River Wensum Restoration Strategy Implementation SSSI Unit 54 Taverham Mill to Mill

FEASIBILITY & ENVIRONMENTAL SCOPING ASSESSMENT

April 2012

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River Wensum Restoration Strategy Implementation SSSI Unit 54: Feasibility and Environmental Scoping Report

River Wensum Restoration Strategy

Implementation SSSI Unit 54

Taverham Mill to Hellesdon Mill Feasibility & Environmental Scoping Assessment

April 2012 Notice

This report was produced by Atkins for the Environment Agency for the specific purpose of assessing the feasibility of restoring favourable condition to the River Wensum SSSI. This report may not be used by any person other than the Environment Agency without Environment Agency express permission. In any event, Atkins accepts no liability for any costs, liabilities or losses arising as a result of the use of or reliance upon the contents of this report by any person other than the Environment Agency. Document History

JOB NUMBER: 5078052 DOCUMENT REF: 5078052/60/DG/101 Revision Purpose Description Originated Checked Reviewed Authorised Date v01 Internal Draft Ian Morrissey 18/02/11 v10 Draft for client review Ian Morrissey Kevin Skinner Kevin Skinner Don Ross 16/05/11 v1.0 Final for issue Ian Morrissey Robin Chase Kevin Skinner Don Ross 05/04/2012

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River Wensum Restoration Strategy Implementation SSSI Unit 54: Feasibility and Environmental Scoping Report

Contents Section Page Non Technical Summary 1 1. Introduction 3 1.1 Context 3 1.2 River Wensum Restoration Strategy 7 1.3 Feasibility Assessment aims 9 1.4 Methodology 9 2. Taverham Mill to Hellesdon Mill Overview 12 2.1 Terminology and site location 12 2.2 Previous works within Unit 54 14 2.3 RWRS restoration vision for Unit 54 15 3. Environmental Baseline 17 3.1 Introduction 17 3.2 Common environment features across all reaches 18 3.3 Environmental baseline for each reach within Unit 54 34 4. Consultation 66 4.1 Introduction 66 4.2 Consultation with key stakeholders 66 4.3 Drop-in session September 2009 68 4.4 Future consultation 68 5. Multi-Criteria Analysis Options Appraisal 70 5.1 Introduction 70 5.2 Constructing the MCA tool 70 5.3 Using the MCA Tool 76 6. Developing Conceptual Design 85 6.1 Introduction and approach 85 6.2 Description of River Restoration and Targeted Maintenance options 85 6.3 Reach 01: Hellesdon Reach 92 6.4 Reach 02: Drayton Reach 98 6.5 Reach 03: Reach 106 7. Cost Estimate 115 7.1 Previous cost estimates 115 7.2 Present cost estimates 116 7.3 Potential cost savings 119 7.4 Delivery 121 7.5 Summary 122 8. Environmental Scoping 124 8.1 Introduction 124 8.2 Method of assessment 126 8.3 Results of scoping 127 9. Consents 135 10. Project Risks 137 Unit 54 Taverham Mill to Hellesdon Mill_final for issue_V1.0.docx

River Wensum Restoration Strategy Implementation SSSI Unit 54: Feasibility and Environmental Scoping Report

11. Conclusions and Recommendations 139 11.1 Conclusions 139 11.2 Recommendations 140 12. References 141 Appendices 144 Appendix A – Multi-Criteria Analysis technical note Appendix B – Costings Appendix C – Ecology tables Appendix D – Terrestrial SSSI unit links to River Wensum SSSI units List of Figures Figure 1.1- Unit 54 River Wensum location plan 4 Figure 1.2 – Environmental and restoration related investigations and events, showing how this assessment fits within the process of realising restoration on the River Wensum. 6 Figure 1.3 - The approach adopted during feasibility assessment for determining the recommended restoration option on individual reaches and the overall river unit 10 Figure 2.1 - Location of Reaches 01, 02 and 03 within Unit 54 13 Figure 3.1 - Environmental constraints on Unit 54 30 Figure 3.2 - Environmental baseline for Reach 01 (Hellesdon Reach) 37 Figure 3.3 - Environmental baseline for Reach 02 (Drayton Reach) 42 Figure 3.4 - Environmental baseline for Reach 03 (Costessey Reach 47 Figure 6.1 - Conceptual restoration plan for Reach 01 (Hellesdon Reach) 97 Figure 6.2 - Location of sub-reaches within Reach 02 (Drayton Reach) 103 Figure 6.3 - Conceptual restoration plan for Reach 02a (Costessey Mill to Marriott’s Way) 104 Figure 6.4 - Conceptual restoration plan for Reach 02a (Marriott’s Way to Wensum Mount Farm) 105 Figure 6.5 - Location of sub-reaches within Reach 03 (Costessey Reach) 112 Figure 6.6 - Conceptual restoration plan for Reach 03a (Taverham Mill to Place Farm) 113 Figure 6.7 - Conceptual restoration plan for Reach 03b (Place Farm to Costessey Mill) 114 Figure 8.1 - Environmental Scoping within the EIA process 125

List of Tables Table 1.1 - Chapters constituting this report 7 Table 2.1- Summary of previous restoration works consented on Unit 54 14 Table 2.2 - Recommended restoration measures for each reach as provided in the RWRS (JBA, 2007) 15 Table 3.1 - Mill details in Unit 54 (Environment Agency, 2007a) 24 Table 3.2 - WFD quality assessment (Environment Agency, 2010b) 25 Table 3.3 - HDERF Thresholds for SAC/SSSI rivers 26 Table 3.4 - Summary of abstraction impacts relative to naturalised flow and the HDERF in the Q70-95 range27 Table 3.5 - Condition summary of Unit 54 attributes (Natural England, 2010) 29 Table 3.6 - Baseline information common to Unit 54 31 Table 3.7 - Baseline information specific to Reach 01 (Hellesdon Reach) 34 Table 3.8 - Baseline information specific to Reach 02 (Drayton Reach) 38 Table 3.9 - Baseline information specific to Reach 03 (Costessey Reach) 43 Table 4.1 - Consultation undertaken to date 66 Table 5.1 - Overview of the process by which the MCA was constructed and applied 70 Table 5.2 - Restoration measures recommended in previous studies 71 Table 5.3 - Options identified for restoration on the River Wensum 72

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Table 5.4 - Description of river restoration measures as defined under option G5 73 Table 5.5 - Criteria defined for the MCA 75 Table 5.6 - Scoring system defined for the Multi-Criteria Analysis 76 Table 5.7 - Results of MCA for Reach 01 (Hellesdon Reach) 78 Table 5.8 - Results of MCA for Reach 02 (Drayton Reach) 79 Table 5.9 - Results of MCA for Reach 03 (Costessey Reach) 80 Table 5.10 - Summary of favourable options and measures for Unit 54 83 Table 6.1 - Different management classes of restoration activity 86 Table 6.2 - Active and passive river restoration measures 86 Table 6.3 - River restoration measures and their potential ecological benefits 89 Table 6.4 - The effect of river restoration measures according to flow condition 90 Table 6.5 - Significant features and possible measures observed for Reach 01 during site visit (February, 2011) 93 Table 6.6 - Review of strategy objectives and recommendations for Reach 01 94 Table 6.7 - Recommended restoration options for Reach 01 95 Table 6.8 – Key characteristics of Reach 14 sub-reaches 98 Table 6.9 - Significant features and possible measures observed for Reach 02 during site visit (February, 2011) 99 Table 6.10 - Review of strategy objectives and recommendations for Reach 02 100 Table 6.11 - Recommended restoration options for Reach 02 101 Table 6.12 – Restoration measure suitability rating for Reach 02 sub-reaches 101 Table 6.13 – Key characteristics of Reach 14 sub-reaches 106 Table 6.14 - Significant features and possible measures observed for Reach 03 during site visit (February, 2011) 107 Table 6.15 - Review of strategy objectives and recommendations for Reach 03 108 Table 6.16 - Recommended restoration options for Reach 03 109 Table 6.17 – Restoration measure suitability rating for Reach 03 sub-reaches 110 Table 7.1 - RWRS Unit 54 cost estimate (JBA, 2007) 115 Table7.2 - Halcrow PSA Unit 54 cost estimate 116 Table7.3 - Comparison of cost estimates between JBA and Halcrow reports for Unit 54 116 Table 7.4 - Unit 54 cost estimates for various river restoration measures (February 2012) 117 Table 7.5 – Unit 54 cost estimates for each reach / sub-reach 118 Table 7.6 - Measures that typically generate or require spoil 119 Table 7.7 - Gravel substitution using surplus fill 120 Table 7.8 - Recommended phasing of work 121 Table 7.9 Recommended phasing of restoration measures for Unit 54 122 Table 7.10 - Comparison of costs between 2007, 2008 and 2011 studies 123 Table 8.1 - Classifying and evaluating the significance of potential environmental effects in the scoping process (adopted from European Commission, 2001) 126 Table 8.2- Environmental scoping assessment for recommended restoration options 129 Table 8.3 - Issues scoped into the EIA process 133 Table 8.4 - Issues scoped out of the EIA process 134 Table 9.1 - Likely planning consents and permissions 135 Table 10.1 – Key project risks that may delay the delivery of the recommended options for Unit 54 138

List of Plates Plate 1 - Costessey Mill tilting gate (February 2009) 23 Plate 2 – Reach 01: Hellesdon Mill main weir structure (NGR TG1987110444, February 2011) 24

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Plate 3 – Reach 01: Top end of reach showing marginal vegetation encroachment along a severely over- widened channel section (looking downstream, NGR TG 19193 11541, February 2011) 48 Plate 4 – Reach 01: Amenity grassland area with mature willows along TLHB (Wensum to right of photo) (NGR TG 19354 11520, February 2011) 48 Plate 5 – Reach 01: IDB drain along TLHB with very clear water and diverse aquatic flora (NGR TG 19366 11526, February 2011) 48 Plate 6 – Reach 01: River Wensum (looking upstream) showing over-widened and deepened channel and poor habitat diversity (NGR TG 19413 11478, February 2011) 49 Plate 7 – Reach 01: Substantial marginal vegetated berm encroachment along very wide section (TRHB), with private gardens along TLHB (NGR TG 19638 11203, February 2011) 49 Plate 8 – Reach 01: Linear willow margin along top of TRHB dredged material embankment (Wensum to right of photo, looking upstream, NGR TG 19684 11151, February 2011) 49 Plate 9 – Reach 01: Tree clearance works by private landowners (NGR TG 19712 11124, February 2011) 50 Plate 10 – Reach 01: Mid reach showing dredging embankment along TRHB (looking upstream, February 2011) 50 Plate 11 – Reach 01: 4.3ha SSSI land parcel formed of an extensive sedge bed and alder carr associated with the River Wensum, looking west from TRHB (NGR TG 19712 11124, February 2011) 50 Plate 12 – Reach 01: Fallen crack willows across over-widened channel upstream of Hellesdon Mill weirs (NGR TG 19770 10596, February 2011) 51 Plate 13 – Reach 01: Upstream view of managed channel of River Wensum immediately upstream of Hellesdon Mill weirs (NGR TG 19791 10555, February 2011) 51 Plate 14 – Reach 01: River Tud automated overshot tilting gate (NGR TG 19797 10551, February 2011) 51 Plate 15 – Reach 01: Main flow route through Hellesdon Mill weir systems (NGR TG 19889 10448, February 2011) 52 Plate 16 – Reach 01: Hellesdon Mill Bridge showing main flow through central archway (NGR TG 19902 10449, February 2011) 52 Plate 17 – Reach 01: View downstream of Hellesdon Mill Bridge (NGR TG 19889 10448, February 2011) 52 Plate 18 – Reach 02: View from road bridge looking downstream to Costessey Mill leat – very little flow and heavy shading (NGR TG 17737 12773, February 2011) 53 Plate 19 – Reach 02: Main River Wensum downstream of Costessey horseshoe weir (NGR TG 17686 12817, February 2011) 53 Plate 20 – Reach 02: Cattle drink area constructed near confluence between main river and Costessey Mill leat with overhanging osier along TLHB (looking upstream, NGR TG 1774713026, February 2011) 53 Plate 21 – Reach 02: Large fallen willow at IDB confluence, within Ketteringham’s Fishery restoration scheme (NGR TG 17677 13180, February 2011) 54 Plate 22 – Reach 02: Artificial gravel riffle / run installed along main river section (former railway bridge in background and wetland habitat along TLHB floodplain) (NGR TG 17705 13190, February 2011) 54 Plate 23 – Reach 02: Adjoining backwater, widened drain section with connection pipe in foreground (otter footprint noted) (NGR TG 17881 13231, February 2011) 54 Plate 24 – Reach 02: View upstream showing wide, consolidated, vegetated berm encroachment post- dredging works along TLHB, with notable, high, gravel-rich embankments along TRHB (NGR TG 18111 13152, February 2011) 55 Plate 25 – Reach 02: Fallen trees across whole river width creating localised increase in flow diversity and scour (NGR TG 18160 13083, February 2011) 55 Plate 26 – Reach 02: Dredged material embankment along TRHB (NGR TG 18219 13013, February 2011) 55 Plate 27 – Reach 02: Gravel within TRHB dredged material embankments, note shell of Lister’ s river snail (Viviparus conectus) 56 Plate 28 – Reach 02: View upstream showing dredged material embankment containing gravel along TRHB and lower, subsequent dredging soil along TLHB (NGR TG 18361 12927, February 2011) 56

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River Wensum Restoration Strategy Implementation SSSI Unit 54: Feasibility and Environmental Scoping Report

Plate 29 – Reach 02: Connected drain to TLHB with raised dredged material embankments (NGR TG 18401 12877, February 2011) 56 Plate 30 – Reach 02: Downstream view of wide meandering river section (NGR TG 18874 12566, February 2011) 57 Plate 31 – Reach 02: Chalky outcrop along TLHB (TG 18878 12361, February 2011) 57 Plate 32 – Reach 02: Floodplain sedge bed along TLHB, note steep natural escarpment to left of photo (NGR TG 18868 12508, February 2011) 57 Plate 33 – Reach 02: Over-widened reach with overhanging trees on TRHB and sedge margins along TLHB (NGR TG 18761 12102, February 2011) 58 Plate 34 – Reach 02: Gas main (left, TG 18770 11991) and oil pipeline (TG 18777 11963) crossings (February 2011) 58 Plate 35 – Reach 02: Large fallen tree across river from TRHB, marginal vegetation encroachment downstream of debris, good otter habitat along this reach (TG 18777 11910, February 2011)58 Plate 36 – Reach 02: Wide channel section on approach to railway siding, heavy tree shading and little in- channel flow variation (NGR TG 18787 11836, February 2011) 59 Plate 37 – Reach 02: Alder carr and wet floodplain area, with adjoining drains along TLHB. Otter footprints found in this area (TG 18833 11732, February 2011) 59 Plate 38 – Reach 02: Downstream end of reach showing marginal vegetation encroachment into deepened and widened channel (NGR TG 18833 11732, February 2011) 59 Plate 39 – Reach 03: Downstream of Taverham weir, note sandy bed substrates with variety of aquatic plants (September 2009) 60 Plate 40 – Reach 03: Large, shallow outer meander area providing good fish fry habitat, poached by horses (NGR TG 16209 13571, February 2011) 60 Plate 41 – Reach 03: Downstream view to River Wensum across horse-grazed paddocks showing meander, overhanging osier, common reed margins along TRHB (NGR TG 19208 13648, February 2011) 60 Plate 42 – Reach 03: Territorial otter spraint marking along TLHB (NGR TG 16212 13481, February 2011) 61 Plate 43 – Reach 03: Dredged meander bend with marginal vegetation encroachment and tall herb growth where TLHB fenced, with isolated mature trees along TRHB (NGR TG 16250 13455, February 2011) 61 Plate 44 – Reach 03: Over-widened section with poplars along TRHB and horse poaching along TLHB (NGR TG 16443 13354, February 2011) 61 Plate 45 – Reach 03: public supply intake at Costessey (NGR TG 16479 13264, September 2009) 62 Plate 46 – Reach 03: Post-dredging recovery of river margin along TLHB (NGR TG 16584 13131, February 2011) 62 Plate 47 – Reach 03: Downstream view of shallow, gravel run habitat with vegetated island and margins (NGR TG 16643 12924, September 2009) 62 Plate 48 – Reach 03: View upstream showing vegetated berm development on TLHB and overhanging osier providing cover to TRHB (NGR TG 16730 12710, February 2011) 63 Plate 49 – Reach 03: Wide, straightened section with shallow water suitable for gravel augmentation (NGR TG 16665 12058, February 2011) 63 Plate 50 – Reach 03: Poaching along TLHB allowing breaching of embankments at high flows, note flint- gravel-chalk layer at water level (NGR TG 17247 12032, February 2011) 63 Plate 51 – Reach 03: Private garden along TRHB (NGR TG 17379 12101, February 2011) 64 Plate 52 – Reach 03: Downstream view towards Costessey Mill, with deep, slack flowing water and dredged material embankments along TLHB (NGR TG 17599 12501, February 2011) 64 Plate 53 – Reach 03: Middle weir at Costessey with fish pass structure (not suitable for coarse fish passage) (NGR TG 17718 12752, February 2011) 64 Plate 54 – Reach 03: Costessey Horseshoe Weir flow measurement site (NGR TG 17663 12742, February 2011) 65

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River Wensum Restoration Strategy Implementation SSSI Unit 54: Feasibility and Environmental Scoping Report

Plate 55 – Reach 03: View upstream to Costessey Horseshoe weir (NGR TG 17671 12771, February 2011)65 Plate 56 – River alteration continuum 85

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River Wensum Restoration Strategy Implementation SSSI Unit 54: Feasibility and Environmental Scoping Report

Abbreviations Acronym Meaning

AOD Above Ordnance Datum

AWS Anglian Water Services

BAP Biodiversity Action Plan

BDC Broadland District Council

CRoW Countryside Right of Way

CWD Coarse Woody Debris (term used in RWRS for LWD)

CWS County Wildlife Site

EIA Environmental Impact Assessment

ECSFDI England Catchment Sensitive Farming Delivery Initiative

ESA Environmentally Sensitive Area

GPDO General Permitted Development Order

GQA General Quality Assessment

IDB Internal Drainage Board

JNCC Joint Nature Conservation Committee

LWD Large Woody Debris

MCA Multi-Criteria Analysis

NACA Anglers Conservation Association

NCC Norfolk County Council

PIT Passive Integrated Transponder

PSA Public Service Agreement

PWS Public Water Supply

RCS River Corridor Survey

RBMP River Basin Management Plan

RWRS River Wensum Restoration Strategy

RRC River Restoration Centre

SAC Special Area of Conservation

SAP Site Action Plan

SI Statutory Instrument

SNC South Norfolk Council

SSSI Site of Special Scientific Interest

STW Sewage Treatment Works

TLHB True Left Hand Bank

TRHB True Right Hand Bank

TWS Total Weighted Score

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River Wensum Restoration Strategy Implementation SSSI Unit 54: Feasibility and Environmental Scoping Report

WFD Water Framework Directive WLMP Water Level Management Plan

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River Wensum Restoration Strategy Implementation SSSI Unit 54: Feasibility and Environmental Scoping Report

Non Technical Summary

Introduction This feasibility and environmental scoping report identifies river restoration options that could be implemented to restore Unit 54 (Taverham Mill to Hellesdon Mill) of the River Wensum Site of Special Scientific Interest (SSSI) to ‘unfavourable recovering’ or ‘favourable’ ecological condition. To achieve this aim, a range of specific technical, economic, environmental and social objectives need to be met. Objective The primary objective is to identify a range of restoration options to deliver physical modifications that will improve the ecological condition of the River Wensum. If river alterations are not implemented there remains a risk that the Government Public Service Agreement (PSA) target for SSSI condition will not be met and the river will not be returned from its current ‘unfavourable no change’ status to ‘unfavourable recovering’ or ‘favourable’ ecological condition. This report leads on from the River Wensum Restoration Strategy by assessing all river management options, including river restoration, in a transparent manner to demonstrate to stakeholders that all options for improving the SSSI condition of the River Wensum have been considered. A key outcome of this report is the development of a conceptual design for the recommended restoration option. The River Wensum is also designated as a “Protected Area” under the European Union’s Water Framework Directive. An objective of the Anglian River Basin Management Plan is to improve the river from its current status of bad ecological potential to good ecological potential by 2027. Measures to meet this objective include large scale habitat improvements, such as removing impoundments on the river, restoring gravel beds, narrowing the channel, increasing the amount of large woody material and modifying the weed cutting regime at critical phases of fish life cycles. Consultation Extensive public and private land owner consultation was undertaken in September 2009 regarding management and restoration of the River Wensum for Unit 54. Consultation was in the form of a public drop in day at Ringland and submission of feedback forms from the public. The Environment Agency communicated with riparian landowners, and organisations including Natural England, Norfolk County Council, Broadland District Council, South Norfolk Council, the Norfolk Rivers Internal Drainage Board, Norfolk Wildlife Trust and water recreation groups including anglers and canoeists. Initial input from these organisations suggests support for implementing restoration options and any other wider environmental enhancements. However a minority remain convinced that more regular maintenance, including dredging, as well as the retention of the impoundments behind mills, is the key to improving river health. Options for restoration The conceptual restoration designs have taken into account the future reductions in surface water abstraction at Costessey that are required as an outcome of the Habitats Directive Review of Consents. Anglian Water Services is aiming to reduce its reliance on abstraction from the River Wensum SSSI by 2015, and to have a long term-solution in place by 2020. Long term solutions will need to assume that the river in its restored condition is the baseline for identifying any site- specific ecological flow requirements that may be required. A Multi-Criteria Analysis (MCA) was applied across a range of strategic river management / restoration options. The MCA allowed the appraisal of all options individually, and against each other, for their technical, economic and environmental constraints and opportunities. This

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River Wensum Restoration Strategy Implementation SSSI Unit 54: Feasibility and Environmental Scoping Report

provided an objective and transparent method for determining the most suitable restoration options for improving the SSSI condition. The result of the MCA for this river unit showed that our recommended option is a combination of river restoration works and targeted maintenance. This includes changing the retained water level at Hellesdon Mill and re-evaluating the current maintenance regime. A conceptual design for river restoration and targeted maintenance has been developed and this can be applied across the entire unit, at a reach level or at a more discrete ‘section’ level. Costs Indicative costs for implementing the preferred river restoration option have been developed based on a per unit length of the main river channel. The estimated cost of the recommended options for this unit is £754,000 (to the nearest thousand). The potential for cost savings has been explored through the re-use of previously excavated spoil to raise the river bed, reducing the extent of certain measures without compromising their function, using locally sourced materials and phasing the work efficiently. Environmental Scoping A high level environmental scoping appraisal has been undertaken against the potential restoration options. The result of this assessment has enabled environmental criteria to be scoped in or out of the Environmental Impact Assessment (EIA) process. In addition, key environmental constraints and opportunities have been identified that will require supplementary appraisal during detailed design of the restoration projects.

