Durham E-Theses A combined catchment and reach-based assessment of historical channel planform change in a UK upland gravel-bed river Wishart, Duncan How to cite: Wishart, Duncan (2004) A combined catchment and reach-based assessment of historical channel planform change in a UK upland gravel-bed river, Durham theses, Durham University. Available at Durham E-Theses Online: http://etheses.dur.ac.uk/2819/ Use policy The full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that: • a full bibliographic reference is made to the original source • a link is made to the metadata record in Durham E-Theses • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders. Please consult the full Durham E-Theses policy for further details. Academic Support Oce, Durham University, University Oce, Old Elvet, Durham DH1 3HP e-mail: [email protected] Tel: +44 0191 334 6107 http://etheses.dur.ac.uk 2 A combined catchment and reach-based assessment of historical channel planform change in a UK upland gravel-bed river Duncan Wishart Thesis submitted for the degree of Doctor of Philosophy Department of Geography University of Durham 2004 A copyright of this thesis rests Avith the author. No quotation from it should be published without his prior written consent and information derived from it should be acknowledged. 1 1 JAN 2005 Declaration I confirm that no part of the material presented in this thesis has previously been submitted by me or any other person for a degree in this or any other university. In all cases, where it is relevant, material from the work of others has been acknowledged. The copyright of this thesis rests with the author. No quotation from it should be published without the prior written consent and information derived from it should be acknowledged. Signed: Lu/fc^fc^) * Date: izjlfj^^ Abstract River channel planform change in upland gravel-bed rivers has consequences for riparian land use, river habitats and flood hazards. Channel planform is predominantly determined by the balance between sediment supply and prevailing discharge regime which is governed by climate and land use, and anthropogenic channel modification. While the nature of channel response to individual factors is in some cases well documented, the complex interaction of theses variables and their relative significance requires further evaluation. This study assesses the nature and extent of historic (1856-1991) channel planform change in the upland catchment of the River Wear, Northern England. A nested research strategy is adopted consisting of catchment wide and reach-scale evaluations of channel planform change using archival maps and aerial photographs. The cause of channel changes is considered with reference to hydrological records (1800-present), catchment land use (metal mining) and accounts of river channel modification (gravel extraction). Comparative historic (reach-scale) and contemporary (trunk channel) data is provided from the upper reaches of the River Tees in Teesdale, Northern England. In the mid nineteenth century a pulse of sedimentation migrated through the upper Wear catchment resulting in the development of eight major sedimentation zones with channel braiding separated by confined single thread reaches. Increased sedimentation was related to a combination of high magnitude floods during the nineteenth century and enhanced sediment supply from extensive metal mining in tributary streams. A decline in flood frequency and magnitude coupled with the cessation of metal mining during the early twentieth century, led to a reduction of sediment supply and lateral channel instability in the catchment. This promoted gravel bar stabilisation through vegetation colonisation, reducing average channel width by 56%. In the sedimentation zones, gravel bar extent declined by up to 87% and this was accompanied by a change to a single thread planform. Gravel extraction operations during the mid-twentieth century lead to local instability and delayed the decline in gravel bar area. In contrast the contemporary channel of the upper Tees is still characterised by localised channel division, around both active gravel bars and vegetated islands. Differences between the two catchments demonstrate the importance of catchment specific controls such as bedrock control and anthropogenic channel interference. A large flood on 30 July 2002 provided significant insight into the mechanism of channel planform change. Substantial increases in gravel bar extents were recorded together with localised changes in flow routing. While local controls such as gravel extraction are significant over decadal time scales, catchment scale controls, primarily changes in the frequency of large floods; determine channel pianform over centennial timescales. In order to discriminate between local and catchment controls, catchment wide assessments are required. Acknowledgements I have been fortunate to have benefited from the help of many people during the production of this thesis. I am particularly grateful to my supervisors Dr Louise Bracken and Dr Jeff Warburton for their help, advice, enthusiasm and encouragement during my research. I consider myself extremely fortunate to have had the opportunity to benefit from their knowledge, experience and dedication. This research was undertaken while I was in receipt of a NERC Studentship (GT4/00/60). I also gratefully acknowledge the Durham Geography Graduates Association who provided a grant to enable the purchase of aerial photographs. I would like to thank John Adamson and Jana Kahl from CEH Merlewood for all their help during my fieldwork in upper Teesdale, particularly during the Foot and Mouth crisis. Access to the Swinhope site was made possible by Mr Dent. I would also like to thank the Environment Agency for kindly providing discharge data for the River Wear at Stanhope and Sunderland Bridge. I would like to thank the various members of staff at Durham County Council. I am particularly grateful to the Records Office staff for making the historical maps available during my many visits to the record office. In addition Paul Everson and Michelle White of the Environment Section assisted with access to aerial photographs. My research also benefited from access to the records of Durham County Council Planning and Development Control Section pertaining to gravel extraction from the River Wear. This was kindly arranged by Ian Airton of Planning and Development Control Section. I would particularly like to thank all my friends in the Department of Geography who have provided me with support over the years. In particular I would like to thank Professor Tim Burt, Dr Antony Long, Dr Ian Evans and Dr Nick Cox, Dr Simon Harris and Professor Michael Church who all provided expertise and encouragement. Special thanks go to my dedicated fieldwork companions Alona Armstrong and Sarah Clement, who always made fieldwork fun, even when things did not go to plan. I must also thank Dr Vicky Holliday for the many visits to Swinhope and Burnhope. Also Simon iv Nelis, Erin McClymont and Eddie Million also ventured into the field to help me and I am very grateful. Technical assistance was provided by the laboratory staff Derek Coates, Eddie Million, Brian Preistley, Frank Davies and Neil Tunstall. I would like to thank Eddie in particular for arranging field kit, often with less than the required period of notice, sorry! I am especially grateful to Derek Hudspeth and Christine Bones who assisted with vehicle bookings, equipment purchasing and other financial matters. My thanks also go to Stella Henderson for binding and copying and also for her cheery and calming influence. I am also grateful to Andy Mills for his introduction to the marvel that is FreeHand, to Nick Cox for providing useful Stata tuition and also Katherine Arrell, Dr Helen Dunsford and Pete Watt who provided valuable advice and tuition with GIS. I would extend special thanks to my 301A officemates and good friends Alison Scott, Colin McFarlane, Dr Doug Lionais, Simon Nelis and Martin Bickl for the great times we had whilst 'working'. I also thank my fellow postgraduates who have been good friends over the years and made my time in Durham so enjoyable. In particular I would like to thank Elizabeth Mackie, Erin McClymont, Sarah Clement, Alona Armstrong, Katherine Arrell, Matt Wright, Dr Kay McManus, Dr Rachel Flanary, Jacqueline Rae, Pau Obrador, Dr Richard Johnson, James Smith, Sarah Woodroffe, Matt Brain, Penny Widdison, Dr Damian Laidler, John Thompson and Dr James Bendle. Thanks also to Uncle George for printing the final copies (and also for his patience and tolerance). Finally special thanks to my wife Sarah who has been a constant source of support and encouragement during my research and to my parents for their support throughout my academic career. List of contents Title page Declaration Abstract Acknowledgements List of Contents vi List of Figures xi List of Tables xx Chapter 1 Introduction 1 1.1 River channel planform change in upland catchments 1 1.2 Research strategy 9 1.3 Aims and objectives 11 1.4 Thesis structure 12 Chapter 2 The nature and causes of river channel planform change in UK upland catchments 15 2.1 Scope of chapter 15 2.2 The nature of planform change in British upland catchments 15 2.2.1 Channel planform classification