River Basin Modelling for Flood Risk Mitigation PDF
Preview River Basin Modelling for Flood Risk Mitigation
RIVER BASIN MODELLING FOR FLOOD RISK MITIGATION SELECTED PAPERS Copyright © 2006 Taylor & Francis Group plc, London, UK BALKEMA - Proceedings and Monographs in Engineering, Water and Earth Sciences Copyright © 2006 Taylor & Francis Group plc, London, UK River Basin Modelling for Flood Risk Mitigation Donald W. Knight The University of Birmingham, UK Asaad Y. Shamseldin The University of Auckland, New Zealand LONDON/ LEIDEN/ NEWYORK/ PHILADELPHIA/ SINGAPORE Copyright © 2006 Taylor & Francis Group plc, London, UK Cover photographs: “The Toyohira River, Japan (courtesy of Ishikari River Development Office)” and, “The Three Gorges Dam, under construction in 2004, on the Yangtze River, China” Copyright © 2006 Taylor & Francis Group plc, London, UK All rights reserved. No part of this publication or the information contained herein may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, by photocopying, recording or otherwise, without written prior permission from the publisher. Although all care is taken to ensure the integrity and quality of this publication and the information herein, no responsibility is assumed by the publishers nor the author for any damage to property or persons as a result of operation or use of this publication and/or the information contained herein. Published by: Taylor & Francis/Balkema P.O. Box 447, 2300 AK Leiden, The Netherlands e-mail: [email protected] www.balkema.nl, www.tandf.co.uk, www.crcpress.com ISBN 0 415 38344 7 Printed in Great-Britain Copyright © 2006 Taylor & Francis Group plc, London, UK Table of Contents Preface vii 1. Introduction to flooding and river basin modelling 1 D.W. Knight 2. The European perspective and research on flooding 21 P.G. Samuels 3. Overview of current perspectives on climate change 59 A. Bronstert 4. The effects of climate change on flooding 77 A. Bronstert 5. The growth and significance of hydroinformatics 93 Roland K. Price 6. The application of hydroinformatics 109 Roland K. Price & Abebe Andualem Jemberie 7. Quantitative precipitation forecasting 127 I.D. Cluckie & D. Han 8. History of radar and radar meteorology 157 G.L. Austin & I.D. Cluckie 9. Topics related to rainfall-runoff models 171 A.Y. Shamseldin 10. Real-time river flow forecasting 181 A.Y. Shamseldin 11. River flow forecasting 197 K.M. O’Connor 12. The Galway real-time river flow forecasting system (GFFS) 215 K.M. O’Connor 13. Introduction to decision support systems 235 M. Bruen 14. Teleflood: forecasting floods in urban areas downstream of steep catchments 249 M. Bruen 15. Present operational flood forecasting systems and possible improvements 267 E. Todini 16. Holistic flood management and decision support systems 285 E. Todini Copyright © 2006 Taylor & Francis Group plc, London, UK VI TABLEOFCONTENTS 17. River flood hydraulics: theoretical issues and stage-discharge relationships 301 D.W. Knight 18. River flood hydraulics: validation issues in one-dimensional flood routing models 335 D.W. Knight 19. Numerical methods for the shallow water equations: 1D approach 387 P. Garcia-Navarro & J. Burguete 20. Numerical methods for the shallow water equations: 2D approach 409 P. Garcia-Navarro & P. Brufau 21. Sediment and debris modelling 429 G.J. Klaassen 22. Case study: flooding conditions at Sondrio on River Mallero 459 G.J. Klaassen 23. Dam break modelling 463 A. Paquier 24. Case studies in dam break modelling 473 A. Paquier 25. Risk and uncertainty in flood management 481 P.G. Samuels 26. The social construction of floods 519 C. Green 27. River basin management: room for the river 537 E. van Beek 28. River basin management: some issues and a case study 555 E. van Beek 29. Barriers inherent in flood forecasting and their treatments 569 R. Khatibi 30. Integration and goal-orientation in flood forecasting and warning 587 R. Khatibi & I.D. Cluckie Copyright © 2006 Taylor & Francis Group plc, London, UK Preface River basin management is now seen to be an increasingly important issue for authorities in many countries. The variety and extent of the issues involved are considerable, ranging from: flooding (protection of life, property and infrastructure), provision of water resources (quality as well as quantity), pollution (water treatment and waste disposal), environmental considerations (river restoration, wetlands and sustainable floodplain development) and land use (drainage requirements, soil loss and morphological changes