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River Wensum Restoration Strategy Implementation SSSI Unit 54: Feasibility and Environmental Scoping Report

1. Introduction 1.1 Context

1.1.1 River Wensum The River Wensum is a low gradient chalk river located in Norfolk, England (see Figure 1.1). The river, and a number of adjacent floodplain land parcels, are of national and international importance for wildlife, being designated as a Site of Special Scientific Interest (SSSI) and as a Special Area of Conservation (SAC). As a chalk river the Wensum is also recognised as a priority habitat within the UK Biodiversity Action Plan (BAP). Past physical modifications to the River Wensum and tributaries have been undertaken to drain adjacent lands to improve their agricultural value and to provide water storage for milling. These modifications have included extensive dredging which has straightened and over-deepened the channel, significantly impacting on the natural geomorphology and ecology of the river. The 14 redundant mill structures along the course of the River Wensum have significant hydrological impounding effects, with river water backing up behind these structures under a range of flows. This results in sluggish flows and accumulation of sediment in the channel, which, over time, have contributed to the River Wensum being in unfavourable ecological condition. The latest condition assessment of the SSSI (Natural England, 2010) found all of the riverine SSSI units to be in ‘unfavourable no change’ condition. Reasons cited for this condition include poor water quality, excessive siltation and physical modifications. Physical modifications of the river, and to some extent siltation, will be addressed through a programme of river restoration measures designed to help return the river to ‘unfavourable recovering’ or ‘favourable’ ecological condition. This Feasibility Report considers various options and measures by which this restoration can be achieved. Issues of poor water quality are being addressed at a strategic level through other projects such as the England Catchment Sensitive Farming Delivery Initiative (ECSFDI) and a review of existing abstraction licences and discharge consents. The Anglian River Basin Management Plan (RBMP) produced by the Environment Agency as required under the EU Water Framework Directive (200/60/EC) identifies the River Wensum upstream of Norwich as a heavily modified water body with bad ecological potential. The river’s bad ecological potential is attributed partly to its hydromorphological limitations resulting from historic alterations and unsympathetic management. The River Basin Management Plan includes a programme of measures, including river restoration, to improve the ecological condition of the river. Also relevant for Unit 54 is the outcome of the Habitats Directive Review of Consents for the River Wensum SAC. The Site Action Plan (SAP) for the SAC (Environment Agency, 2010a) concluded that abstraction was causing an adverse effect on the integrity of the SAC and that the preferred option to address this was to modify Anglian Water’s abstraction at Costessey. The SAP recommended that: “In the first instance, and before 2015, a reduction equivalent to 20Ml/d shall be applied to the total annual licensed quantity to remove the risk to the site in its current condition from fully licensed abstraction”; and “subsequent to this, and following appropriate restoration actions in Unit 54 of the river, further modification of the licence will occur to ensure the required flow standards are met at the Hellesdon Mill”. Conceptual restoration designs therefore need to take into account the future reductions in abstraction and the relative timing of actions needs to be considered. Conversely, the quantification of further abstraction reductions beyond 2015 needs to have the river in its restored condition as the baseline for defining, if appropriate, any site-specific ecological flow requirements. It is important to note that if addressing one reason for Adverse Condition of the SSSI / SAC is problematic or delayed this should not be used to justify delay in addressing other reasons.

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River Wensum Restoration Strategy Implementation SSSI Unit 54: Feasibility and Environmental Scoping Report

Figure 1.1- Unit 54 River Wensum location plan

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River Wensum Restoration Strategy Implementation SSSI Unit 54: Feasibility and Environmental Scoping Report

1.1.2 Feasibility Report This report continues the work commenced through the River Wensum Restoration Strategy (RWRS) (JBA, 2007), and represents the next step in the implementation of restoration. It defines a preferred restoration approach for Unit 54 (Taverham Mill to Hellesdon Mill). The outcomes of this feasibility report will inform the detailed design and implementation of river restoration for this section of channel. The feasibility assessment continues the partnership between the Environment Agency and Natural England (formerly English Nature). It relates specifically to Unit 54 (River Wensum, Taverham Mill to Hellesdon Mill) and the three ‘reaches’, 01, 02 and 03, which fall within this unit (see Section 2.1 for definitions of the terms ‘reach’ and ‘unit’). Figure 1.2 illustrates where this feasibility assessment fits within the planning of restoration on the River Wensum. The reach is approximately 8.7km in length and is delineated upstream by Taverham Mill and downstream by Hellesdon Mill. Feasibility reports are available as separate documents for the following river SSSI units:  Unit 46  Unit 47 Tatterford Common to Fakenham Mill  Unit 48 Fakenham Mill to Great Ryburgh Mill  Unit 49 Great Ryburgh Mill to Bintree Mill  Unit 50 Bintree Mill to North Elmham Mill  Unit 51 North Elmham Mill to Elsing Mill  Unit 52 Elsing Mill to Lenwade Mill  Unit 53 Lenwade Mill to Taverham Mill.

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River Wensum Restoration Strategy Implementation SSSI Unit 54: Feasibility and Environmental Scoping Report

An ecological survey (Holmes, 1980) of the river established that plant communities present in 1980 Ecological survey the upper reaches were typical of chalk rivers. This survey was repeated in 2002 (Grieve et al., 2002).

The Wensum Valley Countryside Management Project was established in 1988 as a joint venture between the Countryside Commission and local authorities. The objectives of the 1988 Wensum Valley Countryside Management Project project included the enhancement of wildlife habitats, landscape and recreational value of the valley.

The entire river was notified as a SSSI in February 1993, as an example of an enriched 1993 SSSI designation calcareous lowland river. The citation describes it as “probably the best whole river of its type in nature conservation terms”.

The Wensum Valley Strategy was published in 1994 by the Wensum Valley Project to provide Wensum Valley Strategy 1994 a framework for taking the project objectives forward and defines policies for future management of the valley.

The River Rehabilitation Feasibility Study of the River Wensum by Econ represented the first River Rehab WLMP 1999 specific review of restoration options for the River Wensum. In 1999, the first Water Level Feas Study Management Plan for the Wensum was also produced.

The Wensum Valley Project hosted a meeting between the Environment Agency, English 2002 Wensum Forum Nature and local landowners / IDB members.

A condition assessment of the SSSI unit was undertaken by English Nature (now Natural SSSI Condition Assessment 2002 England) and concluded that the river was in ‘unfavourable declining’ condition due mainly to water impoundment caused by physical structures (e.g. mills), siltation and water quality.

2004 - Geomorphological appraisal of the Geodata Services assessed the form and function of the river, and provided reach-based

2005 River Wensum SAC guidance on the management required to restore the natural geomorphology.

Wensum Fisheries Action Plan The Wensum Fisheries Action Plan group identified the need to fund and implement further 2004 habitat restoration schemes on the river to aid the sustainable recovery of fish stocks

This steering group was convened in order to consider the outcomes of the geomorphological English Nature Steering Group 2005 appraisal and to determine a way forward for improving the condition of the SSSI through river convened restoration.

Qualifying features for the SAC designation are white-clawed crayfish, Desmoulin’s whorl snail, 2005 SAC designation confirmed brook lamprey, bullhead and water crowfoot vegetation communities This revision of the previous Water Level Management Plan (1999) provides a framework for Water Level Management Plan, managing appropriate water levels, and was driven largely by the need to achieve nature 2007 River Wensum SSSI conservation objectives. Recommendations related to promoting agri-environment schemes and modifying impounding mill structures.

The River Wensum Restoration Strategy (RWRS) was completed by JBA in November 2007 River Wensum Restoration for Natural England, and represents a culmination of much of the previous work. This strategy 2007 Strategy considered the entire River Wensum but identified a range of high level river restoration options on a reach by reach basis.

Condition assessment of the SSSI unit was undertaken by Natural England and concluded that the river was in ‘unfavourable no change’ condition. Reasons cited for the condition include 2010 SSSI Condition Assessment water abstraction, water pollution from agriculture / run off and discharges, inappropriate water levels and inappropriate weirs, dams and other structures.

Feasibility Report: Unit 54 – This report considers a number of restoration options specifically for Unit 54 and recommends the preferred restoration measure, or suite of measures, for each reach within the unit. The Taverham Mill to Hellesdon Mill report makes recommendations as to which of these measures should be progressed to 2011

Present achieve improvement for the unit as a whole. Future Outline and Detailed design of The detailed design of the recommended measures will be undertaken and associated consent applications (e.g. Flood Defence Consent) will be made. recommended options for the unit An environmental assessment of the proposed scheme will be undertaken

Future Construction River restoration measures will be constructed. Future Monitoring Monitoring of the effectiveness of the constructed measures will be on-going.

Figure 1.2 – Environmental and restoration related investigations and events, showing how this assessment fits within the process of realising restoration on the River Wensum.

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1.1.3 Structure of this report This report has been structured to reflect the sequential process by which the recommended restoration options have been determined. Table 1.1 lists the report chapters and provides a brief description of their contents. Table 1.1 - Chapters constituting this report

Chapter Title Description This chapter presents the context of the River Wensum, and 1 Introduction introduces the RWRS. It also discusses the methodology used in this report. Chapter 2 introduces the specific section of river considered in this Taverham Mill to report, namely Unit 54, discussing location, previous restoration 2 Hellesdon Mill initiatives, and those restoration measures recommended by the Overview RWRS. Chapter 3 provides an overview of the environmental baseline for 3 Environmental Baseline the unit. It is provided on a reach by reach basis, focusing on reach- specific information. Chapter 4 provides details of the consultation process undertaken 4 Consultation as part of this feasibility assessment, and the main issues raised. Chapter 5 presents the Multi-Criteria Analysis, explaining the 5 Options Appraisal methodology and those options which scored highest for each reach. Developing Conceptual Chapter 6 presents a conceptual restoration plan for each reach 6 Design based on results from the Multi-Criteria Analysis. Chapter 7 provides an estimate of costs for the preferred restoration 7 Cost Estimates option and identifies potential cost saving efficiencies in materials and phasing of the proposed works. The specific restoration plan proposed for the unit is subjected to an environmental scoping process. This determines the key 8 Environmental Scoping environmental issues to be considered in the environmental assessment. Chapter 9 discusses the consents that would be required prior to 9 Consents construction of the restoration works. This chapter tables the key project risks associated with the 10 Project Risks planning and implementation of the project. Conclusions and Chapter 11 concludes the report with recommendations for taking 11 Recommendations the project forward.

1.2 River Wensum Restoration Strategy The project was initiated in response to a number of key drivers. The most significant of these are listed below.  The Government’s Public Service Agreement (PSA) target for SSSIs constitutes the main driver for physical restoration of the river, and hence the main driver behind the RWRS. River restoration on the Wensum will contribute to the national target of 95% (by area) of SSSIs being in ‘favourable’ or ‘unfavourable recovering’ condition by 31 December 2010. All riverine units within the Wensum SSSI are currently in ‘unfavourable no change’ condition.  As a European Natura 2000 site, measures are required to ensure that the River Wensum moves towards ‘favourable’ conservation status. The European features of the site are; bullhead, brook lamprey, Desmoulin’s whorl snail, white-clawed crayfish and water crowfoot plant communities.  The River Basin Management Plan (RBMP) prepared for the Anglian River Basin District as required by the Water Framework Directive identifies the River Wensum upstream of Norwich as a heavily modified water body currently with Bad overall Potential. The RBMP sets objectives for the water body to reach Good Ecological Potential by 2027 and Good Chemical Status by 2015 and the RWRS is cited as a key action necessary to deliver the measures required for the River Wensum to meet these objectives. Measures include large scale Unit 54 Taverham Mill to Hellesdon Mill_final for issue_V1.0.docx 7

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habitat improvements to address those factors that limit the natural hydromorphological functioning of the river and to restore favourable conditions for a range of fish species. Proposed actions cited by the RBMP for the River Wensum protected area include reducing impoundments on the river, restoring the gravel beds, narrowing the channel, increasing the amount of in-stream woody material and modifying the weed cutting regime at critical phases of fish life cycles.  Chalk rivers are a priority BAP habitat, with England supporting 85% of the world resource. The Environment Agency is the lead authority for this habitat, and objectives are defined in the Chalk River Habitat Action Plan produced jointly by the Environment Agency and Natural England. The Action Plan recognises the quality and importance of chalk rivers ecologically, hydrologically, recreationally and culturally (Environment Agency / Natural England, 2004).  River restoration will also contribute to the objectives of the River Wensum Fisheries Action Plan, River Wensum Water Level Management Plan (Environment Agency, 2007a) and Broadland Rivers Catchment Flood Management Plan. 1.2.1 Approach The RWRS report provided comprehensive high level guidance for restoration of the River Wensum. The chief aim of the strategy was to provide a whole river vision for implementation of restoration by developing restoration delivery plans on a reach by reach basis throughout the SSSI. The undertaking of the RWRS involved, amongst others, the following key activities:  Reviewing of existing baseline information.  Consulting with steering group members including the River Restoration Centre (RRC), as well as with key local stakeholders.  Reviewing the river reaches and restoration measures proposed in the Geomorphological Appraisal.  Mapping current conditions on the River Wensum and comparing them to expected semi- natural conditions in Norfolk.  Determining a cost-band for each of the RWRS reaches. The above culminated in the production of a technical report (JBA, 2007). 1.2.2 Outputs The RWRS identified and recommended a number of restoration and management measures including: 1. Implement structural modification to lower, remove or bypass water control structures at mills.

2. Raise bed levels and restore the gravel bed substrate where appropriate.

3. Narrow over-widened sections of river.

4. Introduction / retention of woody debris.

5. Reconnection of 8km of channel to its original channel.

6. Reconnection of the river to its floodplain through removal of embankments where appropriate.

7. Creation of berms to stabilise silt / control silt deposition in the channel.

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The strategy culminates in a suite of high level recommendations presented for reaches 01 to 03 in Unit 54. This provides a framework for delivering restoration and a starting point for the implementation of restoration on a reach by reach basis. 1.3 Feasibility Assessment aims The overall aim of this feasibility assessment, and hence this report, is to progress the implementation phase of restoration and deliver the measures required for the river to meet its objectives under the Water Framework Directive and to meet the PSA targets for the River Wensum SSSI. The key objectives of this feasibility assessment are to:  Determine the most suitable restoration measure, or suite of measures, for Reach 01, Reach 02 and Reach 03.  To consult with local landowners and stakeholders on the opportunities and constraints for restoration on a reach by reach basis.  To subsequently recommend an overarching restoration and river management conceptual design for Unit 54.  To provide a detailed cost estimate for implementing the conceptual design.  Undertake an environmental scoping assessment of the recommended restoration options. In restoring the hydrological linkage between the river and its floodplain, there should also be consideration of the hydrological linkage between the river SSSI unit and adjacent terrestrial SSSI units. There are six terrestrial SSSI units adjacent to Unit 54 of the River Wensum SSSI (see Appendix D). This feasibility assessment builds on the RWRS by considering the measures recommended in the strategy, as well as new options for river restoration and river management. A process of Multi-Criteria Analysis (MCA) has been used to determine the most suitable restoration measures or suite of measures for each reach. Section 1.4 provides further detail regarding the adopted methodology. 1.4 Methodology This feasibility assessment involved undertaking the following key activities listed in chronological order. These are described in detail in Sections 1.4.1 to 1.4.7, and Figure 1.3 illustrates the process. 1.4.1 The establishment of detailed baseline conditions for a specific reach A large amount of baseline data exists for the River Wensum. Numerous reports and raw data were reviewed as part of this feasibility assessment. The majority of this information relates to the River Wensum as a whole, and detailed reach-specific data is less readily available. Section 3.1 sets out more information. In addition, a number of site visits were undertaken throughout the unit by different members of the project team to confirm the desk-top research. Specific baseline conditions for each reach were mapped on an environmental constraints plan.

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Unit 54: Taverham Mill to Hellesdon Mill Reach 01 Reach 02 Reach 03 Hellesdon Reach Drayton Reach Costessey Reach Establish baseline for each of the reaches individually

MULTI CRITERIA ANALYSIS

Construction of MCA tool: identification of options, and defining the criteria by which they will be evaluated.

Application of MCA tool (Ecology, Project Delivery and Technical aspects considered) for each reach

RIVER RESTORATION OUTLINE SCOPING

MCA identification of preferred (highest scoring) options for each reach

Recommended option and measures for each reach

Recommended options and measures for each of the reaches are considered relative to one another and a cost estimate calculated per measure for the unit as a whole. The cost estimate is further refined by considering how cost savings could be made by using alternative construction materials and phasing the works to reduce double handling

ENVIRONMENTAL SCOPING

Environmental scoping of recommended option for this unit

Consents and permissions identified for the scheme to progress to detailed design and construction

Identification of project risks in progressing conceptual design to detailed design

Conclusion and recommendations

Figure 1.3 - The approach adopted during feasibility assessment for determining the recommended restoration option on individual reaches and the overall river unit

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1.4.2 The identification of a full suite of possible restoration measures, including those recommended in the RWRS A generic list of all management and restoration options possibly applicable to the River Wensum was generated through reviewing key documents such as the RWRS (JBA, 2007) and geomorphological appraisal (Sear et al., 2006), and through public consultation at the drop-in sessions undertaken by the Environment Agency, Natural England and Atkins in late 2008 and early 2009 on units 46, 48, 50, 52 and 53 and late 2009 for units 47, 49, 51 and 54. From the above activities, six main option groups were identified and taken forward for consideration using the Multi-Criteria Analysis (MCA) tool. These options are discussed further in Chapter 5, with further detail given in Appendix A. 1.4.3 The evaluation of restoration, maintenance and alternative options by means of Multi-Criteria Analysis Once identified, the six main option groups were evaluated for each reach using a MCA tool. This was considered necessary to ensure that a transparent, defendable and replicable technique of selecting options could be consistently applied. The MCA technique scores the listed options (and the different measures within the river restoration and alternative options) in terms of the degree to which they meet certain criteria, which are broadly grouped under the headings of ‘Ecological’, ‘Project Delivery’ and ‘Technical’. The highest scoring options / measures were considered to be the ‘preferred suite of options’ for that specific reach and were taken forward for consideration in terms of cost. The MCA technique was carried out on a reach by reach basis. 1.4.4 The development of a conceptual design based on the recommended options and suite of measures for each of the reaches considered The recommended options / measures for each reach were considered and professional judgement was applied to determine the appropriate combination of the reach-specific solutions to realise improved conditions for the SSSI unit as a whole. A conceptual design was developed for each reach and these are displayed on base maps in Chapter 6. 1.4.5 The consideration of costs associated with these options and specific river restoration measures A detailed cost estimate was calculated and this was based on a cost per unit length for the different measures and applied to a conceptual design for each reach. Cost savings from phasing work appropriately and using local materials were explored. Chapter 7 describes this in further detail. 1.4.6 Environmental scoping of the recommended option for the unit The recommended option (conceptual design) was subjected to an environmental scoping exercise, so as to determine the significant environmental issues which would warrant a detailed assessment at the next stage of the process. This includes an Environmental Report to be drafted in parallel with the detailed design. The details of this scoping exercise are provided in Chapter 8. 1.4.7 Identification of potential project risks, permissions and consents As part of the next phase of implementation, consents and permissions that will be required to progress the recommended conceptual design to detailed design and construction were identified along with potential risks to the project. These are described in Chapters 9 and 10, respectively.

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2. Taverham Mill to Hellesdon Mill Overview 2.1 Terminology and site location

2.1.1 Terminology To determine restoration options applicable to the River Wensum, the following terms are used: The term ‘unit’ is used only in reference to particular riverine SSSI units, which are officially demarcated sub-components of the River Wensum SSSI. These units, of which there are 9 within the study area (Units 46-54), are up to 20 kilometres in length. Each feasibility report looks at one SSSI unit, and this report addresses Unit 54 (River Wensum, Taverham Mill to Hellesdon Mill). The term river ‘reach’ is used to describe smaller stretches of the river that have been defined according to their geomorphological environment. Whilst not related to the SSSI designation, a number of these reaches fall within each unit. This report recommends restoration options that may be appropriate to river reaches 01, 02 and 03. Due to their shorter length, reaches are considered preferable to units for planning restoration. The advantage of taking this approach is that many of the restoration options that apply to the entire unit can be broken down and assessed at an individual reach scale. The term ‘section’ has been used as a generic term referring to any portion of the river. For example, ‘the section of river between the bridge and the mill’. The term ‘option’ is used to describe a suite of measures that could be implemented to return Unit 54 to ‘unfavourable recovering’ or ‘favourable’ ecological condition and address WFD hydro- morphological quality issues. For example ‘Do nothing’, ‘Do minimum’, ‘River restoration’ and ‘Targeted maintenance’ are all options. The term ‘measure’ is used to describe a specific technique or work element that falls within an option. For example, bed raising is a measure of the ‘River restoration’ option and silt removal at mill ponds is a measure of the ‘Targeted maintenance’ option. 2.1.2 Site location This feasibility report addresses options for SSSI Unit 54, and its three component reaches, Reach 01, Reach 02 and Reach 03. These are listed below in downstream to upstream order and shown in Figure 2.1.  Reach 01 – Hellesdon Reach (1.65km)  Reach 02 – Drayton Reach (3.16km)  Reach 03 – Costessey Reach (3.91km). This SSSI unit falls within the administrative boundaries of South Norfolk and Broadland councils. The settlements adjacent to this section of the river include Taverham, Drayton, Costessey, New Costessey and Hellesdon.

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Figure 2.1 - Location of Reaches 01, 02 and 03 within Unit 54

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2.2 Previous works within Unit 54 Since its designation as a SSSI in 1993 there have been a variety of engineering and environmental surveys and investigations carried out on the River Wensum. In the past, some river restoration work has been carried out on Unit 54 in Reach 2, as summarised in Table 2.1. In addition, flood risk management work has been undertaken in Reach 01 including the automation of the River Tud overshot tilting gate, upstream of Hellesdon Mill, in 1999. Table 2.1- Summary of previous restoration works consented on Unit 54

Reach Location Previous Works Consented Year

01 Hellesdon Reach None identified n/a

Costessey Point river restoration including the installation of gravel riffles, 2-stage channel, fish 2004 refuges and fencing.

Environment Agency undertook remedial work to 02 Costessey Reach riffles at Costessey Point as they were identified as not “working adequately” due to previous EA requirement to incorporate section of deeper 2007 channel to allow weed cutting boats to pass. Works consisted of filling in weed boat channel and extending length of riffles.

03 Taverham Reach None identified n/a

The River Restoration Centre has undertaken a project appraisal of the restoration works in Reach 02 downstream of Costessey Mill. Works at Costessey are described as being specifically aimed to enhance an over-deep section of watercourse and improve flow diversity to help support a range of aquatic species. In summary, the combination of the riffle / glide sections and the bank re-profiling has resulted in channel narrowing, and appears to have provided more flow pattern diversity, and potential habitat for bullhead spawning. Fencing has been effective in reducing cattle poaching, although monitoring bankside macrophyte communities was recommended to ensure this doesn’t result in a monoculture or aid the spread of any invasive species. Additional benefits include the re- connection to the floodplain (which has resulted from the removal of parts of the spoil bank) and provision of backwaters providing a good refuge for fish fry. Negative elements of the original scheme (before remedial works) included the riffle / glide design which tried to incorporate freeboard for weed cutting boats and as a result led to features that could not be classified as either riffles or glides. The flow regime through this section of channel may have also led to some bankside erosion. Recommendations of the RRC included minimal hand weed cutting and bed raising throughout the reach, in conjunction with some narrowing. Key recommendations were for design calculations to be completed prior to installing riffle structures, as this will ensure they are constructed at the appropriate depth, and wherever possible to avoid inclusion of a weed boat channel. Additional recommendations included the establishment of wooded riparian marginal vegetation, to enhance the habitat in this section, and the inclusion of gravels together with large wood to narrow and create more in-channel flow variability and a range of habitat niches. For further information relating to the river restoration works undertaken at Costessey Point refer to the Norfolk Anglers Conservation Association (NACA) website (http://norfolkanglers.co.uk/).

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2.3 RWRS restoration vision for Unit 54 A condition assessment of the SSSI was conducted by Natural England in 2010. All riverine SSSI units were recorded as being in ‘unfavourable no change’ condition. The vision of the RWRS is to provide a framework that leads to the delivery of restoration that improves the condition of SSSI units from their current ‘unfavourable’ condition towards a more naturally functioning and ecologically sustainable system in ‘unfavourable recovering’ or ‘favourable’ ecological condition. The RWRS recommended a variety of restoration options for each reach. These are listed in Table 2.2. Table 2.2 - Recommended restoration measures for each reach as provided in the RWRS (JBA, 2007)

Reach Length Restoration Recommendation from the RWRS (m)

Initial work required is for bed and bank stabilisation associated with the removal of Hellesdon Mill structures at the downstream end of reach. Appropriate measures required to manage silt deposits upstream of the mill. Augment bed on average by 0.6m using local gravels wherever possible and create up to 16 gravel glides or riffles in the reach. The channel is on average 10.7m over-wide and physical 01 1,645 narrowing (with associated landscaping and fencing) may have to be considered to restore the full functioning of the channel in this reach following works at the mill. Adopt / maintain maintenance regime and riparian management to allow channel to create natural variations in local channel width and habitat niches. Post-project monitoring is required, especially in association with works at the mill structures.

