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Technical Report Beach modelling: Lessons learnt from past scheme performance Project: SC110004/R2 The Environment Agency is the leading public body protecting and improving the environment in England. It’s our job to make sure that air, land and water are looked after by everyone in today’s society, so that tomorrow’s generations inherit a cleaner, healthier world. Our work includes tackling flooding and pollution incidents, reducing industry’s impacts on the environment, cleaning up rivers, coastal waters and contaminated land, and improving wildlife habitats. This report is the result of research commissioned by the Environment Agency’s Evidence Directorate and funded by the joint Environment Agency/Defra Flood and Coastal Erosion Risk Management Research and Development Programme. Published by: Author(s): Environment Agency, Horizon House, Deanery Road, K A Burgess, A P R Frampton, A P Bradbury Bristol, BS1 5AH Dissemination Status: www.environment-agency.gov.uk Publicly available ISBN: 978-1-84911-314-4 Keywords: beach, lessons, modelling, performance, review, © Environment Agency – May 2014 scheme, waves All rights reserved. This document may be reproduced Research Contractor: with prior permission of the Environment Agency. Halcrow, a CH2M Hill company Ash House, Falcon Road, Sowton, Exeter, Devon The views and statements expressed in this report are EX2 7LB those of the author alone. The views or statements expressed in this publication do not necessarily Tel. 01392 444 252 represent the views of the Environment Agency and the Environment Agency cannot accept any responsibility for Environment Agency’s Project Manager: such views or statements. Andy Tan, Evidence Directorate E: [email protected]. Theme Manager: Stefan Laegar, Modelling and Risk R&D Theme Collaborator(s): Channel Coastal Observatory S Herrington (Herrington Consulting Ltd) A Williams (Coastal Engineering UK Ltd) Project Number: SC110004 ii Beach modelling: Lessons learnt from past scheme performance – Technical report Evidence at the Environment Agency Evidence underpins the work of the Environment Agency. It provides an up-to-date understanding of the world about us, helps us to develop tools and techniques to monitor and manage our environment as efficiently and effectively as possible. It also helps us to understand how the environment is changing and to identify what the future pressures may be. The work of the Environment Agency’s Evidence Directorate is a key ingredient in the partnership between research, guidance and operations that enables the Environment Agency to protect and restore our environment. This report was produced by the Scientific and Evidence Services team within Evidence. The team focuses on four main areas of activity: • Setting the agenda, by providing the evidence for decisions; • Maintaining scientific credibility, by ensuring that our programmes and projects are fit for purpose and executed according to international standards; • Carrying out research, either by contracting it out to research organisations and consultancies or by doing it ourselves; • Delivering information, advice, tools and techniques, by making appropriate products available. Miranda Kavanagh Director of Evidence Beach modelling: Lessons learnt from past scheme performance – Technical report iii Executive summary Beach recharge and management, such as re-profiling and recycling, accounts each year for several million pounds of the UK’s coastal flood defence capital and maintenance expenditure. Decisions on the development of such schemes are often informed by beach modelling including numerical, physical and empirical approaches. This document provides the technical detail behind the report on lessons learned from previous schemes that has been developed with the aim of improving understanding in this area. The research has specifically investigated the lessons that can be learned from the actual performance of schemes compared with original model expectations by reviewing case studies for 11 sites, summarised in this report, and drawing on anecdotal information gathered through engagement with industry practitioners. This document describes the staged research approach undertaken as two distinct phases. It also provides details on the range of modelling tools and techniques available and includes the full case studies from which the lessons learned have been taken and which are summarised in the lessons learned report. iv Beach modelling: Lessons learnt from past scheme performance – Technical report Acknowledgements During the project, consultation was undertaken with the following practitioners as part of initial discussions, meetings and wider workshops held in January and November 2012. Practitioner Organisation Project team Alan Frampton (project manager/coastal Halcrow, a CH2M Hill company scientist)1,2 Kevin Burgess (coastal engineer) 1,2 Halcrow, a CH2M Hill company Sam Box (coastal scientist) 1 Halcrow, a CH2M Hill company Andy Bradbury1,2 Channel Coastal Observatory Travis Mason Channel Coastal Observatory Sam Grootveld (project manager, Phase 1)1 Environment Agency Andy Tan (project manager, Phase 2)2 Environment Agency Anne Thurston (project executive)1,2 Environment Agency Project partner organisations Andy Parsons (coastal engineer) Halcrow, a CH2M Hill company Hakeem Johnson (coastal modeller) Halcrow, a CH2M Hill company Darren Price (coastal modeller) Halcrow, a CH2M Hill company Jonathan Rogers (coastal engineer) Halcrow, a CH2M Hill company Jackie Young (coastal engineer) Halcrow, a CH2M Hill company Nigel Pontee (coastal scientist) Halcrow, a CH2M Hill company Mike Stickley (modeller and SANDS) Halcrow, a CH2M Hill company Helen Jay (coastal scientist) Halcrow, a CH2M Hill company Simon Burchett (coastal engineer) Halcrow, a CH2M Hill company Neil Watson1 Environment Agency Uwe Dornbusch1,2 Environment Agency Chris Hayes1 Environment Agency Other contributors Jon Kemp HR Wallingford Alan Brampton1,2 HR Wallingford Malcolm Bray University of Portsmouth Ted Edwards Canterbury City Council Roger Spencer2 Arun District Council Workshop participants (not included above) Ben Carroll1,2 ABPmer Dominic Reeve1 University of Swansea Simon Herrington1 Herrington Consulting John Pos1,2 URS Carl Green1 Wyre Borough Council Alan Williams1,2 Coastal Engineering UK Tim Poate1 University of Plymouth Robert McCall1 University of Plymouth Ian Thomas1,2 Pevensey Coastal Defences Paul Canning1 Atkins Bryan Curtis2 Worthing Borough Council Clare Wilkinson2 Channel Coastal Observatory Sam Cope2 Channel Coastal Observatory Jack Eade2 Channel Coastal Observatory Jackson Harris2 Channel Coastal Observatory Suzana Ilic2 University of Lancaster 1 Attended Phase 1 workshop 2 Attended Phase 2 workshop Beach modelling: Lessons learnt from past scheme performance – Technical report v Contents 1 Introduction 1 1.1 Context 1 1.2 Background 1 1.3 Project delivery 1 1.4 Structure of reports 2 2 Phase 1 work 3 2.1 Overview of approach taken 3 2.2 Categorisation of models and applications of modelling tools and techniques 3 2.3 Identification of benchmark tests 4 2.4 Site selection 5 3 Phase 2 work 6 3.1 Comparative analysis case studies 6 3.2 Generic tests 9 3.3 Phase 2 workshop 9 References 11 List of abbreviations 12 Glossary 13 Appendix A Benchmark tests 19 A.1 Approach for determining benchmark tests 19 A.2 Potential benchmark tests for each model/approach type 19 A.3 Useful sources of additional information 27 Appendix B Site selection 28 B.1 Long list of sites 28 B.2 Short-listing criteria and selection 28 B.3 Candidate sites 36 Appendix C Comparative analysis case studies 37 C.1 Bournemouth 37 C.2 Folkestone 54 C.3 Hurst 64 C.4 Lincshore 92 C.5 Littlestone 109 C.6 Llandudno North Shore 123 C.7 Pett 138 vi Beach modelling: Lessons learnt from past scheme performance – Technical report C.8 Prestatyn 162 C.9 Preston Beach 172 C.10 Seaford 203 C.11 Southend-on-Sea 233 Appendix D Generic tests 246 D.1 Introduction 246 D.2 Model establishment 246 D.3 Results 249 D.4 Conclusions 259 List of Tables Table 3.1 Summary of information and analysis to be found in the comparative case studies 7 Table B.1 Short listed sites for possible testing 31 Table B.2 List of candidate sites 36 Table C.1.1 Summary of replenishment activities 50 Table C.3.1 Wave conditions 67 Table C.3.2 Annual recharge volumes 100 Table C.5.1 Frontage thresholds 114 Table C.5.2 Comparison of predicted and actual scheme performance 119 Table C.7.1 Original scheme programme of works 149 Table C.7.2 Action and emergency trigger levels set by the BMP (2009) 149 Table C.7.3 Proposed scheme compared to actual work to date 150 Table C.7.4 Shingle movements for the scheme up to 2011 155 Table C.8.1 Changes in beach profile 167 Table C.9.1 Recycling volumes 190 Table C.9.2 Extreme wave conditions 192 Table C.10.1 Partial record of annual beach recycling at Seaford 221 Table C.10.2 Extreme wave conditions 222 Table C.11.1 Estimated wave heights 237 Table C.11.2 Trigger levels for flood defence 239 List of Figures Figure B.1 Beach recharge scheme locations 2007 from the Beach Recharge Inventory (CIRIA 2010) 28 Figure B.2 Beach parameters 29 Figure B.3 Distribution of planned investment in beach management in England for period 2009 to 2029 (CIRIA 2010) 30 Figure C.1.1 Location of site 37 Figure C.1.2 BIS4 replenishment locations 38 Figure C.1.3 Volumetric change to Bournemouth beach since 1974 40 Figure C.1.4 Sediment sampling locations along Bournemouth 41 Figure C.1.5 Small-scale regular replenishment option
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