to channels). The European Water Framework Directive is but one example of the new demands being placed upon environmental authorities responsible for river and inland waterways. This book contains edited lectures given by 16 leading European experts at an EU sponsored Advanced Study Course, held at the University of Birmingham, UK. The course was aimed at dis- seminating to young researchers and professionals knowledge and understanding from recent research on river basin modelling, as well as giving them up-to-date views on the management and mitigation of river flood risk. The primary focus was the nature and flow of information needed to mitigate the risk of flooding at a river basin level, with a secondary focus of disseminating under- standing from recent EC research projects related to global and European flooding problems. The Course lasted two weeks and was attended by 45 participants from 14 countries, selected from 76 applicants. In addition to attending lectures and questioning lecturers, participants also took part in two field trips and several other related technical sessions. The book covers many issues, including: a European perspective on flooding, the influence of climate change, hydro-informatics, hydro-meteorology, rainfall forecasting techniques, rainfall- runoff models, river flow forecasting systems, flood management and decision support systems, river flood hydraulics, numerical methods for shallow water equations, sediment and debris model- ling, dam-break modelling, risk and uncertainty issues in flood management, social and economic impacts of floods, developments in flood forecasting and warning systems. The coverage is broad, but integrated, to make it attractive to researchers and professionals working in the field of flood risk management. The editors are grateful to the many authors who prepared and delivered their lectures on the Advanced Study Course, and then edited them subsequently for inclusion in this book. They would also like to express their thanks to the international scientific panel of experts, drawn from six Member States, who advised and monitored the selection of material to be presented on the Course. Particular thanks are due to the European Commission who awarded the University of Birmingham a grant for the Advanced Study Course, under contract EVG1-CT-2001-65001, and to Mrs Karen Fabbri who acted as facilitator. Professor Donald W. Knight & Dr. Asaad Y. Shamseldin The University of Birmingham February 2005 Copyright © 2006 Taylor & Francis Group plc, London, UK 1 Introduction to flooding and river basin modelling D.W. Knight Professor of Water Engineering, Department of Civil Engineering, The University of Birmingham, Edgbaston, Birmingham ABSTRACT: The importance of understanding flood risk management from the perspective of the catchment, rather than at a purely local level is stressed. The reasons why floods occur due to natu- ral and man-made causes are highlighted. The differences between fluvial, urban and coastal flood- ing are summarised, as well as some of the common features between them. Flood disasters are shown to account for about a third of all natural disasters (by number and economic losses), and to be responsible for over half the deaths, with the trend worryingly upwards. The principles of flood alleviation are explained in terms of mainly structural or non-structural measures, and methods for reducing the overall impact of flooding are described. The philosophy of modelling meteorological, hydrological & hydrodynamic processes is shown to lead to problems of definition, as well as limi- tations in the modelling capability at both spatial and temporal scales. 1.1 INTRODUCTION 1.1.1 A catchment perspective Catchment Management Plans (CMPs) are intended to relate strategic issues governing sustain- able development and environmental concerns at a river basin or catchment scale. The topography of each catchment essentially defines the drainage pattern via streams and rivers in such a way that the volume of potential water falling as precipitation (i.e. rainfall/hail/snow) within the catchment stays within that catchment and may be accounted for in various ways via, for example in broad terms, evapotranspiration, surface run-off or groundwater flow. CMPs are thus a means of relating the flux of water through a catchment to the many practical issues related to that catchment, such as water resources, drainage capacity, flood mitigation, economic development, land use, planning