In the 100 to 200m downstream of Costessey Mill and in the immediate scour pool area of good habitat value, no works are required and this area should be conserved and allowed to re-vegetate naturally. Augment bed on average by 0.4m using local gravel wherever possible and create up to 32 gravel glides or riffles in 02 3,155 the remainder of the reach. The channel is on average 9.8m over-wide and physical narrowing (with associated landscaping and fencing) may have to be considered to restore the full functioning of the channel in this reach following works at the mill. Adopt / maintain maintenance regime and riparian management to allow channel to create natural variations in local channel width and habitat niches.

In the 100 to 200m downstream of Taverham Mill and in the immediate scour pool area of good habitat value, no works are required and this area should be conserved and allowed to re-vegetate naturally. Elsewhere, initial work is for bed and bank stabilisation associated with lowering of Costessey Mill structures at the downstream end of reach. Appropriate measures required to manage silt deposits upstream of Costessey Mill. Augment bed on average by 0.3m using local gravel 03 3,910 wherever possible and create up to 42 gravel glides or riffles in the remainder of the reach. The channel is on average 5.2m over-wide and physical narrowing (with associated landscaping and fencing) may have to be considered to restore the full functioning of the channel in this reach following works at the mill. Adopt / maintain maintenance regime and riparian management to allow channel to create natural variations in local channel width and habitat niches. Post-project monitoring is required, especially in association with works at the mill structures.

These measures are relatively broad-scale and will require more detailed appraisal to determine the suitability and extent of each restoration measure. To appraise and define these measures, a detailed understanding of reach-specific baseline conditions is required. Chapter 3 of this report presents this baseline. For Unit 54 the restoration vision also needs to take into account the magnitude and timing of proposed abstraction sustainability reductions at Costessey. Anglian Water has been asked to reduce its Costessey abstraction by up to 46 million litres per day (Ml/d), the aim being to meet a 20 Ml/d reduction by 2015 and, if required, a further reduction of up to 29 Ml/d by 2020 or soon thereafter. Also central to the vision for the unit is the need to address flow impoundment at Hellesdon Mill. The backwater created by this structure affects all of Reach 01 and all but 500m of Reach 02. This equates to approximately half of Unit 54 being affected by the impoundment at

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Hellesdon Mill. Unless this can be addressed, and so restore more freely flowing conditions, other restoration activities are likely to have very limited benefit. During consultation, Natural England has noted that considerable benefits might be achieved by progressively lowering the level at Hellesdon Mill/ River Tud off-take sluice. In particular, such an approach may facilitate re-vegetation of the riparian margin and limit silt remobilisation. In several respects, therefore, the restoration vision for Unit 54 involves careful timing and phasing of actions.

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3. Environmental Baseline 3.1 Introduction This chapter presents environmental baseline information for reaches 01, 02 and 03. An environmental constraints map for Unit 54 is illustrated in Figure 3.1. A review of the existing environmental setting has been undertaken through a combination of desk study and preliminary site surveys. Data has been obtained from existing survey reports, and discussion with a number of individuals and organisations including Environment Agency internal functional specialists (e.g. Fisheries, Recreation and Biodiversity, National Environmental Assessment Service and Operations Delivery), Natural England, and Norfolk County Council (NCC). Information sources consulted include, but are not restricted to, the following:  The Environment Agency, www.environment-agency.gov.uk  English Heritage PastScape, www.pastscape.org.uk  Norfolk County Council, www.norfolk.gov.uk  Norfolk Rivers Internal Drainage Board (NRIDB)  Defra Multi-Agency Geographic Information for the Countryside, www.magic.gov.uk  Natural England, www.naturalengland.org.uk  Norfolk Mills, www.norfolkmills.co.uk  Heritage Gateway, www.heritagegateway.org.uk  Norfolk County Council historic maps, www.historic-maps.norfolk.gov.uk  River Wensum Restoration Strategy (RWRS), JBA (2007)  Water Management Alliance, www.wlma.org.uk  River Restoration Centre (Mant, J. & Fellick, A., 2007)  River Wensum Water Level Management Plan (Environment Agency, 2007a)  Environment Agency National Fisheries Monitoring Programme database  Upper River Wensum Strategy Study (Environment Agency/Babtie, Brown & Root, 2003)  Environment Agency on-line flood mapping (http://maps.environment-agency.gov.uk – accessed April 2011)  Water Vole Monitoring Report – River Wensum and Tributaries (River Wensum Mink Control Project) (Wild Frontier Ecology Ltd, 2007)  River Corridor Surveys for the River Wensum (1995)  River Habitat Surveys for the River Wensum (2006)  Environment Agency Web-Based Flood Mapping (accessed April 2011)  Information from Norfolk Biological Records Centre  Broadland District Local Plan (Replacement) – Adopted May 2006  Broadland District Landscape Character Assessment (Chris Blandford Associates, May 2008) Report for Broadland District Council

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 N. Holmes 2009 macrophyte survey reported in Habitats Directive Review of Consents - Stage 4 Options Appraisal: River Wensum SAC (Entec, 2010). 3.1.1 Approach to presenting baseline information Presenting specific baseline information for each reach allows a better understanding of the existing environmental constraints that need to be considered when developing river restoration options. This information will be included in the options appraisal process and the Multi-Criteria Analysis (MCA). More information about the aims and objectives of the MCA is provided in Chapter 5. Baseline information common to environmental features across all reaches is described in Section 3.2 and baseline information specific to each reach is described in Tables 3.7 to 3.9. Figures 3.1 to 3.5 and supporting plates complement the baseline text. 3.1.2 Applicable environmental legislation and policy Environmental legislation that drives this project will need to be considered alongside associated restoration and management options. Legislation includes:  The Conservation (Natural Habitats &c.) Regulations 1994 (as amended).  The Wildlife and Countryside Act 1981 (as amended).  The Conservation of Habitats and Species Regulations 2010.  The Eels (England and Wales) Regulations 2009. 3.1.3 Limitations to collating baseline information The baseline data has been derived from a review of existing information and preliminary walkover surveys. There are a number of gaps in the baseline data which will need to be addressed during the ongoing Environmental Impact Assessment (EIA) should restoration options identified in this report progress to the detailed design stage. 3.2 Common environment features across all reaches

3.2.1 Defining the character of chalk rivers A prominent feature of the cretaceous deposits of England is successive strata of chalk which dip gently to the west and are exposed along a wide front running roughly diagonally from Hampshire to Norfolk and Lincolnshire. In Norfolk, chalk strata predominate as the underlying geology. However, as one travels north from Hampshire to Norfolk, the influence of the chalk on the land surface becomes increasingly masked by glacial and fluvio-glacial silts, sands, gravels and boulder clays. This reflects the fact that, even during the most severe glaciations over the Pleistocene period, the ice-sheets only extended as far south as the Thames and south of this, the landscape and river features are in closer contact with the underlying chalk layers. All chalk rivers are characterised by a high base flow throughout the year, with buffering of high flows during the winter as water percolates into the underlying aquifer, and buffering of low flows during the summer as water is gradually released from the aquifer. However, the influence of superficial deposits has a profound impact on how the chalk river habitat is expressed on the land. The southern chalk rivers such as the Hampshire Avon, the Frome, and the Test are regarded as ‘classic’ chalk rivers. In some of these, up to 90% of the flow enters the river through its bed, and as a consequence there is a low density of tributaries in the catchment. As these rivers lie very close to the chalk, there tends to be a relatively smooth pattern of flow accretion along the length of the river. Accretion tends to be greatest along those reaches with the highest gradient, and decreases as the river reaches the lower gradients typical of mature river and floodplain. The close association of the river bed to the chalk bedrock means that the headwaters are often

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winterbournes (watercourses which only flow in winter due to a seasonal increase in the water table). The way in which the chalk river is expressed is affected where the chalk is obscured and overlain by a considerable depth of superficial clays, sands and gravels. In most cases, it means that the chalk aquifer is separated from the river by one or more intermediate aquifers within the superficial deposits. Where the properties of the overlying drift change across the catchment, this results in a situation where tributaries from some sub-catchments more closely resemble chalk rivers than others. In situations where the land surface is less permeable, then there will tend to be a higher density of tributaries. Deep deposits of superficial material between the chalk and the land surface prevent the occurrence of winterbournes. Since northern chalk rivers run over material of varying permeability, so the level of accretion is more variable along different reaches. In Norfolk, the hydrology of chalk rivers is further complicated by the fact that the glacially scoured valleys in the chalk run north to south, whereas the rivers tend to run west to east. With northern chalk rivers the nature of the superficial deposits will also influence the proportion of water that reaches the river as overland flow, and also the material that is available to wash into the river and tributaries from rainfall. It will also affect the land use and hence the vulnerability to erosion of soils in the catchment. In Norfolk, intensive arable agriculture is more prevalent than in the south of England, and hence the river faces much greater vulnerability to diffuse water pollution from agricultural sources. Because Norfolk chalk rivers differ from their ‘classic’ counterparts in the south of England, restoration designs that are developed in the south of England may not necessarily be appropriate in Norfolk. The template for a Norfolk chalk river is explored in detail in the Geomorphological Appraisal of the River Wensum by Sear et al. (2006) and also summarised in the River Wensum Restoration Strategy (JBA, 2007). 3.2.2 The chalk river status of the River Wensum As a northern chalk river, the Wensum catchment is characterised by superficial deposits of sands, gravels and clays, resulting in a chalk river habitat which shows some affinities with other lowland river types. These deposits are variable in nature and there tends to be greater permeability towards the north of the catchment, with other areas characterised by more impermeable clays. However, as with other chalk rivers, there is a very high base flow and there is no ambiguity that this is a chalk river, with accretion from the aquifer throughout its length. The variability in overlying substrates, and complex underlying geology and landforms, results in the River Wensum exhibiting a higher density of tributaries than is characteristic of ‘classic’ chalk rivers. It also influences the availability of material that can be washed into the system during rainfall events, and some of the sub-catchments tend to accrete large volumes of sand. The system has been significantly impacted by the influence of intensive arable agriculture, which dominates much of the Norfolk landscape, and has lead to much higher vulnerability of soils to erosion than would have been the case post war, when Norfolk was characterised by a more mixed agricultural system. Whilst the Wensum retains its baseflow connectivity throughout its length, even to Costessey, the increasing thickness of the overlying glacial drift, sands and gravels along the lower catchment (downstream of Fakenham) increasingly dominates the physical character and structure of the river. As a result, the lower Wensum does not exhibit the characteristics of the classic southern England chalk rivers, where the underlying chalk is consistently closer to the river bed and influences the character of the river to a much greater degree. Another feature of the Wensum is that the river course reflects the periglacial conditions that prevailed immediately after the retreat of the last ice age. At this time the river was a high energy system with a wide meandering form that cut down into superficial deposits, creating a wide valley

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and floodplain within the landscape. The low energy system of later periods has modified this large-scale meandering system with secondary sinuosity within the floodplain. This pattern is well represented on the lower reaches of the river between Ringland and Hellesdon. As previously described, the impact of intermediate aquifers in the overlying deposits means that winterbournes are not expressed within the landscape in the way that they are in the ‘classic’ chalk rivers. Despite the majority of the Wensum floodplain remaining relatively natural and managed for grazing, the drainage of the catchment has been substantially altered over time by channel simplification, floodplain drainage and the presence of mills and their associated structures. The mill structures exert a disproportionate impact on the river, so that in many cases the Wensum behaves more like a series of linear lakes than a free-flowing river. A further complexity of impounded reaches is that it is no longer possible to drain the land directly into the river, and a secondary drainage system has been developed on the floodplain on either side of the river, draining back into the river immediately below the mill structures. This pattern is repeated at most of the 14 mill structures along the river, the arterial drains being managed by the Norfolk Rivers Internal Drainage Board. On free-flowing reaches, dredging activities have also had profound impacts on the river, resulting in channel deepening and removal of the gravel bed. The Geomorphological Appraisal demonstrated that the Wensum was such a low gradient system that it was unable to replace these gravels through natural processes, and the only mechanism through which the river is able to reduce the cross-sectional area of the channel is through the development of silt berms which result in a further narrowing and deepening of the system. Despite these changes, in 1980 Holmes classified sections of the upper river as Joint Nature Conservation Committee (JNCC) River Type III (chalk rivers and other base rich rivers with stable flows), with downstream transitions to Type I (lowland rivers with minimal gradients on mixed geology in England). In 2002, CAPM reclassified the upper reaches as Type IIIb to Iva (base rich / neutral impoverished rivers, normally close to source) and the lower reaches were similar to the middle reaches Type Ic to IIc, both of which demonstrated a degraded river type compared to previous surveys. As indicated in the previous section, it is essential to have a clear understanding of the characteristics of a Norfolk chalk river before developing detailed restoration designs. The studies carried out as part of the Geomorphological Appraisal, River Wensum Restoration Strategy and these feasibility assessments have enabled us to refine our knowledge and understanding of the expected form and function of the Wensum. 3.2.3 Historic environment The Broadland and South Norfolk districts are rich in archaeological features (Broadland Landscape Character Assessment, 1999, and South Norfolk Landscape Character Assessment, 2001). Human settlement during Palaeolithic and Mesolithic periods (c. 500,000 to 4,500 BC) is evidenced by finds including flint flakes and tools. The light soils of the river valley have provided good foraging for Neolithic communities and there is evidence of continued habitation through Bronze and Iron Ages as noted by the discovery of flintwork, metalwork and burial sites. Extensive forest removal and formation of agricultural landscapes occurred during the Iron Age and theRomans continued development of cultivation, producing cereals and leaving considerable archaeological evidence including roads, settlements, coins and pottery. Little changed during the subsequent Anglo-Saxon settlement, although evidence of Scandinavian/Viking presence has been recorded. The medieval period led to manorial and parkland developments, brought over by William Duke of Normandy, with peat cutting which subsequently formed the Broads, church construction and the loss of more woodland to tillage. Open, irregular fields with clustered holdings were formed in post medieval periods (16th to 19th Centuries). The Parliamentary Enclosure Acts lead to the partitioning of open landscapes and brought the use of small commons

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into cultivation, and improvements to heath and fenland for agriculture, coupled with increasing settlements. Unit 54 supports Scheduled Ancient Monuments (within the Broadland District) and many Listed Buildings (including Grade I, Grade II and Grade II*). Costessey and parts of Hellesdon contain particular concentrations of listed buildings. Many spot-finds have been recorded on national databases and include finds from the whole range of periods during which humans have occupied the land. The water mills within the unit have been largely demolished and just a few signs remain (none of which are listed). Some associated buildings do survive, as do the mill weirs at Taverham, Costessey and Hellesdon. 3.2.4 Landscape character and visual amenity The entire length of this unit forms the border between the South Norfolk Council and Broadland District Council administrative areas and the Landscape Character Assessments for both areas have been reviewed. The main settlement to the south of the river (within South Norfolk) is Costessey, whilst settlements to the north of the river include the more urbanised villages of Taverham, Drayton and Hellesdon. In Broadland District, parts of Hellesdon village lie within a Conservation Area (including Hellesdon Mill weirs and the river downstream) and some areas are allocated as Open Space. All the villages have set limits for future housing development to protect the rural nature of their settings (Broadland District Council, 2006). The environmental assets of the parishes will be protected in accordance with Policy ENV1 and include consideration of countryside character, and policy ENV8 for Areas of Landscape Value. The river valley landscape character and quality should not be compromised by development, particularly in relation to woodland, open or green spaces and Marriott’s Way. For the South Norfolk area, the Wensum and the River Tud corridors are classified as a ‘Rural River Valley’ landscape, with ‘Fringe Farmland’ further to the south. The river valleys provide most of South Norfolk’s woodland areas, with poplar avenues, pollarded willows and wetland assemblages of nationally important ecological significance in an otherwise agricultural landscape. Mineral extraction is likely to have affected many archaeological features and has altered the landscape form. Unit 54 is a predominantly rural landscape encompassing low-lying arable land, pasture, numerous woodlands and plantations, and historic parkland. The shallow river valleys form the main subtle topographical changes in an otherwise flat or gently undulating landscape (rising up to 30m AOD). Glacial deposits fill the valley bottoms, with the only exposure of the underlying crag and chalk solid geology occurring along the rivers (see Plate 31). Human habitation since Palaeolithic times has substantially altered the landscape with the removal of woodland and creation of a cultivated and semi-enclosed landscape with linear settlements. The more recent use of the area for mineral extraction, housing, recreation, energy generation and other activities have resulted in a general erosion of the character, quality and diversity of the landscapes. Small- scale, incremental change has had a particularly marked effect on landscape character. Key issues affecting the landscape include the loss of woodlands, hedgerows, field margins, ponds and grazing marsh (lost to arable conversions and homogenisation of land uses), soil erosion, loss of ‘marginal land’, exotic tree planting, commercial, urban and suburban encroachment, biomass crops production and management practices along the Wensum. The preservation of landscape quality along the River Wensum, with the retention of ‘gaps’ between settlements, and wetland habitats associated with the river, is increasingly important as the rate of development across Norwich continues. Management strategies and objectives include the following; enhance the River Wensum corridor through creation of wetland habitat (wet meadows, wet woodland); enhance valley sides through

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creation and expansion of all grassland, heathland, shrub and woodland types; minimise eutrophication of waterbodies from agricultural activities; create and manage urban green space within Norwich settlement fringes; restore hedgerows; implement the Wensum Valley Strategy in cooperation with adjoining Districts; maintain existing recreational features and create new recreational opportunities. 3.2.5 Land use The River Wensum valley is designated as a ‘Rural River Valley’ landscape character type, with valley slopes forming a strong division between ‘Woodland Heath Mosaic’, ‘Tributary Farmland’ and ‘Fringe Farmland’ types. Features of importance include the presence of wetland vegetation, wet meadows and pastures, grazing of the valley floor, willows, reeds, marshes, fen, eutrophic waters (e.g. former gravel pits) and a particularly wide river corridor. Unit 54 forms the most downstream rural section of the River Wensum, where the floodplain is generally un-encroached by development, before it flows into the heavily urbanised setting of greater Norwich. Only a small section has been affected by floodplain mineral extraction (near Costessey public water supply intake) and this now forms flooded pits used for angling and supporting a diverse flora and fauna. In other areas the landscape is dominated by floodplain grasslands grazed by horses and cattle. The lower part of the unit is particularly wet and, as a consequence, has not been ‘improved’ for agriculture to the same extent as the upper reaches and supports marshy grazing pastures (extensively managed), wetlands, reedbeds and sedge beds. The Environment Agency (then East Suffolk and Norfolk River Authority) developed a site upstream of Hellesdon Mill to form a series of fish rearing ponds. These ponds still exist, but are no longer used for fish rearing. Encroachment by settlements has been largely restricted to areas outside the floodplain (including Costessey, Taverham, Drayton and Hellesdon), but private gardens and public amenity areas extend to the banks of the Wensum along the lower part of Reach 03 (TRHB) and the middle section of Reach 01 (TLHB). 3.2.6 River management The Environment Agency is the operating authority for the River Wensum within the SSSI, whilst the Norfolk IDB is the operating authority for the other major watercourses (Main Drains) within the Water Level Management Plan (WLMP) area (Environment Agency, 2007a). In Unit 54 the Environment Agency undertake annual weedcutting by boat from Hellesdon (Reach 01) to downstream of Costessey Point (Reach 02). Selective tree trimming may be undertaken to allow the safe passage of the weedboat. IDB main drains are maintained according to their operational maintenance guidelines (NRIDB, 2007). 3.2.7 Water mills Water milling has historically taken place at 14 locations along the River Wensum. At six of these the mill buildings remain in use (residential), with most (but not all) of the mills being Grade II listed structures. In times of flood, mill owners may independently open their structures (if operable) as they see fit, with no consistent river-wide approach (Environment Agency, 2007a). By retaining high water levels upstream, the mill structures have a major influence on the river. They have the potential to constrain the scope and effectiveness of river restoration, especially in sections of channel upstream of the mills. Unit 54 features the following mills:  Costessey Mill (TG 177 127)  Hellesdon Mill (TG 198 104).

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Taverham Mill is located immediately upstream of Reach 03 and has been considered in the Unit 53 Feasibility Report (Atkins, 2010b).

Costessey Mill (Plate 1) Key aspects are as follows:  Remnants of the mill building still exist.  Main structure consists of an automatic tilting gate and fixed weir plus a side sluice fish pass.  The main tilting gate is used to control water levels. The old vertical lifting gate is not in operation.  The bypass is controlled by a horseshoe weir which is used for flow measurement (Plate 54).  The water rights are owned by the Environment Agency.

Plate 1 - Costessey Mill tilting gate (February 2009)

Hellesdon Mill (Plate 2) Technical details of the mill layout are given in the WLMP. Key aspects are as follows:  There is no mill building.  The main structure consists of a flume with a steel control sluice and a horizontal steel penstock. In addition there are 3 fixed weirs with stop-log facilities and weed screens. The sluice is only used during periods of high flow.  An automated bottom-hinged overshot tilting gate occurs upstream of the main structures. This controls the water level upstream in the River Wensum and connects the River Wensum to the River Tud. It also acts as a bypass channel. The automation, which was introduced in 1999, enables quite accurate management of upstream water levels.  The water rights are owned by the Environment Agency.

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Plate 2 – Reach 01: Hellesdon Mill main weir structure (NGR TG1987110444, February 2011)

A draft Mill Operating Protocol (MOP) for the River Wensum has been developed by Atkins (Atkins, 2010a) following consultation with owners and operators, to provide a unified approach to mill gate operation in support of the restoration strategy. The MOP is a first look at the lowering of retained water levels, where this can be achieved through operational modifications only. To date, no modelling has been undertaken in this unit in support of the MOP. Summary information relating to the mill structures in Unit 54 as provided in the WLMP are presented in Table 3.1. This includes information pertaining to the length of backwater created by each structure under mean flow conditions. Table 3.1 - Mill details in Unit 54 (Environment Agency, 2007a)

Mill Name Section Drop at Backwater Backwater Structure Length Structure Length Length Elevation (km)* (mean (mean flow), (% of section (m AOD) flow), (km) length (m) affected by backwater from mill)

Costessey 4.00 1.10 2.25 56 5.38

Hellesdon 5.00 1.21 4.35 87 3.85 Note: *Distance to next mill upstream.

3.2.8 Soils and geology The predominant solid geology of the area is Chalk, a fine grained fissured limestone. The Chalk unit comprises Upper and Middle Chalk overlying Lower Chalk. The Chalk is underlain by the Gault clay, which consists of impervious grey clays. This in turn is followed by undifferentiated Carstone and Sandringham Sands. The Carstone comprises brown, ferruginous, well-jointed medium to coarse grained sandstones. The Sandringham Sands comprise brown, ferruginous fine grained sands which pass down to grey-green glauconitic sands and sandy clays. The predominant soil type occurring adjacent to the River Wensum in Unit 54 is a fen peat occurring over glacio-fluvial drift (Aventurers’ 2 soil association). Outside of the valley floor the soils are dominated by a deep well drained sandy soil (Newport 4) (additional references in Sear et al., 2006; JBA, 2007).

