Feasibility Restoration Report for By Brook , North East Bath Document title: Feasibility Restoration Report for By Brook, North East Bath Status: Final Date: May 2015 Project name: By Brook Restoration Project Project number: PB2707 Client: Bristol and Avon Rivers Trust (BART) Client contact: Ian Mock Reference: PB2707 Authors / Contributions : Peter Brunner, Clare Rodgers, Robin Parry and Benjamin Rostaing Checked by : Peter Thornton Date / initials check: 01/04/2015 Approved by: Peter Brunner Date / initials approval: 29/05/2015 This document and its contents have been prepared and are intended solely for the Bristol and Avon Rivers Trust (BART) for information and use in relation to the By Brook Restoration Project. Royal HaskoningDHV assumes no responsibility to any other party in respect of, arising out of, or in connection with this document and / or its contents. Feasibility Restoration Report for By Brook © HaskoningDHV UK Ltd ii 1 Introduction ................................................................................................................. 1 1.1 Background ........................................................................................................................................................ 2 1.2 Aims and Objectives of the Project ..................................................................................................................... 2 1.3 Scope of Project Works ...................................................................................................................................... 3 1.4 Key Guidance and Legislation ............................................................................................................................ 5 1.5 Structure of this Report ...................................................................................................................................... 6 2 The Study Area – By Brook ........................................................................................ 8 2.1 Introduction ........................................................................................................................................................ 9 2.2 Topography, Geology and Soils ....................................................................................................................... 10 2.3 Hydrology and Hydromorphology ..................................................................................................................... 13 2.4 Channel Geomorphology, Modifications and Structures .................................................................................. 14 2.5 Designated Sites .............................................................................................................................................. 43 2.6 Terrestrial Flora and Fauna .............................................................................................................................. 48 2.7 Freshwater Flora and Fauna with Special Reference to Native Crayfish ......................................................... 49 2.8 Fish Passage Criteria and Target Species ....................................................................................................... 52 2.9 Cultural Heritage and Land Use ....................................................................................................................... 53 2.10 Public Interest and Recreational Activities ....................................................................................................... 56 2.11 Past and Present Management Regime ........................................................................................................... 58 3 Environmental Conditions of the By Brook Catchment ........................................ 60 3.1 Introduction ...................................................................................................................................................... 61 3.2 Past Ecological Condition ................................................................................................................................. 62 3.3 Present Ecological Condition ........................................................................................................................... 65 3.4 Present Standards for Good Ecological Condition ........................................................................................... 67 3.5 By Brook Reach Conditions and WFD Objectives ............................................................................................ 69 4 Proposed Restoration Options for By Brook ......................................................... 74 4.1 Introduction ...................................................................................................................................................... 75 4.2 Assessment Approach ..................................................................................................................................... 75 4.3 Proposed Restoration Options ......................................................................................................................... 75 4.4 Reach 4A1: Ford Mill Weir Restoration Options - Technical Details and Appraisal .......................................... 76 4.5 Reach 4A2: Weir D/S Ford Restoration Options - Technical Details and Appraisal ......................................... 92 4.6 Reach 4A3: Sluice D/S Ford Restoration Options - Technical Details and Appraisal ....................................... 96 4.7 Reach 4A4: Slaughterford Gate Restoration Options - Technical Details and Appraisal................................ 104 4.8 Reach 4A5: Rag Mill (Slaughterford) Weir Restoration Options - Technical Details and Appraisal ................ 114 4.9 Review of BART Restoration Options for the Remaining Reaches of the By Brook Catchment .................... 123 Feasibility Restoration Report for By Brook © HaskoningDHV UK Ltd iii 5 Selection of Preferred Restoration Options for By Book .................................... 133 5.1 Introduction .................................................................................................................................................... 134 5.2 Preferred Restoration Options – Reach 4A: Ford Mill Weir to Rag Mill (Slaughterford) Weir ......................... 134 5.3 Details of Restoration Options – Reach 4A: Ford Mill Weir to Rag Mill (Slaughterford) Weir ......................... 135 5.4 Key Mitigation Measures for Reach 4A River Restoration Solutions .............................................................. 139 5.5 Restoration Solutions for the Remaining Reaches of the By Brook Catchment ............................................. 141 6 Specific Details of the Preferred Restoration Options for By Brook .................. 144 6.1 Introduction .................................................................................................................................................... 145 6.2 Preferred Restoration Options – Reach 4A: Ford Mill Weir to Rag Mill (Slaughterford) Weir ......................... 145 7 Conclusions and 4-5 Year Management Plan ....................................................... 150 7.1 Introduction .................................................................................................................................................... 151 7.2 Next Steps (Licences, Consents) and Challenges ......................................................................................... 151 7.3 Preliminary Long-Term Restoration Programme for the By Brook Catchment ............................................... 151 8 References ............................................................................................................... 155 9 List of Abbreviations .............................................................................................. 157 10 Glossary ................................................................................................................... 159 Appendix A: By Brook Project Phase I Report (BART, 2013/2014) ........................... 161 Appendix B: Crayfish Survey of the By Brook, River Avon and St Catherine’s Brook (OHES, 2014) .................................................................................................................. 163 Appendix C: By Brook Flood Risk Modelling Study (Backwater Effect of Hydraulic Structures at Low Flows) .............................................................................................. 165 Appendix D: By Brook Catchment Walkover Report – Fluvial Audit (BART, 2015) . 167 Appendix E: Ecosystem Services Assessment for By Brook ................................... 169 Appendix F: Costings of Preferred Options ................................................................ 171 Tables Table 1.1 Outline of Report....................................................................................................................... 6 Table 2.1 Historic Timeline of Anthropogenic Change in the By Brook Catchment ............................... 16 Table 2.2 Key Fish Migration Barriers of By Brook ................................................................................ 20 Table 2.3 Upstream Limit of Impoundment for Key Structures .............................................................. 21 Table 2.4 Target Fish Species and Associated River Flow Rates ......................................................... 53 Table 3.1 Ecological Status of Waterbodies