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APPLIED UNCERTAINTY ANALYSIS FOR FLOOD RISK MANAGEMENT P588_9781848162709_tp.indd 1 22/11/13 9:32 AM December9,2013 10:34 9inx6in AppliedUncertaintyAnalysisforFloodRiskManagement b1530-fm TThhiiss ppaaggee iinntteennttiioonnaallllyy lleefftt bbllaannkk APPLIED UNCERTAINTY ANALYSIS FOR FLOOD RISK MANAGEMENT Editors Keith Beven Lancaster University, UK Jim Hall University of Oxford, UK Imperial College Press ICP P588_9781848162709_tp.indd 2 22/11/13 9:32 AM Published by Imperial College Press 57 Shelton Street Covent Garden London WC2H 9HE Distributed by World Scientific Publishing Co. Pte. Ltd. 5 Toh Tuck Link, Singapore 596224 USA office: 27 Warren Street, Suite 401-402, Hackensack, NJ 07601 UK office: 57 Shelton Street, Covent Garden, London WC2H 9HE British Library Cataloguing-in-Publication Data A catalogue record for this book is available from the British Library. Cover images: Upton-upon-Severn floods 23 July 07 © by RogerSmith1946, http://www.panoramio.com/photo/10609559. Mexborough probabilistic flood map, © Lancaster University and JBA Consulting. Background Google Imagery © 2010, Data SIO, NOAA, U.S. Navy, NGA, GEBCO, DigitalGlobe, GeoEye, Getmapping plc, Infoterra Ltd & Bluesky, The GeoInformation Group. Back cover image: © Keith Beven. APPLIED UNCERTAINTY ANALYSIS FOR FLOOD RISK MANAGEMENT Copyright © 2014 by Imperial College Press All rights reserved. This book, or parts thereof, may not be reproduced in any form or by any means, electronic or mechanical, including photocopying, recording or any information storage and retrieval system now known or to be invented, without written permission from the Publisher. For photocopying of material in this volume, please pay a copying fee through the Copyright Clearance Center, Inc., 222 Rosewood Drive, Danvers, MA 01923, USA. In this case permission to photocopy is not required from the publisher. ISBN 978-1-84816-270-9 Typeset by Stallion Press Email: [email protected] Printed in Singapore December9,2013 10:34 9inx6in AppliedUncertaintyAnalysisforFloodRiskManagement b1530-fm Preface Flood risk management is a process of decision making under uncertainty. Traditionalapproachesto analysingfloods assumeda guiseof determinism though concepts such as “design floods”, and dealt with uncertainties implicitly and opaquely through freeboard allowances and other factors of safety.Arisk-basedapproachrecognisesthatunpredictabilityisfundamen- tal to decisions about how to deal with flooding. Uncertainties have to be exposed, scrutinised and incorporated in decision making through rational processes. Suchistheidealoffloodriskmanagement.Yetwhenwereviewresearch and practice in the various fields that relate to flood risk (hydrology, hydraulics, geomorphology, structural reliability, human and economic vulnerabilityandsoon)weobservepatchy,inconsistentandsometimesnon- existent analysis and reporting of uncertainty. Uncertainty analysis takes time and requires expertise. Whilst some principles and methods are well established, and well supported with computer-based tools, other aspects of uncertainty and decision analysisare subject to rather fundamental and sometimes bitter debate. Thesearecircumstancesthatcanbedisconcertingorexciting,depend- ingonyourperspective.Therelativeimmaturityofmethodologyfordealing with uncertainty in many areas of flood risk management is an obstacle to the proper incorporation of uncertainties into decision making. Yet that scarcity of methodology and data for analysis of uncertainty represents an opportunity,forresearchersinparticular,butalsoforpractitionerswhoare motivated by the need to improve flood risk managementdecision making. This book seeks to respond to the challenges and opportunities presentedbyuncertaintyanalysisinfloodriskmanagement.Wehavesought to be as comprehensive as possible, dealing with uncertainties in both the probabilities and consequences of flooding, and addressing a range v December9,2013 10:34 9inx6in AppliedUncertaintyAnalysisforFloodRiskManagement b1530-fm vi Preface of flood risk management decisions, including planning, design and flood forecasting. Chapters deal with fluvial, urban and tidal flooding. Whilst in editing the book we have sought to promote a coherent approachtothetreatmentofuncertainty,itisinevitableinavolumewitha totalof45contributingauthorsthattherewillbeadiversityofperspectives, particularly in a field as contested as uncertainty analysis. We regard this diversity of perspectives as a strength of the book. This is not a manual. The reader will have to apply their judgment in assessing the applicability to the situations that they encounter of the methods and approaches that are described. This book is an outcome of the UK Flood Risk Management Research Consortium (FRMRC), a wide ranging program of research that started in 2004 and ran, in two phases, to 2012. FRMRC involved more than 20 universities and research institutions and was jointly funded by the Engineering and Physical Research Council (EPSRC) in collaboration with the Environment Agency (EA), the Northern Ireland Rivers Agency (DARDNI), United Kingdom Water Industry Research (UKWIR), the Scottish Government (via SNIFFER), the Welsh Assembly Government (WAG) and the Office of Public Works (OPW) in the Republic of Ireland. We thank all of these organisations for the support they have provided to flood risk management research. Further details of the program and its outcomes can be found at http://www.floodrisk.org.uk/. The two editors of the book were both involved in Research Package 3 of the first phase of FRMRC, which was concerned with introducing risk and uncertainty into the flood risk management process. In phase 2, the methodologies developed were used in a variety of applications. That researchis reflected inthechaptersinthisbook,butwehavealsotriedtoreflectawiderrangeof internationalworkinthisarea,byaskingauthorsfromdifferentinstitutions to review progress in their areas of expertise. We are grateful for the time andeffortofalltheauthorswhohavecontributedtothisextensivesummary of progress in the field. Finally, we would like to thank Lynn Patterson at Newcastle University, Maya Kusajima at Kyoto University and Sue King at the University of Oxford, who did important work in assembling and formatting the manuscript. Floods remain the most damaging natural hazard in terms of both fatalitiesandeconomicimpacts.Floodswillcontinuetooccurinthefuture. Residual risk of flooding cannot be eliminated and the resources available for flood risk management will always be finite. So it is important that flood risk management decisions are based upon an appraisal of risks that December9,2013 10:34 9inx6in AppliedUncertaintyAnalysisforFloodRiskManagement b1530-fm Preface vii is as far as possible accurate but is also accompanied by a well-informed appraisal of the associated uncertainties and their potential impact upon decision making. We hope that this book is a useful contribution towards that end. Keith Beven Jim W. Hall December9,2013 10:34 9inx6in AppliedUncertaintyAnalysisforFloodRiskManagement b1530-fm TThhiiss ppaaggee iinntteennttiioonnaallllyy lleefftt bbllaannkk December9,2013 10:34 9inx6in AppliedUncertaintyAnalysisforFloodRiskManagement b1530-fm Contents Preface v Section I: Introduction 1 Chapter 1: Flood Risk Management: Decision Making Under Uncertainty 3 Jim W. Hall Chapter 2: Use of Models in Flood Risk Management 25 Keith Beven Section II: Theoretical Perspectives 37 Chapter 3: A Framework for Uncertainty Analysis 39 Keith Beven Chapter 4: Classical Approaches for Statistical Inference in Model Calibration with Uncertainty 60 R.E. Chandler Chapter 5: Formal Bayes Methods for Model Calibration with Uncertainty 68 Jonathan Rougier Chapter 6: The GLUE Methodology for Model Calibration with Uncertainty 87 Keith Beven ix