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In terms of ground contamination, chemical analysis of in-river silts was undertaken by JBA in 2007 (through the Environment Agency National Laboratory Service) at different points along the River Wensum. Data was generally collected upstream of mills, including Costessey and Hellesdon. Analysis showed non compliance with the soil guidance value for arsenic at Hellesdon. 3.2.9 Water environment Quality assessment Since the adoption of the European Water Framework Directive (WFD), water quality is reported through a continuous process of planning and delivery as identified in the Anglian River Basin Management Plan (RBMP) (Environment Agency, 2009d). The WFD has introduced a formal series of 6 year cycles, the first ending in 2015. After further planning and consultation the plan will be updated and reissued. The WFD sets an objective of aiming to achieve at least ‘good status’ or ‘good potential’ in all water bodies by 2015 or, provided that certain conditions are satisfied, seek to achieve the objective by 2021 or 2027. The Anglian RBMP identifies the River Wensum upstream of Norwich as a heavily modified water body. By definition, surface waters classified as heavily modified are not able to achieve natural conditions, and therefore it is not possible for such water bodies to reach ‘good ecological status’. Quality in heavily modified water bodies is measured in terms of ecological potential. This is a measure of biological, chemical and hydromorphological conditions. The current overall ecological quality of the water body relevant to Unit 54 has been assessed as bad ecological potential. This is attributed to the water body not supporting good quantity and dynamics of flow as well as biological failures, namely ‘bad’ diatom communities (Table 3.2). The water body has objectives to reach good ecological potential by 20271 and good chemical status by 2015. Table 3.2 - WFD quality assessment (Environment Agency, 2010b)

Waterbody Name Current Ecological Physico-chemical Hydro Morphological Quality Supporting Element Supporting Element Quality Quality Wensum US Norwich Overall - bad potential Overall - Good quality Overall – not high

(GB 105034055881) Diatoms (bad) Ammonia (high) Hydrology (moderate) Fish (moderate) Dissolved oxygen (high) Macroinvertebrates (high) pH (high) Phosphate (good)

Abstractions and river flows Abstraction in the Wensum catchment from groundwater has risen from an annual average of 12- 15 Ml/d in the 1970s to 22-25 Ml/d since 1990. For surface water the total quantities of abstraction are greater but the increase has been less: from 35-45 Ml/d in the 1970s to 38-50 Ml/d since 1990. Typically in catchments the quantitative impact of abstraction on river flows will tend to increase downstream, subject to being offset by flow additions from discharges. In the case of the River Wensum, impacts are also greater at the bottom of the catchment as a consequence of public water supply abstraction to supply the demand of Norwich. Particularly relevant for Unit 54 is the relocation of public water supply abstraction from Heigham, downstream of the lower limit of the SAC river designation, to the Costessey intake approximately

1 The RBMP recognises that the River Wensum upstream of Norwich will not reach good ecological potential by the earlier target of 2015 due to mitigation measures being either disproportionately expensive or technically infeasible. Unit 54 Taverham Mill to Hellesdon Mill_final for issue_V1.0.docx 25

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9km upstream of the downstream limit of the SAC. This switch occurred in January 1988 and was needed to utilise the greater storage and settlement available at Costessey Pits. Since 1988 the intakes at Heigham have only been used when the Costessey intake has not been available (for reasons of low flow or other emergencies). As a result of the relocation of abstraction to the Costessey intake, located some 770m downstream from Taverham Mill, the majority of Unit 54 will have been subject to greater impacts from abstraction since 1988. Because the River Wensum is a SAC it has been subjected to a comprehensive assessment of flow requirements and abstraction impacts. In 2010 the Review of Consents (RoC), required under Regulation 50 of the Conservation (Habitats &c.) Regulations (1994), was completed by the Environment Agency. The generic Environmental Outcomes relating to water quantity were supplied by Natural England and stated that for the in-channel features flow throughout the whole of the SAC river should be above the Habitats Directive Ecological River Flow (HDERF) objective and that the hydrological regime should reflect the natural flow regime for the river for all time periods (e.g. seasonally and diurnally). HDERF Thresholds for SAC/SSSI rivers are summarised in Table 3.3. Table 3.3 - HDERF Thresholds for SAC/SSSI rivers

EW Band HD ERF Maximum % Reduction From Daily Naturalised Flow Sensitivity Qn95

Very High 10% 10% 1-5% High 15% 10% 5-10% Moderate 20% 15% 10-15% Low NA NA NA Very Low 20% 20% 20%

Note: The Environmental Weighting Band assigned at the CAMS Assessment Point at Hellesdon is that of Moderate sensitivity.

During the RoC process attempts were made to define site-specific flow hydro-ecological targets. However, following discussion between Environment Agency and Natural England specialists it was concluded that both macrophyte and invertebrate communities were strongly affected by other factors (e.g. water quality, siltation, channel condition, flow barriers) and that no reliable site- specific flow targets could be derived (Entec, 2010; Environment Agency, 2010a). As a result, flows generated from the Yare and North Norfolk Groundwater model for different scenarios were compared with the HDERF objective. Historic abstraction The results of the RoC comparison of historic abstraction impacts, and potential fully licensed impacts of river flows, compared with the HDERF at Hellesdon Mill, are summarised in Table 3.4. More details of the analysis are presented in the Options Appraisal (Entec, 2010) and the Site Action Plan (Environment Agency, 2010a), but in summary actual historic abstraction, and to an even greater degree potential fully licensed abstraction, are significantly below the HDERF objective.

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Table 3.4 - Summary of abstraction impacts relative to naturalised flow and the HDERF in the Q70-95 range

Flows / Flow differences in Ml/d

Flow Naturalised HDERF Historic Historic- Fully Percentile HDERF Licensed- HDERF Q70 244.6 207.9 195.8 -12.1 -31.3

Q90 166.0 141.1 118.3 -22.8 -43.4 Q95 129.9 110.4 83.1 -27.3 -48.2

Note: Data are from 1988-2005, i.e. post the relocation of public water supply abstraction to Costessey. Source: Environment Agency, 2010a. Historic abstraction and potential future abstraction levels are clearly relevant to the identification of a baseline for Unit 54. With regard to historic abstraction, Nigel Holmes compared macrophyte communities including Ranunculus at equivalent locations between 2009, 2002 and 1985 and concluded that “there are no demonstrable impacts on the flora of the Wensum in the Costessey reach arising from abstractions that began in the area after the 1985 surveys were completed.” (Entec, 2010). Natural England and local Environment Agency specialists have suggested that it is more appropriate to conclude that there appears to be no evidence to suggest that “historical levels of abstraction have caused the macrophyte community to change significantly between 1985 and the present day in this section of the river. This new evidence suggests that historical levels of abstraction from the Costessey PWS surface water intake have not caused the condition of the Ranunculus habitat in this ”unfavourable” section of the river to deteriorate since it was commissioned in 1988. However, this does not preclude the possibility that Ranunculus habitat could be more widely distributed, or of a better quality, if all factors adversely affecting the condition of the river were removed” (Environment Agency, 2010a). It is important to be aware that Ranunculus habitat does not have to have Ranunculus species as a dominant or co-dominant; in some rivers, the cover of other species “may exceed that of Ranunculus species, and indeed Ranunculus species may not be present”. A full definition is provided by the Joint Nature Conservation Committee (JNCC, 2007). Future reductions in abstraction The Site Action Plan (SAP) (Environment Agency, 2010a) concluded that abstraction was causing an adverse effect on the integrity of the SAC and that the preferred option to address this was to modify Anglian Water’s abstraction at Costessey (licence number 7/34/11/*S/0399). The SAP recommended that: “In the first instance, and before 2015, a reduction equivalent to 20Ml/d shall be applied to the total annual licensed quantity to remove the risk to the site in its current condition from fully licensed abstraction”; and “subsequent to this, and following appropriate restoration actions in Unit 54 of the river, further modification of the licence will occur to ensure the required flow standards are met at the Hellesdon Mill”. The reductions being considered are very large and any solution is likely to have significant costs to AWS which would ultimately need to be recovered via customer charges. Natural England, the Environment Agency and AWS are discussing the best way to proceed and recently provided a public statement of common understanding in November 2010 to the Joint Core Strategy for Broadland, Norwich and South Norfolk2. The statement of common understanding noted the following:

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 Anglian Water has been asked to reduce its Costessey abstraction by up to 49 million litres per day (Ml/d). This can be achieved progressively over successive business planning cycles as follows : 1. a 20 Ml/d reduction by 2015 2. and if required a further reduction of up to 29 Ml/d by 2020 or soon thereafter.  Anglian Water may choose to implement the required reduction via a single solution if this is more cost-effective. This has implications for the period of time the SAC will remain in unfavourable condition.  During this interim period there is a legal requirement to prevent any further deterioration of the River Wensum SAC. It is therefore necessary that until the solution is in place, the level of abstraction at Costessey should not increase beyond historic levels for the period up to 2015.  In the short term, maintaining the Costessey licence at its historical levels of abstraction would satisfy Natural England’s concerns for the interim period.  All three parties have signed off a commitment that Anglian Water will aim to meet the first part of the solution by 2015.  Anglian Water is presently appraising its options to achieve the initial reduction of 20 Ml/d and will have identified its preferred option by January 2012…..if a solution to deliver a 20 Ml/d reduction cannot be found then Anglian Water will deliver as much of a reduction as they are able to by 2015.  Once the preferred option is identified, Anglian Water will need to secure funding from Ofwat for the scheme.  The earliest that Anglian Water is likely to be able to begin implementation of the interim (or full) scheme required to meet the Review of Consents solution is April 2015.

Summary of water resources considerations for this Feasibility Report Since 1988 when AWS’ abstraction intake was relocated to Costessey, abstraction impacts on river flows in Unit 54 have been greater than for any other unit of the River Wensum SAC. Designs for river restoration, and the programme for implementation of river restoration in Unit 54, need to take into account the magnitude and timing of proposed abstraction sustainability reductions. This is explained further in Section 6: Developing Conceptual Design. Any information from the restoration work to date that would help define robust, site-specific ecological flow targets for Unit 54 would be a valuable contribution to ongoing discussions on the scale of sustainability reductions required. Review of Environment Agency GIS data (Environment Agency, 2009c) shows that in addition to the Costessey abstraction there are two further surface water abstractions (for agricultural purposes) in Unit 54 (7/34/11/*G/0080 and 7/34/11/*G/0260) licensed at <1.0 Ml/d. Fourteen licensed groundwater abstractions occur within 1km of the main river channel in this unit, each licensed for quantities below 1 Ml/day. There are two consented non sewage treatment works (STW) discharges. Surface water drainage The Norfolk Rivers IDB drains areas of agricultural land, and residential surface water run-off, by using tributaries along the River Wensum. Local surface water flooding tends to occur in flashy rainfall events. This can be exacerbated in the event that main river flows overtop and water from the river drains into IDB drains which outfall near built-up urban areas.

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A wider initiative called the England Catchment Sensitive Farming Delivery Initiative (ECSFDI) was launched in 2005 and is being promoted by Natural England with the aim of raising awareness of diffuse water pollution and encouraging voluntary action from farmers to reduce the risks of diffuse pollution. The 50 priority catchments, including the Wensum, were identified jointly by the Environment Agency and English Nature, and cover about 40% of the agricultural area of England (with about 50,000 farmers, of which some 30,000 manage holdings of over 20 hectares in size). Catchments were identified using data gathered for Water Framework Directive (WFD) purposes on nitrate, phosphate and sediment pollution, combined with data on sensitive freshwater fisheries, chalk streams, failing bathing waters, groundwaters and SAC-designated lakes. The ECSFDI has contributed to the achievement of the Government’s PSA target, and will assist with WFD objectives for the Wensum. A specific sediment fingerprinting exercise, to distinguish different sources of sediment, is being undertaken on the River Wensum. The findings of this study may contain further baseline information which will input to the RWRS, in particular the strategy’s ecological improvement objectives. In much of the River Wensum it is considered that diffuse pollution from agriculture comes from tributaries whereas the immediate floodplain does not pose such a threat. 3.2.10 Utilities At the time of submitting this report, comprehensive information regarding utilities had not been obtained for Unit 54. More information will be collected at the detailed design stage. Field observations (Atkins, 9th February 2011) showed there to be oil and gas pipelines crossing beneath the main channel within Reach 02. 3.2.11 Condition of attributes in Unit 54 For units of river SSSIs to be regarded as in ‘favourable’ condition, targets on various attributes need to be met. Currently, Unit 54 (reaches 01 to 03) is classified as ‘unfavourable no change’. The main reasons for the adverse condition of the SSSI Unit 54, according to the condition survey undertaken by Natural England in March 2010, are inappropriate water levels, inappropriate weirs dams and other structures, invasive freshwater species, siltation, water abstraction, water pollution, agriculture / run-off and water pollution discharge (Table 3.5). Table 3.5 - Condition summary of Unit 54 attributes (Natural England, 2010)

Location European Features Siltation JNCC Type Water Quality Access Structures Channel Disturbance Biological Flow Management

River Wensum from Taverham Mill to Hellesdon Mill U U U U U U U U F (Unit ID 1025559)

Key: U=Unfavourable’ F=Favourable

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Figure 3.1 - Environmental constraints on Unit 54 Unit 54 Taverham Mill to Hellesdon Mill_final for issue_V1.0.docx 30

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Table 3.6 - Baseline information common to Unit 54

Environmental Baseline Information Feature

 Water voles have been recorded in each of the three reaches along this unit between 1997 and 2007, but presence is patchy and variable over time (Wild Frontier Ecology, 2007; EA database information 1970-2010).  White-clawed crayfish have been recorded at various times in all reaches but appear to be found less often in recent years (EA database information Ecology 1970-2010). (Protected Species)  Otter have been found in reaches 01 and 02 (EA database information 1970-2010) and an on-the-day sighting was reported by an angler during the Atkins field survey (February 2011).  The river corridor and associated habitats support a wide diversity of bird species from garden birds to waterfowl and provides breeding, resting and foraging habitats.

 SAC and SSSI units: Unit 38: Costessey Common South Foster and Mann. Unit 39: Costessey Common South Costessey Parochial Trust. Ecology Unit 40: Rogers Farm Joyhold Ltd. (Statutory Unit 41: Rogers Farm The Great Hospital. Designated Areas) Unit 42: Rogers Farm NRA. Unit 43: Rogers Farm Mallett. Unit 44: Riverside Close Hellesdon Jefferys. Unit 54: River Wensum.

Ecology (Non-  County Wildlife Site (CWS) – There are 13 CWSs within 1km of the River Wensum in this unit (see Figure 3.1). Five of these are not considered to be Statutory influenced by either the River Wensum or the River Tud (the tributary that joins the Wensum just downstream of Hellesdon Mill). Only those sites Designated adjacent to these rivers are listed in the following tables. Areas)

 Fisheries: Routine Environment Agency fisheries data is available at three sites in this unit. These surveys indicate a predominance of cyprinid species, a number of which are associated with lentic habitats.  Two species of European interest, namely eel (Anguilla anguilla) and brook lamprey (Lampetra planeri), have been recorded in this unit. Ecology  Targeted barbel (Barbus barbus) and roach (Rutilus rutilus) studies have been undertaken in this unit. These have shown both adult and juvenile barbel (Fisheries, to be present (Environment Agency, 2007c, APEM, 2009). For roach, greater numbers of both adult and juvenile roach were found at sites sampled in Invertebrates & this unit compared with sites in the upper river (Environment Agency, 2007b). Flora)  Macroinvertebrates: There is only one Environment Agency routine biological sampling site (Taverham Bridge) along this unit. A good diversity of chalk river species that thrive in good flow conditions and good water quality (see Table 3.4 for Reach 03) have been recorded at this site. The 1995 RCS also noted that (during August) there was a good diversity of adult dragonflies along the watercourse.  Macrophytes: Plant communities vary between shallow and faster-flowing sections (supporting water-crowfoot, horned pondweed, common water moss, Unit 54 Taverham Mill to Hellesdon Mill_final for issue_V1.0.docx 31

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Environmental Baseline Information Feature spiked water-milfoil, common club rush, curled pondweed) and deep, slow-flowing sections upstream of mill structures (dominated by unbranched bur- reed, perfoliate pondweed and Cladophora (algae) together with fennel pondweed and yellow water-lily). Marginal fringes are generally dominated by reed sweet-grass and reed canary-grass, with flowering rush, lesser water-parsnip, Canadian and Nuttall’s pondweed, branched bur-reed and common reed also present. Margins are frequently grazed or suffer from poaching (horses and cattle) and vertical, deep bank sides limit vegetation encroachment in some sections. IDB drains support clean water and a variety of plants including common reed, water starwort, branched bur-reed, common club rush, brooklime, water violet, greater pond sedge and fools’ water-cress (1995 RCS; Grieve et al., 2002; Entec, 2010 and Atkins field observations February 2011).

 Himalayan balsam was identified in the 1995 RCS. Ecology  Water fern (Azolla filiculoides) was noted by Holmes in 2009 (Entec, 2010). (Invasive / Non- Native Species)  Canadian and Nuttall’s pondweeds (Elodea canadensis and E. nuttallii) are both present (Entec, 2010).  Potamopyrgus antipodarum is a non-native but naturalised aquatic snail (found in Environment Agency routine samples at Taverham Bridge).

 Riparian tree cover is not extensive along this unit and tends to consist of individual trees, isolated clumps or small woodland areas. There are significant lengths of channel lacking in tree cover. Ecology (Trees)  Species most often found include crack willow, white willow, osier, alder, ash, elder, beech, oak, and hawthorn.  There are some areas of alder and poplar woodland. Gardens contain ornamental species of shrubs and trees.

 The majority of this reach has not been subject to significant channel alterations or straightening in terms of its planform, but it has been subject to significant historical dredging and widening for mill development and for land drainage.  The uppermost sections of reaches 03 and 02 support shallow, sandy-gravelly substrates and a variety of flow forms, despite much of the rest of the unit having been deepened and over-widened. Where conditions are suitable, vegetation encroachment and natural channel narrowing processes occur, Geomorphology though grazing and landowner management often reduces the extent of growth.  The approaches to mill structures have been formed into over-wide, deep and slow-flowing channels, often with near-vertical banks and trapezoidal channel forms. Embankments formed by dredging works are visible linear features that often reduce floodplain connectivity and contain high proportions of gravel and the empty shells of river molluscs removed during the dredging works. Channel substrates become increasingly silt-laden. Reach 01 is wholly influenced by the backwater from Hellesdon Mill.

Previous  Restoration works have been undertaken downstream of Costessey Point in Reach 02. Restoration Works

 Relatively few residential buildings are located within identified flood zones and the remaining mill buildings are above indicative flooding levels. New housing developments have been built along the outskirts of the 1 in 1000 year return period flood zone. Flood Risk  Minor roads are occasionally at risk of flooding (e.g. Low Road between Drayton and Hellesdon, Taverham Lane, and Costessey Lane near Costessey Mill) (Environment Agency on-line flood mapping accessed April 2011).

Human  Public access is limited along most of this unit, with few footpath crossings, though the Mariott’s Way path (a former railway line) provides valley views Environment and a river crossing for cyclists and walkers along reaches 01 and 02. A short, dead-end footpath off Low Road provides riverside access within Reach Unit 54 Taverham Mill to Hellesdon Mill_final for issue_V1.0.docx 32

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Environmental Baseline Information Feature 02, but connectivity across the river or adjoining landscape is poor.  Fishing rights are held by a number of angling clubs and individual landowners.

 Many listed buildings and some scheduled monuments are located in nearby villages.  The area has a rich diversity of recorded spot finds, varying in age from Prehistoric periods (mainly flint artefacts and a possible flint mine), through Historic Bronze and Iron Age (axe heads), Roman and Saxon finds (coins, metal objects, burial site, pottery) and medieval and post-medieval finds and features Environment (including a potential former village, windmill site, pendants, clothing items).  The former mill sites each have their own unique history and further checks should clarify if any weir structures are listed features in their own right (though none were found during checks on Listed Buildings Online web searches).

 The majority of the land adjacent to the Wensum is semi-improved or improved grassland grazed by horses and cattle. Field boundaries are marked by fences or by ditches and dykes.  There are a number of disused gravel workings adjacent to the river at the upstream end of the unit. Land Use  The mid to lower sections of the unit are less intensively managed, as soils are particularly wet, supporting large areas of common reed, sedge beds or tall ruderal grasses and herbs. IDB drainage systems are present, often intercepting spring sources in the floodplain.  Linear village settlements are present to the south of Reach 03 (Costessey) and to the east of Reach 01 (Hellesdon), with an increasingly urbanised landscape as the river flows towards the outskirts of Norwich.

 Road access to the river is possible only at crossings associated with the former mills at Taverham, Costessey and Hellesdon. Traffic and  Minor roads run alongside some sections of this unit, with some located within the floodplain (Low Road, Taverham Lane and Costessey Lane). Transport  Marriott’s Way provides pedestrian access but only crosses the Wensum in one location, and passes close to the river at the downstream end of Reach 02.

 Overhead electricity cables are present. Utilities  Oil and gas pipelines cross beneath the main channel within Reach 02.

 The Environment Agency undertake an annual weed cut between Hellesdon and Costessey Point. River  Angling clubs carry out their own site-specific measures (e.g, tree trimming). Maintenance  Occasionally, land managers have re-profiled banks where marginal vegetation is encroaching.

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3.3 Environmental baseline for each reach within Unit 54 Specific baseline information for reaches 01, 02 and 03 is described in Tables 3.7, 3.8 and 3.9, respectively, with accompanying Figures 3.2 to 3.4 and Plates 1 to 55. Table 3.7 - Baseline information specific to Reach 01 (Hellesdon Reach)

Environmental Baseline Information Feature

 Water vole were recorded in 2005, but surveys in 2007 at the same sites failed to find signs of this species (Wild Frontier Ecology, 2007).  White-clawed crayfish have been noted at various locations along the reach between 1989 and 2006 (EA database information 1970-2010) and found at Ecology Hellesdon in 2003 (EA, 2004). (Protected  Otter have been recorded at Hellesdon footbridge between 1997 and 2000 (EA database information 1970-2010). Species)  Many bird species were recorded in the 1995 RCS, including moorhen, coot, wren, dunnock, sedge and willow warblers, garden warbler, reed bunting, mute swan, tufted duck, grey heron, mallard, common tern, sand martin, goldfinch, whitethroat, blackcap, yellowhammer, greenfinch, kestrel, great spotted woodpecker and starling. Grey wagtail have also been recorded (Atkins field survey, February 2011).

 SAC and SSSI Units: Unit 40: Rogers Farm Joyhold Ltd. (1.94 ha of lowland grassland – neutral). Ecology Unit 41: Rogers Farm The Great Hospital (4.32 ha of lowland grassland – neutral). (Statutory Unit 42: Rogers Farm NRA (4.44 ha of neutral grassland – neutral). Designated Areas) Unit 43: Rogers Farm Mallett (4.18 ha of neutral grassland – lowland). Unit 44: Riverside Close Hellesdon Jefferys (3.17 ha of neutral grassland – lowland). Unit 54: River Wensum.

 County Wildlife Sites (CWS): CWS 251, Wensum Meadow (wet meadow). Ecology (Non- Statutory CWS 246, Red Bridge (fen, carr woodland, scrub and ponds). Designated CWS 243/244, Land South of River Tud (wet alder woodland and neutral grassland). Areas) CWS 1454, Hellesdon Mill Meadow (marshy semi-improved grassland with ditches). CWS 2106, Wensum Mount Farm (wet grassland and fen).

 Fisheries: Targeted barbel (Barbus barbus) surveys across this reach and Reach 02 recorded four adult barbel in 2005 and two adult barbel in 2006. Ecology Follow-up surveys conducted in 2007 recorded juvenile barbel (Environment Agency, 2007c). (Fisheries, Invertebrates &  Macroinvertebrates: There are no EA routine surveillance sites within this reach (the nearest being downstream of Hellesdon Bridge). Flora)  Macrophytes: Surveys in 2009 (Entec, 2010), which included sections of the river downstream of Hellesdon Mill (i.e. beyond the reach boundary) found arrowhead and unbranched bur-reed to be dominant. Other species included Cladophora agg., reed sweet-grass, yellow water-lily, perfoliate and fennel

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Environmental Baseline Information Feature pondweeds and branched bur-reed. Spiked water-milfoil was rare but found in most survey sections, water-crowfoot was rarely found (less so than in 1985 surveys), whilst water-cress, fool’s water-cress and water-speedwell were widespread. Hemlock water-dropwort was found less often than in 1985, with lesser water-parsnip along margins. Frogbit (Hydrocharis morus-ranae) occurred in small patches and whorl grass (Catabrosa aquatica) in amphibious patches. Nuttall’s pondweed increased upstream of the mill compared to 1985.  Surveys within this reach by CAPM (Grieve et al, 2002) recorded the algae Cladophora agg. as dominant, with unbranched bur-reed and arrowhead present. Margins supported reed sweet-grass, flowering rush and algae (Enteromorpha spp.). Less frequently found were water-milfoil, perfoliate pondweed, branched bur-reed, fool’s water-cress, another alga (Batrachospermum), lesser water-parsnip, water starwort and Canadian pondweed.  1995 RCS surveys of this reach found in-channel vegetation to include yellow water-lily, unbranched bur-reed, water starwort and Canadian pondweed. Marginal fringes, often restricted and patchy, supported common reed, willowherbs, reed canary-grass, nettle, cleavers, reed sweet-grass, greater pond sedge, greater reedmace, water forget-me-not and other tall ruderals and grasses.  Floodplain drains were noted to support common reed, great willowherb, fool’s water-cress, water figwort and greater pond sedge.  The wet meadows along the lower TRHB were noted to support southern marsh orchid and bogbean (1995 RCS).

