The Drainage Channel Biodiversity Manual Integrating wildlife and flood risk management The Drainage Channel Biodiversity Manual Integrating wildlife and flood risk management This document should be cited as: Buisson, R. S. K., Wade, P. M., Cathcart, R. L., Hemmings, S. M., Manning, C. J. & Mayer, L. (2008). The Drainage Channel Biodiversity Manual: Integrating Wildlife and Flood Risk Management. Association of Drainage Authorities and Natural England, Peterborough. Contents Page Foreword 1 Introduction 1 2 Background A manual for drainage channel biodiversity 2 Historical background 2 Wetland visions 4 Flood risk management 5 Flooding – processes and consequences 5 A changing climate 7 3 The drainage channel system and its management Multiple functions of drainage channels 9 The system – flood risk management 10 The system – biodiversity value 13 Underpinning ecological processes 15 The system – its biodiversity potential 18 4 Making decisions about intervention The wider-system approach 19 Planning for nature conservation 20 Targeting drainage channels for biodiversity enhancement 20 Making decisions – consultation 21 Compliance with legislation and policy 21 Government policy requirements 29 Water Level Management Plans 30 IDB Biodiversity Action Plans 31 Making decisions - emergency works 31 5 Management techniques Introduction 33 Choosing techniques 33 Core components of a channel management programme 34 Timing of vegetation cutting 34 Use of machinery 38 Techniques for specific interests 40 Techniques to apply for protected species 41 Techniques to apply for invertebrates 46 Techniques to apply for non-native and invasive plants 47 Drainage Channel Biodiversity Manual Page Techniques available 49 Channel Annual maintenance 53 Long-term maintenance 61 Capital works 65 Margin Annual maintenance 74 Long-term maintenance 80 Capital works 81 Banks Annual maintenance 84 Capital programmes 102 Outside Annual maintenance 111 Capital works 112 Techniques for habitats beyond the channel 114 6 Survey and monitoring Introduction 117 Surveys 117 Conducting or commissioning a desk study 117 Conducting or commissioning simple surveys 119 Monitoring 122 7 Opportunities for landowners and tenants Introduction 124 Management of landowner drainage ditches 124 Opportunities under Environmental Stewardship 127 Facilitating schemes 129 Appendices 1 Glossary 130 2 List of scientific names 134 3 Index to techniques by channel size 136 4 Herbicides 138 5 Key species for Internal Drainage Boards 140 6 Management for BAP priority plant species in drainage channels 142 7 Management for non-native and invasive plants 149 8 Bird nesting seasons 157 9 Protected species guidance 160 Index 186 Drainage Channel Biodiversity Manual Foreword We believe that The Drainage Channel Biodiversity Manual will provide invaluable assistance for operating authorities engaged in the complex management of our lowland drainage systems. The challenge has always been to manage the balance of benefits for flood risk, agricultural drainage and biodiversity. And as recent severe flooding has illustrated, the prospect of increased flood risk brought about by climate change means that this challenge is likely to grow in scale and complexity. At the same time, there is a growing need to address the plight of some of our most important wetland plants and animals. As Natural England’s State of the Natural Environment 2008 report has shown, breeding waders such as snipe remain in decline outside of Sites of Special Scientific Interest (SSSI), while numbers of water voles, great crested newts and the European eel also continue to fall. Internal Drainage Boards are uniquely equipped to make a vital contribution to the conservation of wetland wildlife: G Collectively, the IDBs are one of the biggest managers of freshwaters and wetlands in the country and thus have a significant role in maintaining and enhancing biodiversity. G The thousands of kilometres of IDB ditches and drainage channels are biodiversity-rich networks comparable in conservation importance with England’s hedgerows. G Water level management by IDBs supports distinctive wetland habitats and, more widely, characteristic landscapes such as the Norfolk Broads and Somerset Levels. G Hundreds of wetland plant and animal species that are targeted as priorities under the UK Biodiversity Action Plan can be found in IDB districts – from lichens to wildflowers and from insects to mammals. G And IDB drainage districts host scores of SSSIs and Local Nature Reserves. We hope that this manual will assist IDBs to fulfil their role as custodians of wetlands and watercourses and, importantly, help to tackle the challenge of making space for both flood waters and wildlife through the integrated planning and management