invented, including photocopying, microfilming, and recording, or in any information storage or retrieval system, without written permission from the publishers. For permission to photocopy or use material electronically from this work, please access www.copyright.com (http://www.copyright.com/) or contact the Copyright Clearance Center, Inc. (CCC), 222 Rosewood Drive, Danvers, MA 01923, 978-750-8400. CCC is a not-for-profit organization that provides licenses and registration for a variety of users. For organizations that have been granted a photocopy license by the CCC, a separate system of payment has been arranged. Trademark Notice: Product or corporate names may be trademarks or registered trademarks, and are used only for identification and explanation without intent to infringe. Visit the Taylor & Francis Web site at http://www.taylorandfrancis.com and the CRC Press Web site at http://www.crcpress.com table of contents Preface ix List of contributors xi Illustration credits xv introduction to urban flood management 1 What is this book all about? 3 I SettIng Up the FraMework 7 1 setting the stage for integrated Urban Flood Management 9 1.1 Why are cities special cases? 9 1.2 The city as a living organism 15 1.3 Vulnerability of urban areas: a rough guide 18 1.4 Types of uncertainty 20 1.5 Adoption of a system approach 26 2 Urban floods 37 2.1 The influence of climate and other factors 37 2.2 Types of flooding 42 2.3 Pitfalls in using the historical record (or ‘stationarity is dead’) 54 II drIverS For change 61 3 Urbanisation 63 3.1 Principles of land-use planning 63 3.2 Urban typologies: from central square to edge city 67 3.3 Growing and shrinking: density issues induced by globalisation 71 3.4 Megacities in the delta 73 4 Climate change: key uncertainties and robust findings 79 4.1 A review of the past 79 4.2 Signs of change 85 4.3 Expected consequences 86 III Urban Flood rISk 95 5 the hydrology of cities 97 5.1 The hydrological cycle 97 5.2 Land use and runoff 103 5.3 Modelling surface runoff 107 5.4 Modelling pluvial flooding 113 5.5 Modelling coastal flooding 118 6 Urban flood-risk assessment 123 6.1 Introduction to the theory of risk 123 6.2 Quantifying flood probability 126 v Zevenberg_Book.indb 5 9/3/2010 2:30:41 PM Table of contents 6.3 Tangible and intangible damages 138 6.4 Loss of life estimation in flood-risk assessment 141 6.5 Cross-scale factors and indirect damages 142 6.6 Flood-risk mapping 146 Iv reSponSeS 155 7 responding to flood risk 157 7.1 Responses 157 7.2 Performance standards and expectations 159 7.3 Resilience, vulnerability, robustness and sustainability 164 7.4 Precautionary and adaptive responses 167 7.5 Confronting flood management with land-use planning: lessons learnt 173 7.6 Building types, infrastructure and public open space 177 8 Urban drainage systems 183 8.1 A historical perspective 183 8.2 Major and minor flows 184 8.3 SUDS/LIDS 186 8.4 Practices in water sensitive urban design 198 9 Flood proofing the urban fabric 205 9.1 Managing flooding through site design: basic principles 205 9.2 Managing flooding through detailed design (individual properties/buildings) 208 9.3 Flood resilient repair and retrofitting 215 9.4 Urban flood defences and barriers 219 10 enhancing coping and recovery capacity 227 10.1 Flood forecasting, warning and response 227 10.2 Emergency planning, management and evacuation 235 10.3 Compensation and flood insurance 240 v towardS Flood reSIlIent cItIeS 253 11 Managing for resiliency 255 11.1 Asset management, some basic principles 255 11.2 Assessing resilience in flood-risk management 259 11.3 Transitioning from entrapment to resilience approaches 261 12 Capacity building and governance 269 12.1 Risk perception, acceptance and communication 269 12.2 Adaptive capacity 273 12.3 Characteristics of effective learning initiatives 274 13 shelter for all 281 13.1 What does the future hold? 281 13.2 Challenges and opportunities 282 13.3 Turning ideas into action 285 13.4 Success stories: seizing windows of opportunity 290 vi Zevenberg_Book.indb 6 9/3/2010 2:30:41 PM Table of contents References 297 Abbreviations and acronyms 309 Glossary 311 Subject index 319 vii Zevenberg_Book.indb 7 9/3/2010 2:30:41 PM Zevenberg_Book.indb 8 9/3/2010 2:30:41 PM preface Floods have a significant impact on cities. Since the beginning of civilisation, people have had to cope with them and, if possible, to adapt to them. As a consequence, the various human civilisations have observed the effect of such natural phenomena and have tried to understand the underlying causes. At first they provided mythological or religious explanations; floods were seen as an act of the gods. With the Enlightenment, floods were conceived as due to ignorance or neglect on the part of man; resulting in the development of more rational approaches to manage the occurrence of flooding. Since the latter half of the twentieth century flood-risk management has evolved as a discipline in its own right. As it is currently practised this involves a very broad range of expertise, corresponding to the different scientific domains including physics, biology, geographical science and of course civil and other branches of engineering. It increas- ingly draws in contributions from the social sciences, planning and politics. The UN has estimated that there will be a global increase from 2.9 billion urban resi- dents in the 1990s to 5.0 billion by 2030. More than 50% of the world’s population now live in urban areas. Most of the growth in urban populations will occur in developing countries in Asia: in small- and medium-sized cities and in mega-cities. The urban pop- ulation of industrialised countries is now expected to grow by 11% over the next thirty years. An unintended side effect of this concentration of population is that the number exposed to floods is growing as well. Especially, with the unprecedented growth of Asian mega-cities, this will contribute substantially to a global increase of flood risk. While trend changes caused by climate change pose major challenges for cities, especially in developing countries, the increasing frequency of extreme events could induce major demographic and economic disruptions. Exchanging and sharing experiences and good practices must therefore be a main priority. Moreover, it has become increasingly clear that current curricula in planning and engineering schools are outdated and have not kept pace with the changing demands of the cities of today. Educational programmes should embrace innovative planning ideas, including the ability to engage in participa- tory planning, negotiation and communication. This book attempts to cover the basic components needed to understand the urban flooding system including the urban fabric, green spaces, coasts and surface waters such as rivers and canals, groundwater, etc. We believe, however, that a holistic and system- atic conceptualisation of urban flood risk must expand its scope beyond the traditional components of flood-risk management: which is predominantly focused on assess- ing, preventing and controlling the extent of damage and probability of occurrence. Therefore, a brief analysis of a spectrum of components of the urban system and of the interactions between them is also part of the scope this textbook. We have chosen here to provide an overview of the processes that rule the behaviour of cities and citizens. Our goal is to provide the reader with enough information on the interactions between the different elements of the flooding system and on the dominant feedbacks so that you can analyse the urban flooding system in an integrated way. By this means, the reader should be able to understand the dominant causes of urban flooding and to develop appropriate responses, at least conceptually. The reader should, however, recognise that this is a rapidly developing field. Knowledge is advancing about the causes and impacts of floods and the way in which the drivers are changing due to climate and other causes, as well as how best to address this. For this reason, as a reader, you should see this book as a first step on ‘the active learning’ pathway that you need to commit to, as by the time ix Zevenberg_Book.indb 9 9/3/2010 2:30:41 PM