Ecology  Azolla filiculoides (water fern) was found in 2009 surveys (Entec, 2010). (Invasive / Non-  Canadian pondweed (Elodea canadensis) and Nuttall’s pondweed (E. nuttallii) have both been recorded in this reach. Native Species)

 Tree cover along this reach is patchy and tends to consist of a single line of trees, particularly crack willow, along the bank top. This is particularly noticeable along the upper section on the TLHB and the lower section of the reach along the TRHB. Private gardens along the TLHB have few trees to Ecology (Trees) maintain an open view to the river, apart from those marking boundaries between properties. The extensive floodplain along the TRHB is mostly devoid of trees, though there are some isolated trees including clumps of alder.  The 1995 RCS recorded white and crack willows, osier, alder, ash, Italian poplar, ornamental species (associated with garden sections) and elder.

 This section is wholly influenced by the backwater from Hellesdon Mill. The channel has been severely over-widened and deepened to provide substantial storage volume of water upstream of the weirs. Since the last dredging activities in 1960, some vegetation encroachment and consolidation Geomorphology of berms has occurred along the TRHB, but this has been limited due to the depth of the channel and tree clearance works upstream of the weirs.  There are no shallow gravel areas and river depths are typically >1m. The river bed is likely to be silt-laden due to sluggish flow conditions.  Dredging spoil heaped along the TRHB has created embankments with mature willows established along much of the reach length.

Previous  None identified. Restoration Works

 Environment Agency on-line flood mapping (accessed April 2011) indicates that there is a wide floodplain along the lower half of this reach (see Figure Flood Risk 3.2). This extends to include the Environment Agency’s former fish farm at Hellesdon.

 The main developments within the floodplain are the Environment Agency former fish farm and the buildings associated with the former mill at Human Hellesdon. Environment  The river is flanked by the villages of Costessey (to the south-west) and Hellesdon (to the north-east). There is a small public open space, consisting of

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Environmental Baseline Information Feature mown amenity grassland, along the TLHB between the river and the housing development at Wensum Valley Close.  Gardens of houses along Low Road abut the mid-reach of the river along the TLHB.  The remainder of the reach is generally inaccessible to the general public as there are no footpaths adjacent to the river.  Norwich Union Angling Club has approximately 1km of fishing from the TRHB in this reach.

 There are four listed buildings in the local area; Hellesdon House, The Old Stables at Hellesdon House (both Grade II), St Mary’s Church (II*) and a barn at Hill House Farm (II). Parts of Hellesdon village, including the Wensum and the former mill site, are within a Conservation Area designated by Norwich City Council.  A Historic Environment Records and Past Scape search identified more than 70 records dating from Prehistoric periods (flint artefacts and pot boiler), Meso- and Neo-lithic finds (core, flint flakes and arrowhead) through Bronze Age (axe head), Saxon and Roman finds (coins, metal objects, pottery, possible burial site) and medieval and post-medieval records (whetstone, pendants, possible former village, windmill site (1540-1900), circular enclosure Historic and a brick kiln site). Hellesdon Hospital was formerly Norwich City Asylum with period architecture buildings. Environment  The site of the post-medieval mill is at Hellesdon weir. Records of a mill date from 1460, but by 1536 only the dam remained. It was rebuilt in 1683, and a mill house added in 1719, and used for paper production between 1778-1804. This was burnt down in 1805 and rebuilt. This was rebuilt again in 1851 as a much larger mill with 4 storeys, 66 windows in the south wall and 4 mill channels for paper making (1850-60), but demolished in 1920. In 1972 only brick fragments and a mill stone remained.  Reference: search on Heritage Gateway website at TG195112 on 01/04/2011 (http://www.heritagegateway.org.uk/Gateway/) which covers the area within 1km of the search point.

 The main land use along the TLHB is pasture used for grazing livestock. In addition there are small areas of amenity grassland and private gardens. Land Use  Most of the land along the TRHB is managed as grazing marsh. This includes the River Wensum SSSI terrestrial units 40 to 43. Ponds comprising a former fish farm are located adjacent to this bank a short distance upstream of Hellesdon Mill.

 This reach is inaccessible by road, the only exception being the crossing to the EA fisheries depot at the downstream end of the reach. Traffic and  There would be some access possible for river restoration across private farmland, but much of the area is wet ground and not suitable for heavy Transport machinery, with some exceptions where embankments (of former dredgings) are present, but mature willow and other tree cover would reduce accessibility.

Utilities  A detailed utilities search has yet to be conducted for this unit.

River  The Environment Agency undertakes an annual weed cut by boat in this reach. Maintenance  There have been no dredging activities carried out since the 1960s, but embankments of dredged spoil are still clearly apparent along the TRHB.

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Figure 3.2 - Environmental baseline for Reach 01 (Hellesdon Reach) Unit 54 Taverham Mill to Hellesdon Mill_final for issue_V1.0.docx 37

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Table 3.8 - Baseline information specific to Reach 02 (Drayton Reach)

Environmental Baseline Information Feature

 White-clawed crayfish were recorded in 1997 (EA database information 1970-2010).  Water voles have been recorded south of Drayton in 1997 (EA database information 1970-2010). Ecology  Otter have been recorded at Marriots Way (old railway line crossing) in 1997 (EA database information 1970-2010). Otter footprints were seen along (Protected this reach during the Atkins field surveys (February 2011). Species)  Many bird species were recorded during the 1995 RCS, including mute swan, moorhen, coot, skylark, reed bunting, sedge warbler, whitethroat, willow warbler, Canada goose, mallard, tufted duck, grey heron, lapwing, swallow, long-tailed tit, yellowhammer, blackcap, wren, dunnock, robin, blackbird, chaffinch, blue-tit and common tern. Many of these species may hold breeding territories, feed or temporarily stay along the river corridor, utilising river fringes and patches of scrub.

Ecology  SAC and SSSI units: (Statutory Unit 54: River Wensum. Designated Areas)

Ecology (Non-  County Wildlife Sites (CWS): Statutory CWS 255, Low Road meadow (species-rich meadow with dykes). Designated Areas) CWS 2106, Wensum Mount Farm (wet grassland and fen).

 Fisheries: Routine Environment Agency fisheries data is available for two sites in this reach, at Blake’s Meadow and Drayton Green (EA site codes NOR39 and 41, respectively). Seven surveys have been conducted at Blake’s Meadow since 1986, the most recent being in 2009. Seventeen species have been recorded in total, with the population being dominated by cyprinid fish species, although salmonids have also been recorded. Eleven species were recorded in the latest survey in 2009. Density and standing crop estimates in 2009 were the highest recorded at this site, mainly due to higher than average captures of chub (Leuciscus cephalus), dace (Leuciscus leuciscus) and minnow (Phoxinus phoxinus).  Two species of European interest, namely eel (Anguilla anguilla), which have shown a significant decline at this site post 1997, and brook lamprey (Lampetra planeri), have been recorded at Blake’s Meadow. Ecology (Fisheries,  Seven surveys have been conducted at Drayton Green since 1986, the most recent being in 2009. Fourteen species have been recorded in total, with Invertebrates & the population being dominated by cyprinid fish species, with no salmonids having been recorded. Of the 11 species recorded in 2009, gudgeon (Gobio Flora) gobio), perch (Perca fluviatilis), minnow and roach (Rutilus rutilus) were the most numerically abundant species. Both eel (Anguilla anguilla) and brook lamprey (Lampetra planeri) have been recorded at this site.  Targeted barbel (Barbus barbus) surveys conducted downstream of Costessey Weir in 2007 resulted in the capture of 16 fish, indicating good juvenile habitat in this location (Environment Agency, 2007c). Subsequent surveys conducted in 2009 at two locations (Costessey and Costessey Point) did not indicate any successful natural recruitment of barbel populations in this reach (APEM, 2009). Follow-up Environment Agency targeted barbel surveys in 2010 and 2011 yielded three and 14 barbel respectively.  In January and December of 2010 approximately 200 2+ and 250 1+ barbel, each implanted with a Passive Integrated Transponder (PIT) tag, were introduced to the Wensum in the mill bypass channel downstream of Costessey Mill to enable them to be tracked and monitored. Monitoring equipment

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River Wensum Restoration Strategy Implementation SSSI Unit 54: Feasibility and Environmental Scoping Report

Environmental Baseline Information Feature installed downstream of the release site at Costessey Point is being used to track the movement of the tagged fish (pers. com. Tom Howard, Environment Agency Fisheries Officer). Targeted barbel surveys conducted at Costessey Point in October 2011 resulted in the capture of 14 barbel, of which eight were identifiable as fish stocked as 1+ fish in 2010 (Environment Agency datat).  Macroinvertebrates: There are no EA routine monitoring sites along this reach and no information is currently available.  Macrophytes: Holmes (2009) surveyed the reach in 2009 and found dominant macrophytes included unbranched bur-reed and arrowhead. Perfoliate and fennel pondweeds, Cladophora, reed sweet-grass, yellow water-lily, flowering rush, reed canary-grass and branched bur-reeds were frequently found. The banks were dominated by reed canary-grass, reed sweet-grass, willowherb and branched bur-reed. Spiked water milfoil was recorded, along with stream water-crowfoot, the latter being less widespread than records from 1985 but still found in suitably shallow and fast flowing sites. Horned pondweed, fan-leaved water-crowfoot, water-cress, fool’s water-cress and water-speedwell were also noted. Azolla (water fern) was recorded in 2009 but hemlock water-dropwort was no longer found. Nuttall’s pondweed had replaced Canadian pondweed and rigid hornwort and small pondweeds were recorded in 1985 but not in 2009. Club rush had increased its range in 2009 compared with the earlier survey.  Surveys of 500m channel sections by CAPM (Grieve et al., 2002) found some channel widths reduced to 6m, due to encroachment by edge species, creating areas of clean gravel bed. Perfoliate pondweed dominated the channel, with unbranched and branched bur-reed, reed sweet-grass, arrowhead, water-milfoil, fool’s water-cress, water starwort, algae (Enteromorpha spp. and Cladophora agg.), flowering rush, common water moss, water forget-me- not and occasional Himalayan balsam.  The 1995 RCS recorded curled pondweed, unbranched bur-reed, Canadian pondweed and water starwort.  Marginal fringes supported reed sweet-grass, water-cress, water forget-me-not, willowherbs, water figwort and branched bur-reed. Some areas of low- lying floodplain are dominated by willowherb, reed canary-grass, reed sweet-grass and water figwort ( e.g. TLHB upstream of the railway bridge). Common reed across expansive TRHB floodplain areas (mid-reach section).  Bankside vegetation consisted of nettle, cleavers, willowherbs, Himalayan balsam, curled dock and meadowsweet.

Ecology  Azolla filiculoides (water fern) was found during the 2009 surveys (Entec, 2010). (Invasive / Non-  Himalayan balsam (Impatiens glandulifera) was recorded in 1995 RCS surveys. Native Species)  Canadian pondweed (Elodea canadensis) and Nuttall’s pondweed (E. nuttallii) have both been recorded in this section.

 The upper part of this reach supports a line of trees (mainly willows) though the majority of the reach is relatively devoid of tree cover. Ecology (Trees)  Sallow, alder, beech, holly, ash, crack willow, hawthorn, and poplar have been recorded along this reach.

 The reach retains a meandering planform, but it has been somewhat simplified and formalised by dredging works.  This reach has been extensively dredged on more than one occasion with evidence of spoil deposition on the TRHB in which gravel substrates and shells of riverine molluscs were also present (see Plate 27). Lower level spoil embankments along the TLHB possibly indicate where subsequent dredging works were undertaken. These appear generally to be less gravel-rich. Geomorphology  Very few shallow areas are present along this reach, the exception being the various restoration works at Costessey Point, notably the installation of three gravel glides/riffles. The rest of the reach is relatively uniformly deep as it is impacted by the backwater from Hellesdon Mill, with extensive widening where the river approaches the former railway line (now Marriot’s Way) at the downstream end of the reach.  Between Rogers Farm and Cliff Bend (TG 188 122) the river shallows substantially. Depths in this section on 07/09/2011 were estimated at around 600mm with upstream and downstream depths in the order of 2m (Atkins, 2011).

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Environmental Baseline Information Feature

Previous  Restoration works were carried out at Costessey Point in 2004 and 2007. Restoration Works

 Environment Agency on-line flood mapping (accessed April 2011) indicates that the floodplain is extensive along this reach, particularly along the right bank (see Figure 3.3). Flood Risk  No occupied dwellings, other than those at, and around, Costessey Mill are present within the identified floodplain. A small, unoccupied bungalow is situated in the floodplain mid-way along the TRHB of the reach.  Some of the local roads, including Low Road and Costessey Lane, are prone to flooding.

 Public access is limited along this reach. A short (only a few hundred metres) section of public footpath follows the steep escarpment section along the TLHB from Low Road and links to the A1067 to the north, but is generally well used by walkers. Marriot’s Way is a well used public footpath and Human cycleway which crosses the Wensum in the upper end of the reach and passes close to the TRHB of the river in the lower part of the reach, providing Environment views across the Wensum valley.  There are two parcels of Countryside Right Of Way (CROW) access land alongside the left hand bank of the river in this reach.  NACA Ketteringham’s Fishery hold the fishing rights along part of this reach.

 The village of Drayton and the surrounding area has many listed buildings that characterise the area’s historical contexts. These include several houses and buildings along Low Road, Drayton Lodge (Grade II*, ruined medieval house), Tudor Barn, Riverside House, Church of St Edmund and an associated tombstone, Church Farm Barn, The Red Lion and a restored Village Cross.  Historic Environment Records and PastScape searches found a large number of recorded findspots, features and monuments. These include prehistoric periods (including Palaeo-, Meso- and Neo-lithic flint objects, scrapers, blades and axe heads and the possible site of a flint mine); Iron Age Historic finds; Roman finds (including bracelets, brooches, buckles, coins, pots); Saxon finds (cremation cemetery of 40 urns of early Anglian origin, metal Environment objects and coins); Medieval finds (bell, brooch, buckle, buttons, coins, figurines, padlock, scabbard and seal); Post-Medieval items (purse, jewellery, clothing metalworks). Later features include a cold war nuclear bunker, lime kilns, former Drayton Station site, cropmarks of unknown origin and the 19th Century site of the former Costessey Mill.  Reference: search on Heritage Gateway website at TG 182 127 on 01/04/2011 (http://www.heritagegateway.org.uk/Gateway/), which covers the area within 1km of the search point in Reach 02.

 The floodplain consists predominantly of improved or semi-improved grassland for grazing cattle and/or sheep. Some areas are particularly wet and have formed well established reedbeds or wet, rough grassland areas. There are frequent ditches dug into the floodplain to reduce the wetness of soils Land Use and improve drainage, and small areas of wet, alder carr woodland.  Away from the floodplain to the north lie the villages of Drayton and Hellesdon, whilst to the south-west lies Costessey and New Costessey. The river corridor and adjacent land provide a ‘green wedge’ as the outskirts of Norwich begin to encroach on the wider landscape.

Traffic and  Low Road runs to the north of the river, providing access to private farmland adjacent to the river. Transport  The only other public access point is the road crossing at Costessey Mill (Costessey Lane).

Utilities  During the field survey (Atkins, 9th February 2011) oil and gas pipelines crossing beneath the main channel within Reach 02 was noted. A detailed

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Environmental Baseline Information Feature utilities search has not been conducted for this reach so information is not yet available.

River  The Environment Agency undertakes an annual weed cut by boat in this reach, from the downstream end of the reach to a point below the restoration Maintenance works at Costessey Point.

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Figure 3.3 - Environmental baseline for Reach 02 (Drayton Reach) Unit 54 Taverham Mill to Hellesdon Mill_final for issue_V1.0.docx 42

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Table 3.9 - Baseline information specific to Reach 03 (Costessey Reach)

Environmental Baseline Information Feature

 Water voles were recorded on the Wensum at Taverham in 1999 and at Costessey Bridge in 2000 (EA database information 1970-2010). More recently, they were found south of Drayton in 2007, but not since 1997 at Costessey pits (Wild Frontier Ecology, 2007). Ecology  White-clawed crayfish were recorded at Taverham in 1997 (EA database information 1970-2010), but there were no positive records during a 2003 (Protected survey (EA, 2004). Species)  Many bird species were recorded during the 1995 RCS. These included mallard, moorhen, coot, blackbird, willow and reed warblers, reed bunting, whitethroat, mute swan, Canada goose, sand martin, robin, chaffinch, great spotted woodpecker, wren, grey heron, swallow, blue and great tits, song thrush, blackcap, goldfinch and carrion crow.

 SAC and SSSI units: Ecology (Statutory Unit 38: Costessey Common South Foster and Mann (2.03 ha of neutral grassland – lowland). Designated Unit 39: Costessey Common South Costessey Parochial Trust (2.39 ha of neutral grassland – lowland). Areas) Unit 54: River Wensum.

Ecology (Non-  County Wildlife Sites (CWS): Statutory CWS 256, Taverham Mill Fishery. Lake and adjacent grassland and woodland. Designated Areas) CWS 253, Costessey Pits (East). Complex of grassland, alder woodland, lakes and dykes.

 Fisheries: Routine Environment Agency fisheries data is available for one site in this reach, Alders Spinney (EA site code NOR34). Nine surveys have been conducted since 1986, the most recent being in 2008. Fifteen fish species have been recorded in total with the population being dominated by cyprinids. Brown trout (Salmo trutta) have been recorded on one occasion, in 2002. Of the nine species recorded in 2008, chub (Leuciscus cephalus), minnow (Phoxinus phoxinus) and pike (Esox lucius) were the most numerically abundant.  Two species of European interest, namely eel (Anguilla anguilla) and brook lamprey (Lampetra planeri) have been recorded in this reach.  Targeted juvenile barbel (Barbus barbus) surveys conducted on the Mack’s Farm stretch of river in 2007 resulted in the capture of four fish between 70 and 89mm in length. Adult surveys conducted on the same stretch of river in 2005 did not yield any adult barbel (Environment Agency, 2007c). Ecology  Macroinvertebrates: The EA has a routine biological monitoring site located downstream of Taverham Bridge. The site supports a wide diversity of (Fisheries, invertebrates, including some that are characteristic of chalk systems with good flows and water quality, such as the water/river bug Aphelocheirus Invertebrates & aestivalis (of local conservation significance), mayflies (Heptageniidae) and caddis flies (Lepidostomatidae). Samples have also recorded a wide Flora) diversity of molluscs, including snails (e.g. Theodoxus fluviatilis, Lymnaeidae, Physidae, Planorbidae), leeches, shrimps and water hoglice, occasional stoneflies, beetles and true fly larvae. BMWP scores are high, ranging from 119 to 174, ASPT are usually above 5 (indicating a good diversity of BMWP taxa from across the scoring range of 1-10 are present). The 1995 RCS recorded good numbers and diversity of adult dragonflies during August.  Macrophytes: A survey of macrophytes was conducted by the EA at Taverham Bridge on 1st August 2007. The area was dominated by Ranunculus and clubrush, with perfoliate pondweed, reed canary-grass, fennel pondweed, unbranched bur-reed, water milfoil and reed sweet-grass present. Additional species included horned pondweed, pink water-speedwell, branched bur-reed, arrowhead, curled pondweed, duckweed, iris, water starwort, lesser water parsnip and water forget-me-not. The Mean Trophic Rank score was 36.3 and the MFR score 1.95.  Surveys of contiguous 500m sections along this reach (Entec, 2010) in 2009 were compared to results of 1985 studies. In 2009 dominant taxa were unbranched bur-reed, algae (Cladophora agg.), perfoliate and fennel pondweeds and arrowhead. Frequent taxa included yellow water-lily, branched Unit 54 Taverham Mill to Hellesdon Mill_final for issue_V1.0.docx 43

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Environmental Baseline Information Feature bur-reed, reed sweet-grass, flowering rush and reed canary-grass. Spiked water-milfoil was also recorded, along with both fan-leaved and stream water- crowfoots. Banks were dominated by reed canary-grass and reed sweet-grass, with fool’s water-cress and water-cress in marginal areas. Lesser water parsnip was recorded in one section. There were generally few differences between species recorded in 1985 and 2009. Clubrush was recorded in 2009 but not in 1985, and Nuttall’s pondweed (recorded in 2009) had largely replaced Canadian pondweed (recorded in 1985). Curled pondweed was present in 1985 but absent in 2009.  In 2002, CAPM surveyed several 500m sections along this reach and found shallow areas dominated by water-milfoil, water crowfoot and unbranched bur-reed, with deeper sections dominated by unbranched bur-reed, perfoliate pondweed and branched bur-reed. Occasional flowering rush, arrowhead, fennel pondweed, reed sweet-grass and reed canary-grass were recorded. The alga Enteromorpha sp was frequently found, particularly where poaching by grazing animals reduced other vegetation. A large silt bar had formed in the channel at one location and was covered by common reed. Stream water-crowfoot was recorded in one survey section where the water shallows, downstream of the southern tip of the large meander loop.  1995 RCS surveys recorded water crowfoot, horned pondweed, flowering rush and spiked water-milfoil in shallow sections. Other species included curled pondweed, perfoliate and fennel pondweeds, yellow water lily, arrowhead, broad-leaved pondweed, club-rush, Canadian and opposite-leaved pondweed, unbranched bur-reed and algae (Cladophora agg and Enteromorpha spp). Fan-leaved water crowfoot was recorded near the Costessey intake.  Emergent fringes supported reed sweet-grass, water-cress, occasional lesser water-parsnip, pink/blue water-speedwell, water forget-me-not and brooklime with occasional common reed, branched bur-reed, reed canary-grass and yellow flag-iris. Cattle grazing often results in cropped vegetation cover down to the water’s edge, or vertical banks providing poor habitat for marginal fringe establishment.  Bankside vegetation consisted of Himalayan balsam, willowherbs, water figwort, water mint, gipsywort, thistles and nettles, occasional nodding bur- marigold, marsh valerian, yellow rattle, ragged Robin, wild angelica, hemlock and occasional greater pond sedge.  IDB drains supported water starwort, branched bur-reed, common club rush, brooklime, ragged Robin, yellow rattle and water violet (the latter species noted during Atkins walkover surveys 08/02/2011).

 Potamopyrgus antipodarum is a non-native, naturalised hydrobid aquatic snail that is established across most water habitats across England. Ecology  Canadian pondweed (Elodea canadensis) and Nuttall’s pondweed (E. nuttallii) have both been recorded in this reach. Both species are introduced but (Invasive / Non- naturalised. Native Species)  Himalayan balsam (Impatiens glandulifera) was recorded in 1995 RCS surveys.

 Several small plantations are present along the river corridor.  Gardens backing onto the river contain ornamental shrubs and trees. Ecology (Trees)  There are scattered trees and shrubs along the river banks, though tree cover along the left bank is particularly scarce.  Trees or shrubs noted in 1995 RCS surveys include ash, oak, weeping willow, yew, sycamore, alder, crack and grey willow, hawthorn, occasional gorse and elder. Planted osier trees along the TRHB provide flow and habitat variation along straighter sections of this reach.

 This reach is extensively affected by the backwater from Costessey Mill. The lower half of the reach has undergone dredging works, whilst in the upper part of the reach, beyond the backwater influence, there are some semi-natural sections with good river habitat and some good opportunities for Geomorphology enhancement works, although poaching by cattle and horses causes localised bank erosion and sediment release.  Upstream of the backwater influence, much of this reach provides a variety of flow types and water depths. There is extensive marginal encroachment and establishment of semi-natural habitats in some locations following adoption of a less intensive maintenance regime (see Plates 46, 47 and 48). Unit 54 Taverham Mill to Hellesdon Mill_final for issue_V1.0.docx 44

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Environmental Baseline Information Feature Deeper sections of channel in the lower reach have struggled to establish consolidated vegetated margins and these are replaced here by narrower floating margins.  Macrophyte surveys by CAPM (Grieve et al, 2002) noted a higher proportion of sand and gravel substrates in the upper part of the reach, changing to become more silty, deep, wide and slow-flowing as the backwater influence increased towards Costessey Mill.