of drainage catchments. Dr Helen Phillips Jean Venables OBE FREng Chief Executive Chief Executive Natural England Association of Drainage Authorities September 2008 Drainage Channel Biodiversity Manual One Introduction This new manual for the biodiversity management of drainage channels, with its aim of integrating the requirements of wildlife and flood risk management, supercedes Nature Conservation and the Management of Drainage Channels, jointly published nearly 20 years ago by the Nature Conservancy Council and the Association of Drainage Authorities. We have sought to keep firmly within the spirit of that earlier, ground-breaking publication by providing an accessible and practical guide to channel management techniques that are sympathetic or beneficial to wildlife. The manual has been written principally for the staff and members of Internal Drainage Boards operating in England. However, the techniques described should be just as useful for other public authorities undertaking flood risk and water level management activities – the Environment Agency and local authorities. Many of the techniques, particularly those that are relevant to the smaller drainage channels, could also be deployed by private landowners and conservation bodies on their landholdings. The techniques are also applicable in other parts of the United Kingdom where drainage channel networks occur, with the caveat that different laws and policies may pertain to the management of flood risk and wildlife conservation. The focus of the guidance is on artificial channels and modified natural watercourses containing slow-flowing water. The waters in these systems are often retained behind sluices and pumped out into main rivers or the sea. We use the term “drainage channel” to collectively address these types of watercourses. Guidance on managing watercourses with a more natural structure and swifter flows can be found elsewhere, particularly in The New Rivers and Wildlife Handbook (Ward, D., Holmes, N. and Jose, P. 1995) and the Manual of River Restoration Techniques (River Restoration Centre 2002). Our task in producing this new guide has been greatly helped by the willing input of the staff of Internal Drainage Boards and Natural England. We would particularly like to thank our principal authors Dr Roger Buisson and Professor Max Wade of RPS Group plc, and our illustrator and designer Coral Walton of Coral Design Management. Finally, we would like to acknowledge our debt to the earlier authors of Nature Conservation and the Management of Drainage Channels – Chris Newbold, John Honnor and Karen Buckley. Their authoritative work has largely stood the test of time and formed the foundations of this new publication. The Drainage Channel Biodiversity Manual Steering Group Rob Cathcart, Natural England Stuart Hemmings, Association of Drainage Authorities Chris Manning, Association of Drainage Authorities Lou Mayer, Association of Drainage Authorities 1 Drainage Channel Biodiversity Manual Introduction Chapter one Two Background A manual for drainage channel biodiversity In 1989, the Nature Conservancy Council and the Association of Drainage Authorities jointly published guidance titled Nature Conservation and the Management of Drainage Channels. It was a time of growing awareness of the potentially important contribution to wildlife conservation represented by drainage channels. The guidance sought to capture the techniques that were being applied in drainage systems by some Internal Drainage Boards (IDBs) for the benefit of wildlife, and to bring them to the attention of a wider audience. The publication proved to be very popular with other flood operating authorities and with landowners and conservation bodies, but eventually went out of print. Since 1989 there have been advances in our understanding of the characteristics of channels – both in terms of structure and management regime – which are beneficial to wildlife; and new techniques have been developed to deliver appropriate management. There have been several phases of reform of the Common Agricultural Policy and the subsequent revision of agri-environment schemes. In England, the Environmental Stewardship scheme has created a new agri-environment framework that provides a range of options for ditch and wetland maintenance, restoration and creation. The scheme agreements are with landowners and occupiers but IDBs can and do play a significant role in facilitating the habitat restoration and creation options that require management of water levels and drainage systems. Given these developments, Natural England and the Association of Drainage Authorities decided that it would be timely to publish a new guide to the management of drainage channels for biodiversity. The aim of this manual remains