controls, floodplain development, transport planning, environmental concerns, pollution control, nutrient supply, aquatic habitats, river corridor ecology and alluvial morphodynamics. These issues typically touch on a wide range of political and environmental objectives, and as such demand multi-objective management. The concept of multi-purpose river basins in the UK was first enunciated in 1871 by Lord Montague who argued that ‘The various interests on land and river, navigation and mills, drainage and water supply, fishing and manufacturers, can be adjusted and developed only by one manage- ment over the whole river’(Bailey, 1991). This well-founded concept of river basin management has survived the many changes to river management in the UK over the last 125 years (Knight, 1997), and will assume an even greater significance in the UK and Europe through the imple- mentation of the EU Water Framework Directive (2000). From the perspective of flood risk man- agement, it is self evident that individual flood alleviation schemes cannot be considered in isolation. What happens in one part of the catchment will have some effect on other parts some distance away. The move to a more strategic, catchment-based approach does not simply mean a wider view on investment in flood defences. It means taking a holistic view of flood risk manage- ment, including built development and land management patterns, nature conservation constraints Copyright © 2006 Taylor & Francis Group plc, London, UK 2 RIVER BASIN MODELLING FOR FLOOD RISK MITIGATION Map 3 - Distribution of Rainfall Figure 1.1. Distribution of rainfall in River Tone catchment (NRA, 1995). and opportunities and emergency planning arrangements. This needs to be based on a long-term view up to 50 years ahead, backed by sophisticated modelling of the dynamic physical processes at work in the catchment. An example of how the distribution of rainfall might vary with ground level within a catchment is shown in Figures 1.1 & 1.2, taken from the River Tone Catchment Management Plan (NRA, 1995). The River Tone CMP deals not only with precipitation, but also with the geology & hydro-geology, water abstraction, pollution, ecology and flood risk issues of the entire catchment. Figure 1.2 shows the land area above 100 m AOD, the floodplain area and where there are maintained flood defences. The modelling at a catchment level of the rainfall-runoff process (using a hydrological model) and the surface runoff (using a hydrodynamic model) are complex tasks. Figure 1.3 shows a simple schematic representation of a typical catchment, and how the surface run-off from vari- ous sub-catchments are combined and then modelled in a 1-D system. Sustainable development and management of floodplains and urban areas requires that a broad view be taken of river, sewerage and drainage issues. Essentially water can only be ‘stored’ or ‘moved’, and usually there are limitations on both possibilities within particular parts of a catch- ment. The most sustainable of solutions are likely to be those that address the issue of runoff at source. The introduction (or re-introduction) of storage into the rainfall-runoff relationship can be particularly effective when applied near to the point where runoff begins. Storage is also very effective further down the system, as demonstrated by the Leigh Barrier on the River Medway in the UK and the Watarase Retention Basin in Japan (23 km2). The least sustainable of options include further raising of flood defences to constrain a river ‘within bank’, or the construction of new defences to provide protection to new urban areas on the floodplain. Such solutions generally worsen the problem for other riparian developments, and it would be easy to say that they should generally only be considered when no other option is appro- priate or viable. However, this is too simplistic an approach, and the quest should be to find a solu- tion that suits the circumstances in each particular case. For example, the extremely successful Gainsborough Flood Alleviation Scheme in the UK, which combined the need for flood risk Copyright © 2006 Taylor & Francis Group plc, London, UK INTRODUCTIONTOFLOODINGANDRIVERBASINMODELLING 3 Map 11 - Floodplain Figure 1.2. High ground and floodplain areas in the River Tone catchment (NRA, 1995). Figure 1.3. Schematic representation of modelling runoff in a typical catchment (after Shaw, 1994). Copyright © 2006 Taylor & Francis Group plc, London, UK
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