Previous  Isolated osier shrubs have been planted along the TRHB, providing overhanging tree cover and flow diversity where they have established. Restoration Works

 Environment Agency on-line flood mapping (accessed April 2011) indicates that this reach has a wide floodplain, predominantly along the TRHB in the upper part of the reach and along the TLHB along the Costessey part of the reach. Flood Risk  The floodplain outline does not appear to affect any dwellings but parts of Taverham Lane and Costessey Lane will be flooded and the buildings at Taverham Mill may be flooded in extreme events.

 Public access to this reach is extremely limited as there are no public footpaths along the river. The road crossings at either end of the reach are the only public access points. Human  The Costessey public water supply intake is located along this reach and is adjoined by storage lakes. Environment  Much of the riparian land on the left hand bank is owned by one landowner who retains the fishing rights. The Norwich and District Angling Association has fishing along approximately 1km on the TRHB downstream of the Costessey public water supply intake south of the Taverham road bridge.

 There are numerous listed buildings in Taverham, Drayton and Costessey villages. Many are along The Street and West End in Costessey. Others include Costessey Hall (remains of) and associated kennels, Park House and other buildings. The Church of St Edmund is a 14th century church built of brick and flint and is the oldest building in the village.  Historic Environment Records and PastScape searches found many recorded findspots and features of interest in the area. Prehistoric finds included flint objects and transitional objects between Stone and Bronze Ages including flintworkings and knives, axeheads, and a possible round barrow site along the RHB of the Wensum downstream of the Costessey water intake. Finds also date from Saxon and Roman eras (coins, brooches, straps, whetstone, pin, pottery); a Viking brooch, Medieval finds (furniture pieces, seals, coins, buckles, pottery) and Post-Medieval finds (jetton, lead ampulla, a Historic former bridge at Taverham, buckles, coins, tokens, possible site of a wind pump draining to the Wensum near Paradise Plantation and lime kilns). Environment  Taverham Mill was the site of a Medieval watermill recorded in the Domesday Book. It originally grinded corn and then bone for fertilizer and furze for animal fodder, before operating as a sawmill. Paper manufacturing began in 1701, providing cheap paper by reusing rags and the addition of lime from nearby pits. Paper production continued for around 200 years, supplying paper for The Times and the Oxford Dictionary, bank notes and the 1st revised edition of the Bible and making both brown and white paper. At its height it had 11 steam engines, 3 water wheels and 150 workers, but it failed within 10 years of a new owner taking over in 1890.  Reference: search on Heritage Gateway website at two points TG 168 118 and TG 164 131 on 01/04/2011 (http://www.heritagegateway.org.uk/Gateway/), which cover the area within 1km of each search point.

 The entire length of the TLHB floodplain is semi-improved grassland used either for horse grazing (uppermost sections) or sheep/cattle grazing. There Land Use is also a small pine plantation and a small broadleaved plantation (mainly alder). Land out of the floodplain is mainly used for arable farming.  The TRHB has mixed land use including a series of flooded gravel extraction pits associated with the Anglian Water Costessey abstraction point and

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Environmental Baseline Information Feature areas of grassland and woodland. These include two SSSI land parcels (units 38 and 39, neutral grassland). In the lower parts of the reach the river provides the frontage to smallholdings, the swan sanctuary and private gardens bound by a series of drainage ditches. Further from the river, the linear village of Costessey follows the outside of the large meander loop, with occasional broadleaved woodland. This includes Costessey Park Golf Course and a substantial new housing development to the west across former sand and gravel extraction areas.

Traffic and  Minor roads cross the river at the upstream (Taverham Lane) and downstream (Costessey Lane) ends of this reach. Transport  A private track runs due south from Place Farm giving access, across pastures, to the river.

Utilities  A detailed utilities search has yet to be conducted for this reach.

 The Environment Agency undertakes an annual weed cut by boat. River Maintenance  The 2002 survey by CAPM (Grieve et al., 2002) noted one section of the TLHB had been re-sectioned and a 4m berm created (reach NGR: TG 163 134).

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Figure 3.4 - Environmental baseline for Reach 03 (Costessey Reach

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Plate 3 – Reach 01: Top end of reach showing marginal vegetation encroachment along a severely over-widened channel section (looking downstream, NGR TG 19193 11541, February 2011)

Plate 4 – Reach 01: Amenity grassland area with mature willows along TLHB (Wensum to right of photo) (NGR TG 19354 11520, February 2011)

Plate 5 – Reach 01: IDB drain along TLHB with very clear water and diverse aquatic flora (NGR TG 19366 11526, February 2011)

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Plate 6 – Reach 01: River Wensum (looking upstream) showing over-widened and deepened channel and poor habitat diversity (NGR TG 19413 11478, February 2011)

Plate 7 – Reach 01: Substantial marginal vegetated berm encroachment along very wide section (TRHB), with private gardens along TLHB (NGR TG 19638 11203, February 2011)

Plate 8 – Reach 01: Linear willow margin along top of TRHB dredged material embankment (Wensum to right of photo, looking upstream, NGR TG 19684 11151, February 2011)

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Plate 9 – Reach 01: Tree clearance works by private landowners (NGR TG 19712 11124, February 2011)

Plate 10 – Reach 01: Mid reach showing dredging embankment along TRHB (looking upstream, February 2011)

Plate 11 – Reach 01: 4.3ha SSSI land parcel formed of an extensive sedge bed and alder carr associated with the River Wensum, looking west from TRHB (NGR TG 19712 11124, February 2011)

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Plate 12 – Reach 01: Fallen crack willows across over-widened channel upstream of Hellesdon Mill weirs (NGR TG 19770 10596, February 2011)

Plate 13 – Reach 01: Upstream view of managed channel of River Wensum immediately upstream of Hellesdon Mill weirs (NGR TG 19791 10555, February 2011)

Plate 14 – Reach 01: River Tud automated overshot tilting gate (NGR TG 19797 10551, February 2011)

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Plate 15 – Reach 01: Main flow route through Hellesdon Mill weir systems (NGR TG 19889 10448, February 2011)

Plate 16 – Reach 01: Hellesdon Mill Bridge showing main flow through central archway (NGR TG 19902 10449, February 2011)

Plate 17 – Reach 01: View downstream of Hellesdon Mill Bridge (NGR TG 19889 10448, February 2011)

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Plate 18 – Reach 02: View from road bridge looking downstream to Costessey Mill leat – very little flow and heavy shading (NGR TG 17737 12773, February 2011)

Plate 19 – Reach 02: Main River Wensum downstream of Costessey horseshoe weir (NGR TG 17686 12817, February 2011)

Plate 20 – Reach 02: Cattle drink area constructed near confluence between main river and Costessey Mill leat with overhanging osier along TLHB (looking upstream, NGR TG 1774713026, February 2011)

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Plate 21 – Reach 02: Large fallen willow at IDB confluence, within Ketteringham’s Fishery restoration scheme (NGR TG 17677 13180, February 2011)

Plate 22 – Reach 02: Artificial gravel riffle / run installed along main river section (former railway bridge in background and wetland habitat along TLHB floodplain) (NGR TG 17705 13190, February 2011)

Plate 23 – Reach 02: Adjoining backwater, widened drain section with connection pipe in foreground (otter footprint noted) (NGR TG 17881 13231, February 2011)

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Plate 24 – Reach 02: View upstream showing wide, consolidated, vegetated berm encroachment post- dredging works along TLHB, with notable, high, gravel-rich embankments along TRHB (NGR TG 18111 13152, February 2011)

Plate 25 – Reach 02: Fallen trees across whole river width creating localised increase in flow diversity and scour (NGR TG 18160 13083, February 2011)

Plate 26 – Reach 02: Dredged material embankment along TRHB (NGR TG 18219 13013, February 2011)

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Plate 27 – Reach 02: Gravel within TRHB dredged material embankments, note shell of Lister’ s river snail (Viviparus conectus)

Plate 28 – Reach 02: View upstream showing dredged material embankment containing gravel along TRHB and lower, subsequent dredging soil along TLHB (NGR TG 18361 12927, February 2011)

Plate 29 – Reach 02: Connected drain to TLHB with raised dredged material embankments (NGR TG 18401 12877, February 2011)

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Plate 30 – Reach 02: Downstream view of wide meandering river section (NGR TG 18874 12566, February 2011)

Plate 31 – Reach 02: Chalky outcrop along TLHB (TG 18878 12361, February 2011)

Plate 32 – Reach 02: Floodplain sedge bed along TLHB, note steep natural escarpment to left of photo (NGR TG 18868 12508, February 2011)

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Plate 33 – Reach 02: Over-widened reach with overhanging trees on TRHB and sedge margins along TLHB (NGR TG 18761 12102, February 2011)

Plate 34 – Reach 02: Gas main (left, TG 18770 11991) and oil pipeline (TG 18777 11963) crossings (February 2011)

Plate 35 – Reach 02: Large fallen tree across river from TRHB, marginal vegetation encroachment downstream of debris, good otter habitat along this reach (TG 18777 11910, February 2011)

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Plate 36 – Reach 02: Wide channel section on approach to railway siding, heavy tree shading and little in-channel flow variation (NGR TG 18787 11836, February 2011)

Plate 37 – Reach 02: Alder carr and wet floodplain area, with adjoining drains along TLHB. Otter footprints found in this area (TG 18833 11732, February 2011)

Plate 38 – Reach 02: Downstream end of reach showing marginal vegetation encroachment into deepened and widened channel (NGR TG 18833 11732, February 2011)

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Plate 39 – Reach 03: Downstream of Taverham weir, note sandy bed substrates with variety of aquatic plants (September 2009)

Plate 40 – Reach 03: Large, shallow outer meander area providing good fish fry habitat, poached by horses (NGR TG 16209 13571, February 2011)

Plate 41 – Reach 03: Downstream view to River Wensum across horse-grazed paddocks showing meander, overhanging osier, common reed margins along TRHB (NGR TG 19208 13648, February 2011)

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Plate 42 – Reach 03: Territorial otter spraint marking along TLHB (NGR TG 16212 13481, February 2011)

Plate 43 – Reach 03: Dredged meander bend with marginal vegetation encroachment and tall herb growth where TLHB fenced, with isolated mature trees along TRHB (NGR TG 16250 13455, February 2011)

Plate 44 – Reach 03: Over-widened section with poplars along TRHB and horse poaching along TLHB (NGR TG 16443 13354, February 2011)

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Plate 45 – Reach 03: Anglian Water public supply intake at Costessey (NGR TG 16479 13264, September 2009)

Plate 46 – Reach 03: Post-dredging recovery of river margin along TLHB (NGR TG 16584 13131, February 2011)

Plate 47 – Reach 03: Downstream view of shallow, gravel run habitat with vegetated island and margins (NGR TG 16643 12924, September 2009)

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Plate 48 – Reach 03: View upstream showing vegetated berm development on TLHB and overhanging osier providing cover to TRHB (NGR TG 16730 12710, February 2011)

Plate 49 – Reach 03: Wide, straightened section with shallow water suitable for gravel augmentation (NGR TG 16665 12058, February 2011)

Plate 50 – Reach 03: Poaching along TLHB allowing breaching of embankments at high flows, note flint-gravel-chalk layer at water level (NGR TG 17247 12032, February 2011)

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Plate 51 – Reach 03: Private garden along TRHB (NGR TG 17379 12101, February 2011)

Plate 52 – Reach 03: Downstream view towards Costessey Mill, with deep, slack flowing water and dredged material embankments along TLHB (NGR TG 17599 12501, February 2011)

Plate 53 – Reach 03: Middle weir at Costessey with fish pass structure (not suitable for coarse fish passage) (NGR TG 17718 12752, February 2011)

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Plate 54 – Reach 03: Costessey Horseshoe Weir flow measurement site (NGR TG 17663 12742, February 2011)

Plate 55 – Reach 03: View upstream to Costessey Horseshoe weir (NGR TG 17671 12771, February 2011)

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4. Consultation 4.1 Introduction This chapter summarises comments received from key statutory stakeholders and the public. A drop-in session covering this river unit was held at Ringland in September 2009. In addition, one- to-one interviews have been conducted with a number of stakeholders in this unit. 4.2 Consultation with key stakeholders Since 2008, the project team has been communicating with various internal and external stakeholders during the feasibility assessment and the Environment Agency has contacted key staff within different organisations regarding various EIA and planning matters for the River Wensum as a whole. Table 4.1 summarises the responses of these organisations. It should be noted that many of these responses are generic, rather than specific to this particular unit. Table 4.1 - Consultation undertaken to date

Date Nature of Consultation / Consultee Responses Organisation Consulted Statutory Consultees The first meeting presented the objectives of the Strategy. The IDB did not disagree with the overall proposals but expressed concern over Environment Agency maintenance on the main river. The second meeting discussed a number of potential joined Norfolk Rivers IDB / up approaches to targeted river maintenance. This September 2008 Water Management collaborative approach would see a shift to river maintenance and May 2009 Alliance practices which are likely to benefit both river restoration and angling interests whilst addressing some of the key landowner concerns. There remains a requirement for dialogue over linkage between Langor Drain feasibility work and river restoration of main river. A reply was received in April 2009. The landscape team would like further EIA assessment to make a more detailed Norfolk County March 2009 appraisal of potential impacts (good and bad) to the Council – Landscape landscape character and visual amenity of the River Wensum. Key staff were briefed on the proposal, including the issue of winning gravels from site or from an external source e.g. Norfolk County existing gravel pit site. Council provided their “in principle” November 2008 Council – Minerals support for restoration and indicated that if gravels had to be brought to site from elsewhere then planning permission may be required. Internal meeting held in November 2008 to raise awareness of project and to identify issues of implementation. The Development and Flood Risk Team has confirmed that a Internal Environment Flood Risk Assessment will be required. The Flood Risk November 2008 Agency Functions Assessment will have to show: 1) Any changes in the extent of floodplain. 2) Any changes in depth of flooding. 3) Likely impact on any properties. Recognises the need to implement a recommended option to Natural England 2008 deliver ‘favourable’ condition to the SSSI.

The initiative is a partnership between Defra, Natural England England Catchment and the Environment Agency. Ongoing consultations with Sensitive Farming April 2008 local Catchment Sensitive Farming Officer to identify specific Delivery Initiative problems from diffuse pollution from agriculture.

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Date Nature of Consultation / Consultee Responses Organisation Consulted Non-Statutory Consultees Landowners Ongoing All landowners were invited to the Drop-in Session to inform them of the likely timetable for the Feasibility Report. Since that time landowners have been contacted with regard to access for field walk over surveys. This prompted some dialogue, the results of which have been incorporated into the outline designs. It is expected that dialogue will continue where opportunities arise to change the river and/or its management to benefit ecology. Contact with the wider public, including landowners, is achieved with e-mailing of the regular River Wensum Restoration Strategy Newsletter. This was a joint presentation with a representative from the England Catchment Sensitive Farming Delivery Initiative Broads Forum October 2008 highlighting the benefits of reducing sediment input into the Wensum. Another key message was the need to prevent silt ingress into river reaches downstream of restoration sites. Presentation was given to the Steering Group which focused on the benefits of re-establishing the hydrological relationship Norfolk Biodiversity January 2007 between river and floodplain and the potential benefits to BAP Partnership habitat. The Group was enthusiastic, but as a policy they do not express support for specific projects. The meeting focused on understanding their objectives for the Wensum Valley Trust July 2008 Wensum Valley, particularly in relation to river restoration. Norfolk Anglers The presentation focused on the synergy between river Conservation May 2008 restoration and benefits for fisheries. Support was expressed Association for implementation of the Strategy. The meeting brought the National Farmers Union up to speed with the development of the Strategy and gave them an April 2008 understanding of what we are trying to achieve.

National Farmers

Union Project staff attended an NFU organised meeting to discuss

progress with a number of Wensum issues, including diffuse January 2011 pollution, access on the river, river restoration and water resources. Waterbodies BAP The Group expressed a general support for the October 2007 Topic Group implementation of the Strategy. River Restoration Presentation focused on how the Strategy was developed, Centre Annual April 2007 the issues that it will address and how we intend to take it Network Conference forward.

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4.3 Drop-in session September 2009 A drop-in session about the implementation of the River Wensum Restoration Strategy was held in September 2009 at Ringland. The objectives of the session were:  To engage with people who live within the vicinity of this part of the river, and are likely to be affected by the proposed restoration works.  To identify the key environmental concerns / constraints and opportunities with respect to strategic options available for implementing river restoration.  To gain an insight into local knowledge of the river.  To help identify acceptable options, that are environmentally, technically and economically feasible, to deliver ‘unfavourable recovering’ or ‘favourable’ ecological condition. The drop-in was designed to ensure that the local landowners, parish councillors and interested stakeholders had an opportunity to comment and present their views on river restoration. A total of 28 people attended the drop-in session. Attendees recognised that there has been a general decline in the river’s condition, particularly its ecological character and many agreed that the river is in need of some work to improve its condition. Comments recorded on the feedback forms completed by attendees related to:  Poor maintenance of the river including inappropriate weed cutting activities.  Continued neglect by river authorities, past and present.  The failure to instigate a planned maintenance system.  The lack of regular dredging.  Concerns about increasing flood risk.  How compatible new restoration measures will be on existing structures, such as the mills, which are of importance for local heritage and landscape character.  The financial costs of the proposed measures.  The need to explore the possibilities of utilising mill structures to generate electricity and the compatibility of hydropower schemes with river restoration.  The lack of public access to the river, in particular where restoration is proposed. Many attendees were not convinced by the restoration measures presented and requested that they are consulted when further details are available. Particular concerns related to necessity and the economic justification for restoration measures. 4.4 Future consultation Some specific constraints and opportunities identified following the Atkins site visits on this unit are considered below, and include, but are not limited to: Constraints:  Legal agreements: Water levels at Costessey Horseshoe Weir are subject to historic legal agreements making changes in level more difficult. Presence of gauging station may constrain opportunities for river restoration.  Access: Ground conditions are prone to deterioration with high river levels. Privately owned water frontage along garden boundaries in Reach 01 practically restricts access to the opposite bank.

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River Wensum Restoration Strategy Implementation SSSI Unit 54: Feasibility and Environmental Scoping Report

 Ecology: The environmental impact on improving habitats for some flora and fauna could be detrimental for others. Opportunities:  Ecology: Site won materials can be used to create and improve in-stream conditions. This includes felling of trees to be used as large woody debris, and also to reduce shading and so encourage vegetated berm development.  Ecology: Use of existing minor channels as backwater habitats will improve the availability of fish habitat, potentially increasing recruitment.  Ecology: Selective embankment removal, combined with reconnection works, will potentially improve condition of adjacent terrestrial SSSI units.  Land-use: Significant single riparian ownership improves the possibility of securing access for both in-stream and bankside restoration activates in this unit.  Flood risk: Additional flood storage capacity created by embankment removal could potentially reduce downstream flood risk without the need for in-stream weed management. Further consultation with local landowners and internal and external stakeholders will be undertaken as restoration schemes are taken forward into detailed design.

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River Wensum Restoration Strategy Implementation SSSI Unit 54: Feasibility and Environmental Scoping Report

5. Multi-Criteria Analysis Options Appraisal 5.1 Introduction A Multi-Criteria Analysis (MCA) system, based on weighted numerical scoring, has been used to help select appropriate restoration options / measures for each river reach. This was considered necessary to ensure that a transparent, defendable and replicable technique of selecting options / measures was applied. This chapter describes the process by which the MCA tool was designed and subsequently applied. A number of options have been considered which could be implemented individually, or as a group, to restore ‘unfavourable recovering’ or ‘favourable’ condition to the River Wensum. The chapter concludes by presenting the most favourable scoring options / measures for the study reaches. Costs have been excluded from this MCA process and are considered subsequently in Chapter 7. Further details of the MCA process (MCA technical note and MCA table) can be found in Appendix A to this report. Table 5.1 provides an overview of the steps involved in constructing and applying the MCA tool, and Section 5.2 provides more detail. Table 5.1 - Overview of the process by which the MCA was constructed and applied A Constructing the MCA Tool 1 Identification of options / measures 2 Selection of success criteria 3 Ranking of success criteria 4 Setting up the MCA table B Applying the MCA Tool (Spreadsheet) to Specific Reaches 1 Is the option / measure applicable to the reach? If no, discard. 2 Work through each criterion by option / measure. 3 Apply weighting and determine total weighted score (TWS) 4 Mill structure measures: Apply the best scoring measure.

Other measures: Undertake statistical analysis and discard measures scoring 5 below lower limit.

Other measures: Apply remaining measures in order of highest to lowest 6 scoring. 7 Gravel works: Apply best scoring measure.

5.2 Constructing the MCA tool The MCA Table provides the framework for the options appraisal process, and scores the degree to which all the proposed restoration options / measures meet the defined criteria. The initial stage in the options appraisal was the construction of the Table, which involved defining the options / measures to be considered, and defining the criteria against which the options / measures are evaluated. Following the construction of the Table, it was applied as a tool to determine the highest scoring options / measures for each reach. Unit 54 Taverham Mill to Hellesdon Mill_final for issue_V1.0.docx 70

River Wensum Restoration Strategy Implementation SSSI Unit 54: Feasibility and Environmental Scoping Report

5.2.1 Identification of options / measures A generic list of all restoration options / measures possibly applicable to the River Wensum was generated through the following activities:  Document review: All options and restoration measures recommended in the RWRS and the Geomorphological Appraisal were considered and all were included in the final list of options. Table 5.2 lists the measures recommended in these two reports. Table 5.2 - Restoration measures recommended in previous studies Reach Geomorphological Appraisal River Wensum Restoration Strategy All works must integrate with removal of Desilt reach. Removal of Hellesdon weir Hellesdon Mill and associated river works. De- to drop water levels. Re-establishment silt channel just upstream of the current water of riparian wooded margins. Fix control structure and augment the bed using 01 sediment ingress points. Narrow the gravels. Physical narrowing is required owing channel with material derived from to the wide nature of the channel. Remove removal of embankments and dredging embankments to reconnect river to its spoil. floodplain. Develop marginal / bankside vegetation.

All works must integrate with removal of Hellesdon Mill and lowering of structure at Fix sediment ingress points. Narrow the Costessey Mill and associated river works. channel with material derived from Restoration must link with the existing scheme removal of embankments. Augment bed at Costessey Point. Physically narrow the 02 to restore bed levels. Establish debris channel and augment the bed using gravels. recruitment and wooded riparian margin. Remove embankments along both banks Reduce level of Costessey Mill weirs. downstream of Marriott’s Way and improve marginal / bankside vegetation, such as tree planting.

All works must integrate with removal of Taverham Mill, lowering of structure at Monitor changes with reduced mill weir Costessey Mill and associated river works. De- levels. Desilt reach. Narrow the channel silt channel just upstream of Costessey Mill and using former dredgings and remove augment the bed using gravels. Physically 03 embankments. Augment bed levels with narrow the channel where substantially over- gravels. Establish patchy wooded wide. Reconnect river to its floodplain by riparian margin. removing embankments. Develop marginal / bankside vegetation by planting trees at meander bends.

Consultation: This took the form of a public drop-in session, as described in Chapter 4 of this report. Consultation with authorities such as Broadland District Council and South Norfolk District Council was also undertaken. Workshop: An MCA workshop, attended by the Environment Agency, Natural England and Atkins, was held on 29th January 2009 with the purpose of working through the MCA approach. From the above sources, six main option groups were identified namely ‘Do nothing’, ‘Do minimum’, ‘Targeted maintenance’, ‘Continue as present’, ‘River restoration ’ and ‘Alternative options’. These are explained in Table 5.3. Appendix A provides further information regarding the options.

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River Wensum Restoration Strategy Implementation SSSI Unit 54: Feasibility and Environmental Scoping Report

Table 5.3 - Options identified for restoration on the River Wensum

No. Option Description No maintenance to main river or IDB channels. No restoration to G1 Do nothing any channels or floodplain. No operational activities such as weed cutting. No maintenance to main river or IDB channels. Opportunistic restoration in certain areas (e.g. trees may be felled where G2 Do minimum appropriate thereby reducing channel shading). No operational activities such as weed cutting. Reduced maintenance to include only reactive activities e.g. removal of debris posing an immediate flood risk or removal of silt G3 Targeted maintenance in specific locations. Mitigation for activity in the form of small scale restoration. Limited operational activities e.g. sluice management for high flows. Continuation of existing activities which includes maintenance (debris removal, bank repairs, selected desilting and selected weed G4 Continue as present cutting). Undertaking small scale, opportunistic restoration activities. Continuation of operational activities such as sluice management during high flows. Active restoration measures of which 21 such measures have been identified and grouped into three sub-groups namely ‘Mill G5 River restoration structures’, ‘Gravel works’ and ‘Other’. See Appendix A for a full list of these measures. Three options have been considered within this group, namely ’Increasing main river maintenance’, ‘Increased main river and IDB G6 Alternative options maintenance’, and ‘Mills re-used for hydro-power’. These are explained further in Appendix A.

Three groups of ’measures’ have been defined under the option G5 (see Table 5.4 for full details). These include:  Various works around mill structures including changes to operating protocol, lowering mill sill levels and constructing / utilising existing bypass channels.  Various gravel works including large scale bed raising.  Other measures.

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River Wensum Restoration Strategy Implementation SSSI Unit 54: Feasibility and Environmental Scoping Report

Table 5.4 - Description of river restoration measures as defined under option G5

Group Restoration Measure Description Modify existing mill operating protocols to ensure Improve operation water level management is in line with SSSI protocols Mill Structure management. Works Remove flow control Remove all sluice control mechanisms and allow These works mechanisms the river to be free flowing. Lower the level of the mill sill to reduce the extent need to be Lower mill sill levels undertaken first of backwater in low flows. Construction of channel around mill to split flows to ensure the Create bypass channel to allow fish passage and continuity of stream success of any around mill subsequent processes. Construction of fish pass alongside mill structure measures Install fish pass to enable free passage of fish upstream. Remove mill structure Remove entire mill structure. Creation of short lengths of full width raised bed, Gravel Works Gravel glides dressed in gravel, to create variation in flow and Need to be habitat for fish and invertebrates. considered (and Creation of short lengths of raised gravel bed with constructed) Gravel glides and hurdles made from post and faggots to trap after Mill transverse hurdles suspended sediment thereby extending the Structure Works length of the glide over time. have been Creation of extended lengths of full width raised completed Bed raising bed – to reduce water depth and allow characteristic plant communities to develop. Fencing constructed landward of the river bank to Fencing prevent bank erosion from the impacts of cattle grazing. Tree planting to cast shade over the water to control macrophyte growth, provide cover for fish, Tree planting and to develop erosion resistance from root reinforcement. Selective felling or lopping to provide light onto Tree thinning the water to encourage macrophyte or emergent plant growth, and generate arisings for deflectors. Other Deflector (using Large Downstream pointing LWD placed at the Measures Woody Debris (LWD) upstream side of deflector to create flow diversity;

and filled in with brush in-filled downstream with brush to promote silt These need to mattress) deposition and plant growth. be considered Removal of dredging based informal after Mill Lower spoil embankments to allow out of bank flow across Structure embankments the floodplain, and back into the river. Use of Works and arisings for riffles / general bed raising if needed. Gravel Works Horizontal lowering of bank top up to 1/2 channel have been width to increase flood flow capacity and identified Berm creation generate arisings for bed raising where no

embankments. Backchannels – Utilizing existing wet features by connecting them reconnections to IDB to the river to create essential habitat for fish and and existing field drains other fauna. Creating habitat where no other water bodies Backchannels – create exist e.g. dog-leg with downstream end open and new features upstream end fed by percolation. Full depth excavation from bank top to increase Channel realignment to lateral variation in planform either one bank or increase river sinuosity both with arisings used to infill opposite bank.

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River Wensum Restoration Strategy Implementation SSSI Unit 54: Feasibility and Environmental Scoping Report

5.2.2 Selection of success criteria ‘Criteria’ refer to the various standards against which the proposed options / measures are evaluated. A range of criteria (12 in total) were defined during a workshop between Atkins, Environment Agency and Natural England in January 2009. These criteria have been grouped under the following three broad headings: 1. Ecology: This includes criteria relating to legally protected ecology, such as compliance with the SSSI designation, as well as that which is not legally protected, but where the proponents of the works still have a responsibility to safeguard and improve ecological value of the site. Three of the criteria within this group relate to three levels of legal designations, and the final criterion covers all non-legal responsibilities.

2. Project delivery: This considers compliance with the objectives of the RWRS and takes into account stakeholder opinion. Hence compliance/agreement with requirements of statutory and non-statutory stakeholders is considered.

3. Technical: This group considers delivery of the technical aspects of the RWRS objectives including technical feasibility, geomorphic form, flood risk and climate change.

All criteria and accompanying descriptions are provided in Table 5.5. 5.2.3 Ranking success criteria While all of the defined criteria groups are significant, it is acknowledged that some are more so than others. For example, ecology is the main driver of the project and the primary objective is to improve the ecology of the River Wensum. Hence, compliance with these criteria can be considered as more important than, for example, technical considerations and hence a weighting system has been applied to these groups. Similarly, different criteria within a single group such as ‘Ecology’ are not necessarily of equal importance. For example, the criterion ‘Compliance with National Designation’ (such as SSSI), which falls within the ‘Ecology’ group, is the main driver for this project, and hence compliance with this criterion is considered essential for achieving project objectives. The criterion ‘Contribution to overall ecology’ would be considered less important. Hence, a similar weighting system has been applied to individual criteria within the three groups. Professional judgement was applied in determining the numerical weighting for each criteria group and each criterion. A weighted score between zero and one was applied and agreed to in the MCA workshop. An ‘effective weighting factor’ for each criterion was calculated by multiplying the group criteria weighting and the individual criteria weighting. Table 5.5 presents the criteria and applied weightings and Appendix A provides a detailed explanation for the weighting of criteria.

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River Wensum Restoration Strategy Implementation SSSI Unit 54: Feasibility and Environmental Scoping Report

Table 5.5 - Criteria defined for the MCA

Group Weighting Effective (group Criterion Description / Example Within Weighting weighting) Group Factor SSSI requirements for the Compliance with river e.g. improved flow 1 1 national designation regime, water quality and channel form. SAC requirements Compliance with including maintaining international 0.8 0.8 favourable habitat for EU designation Ecology designated species. (1) BAP requirements such as Compliance with maintaining flora and fauna regional / local 0.6 0.6 characteristic of chalk designations rivers. Compliance with the Contribution to Environment Agency’s 0.5 0.5 overall ecology general duty to further conservation Meeting objectives of the Compliance with RWRS as well as the strategy (RWRS) 1 0.9 specific reach objectives recommendations. Stakeholders include Environment Agency, Compliance with Natural England, Broadland statutory 0.9 0.81 Project District Council, South stakeholders delivery Norfolk Council and Norfolk (0.9) County Council. Agreement with non- Angling clubs, land owners statutory 0.9 0.81 and tenants. stakeholders Consideration of or improvements to Human environment 0.4 0.36 archaeology, landscape, and recreation value. Consideration of design, Technical feasibility & construction process, 1 0.8 practicality commercial risk, and maintenance. Geomorphic form Consideration of the shape 1 0.8 Technical and function and flow of the river. (0.8) Consideration of the impact Flood risk 1 0.8 of restoration on flood risk. Considers the robustness Climate change and of the measures in terms of 0.8 0.64 sustainability future flood risk and carbon footprint.

5.2.4 Setting up the MCA Table Defining the scoring system The MCA Table lists all of the options / measures against the 12 defined criteria and a score is allocated depending on the degree to which the individual options / measures comply with the criteria.

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River Wensum Restoration Strategy Implementation SSSI Unit 54: Feasibility and Environmental Scoping Report

The term ‘relevance’ is used to describe where a particular option / measure complies with the criteria or brings about betterment of the features pertaining to those criteria. The term ‘detriment’ is used where a particular option / measure does not comply with the criteria or results in an adverse change to a particular feature pertaining to those criteria. A five point scoring system is utilised with +2 allocated if the option / measure is of high relevance and -2 allocated where the option / measure is of high detriment. These terms are presented in Table 5.6. Table 5.6 - Scoring system defined for the Multi-Criteria Analysis

Score Description +2 High relevance +1 Low relevance 0 Neutral

-1 Low detriment -2 High detriment

These are applied as ‘raw scores’. From here, a ‘weighted score’ is derived by multiplying the ‘raw score’ by the ‘effective weighting factor’. A ‘total weighted score’ for an individual option / measure is derived by summing all of the ‘weighted scores’ for that option / measure. The consideration of costs was deliberately excluded from the MCA analysis so as not to discriminate against any options or measures, and so determine the best technical solution irrespective of cost. 5.3 Using the MCA Tool The MCA tool has been applied to each of the reaches separately on a reach by reach basis. The following main steps were undertaken:  The applicability of the option / measure was considered. Where the option / measure is not applicable (e.g. ‘Changing primary and secondary channels’ may not be applicable if no secondary channel exists) then this option / measure has been discarded.  The remaining criteria were then worked through for one option / measure at a time and raw scores allocated. Working through by option / measure allowed greatest consistency of scoring.  Weightings were applied to the raw scores to generate weighted scores.  Total weighted scores (TWS) were calculated for each option / measure by summing all of the weighted scores.  Statistical analysis was applied to the scores within the ‘River Restoration’ (G5) options category. Those scoring below a defined statistically lower limit were discarded. Appendix A provides further information on the statistical methods.  The measures with the highest TWS represent the preferred suite of options and associated measures for that specific reach. These were applied, in their scored order, for designing a preferred restoration plan for the reach. The results of the MCA analysis for Reach 01, 02 and 03 are displayed in Tables 5.7, 5.8 and 5.9, respectively.

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River Wensum Restoration Strategy Implementation SSSI Unit 54: Feasibility and Environmental Scoping Report

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Table 5.7 - Results of MCA for Reach 01 (Hellesdon Reach)

River Wensum Multi Criteria Analysis River 54 Criteria Group Ecology [A] Project Delivery [B] Technical [C] Unit: Wensum Group weighting 1 0.9 0.8 Reach: 1 Hellesdon Individual weighting within group 0.8 1 0.6 0.5 1 0.9 0.9 0.4 1 1 1 0.8 Length: 1650m Criteria Option / Compliance Compliance Compliance Contribution Compliance Compliance Agreement Human Technical Geomorphic Flood Risk Climate Total Rank order measure with with with to overall with Strategy with with Environment: Feasibility form & [C.c] Change & Raw applicable to International National Regional/Local ecology [A.d] objectives Statutory Non‐statutory Archaeology; & function [C.b] sustainability Score reach Designation Designation designation (Wildlife & Stakeholders Stakeholders landscape; practicality [C.d] (highest (SAC) [A.a] (SSSI) [A.b] (BAP) [A.c] Fisheries & (EA; NE; BDC; (anglers; recreation [C.a] possible River Form & NCC) [B.b] owners; [B.d] score 24) Process) [B.a] occupiers) [B.c] Individual w eighting factor = 0.8 1 0.6 0.5 0.9 0.81 0.81 0.36 0.8 0.8 0.8 0.64 Option No. Option / measure G1: Do Nothing: No maintenance or restoration: Raw score Y 0001‐1 ‐1 ‐2 0200 0‐1 Weighted score 0000.5‐0.9 ‐0.81 ‐1.62 0 1.6 0 0 0 ‐1.23 G2: Do M inim um : Minimal restoration: Raw score Y 000‐1 ‐1 ‐1 ‐1 0200 0‐2 Weighted score 000‐0.5 ‐0.9 ‐0.81 ‐0.81 0 1.6 0 0 0 ‐1.42 G3: Targeted Maintenance: Raw s core Y 000‐1111010003 Weighted score 000‐0.5 0.9 0.81 0.81 0 0.8 0 0 0 2.82 10 L G4: Continue as present: Raw s core Y 000‐1 ‐2 ‐1 ‐102‐10 0‐4 Weighted score 000‐0.5 ‐1.8 ‐0.81 ‐0.81 0 1.6 ‐0.8 0 0 ‐3.12 G5: River Restoration G5a Mill Structures: 5.1m Mill structures - improve operability + protocols: Raw score Y 2 2 2 2 1220211118 w eighted score 1.6 2 1.2 1 0.9 1.62 1.62 0 1.6 0.8 0.8 0.64 13.78 1 H 5.2m Mill structures - remove flow control mechanisms: Raw score Y 2 2 2 2 1100210013 w eighted score 1.6 2 1.2 1 0.9 0.81 0 0 1.6 0.8 0 0 9.91 5.3m Mill structures - low er mill sills levels: Raw score Y 22221‐1 ‐1 ‐1 ‐12 1 19 Weighted score 1.6 2 1.2 1 0.9 ‐0.81 ‐0.81 ‐0.36 ‐0.8 1.6 0.8 0.64 6.96 Mill structures – bypass channels: Raw score N 5.4m 0 Weighted score 0 0 0 0 00000000 0 5.5m Fish passes: Raw score Y 2 2 2 2 1210‐10 0 112 Weighted score 1.6 2 1.2 1 0.9 1.62 0.81 0 ‐0.8 0 0 0.64 8.97 5.6m Mill structures - remove all: Raw score Y 222220‐2 ‐1 ‐22 1 19 Weighted score 1.6 2 1.2 1 1.8 0 ‐1.62 ‐0.36 ‐1.6 1.6 0.8 0.64 7.06 G5b Gravel works: 5.7g Gravel glides: Raw score Y 1 1 1 1 2111110112 w eighted score 0.8 1 0.6 0.5 1.8 0.81 0.81 0.36 0.8 0.8 0 0.64 8.92 7 5.8g Gravel glides + transverse hurdles: Raw score Y 1 1 1 1 2111110112 w eighted score 0.8 1 0.6 0.5 1.8 0.81 0.81 0.36 0.8 0.8 0 0.64 8.92 5.9g Bed raising (large scale): Raw score N 0 Weighted score 0 0 0 0 00000000 0 G5c Other: 5.10 Fencing: Raw score Y 00002‐1 ‐1 ‐1200 01 Weighted score 00001.8‐0.81 ‐0.81 ‐0.36 1.6 0 0 0 1.42 11 L 5.11 Tree planting on top of bank: Raw score Y 1 1 1 1 0111200110 Weighted score 0.8 1 0.6 0.5 0 0.81 0.81 0.36 1.6 0 0 0.64 7.12 9 5.12 Tree thinning: Raw score Y 1 1 1 1 1221200113 Weighted score 0.8 1 0.6 0.5 0.9 1.62 1.62 0.36 1.6 0 0 0.64 9.64 6 5.13 Deflector: Raw score Y 1 1 1 1 2111210113 Weighted score 0.8 1 0.6 0.5 1.8 0.81 0.81 0.36 1.6 0.8 0 0.64 9.72 5 5.14 Low er spoil embankments: Raw score Y 1 1 1 2 2111012215 Weighted score 0.8 1 0.6 1 1.8 0.81 0.81 0.36 0 0.8 1.6 1.28 10.86 2 5.15 Channel re-sectioning N 0 Weighted score 0 0 0 0 00000000 0 5.16 Berm creation: Raw score Y 1 1 1 2 2111210114 Weighted score 0.8 1 0.6 1 1.8 0.81 0.81 0.36 1.6 0.8 0 0.64 10.22 4 Backw aters – reconnections to IDB, field drains: Raw score Y 5.17 1 1 2 2 0111101112 Weighted score 0.8 1 1.2 1 0 0.81 0.81 0.36 0.8 0 0.8 0.64 8.22 8 5.18 Backwaters - new : Raw score N 0 Weighted score 0 0 0 0 00000000 0 5.19 Channel realignment: Raw score N 0 Weighted score 0 0 0 0 00000000 0 5.20 Changing primary and secondary channels: Raw score N 0 Weighted score 0 0 0 0 00000000 0 5.21 Low er embankments: Raw score Y 1 1 1 2 2111012215 Weighted score 0.8 1 0.6 1 1.8 0.81 0.81 0.36 0 0.8 1.6 1.28 10.86 2

G6: Alternative Options 6.1 Increase Main river maintenance: Raw score Y ‐1 ‐1 ‐1 ‐1 ‐2 ‐12 01‐10‐1 ‐6 Weighted score ‐0.8 ‐1 ‐0.6 ‐0.5 ‐1.8 ‐0.81 1.62 0 0.8 ‐0.8 0 ‐0.64 ‐4.53 6.2 Increase main river & IDB channel maintenance: Raw score Y ‐2 ‐2 ‐2 ‐2 ‐2 ‐22‐11‐10‐1 ‐12 Weighted score ‐1.6 ‐2 ‐1.2 ‐1 ‐1.8 ‐1.62 1.62 ‐0.36 0.8 ‐0.8 0 ‐0.64 ‐8.6 6.3 Mill Structures - reinstatement + hydropow er: Raw score Y ‐2 ‐2 ‐2 ‐2 ‐2 ‐2 ‐1 ‐1 ‐10‐10‐16 Weighted score ‐1.6 ‐2 ‐1.2 ‐1 ‐1.8 ‐1.62 ‐0.81 ‐0.36 ‐0.8 0 ‐0.8 0 ‐11.99 Total Score 25.2 28 24 23 23.8 11.86 18.29 5.44 35.8 16.2 12.6 21.32 Key Score Description Mean: 8.51 2High Relevance SD: 3.43 1Low Relevance 0Neutral High imp: >11.94 ‐1Low Detriment Low imp: <5.08 ‐2High Detriment Unit 54 Taverham Mill to Hellesdon Mill_final for issue_V1.0.docx 78

River Wensum Restoration Strategy Implementation SSSI Unit 54: Feasibility and Environmental Scoping Report

Table 5.8 - Results of MCA for Reach 02 (Drayton Reach)

River Wensum Multi Criteria Analysis River 54 Criteria Group Ecology [A] Project Delivery [B] Technical [C] Unit: Wensum Group weighting 1 0.9 0.8 Reach: 2 Individual weighting within group 0.8 1 0.6 0.5 1 0.9 0.9 0.4 1 1 1 0.8 Length: 3160m Criteria Option / Compliance Compliance Compliance Contribution Compliance Compliance Agreement Human Technical Geomorphic Flood Risk Climate Total Total Rank order measure with with with to overall with Strategy with with Environment: Feasibility form & [C.c] Change & Raw weighted applicable to International National Regional/Local ecology [A.d] objectives Statutory Non‐statutory Archaeology; & function [C.b] sustainability Score score reach Designation Designation designation (Wildlife & Stakeholders Stakeholders landscape; practicality [C.d] (highest (SAC) [A.a] (SSSI) [A.b] (BAP) [A.c] Fisheries & (EA; NE; BDC; (anglers; recreation [C.a] possible River Form & NCC) [B.b] owners; [B.d] score 24) Process) [B.a] occupiers) [B.c] Individual w eighting factor = 0.8 1 0.6 0.5 0.9 0.81 0.81 0.36 0.8 0.8 0.8 0.64 Option No. Option / measure G1: Do Nothing: No maintenance or restoration: Raw score Y 0 ‐100‐1 ‐1 ‐2 0200 0‐3 Weighted score 0 ‐10 0‐0.9 ‐0.81 ‐1.6201.6000 ‐2.73 G2: Do Minimum: Minimal restoration: Raw score Y 0 00001‐1 0100 01 Weighted score 0 00000.81‐0.8100.8000 0.8 G3: Targeted Maintenance: Raw s core Y 1 111121010009 Weighted score 0.8 1 0.6 0.5 0.9 1.62 0.81 0 0.8 0 0 0 7.03 9 L G4: Continue as present: Raw score Y ‐1 ‐1 ‐1 ‐1 ‐1 ‐1 ‐1 0200 0‐5 Weighted score ‐0.8 ‐1 ‐0.6 ‐0.5 ‐0.9 ‐0.81 ‐0.8101.6000 ‐3.82 G5: River Restoration G5a M ill Structures: 5.1m Mill structures - improve operability + protocols: Raw score Y 2 2221220222120 w eighted score 1.6 2 1.2 1 0.9 1.62 1.62 0 1.6 1.6 1.6 0.64 15.38 1 H 5.2m Mill structures - remove flow control mechanisms: Raw score Y 2 222110‐1220 114 w eighted score 1.6 2 1.2 1 0.9 0.81 0 ‐0.36 1.6 1.6 0 0.64 10.99 5.3m Mill structures - low er mill sills levels: Raw score Y 2 22210‐1 ‐1 ‐12 0 08 Weighted score 1.6 2 1.2 1 0.9 0 ‐0.81 ‐0.36 ‐0.8 1.6 0 0 6.33 Mill structures – bypass channels: Raw score N 5.4m 0 Weighted score 0 00000000000 0 5.5m Fish passes: Raw score N 0 Weighted score 0 00000000000 0 5.6m Mill structures - remove all: Raw score Y 2 2222‐1 ‐2 ‐2 ‐22 1 17 Weighted score 1.6 2 1.2 1 1.8 ‐0.81 ‐1.62 ‐0.72 ‐1.6 1.6 0.8 0.64 5.89 G5b Gravel works: 5.7g Gravel glides: Raw score Y 2 2222221210119 w eighted score 1.6 2 1.2 1 1.8 1.62 1.62 0.36 1.6 0.8 0 0.64 14.24 2 H 5.8g Gravel glides + transverse hurdles: Raw score Y 2 2221110210115 w eighted score 1.6 2 1.2 1 0.9 0.81 0.81 0 1.6 0.8 0 0.64 11.36 5.9g Bed raising (large scale): Raw score N 0 Weighted score 0 00000000000 0 G5c Other: 5.10 Fencing: Raw score Y 0 000211‐1200 05 Weighted score 0 0001.80.810.81‐0.36 1.6 0 0 0 4.66 10 L 5.11 Tree planting on top of bank: Raw score Y 1 1112111200112 Weighted score 0.8 1 0.6 0.5 1.8 0.81 0.81 0.36 1.6 0 0 0.64 8.92 7 5.12 Tree thinning: Raw score Y 1 1111111200111 Weighted score 0.8 1 0.6 0.5 0.9 0.81 0.81 0.36 1.6 0 0 0.64 8.02 8 5.13 Deflector: Raw score Y 1 1112111220114 Weighted score 0.8 1 0.6 0.5 1.8 0.81 0.81 0.36 1.6 1.6 0 0.64 10.52 4 5.14 Low er spoil embankments: Raw score Y 1 1122112211116 Weighted score 0.8 1 0.6 1 1.8 0.81 0.81 0.72 1.6 0.8 0.8 0.64 11.38 3 5.15 Channel re-sectioning N 0 Weighted score 0 00000000000 0 5.16 Berm creation: Raw score Y 1 1112111220114 Weighted score 0.8 1 0.6 0.5 1.8 0.81 0.81 0.36 1.6 1.6 0 0.64 10.52 4 Backw aters – reconnections to IDB, field drains: Raw score Y 5.17 1 1122111201114 Weighted score 0.8 1 0.6 1 1.8 0.81 0.81 0.36 1.6 0 0.8 0.64 10.22 6 5.18 Backw aters - new : Raw score N 0 Weighted score 0 00000000000 0 5.19 Channel realignment: Raw score N 0 Weighted score 0 00000000000 0 5.20 Changing primary and secondary channels: Raw score N 0 Weighted score 0 00000000000 0 5.21 Low er embankments: Raw score N 0 Weighted score 0 00000000000 0

G6: Alternative Options 6.1 Increase Main river maintenance: Raw score Y ‐1 ‐1 ‐1 ‐1 ‐2 ‐21‐11‐20‐2 ‐11 Weighted score ‐0.8 ‐1 ‐0.6 ‐0.5 ‐1.8 ‐1.62 0.81 ‐0.36 0.8 ‐1.6 0 ‐1.28 ‐7.95 6.2 Increase main river & IDB channel maintenance: Raw score Y ‐2 ‐2 ‐2 ‐2 ‐2 ‐21‐11‐20‐2 ‐15 Weighted score ‐1.6 ‐2 ‐1.2 ‐1 ‐1.8 ‐1.62 0.81 ‐0.36 0.8 ‐1.6 0 ‐1.28 ‐10.85 6.3 Mill Structures - reinstatement + hydropow er: Raw score Y ‐2 ‐2 ‐2 ‐2 ‐2 ‐2 ‐1 ‐1 ‐10‐10‐16 Weighted score ‐1.6 ‐2 ‐1.2 ‐1 ‐1.8 ‐1.62 ‐0.81 ‐0.36 ‐0.8 0 ‐0.8 0 ‐11.99 Total Score 23.4 25 20.8 22.5 27.6 13.67 14.67 0 44.8 19.8 7.2 11.48 Key Score Description Mean: 10.09 2High Relevance SD: 3.03 1Low Relevance 0Neutral High imp: >13.12 ‐1Low Detriment Low imp: <7.06 ‐2High Detriment Unit 54 Taverham Mill to Hellesdon Mill_final for issue_V1.0.docx 79

River Wensum Restoration Strategy Implementation SSSI Unit 54: Feasibility and Environmental Scoping Report

Table 5.9 - Results of MCA for Reach 03 (Costessey Reach)

River Wensum Multi Criteria Analysis River 54 Criteria Group Ecology [A] Project Delivery [B] Technical [C] Unit: Wensum Group weighting 1 0.9 0.8 Reach: 3 Costessey Individual weighting within group 0.8 1 0.6 0.5 1 0.9 0.9 0.4 1 1 1 0.8 Length: 3910m Criteria Option / Compliance Compliance Compliance Contribution Compliance Compliance Agreement Human Technical Geomorphic Flood Risk Climate Total Total Rank order measure with with with to overall with Strategy with with Environment: Feasibility form & [C.c] Change & Raw weighted applicable to International National Regional/Local ecology [A.d] objectives Statutory Non‐statutory Archaeology; & function [C.b] sustainability Score score reach Designation Designation designation (Wildlife & Stakeholders Stakeholders landscape; practicality [C.d] (highest (SAC) [A.a] (SSSI) [A.b] (BAP) [A.c] Fisheries & (EA; NE; BDC; (anglers; recreation [C.a] possible River Form & NCC) [B.b] owners; [B.d] score 24) Process) [B.a] occupiers) [B.c] Individual w eighting factor = 0.8 1 0.6 0.5 0.9 0.81 0.81 0.36 0.8 0.8 0.8 0.64 Option No. Option / measure G1: Do Nothing: No maintenance or restoration: Raw score Y ‐1 ‐100‐1 ‐1 ‐2 0210 0‐3 Weighted score ‐0.8 ‐10 0‐0.9 ‐0.81 ‐1.62 0 1.6 0.8 0 0 ‐2.73 G2: Do Minimum: Minimal restoration: Raw score Y 0 00011‐1 0111 04 Weighted score 00000.90.81‐0.81 0 0.8 0.8 0.8 0 3.3 G3: Targeted Maintenance: Raw score Y 1 1111110111111 Weighted score 0.8 1 0.6 0.5 0.9 0.81 0.81 0 0.8 0.8 0.8 0.64 8.46 7 G4: Continue as present: Raw score Y ‐1 ‐1 ‐1 ‐1 ‐1 ‐1 ‐102‐11 0‐5 Weighted score ‐0.8 ‐1 ‐0.6 ‐0.5 ‐0.9 ‐0.81 ‐0.81 0 1.6 ‐0.8 0.8 0 ‐3.82 G5: Rive r Re s tor ation G5a M ill Structures: 5.1m Mill structures - improve operability + protocols: Raw score Y 1 1111220201113 w eighted score 0.8 1 0.6 0.5 0.9 1.62 1.62 0 1.6 0 0.8 0.64 10.08 5.2m Mill structures - remove flow control mechanisms: Raw score Y 1 11111‐1 0111 19 w eighted score 0.8 1 0.6 0.5 0.9 0.81 ‐0.81 0 0.8 0.8 0.8 0.64 6.84 5.3m Mill structures - low er mill sills levels: Raw score Y 2 22221‐1 ‐1 ‐22 2 213 Weighted score 1.6 2 1.2 1 1.8 0.81 ‐0.81 ‐0.36 ‐1.6 1.6 1.6 1.28 10.12 1 Mill structures – bypass channels: Raw score N 5.4m 0 Weighted score 0 00000000000 0 5.5m Fish passes: Raw score N 0 Weighted score 0 00000000000 0 5.6m Mill structures - remove all: Raw score Y 2 22210‐2 ‐2 ‐22 2 29 Weighted score 1.6 2 1.2 1 0.9 0 ‐1.62 ‐0.72 ‐1.6 1.6 1.6 1.28 7.24 G5b Gravel works: 5.7g Gravel glides: Raw score Y 1 1112110210112 w eighted score 0.8 1 0.6 0.5 1.8 0.81 0.81 0 1.6 0.8 0 0.64 9.36 6 5.8g Gravel glides + transverse hurdles: Raw score Y 0 011111021019 w eighted score 0 0 0.6 0.5 0.9 0.81 0.81 0 1.6 0.8 0 0.64 6.66 5.9g Bed raising (large scale): Raw score N 0 Weighted score 0 00000000000 0 G5c Other: 5.10 Fencing: Raw score Y 1 1112111210113 Weighted score 0.8 1 0.6 0.5 1.8 0.81 0.81 0.36 1.6 0.8 0 0.64 9.72 3 5.11 Tree planting on top of bank: Raw score Y 1 1112211200113 Weighted score 0.8 1 0.6 0.5 1.8 1.62 0.81 0.36 1.6 0 0 0.64 9.73 2 5.12 Tree thinning: Raw score N 0 Weighted score 0 00000000000 0 5.13 Deflector: Raw score Y 1 1112101220113 Weighted score 0.8 1 0.6 0.5 1.8 0.81 0 0.36 1.6 1.6 0 0.64 9.71 4 5.14 Low er spoil embankments: Raw score Y 0 0012101211110 Weighted score 0 0 0 0.5 1.8 0.81 0 0.36 1.6 0.8 0.8 0.64 7.31 8 5.15 Channel re-sectioning N 0 Weighted score 0 00000000000 0 5.16 Berm creation: Raw score Y 1 1112101220113 Weighted score 0.8 1 0.6 0.5 1.8 0.81 0 0.36 1.6 1.6 0 0.64 9.71 4 Backw aters – reconnections to IDB, field drains: Raw score Y 5.17 0 011010120118 Weighted score 0 0 0.6 0.5 0 0.81 0 0.36 1.6 0 0.8 0.64 5.31 9 5.18 Backw aters - new : Raw score Y 0 011010120017 Weighted score 0 0 0.6 0.5 0 0.81 0 0.36 1.6 0 0 0.64 4.51 10L 5.19 Channel realignment: Raw score N 0 Weighted score 0 00000000000 0 5.20 Changing primary and secondary channels: Raw score N 0 Weighted score 0 00000000000 0 5.21 Low er embankments: Raw score N 0 Weighted score 0 00000000000 0

G6: Alternative Options 6.1 Increase Main river maintenance: Raw score Y ‐2 ‐2 ‐2 ‐2 ‐2 ‐22‐11‐21‐1 ‐12 Weighted score ‐1.6 ‐2 ‐1.2 ‐1 ‐1.8 ‐1.62 1.62 ‐0.36 0.8 ‐1.6 0.8 ‐0.64 ‐8.6 6.2 Increase main river & IDB channel maintenance: Raw score N 0 Weighted score 0 00000000000 0 6.3 Mill Structures - reinstatement + hydropow er: Raw score Y ‐2 ‐2 ‐2 ‐2 ‐2 ‐21‐1 ‐10‐10‐14 Weighted score ‐1.6 ‐2 ‐1.2 ‐1 ‐1.8 ‐1.62 0.81 ‐0.36 ‐0.8 0 ‐0.8 0 ‐10.37 Total Score 11.8 13 16 16.5 27.6 19.1 5.62 2.72 39.4 22.4 19.8 24.6 Key Score Description Mean: 8.39 2High Relevance SD: 3.17 1Low Relevance 0Neutral High imp: >11.57 ‐1Low Detriment Low imp: <5.22 ‐2High Detriment Unit 54 Taverham Mill to Hellesdon Mill_final for issue_V1.0.docx 80

River Wensum Restoration Strategy Implementation SSSI Unit 54: Feasibility and Environmental Scoping Report

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River Wensum Restoration Strategy Implementation SSSI Unit 54: Feasibility and Environmental Scoping Report

5.3.1 Results of the MCA options appraisal The MCA is not just about which options improve ecology. As discussed, implicit in the MCA is the assessment of options and measures against other issues such as flood risk, the human environment, construction feasibility and agreement with landowners and stakeholders. Assessing these issues alongside ecological factors allows the options and measures to be assessed realistically, and to identify where other issues may conflict with the objective of achieving ‘unfavourable recovering’ or ‘favourable’ ecological condition for the SSSI, and good ecological potential for the Wensum under the Water Framework Directive.. It should be noted that information from the environmental baseline and stakeholder consultation specific to each reach was applied to the MCA for that reach. The results from the MCA do differ for each of the reaches in Unit 54 but have a number of similarities including:  ‘Do nothing’ and ‘Continue as present’ scored negatively for all three reaches.  The option of ‘Targeted maintenance’ produced positive scores for all reaches in the unit.  Options relating to mill operability and structural modifications to mill structures all scored positively for each of the reaches. For reaches 01 and 02 improving operability of the Hellesdon Mill structures was the highest ranked measure. For Reach 03 lowing mill sill levels at Costessey was the highest ranked measure.  Where applicable to the individual reaches all ‘Alternative options’ scored negatively. A negative score indicates that the option is detrimental to the project’s objectives of achieving ‘unfavourable recovering’ or ‘favourable’ condition status for the River Wensum. This suggests that ‘Do nothing’ (i.e. abandoning the river) is not an option and work is required to achieve the objective. This is surprising as a popular notion within the river restoration community is that sometimes allowing the river ‘to sort itself out’ can be viewed as the best option, particularly if maintenance is considered to be harming the river condition rather than improving it. In the case of Unit 54, the overall impact of Hellesdon Mill and Costessey Mill structures on the form, function and ecology of the impounded upstream reaches is so significant that the ‘Do nothing’ option will not change this impact. Action is required prior to the implementation of any in-stream restoration measures in sections affected by the backwater from these mills. The option of ‘Continue as present’ is considered detrimental to the project although ‘Do minimum’ scores positively for reaches 02 and 03 as some restoration will provide beneficial effects. The ‘Alternative options’ measures also received negative scores and this is largely a consequence of the scores attributed to the ‘Ecology’ criteria. This applies to hydropower options, which involve the generation of energy through harnessing the kinetic energy of water. Hydropower is seemingly attractive, as it is a form of renewable and ‘clean’ energy with added benefits such as reusing historic structures along watercourses. Hydropower is being implemented elsewhere and the Environment Agency has produced a position statement (2009a) and guidance (2009b) on how such projects should be developed, assessed and implemented. Similarly, Natural England has also developed a position on hydropower which is available on their website. When assessed against both the MCA and Environment Agency and Natural England guidance, the implementation of hydropower schemes for the River Wensum has been found to score negatively. Impacts on geomorphology, hydraulics, flow regimes and biological connectivity may have an adverse effect on flora and fauna (e.g. fish). Thus, whilst providing some benefits, hydropower ultimately runs counter to the high-level project objectives for geomorphological and ecological enhancement. Any likely wider benefits of renewable energy are negated by the potential for adverse local effects on other natural resources and receptors.

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River Wensum Restoration Strategy Implementation SSSI Unit 54: Feasibility and Environmental Scoping Report

Options and measures with negative scores will not be progressed as part of the River Wensum Restoration Project as they will not improve the ecological or geomorphological condition of the river. The MCA has demonstrated that the options of ‘River restoration’ and ‘Targeted maintenance’ will help Unit 54 to achieve ‘unfavourable recovering’ or ‘favourable’ ecological condition. The ‘River restoration’ option has a number of associated measures with different scores. All of these scores are positive, indicating they should be included as part of the preferred restoration design. Additionally, each reach has a different score for each measure due to the results of the MCA reflecting the baseline condition of the reach. The top scoring measures for each reach are given in Table 5.10. Table 5.10 - Summary of favourable options and measures for Unit 54

Term Reach 01 Reach 02 Reach 03 River restoration River restoration River restoration Targeted Targeted Targeted Favourable options maintenance maintenance maintenance Do minimum Do minimum Mill structures - Mill structures - Mill structures - lower improve operability + improve operability + mill sills levels protocols protocols Tree planting Top 5 Lower spoil Gravel glides Fencing embankments River Restoration Lower spoil Measures Deflector Lower embankments embankments Berm creation Berm creation Deflector Deflector Berm creation

The value of the weighted scores provides an indication of the relative importance of the measures in achieving ‘unfavourable recovering’ or ‘favourable’ ecological condition for the reach and suggests the order in which measures could be applied. This provides a useful indicator for identifying which opportunities to look for first in a reach. For example, in Reach 01 the highest scoring measure is the improvement to mill operability, so this is the first opportunity looked for in the reach, followed by the second highest measure, lowering of spoil embankments and so on. All of the measures are valid so it is not recommended that a cut-off be imposed at a certain value. However, the positively scoring measures have been grouped into bands of importance to give an indication of their relative importance in restoring the reach to favourable condition (see section 6 for further details). The frequency, location and manner in which measures are applied requires professional judgement, informed by in-depth understanding of the baseline conditions of the reach. For this particular SSSI unit particular care is needed to match the restoration measures to flows that will be achieved following any sustainability reductions that arise from the Habitats Directive Review of Consents. It is important to highlight that cost has not been included in the MCA as it is imperative that options and measures that move the reach towards achieving ‘unfavourable recovering’ or ‘favourable’ ecological condition are identified regardless of cost. Whilst cost is an important factor, it should not preclude an option or measure being identified and implemented. Instead, costs should be considered in terms of how options are implemented, and used to identify savings by using local material, phasing work appropriately or using different techniques (e.g. a LWD deflector compared with a rock deflector) to achieve the same result at a lower cost.

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River Wensum Restoration Strategy Implementation SSSI Unit 54: Feasibility and Environmental Scoping Report

The MCA provides a powerful tool for appraising all options and associated measures in a consistent, replicable and transparent way. It should be noted that the MCA should be viewed as a filtering tool to allow favourable options to be identified and unfavourable options to be dropped. How those favourable options and measures are applied to a reach is a case of professional judgement, and this is discussed in Chapter 6.

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River Wensum Restoration Strategy Implementation SSSI Unit 54: Feasibility and Environmental Scoping Report

6. Developing Conceptual Design 6.1 Introduction and approach This chapter explains how the recommended options of ‘River restoration’ and ‘Targeted maintenance’ can be applied to each reach. To set this in context, the chapter initially details:  The project in the context of river restoration (Section 6.2.1).  How ecology has been integrated into the conceptual design process (6.2.2).  How ‘Targeted maintenance’ is included within the recommended option (Section 6.2.3). Reach objectives, their review, and preferred restoration measures for Reach 01, 02 and 03 are outlined in Sections 6.3 to 6.5. As noted in Section 3.2.9, designs for river restoration, and the programme for implementation in Unit 54, need to take into account the magnitude and timing of proposed abstraction sustainability reductions at Costessey. Anglian Water has been asked to reduce its Costessey abstraction by up to 49 million litres per day (Ml/d), the aim being to meet a 20 Ml/d reduction by 2015 and if required a further reduction of up to 29 Ml/d by 2020 or soon thereafter. It is important to recognise that the conceptual / outline design aims to set out the types, locations and densities of particular restoration measures. Specific design levels and flows are not considered until the detailed design stage which is beyond the scope of this Feasibility Report. Hence, outline designs can be developed whilst there is remaining uncertainty regarding sustainability reductions, but the scale of reductions would need to be known before detailed designs can be completed. Again, it is important to note that addressing the flow impoundment at Hellesdon will impact on the feasibility of proposed designs for restoring much of the unit. 6.2 Description of River Restoration and Targeted Maintenance options

6.2.1 River restoration theory The term river restoration can be used to describe a number of different activities that require different levels or magnitudes of change. River alteration projects form a continuum from ‘full restoration’ through to ‘erosion control’ (Plate 56). The range reflects the varying level of human intervention in natural systems to manage risk (Gillian et al., 2005).

Plate 56 – River alteration continuum Unit 54 Taverham Mill to Hellesdon Mill_final for issue_V1.0.docx 85

River Wensum Restoration Strategy Implementation SSSI Unit 54: Feasibility and Environmental Scoping Report

This distinction between levels of work and sustainability was developed further in the geomorphological appraisal of the River Wensum, where Sear et al. (2006) categorised the geomorphology of reaches on the River Wensum into six management classes of river restoration (Table 6.1). This provides a method of quantifying the magnitude of restoration needed on a reach by reach basis depending on the baseline conditions and opportunity for change. Table 6.1 - Different management classes of restoration activity

Term Definition Restoration of channel processes and forms to pre-disturbance Restoration conditions. Physical modification to the river form to re-create physical habitats Rehabilitation (e.g. re-meandering, riffle installation, bed level raising). Addition of structural features to improve physical habitat diversity Enhancement (e.g. narrowing, woody debris). Afford legal protection to the site and monitor for change in status. Protect & monitor Given that the site has legal protection (SSSI / SAC), monitor to ensure that the status is maintained and take action if required. Amplification of existing processes to encourage recreation of physical Assisted natural habitats (e.g. encouraging berm formation to narrow channel, removal recovery of bank revetment to create sediment supply). Protect site against further degradation not necessarily with legal Conserve statute.

Sear et al. (2006) developed this further by categorising river restoration techniques into active and passive restoration based on the restoration approach of form mimicry or process based restoration (Table 6.2). This presents a range of typical river restoration measures that can be followed and all of these were included in the MCA analysis as all are applicable to the Wensum to varying degrees. Table 6.2 - Active and passive river restoration measures

Active Restoration – Passive Restoration – (physical (physical creation of forms manipulation of flow and or removal of structures to sediment transport regime to improve degraded create physical habitat and to ecosystems.) improve degraded ecosystems.) Form-mimicry – The re-creation of physical Gravel augmentation which then Riffle recreation. habitat features without is moulded by river flows into bed Re-meandering. reference to the processes features (riffles). required to create them. Process-based restoration Mill weir removal – restores Reduction in catchment sediment The use of physical sediment connectivity and supply. processes to restore hydraulic gradient. Management of flow regime (flow degraded physical habitats to Re-occupation of an old re-naturalisation). a more natural form. channel course.

All reaches in Unit 54 have been categorised into the ‘Rehabilitation’ Management class (see Table 6.1) (Sear et al., 2006; JBA, 2007). This is defined as: “Physical modification of the channel to re-create self sustaining physical habitats (e.g. riffles, side berms), generally where the channel is currently substantially over deep and / or over wide’’.

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River Wensum Restoration Strategy Implementation SSSI Unit 54: Feasibility and Environmental Scoping Report

 Return the river and floodplain to pre disturbance conditions;  Return the river to its high maintenance regime of wholesale dredging of the river channel; or  Return the functionality of the mill systems. The emphasis for Unit 54 is on changing present river form and flow processes to help the river develop conditions more typical of its chalk river type. This does not mean that this is undertaken in isolation to the wider issues and constraints of the catchment (e.g. flood risk to people and property). Rather, improving the river condition should aim to provide multiple benefits in terms of reducing flood risk, reducing the need for regular extensive maintenance by creating a self- sustaining system, creating managed ‘hotspots’ for ‘Targeted maintenance’, improving amenity value and improving habitat condition and diversity for a variety of flora and fauna. To do this, different restoration measures can be used to varying degrees. The density and type of river restoration measures can be applied in three ways to provide the following design philosophies:  Total Restoration Design Philosophy (High-density application of fully formed restoration features) – This approach provides ‘complete’ river restoration and is applicable when the river does not have the capacity to form features itself.  ‘Kick Start’ Restoration Design Philosophy (Medium-density application of partially formed features) – This approach uses the existing form and function of the river and provides in channel and out of channel features to allow the river to kick start natural geomorphological process by building upon the features provided.  Opportunistic Restoration Design Philosophy (Low-density application of fully formed features) – This approach is indicative of opportunistic river restoration design where restoration measures are applied to a short length of river due to favourable circumstances. This often provides improvement to the river condition locally but can have limited benefit for the river condition on a SSSI unit basis. River restoration that has been undertaken on the River Wensum in the past has been undertaken within the Opportunistic Restoration Design Philosophy. The RWRS has provided the opportunity to change this philosophy by providing a whole river vision and mechanism to achieve river restoration on a catchment scale. To achieve the vision of the RWRS, it is recommended that the ‘Kick Start’ Restoration Design Philosophy is applied for the following reasons:  The river is slowly recovering naturally from legacy maintenance practices, demonstrating the capacity to develop morphology features and ‘self heal’.  Whilst not ideal or recommended, modifications to mill operating regimes are likely to be undertaken at different timescales to river restoration. Consequently, implementing total restoration while mill structures are unchanged represents a future risk to the design if water levels change significantly.  It provides value for money by not installing features that the river can form naturally over time.  It allows a phased approach to be adopted by allowing the river time to adapt to river restoration measures before determining if additional measures are required. Therefore, the approach of ‘Kick Start’ Restoration Design Philosophy, within the context of the ‘Rehabilitation’ management class for the River Wensum, is to deliver the minimal amount of physical works in the river that will achieve sufficient change in hydromorphological form and fluvial processes to accelerate the river’s natural ability to ‘self-heal’. More specifically the design philosophy is to: 1. Restore the river to a form and function characteristic of a Norfolk chalk river. Unit 54 Taverham Mill to Hellesdon Mill_final for issue_V1.0.docx 87

River Wensum Restoration Strategy Implementation SSSI Unit 54: Feasibility and Environmental Scoping Report

2. Put forward recommendations that will see restoration measures implemented to help restore ‘unfavourable recovering’ or ‘favourable’ ecological condition to the SSSI habitat features.

3. Provide a ‘kick-start’ by only undertaking works to create features that the river would not be able to do itself.

4. Provide an increase in the patchiness and diversity of features that are sufficient to allow an improvement in natural processes and which will increase both the rate, and amount, of self- restoration at any point along the unit.

5. Provide sufficient strength of processes that will allow significant self-restoration by 2015 to meet WFD timeframes.

6. Place measures at an appropriate frequency of 20m to match present day flow rates and erosion / deposition patterns. However, they must also respect the larger channel form features such as the relic bend length of 35m derived from ancient river flow rates. This will ensure there is sustainability over any likely range of flow rates, and their associated erosion / deposition patterns.

7. Ensure that the channel forms provide durable results against the varying flows and water levels generated by long-term climate change impacts, and in-channel vegetation growth in the short-term.

In respect to point 1 above, it is recognised that the River Wensum, and other Norfolk chalk rivers, are slightly different from ‘classic’ chalk rivers. This is explored in detail in 3.2.1 and the Geomorphological Appraisal of the River Wensum by Sear et al. (2006) and also summarised in the JBA report (2007). 6.2.2 Designing for ecology The restoration strategy applied to each reach must provide a measurable ecological benefit at both a species and community scale in order for the River Wensum to achieve ‘favourable’ ecological condition. Ecological monitoring of river restoration sites will be one of the key ways of assessing the success of implementing the strategy. Equally, prior to the implementation of specific river restoration measures, consideration must be given to the potential for harm to be caused to existing ecological features through direct damage, loss of habitat, or alteration to existing river form and function. The permanency of any effect, adverse or beneficial, will need to be assessed as well as the potential for natural recovery within the system. This process has required an extensive ecological baseline review of the distribution and status of ecological features in the River Wensum, as discussed in Section 3. This has been coupled with the identification of physical habitat constraints and catchment scale pressures that are influencing condition status. Furthermore, a detailed review of the SSSI / SAC interest features has been undertaken to promote appropriate restoration measures for these key species and community assemblages. It is important to note that at this stage the review has concentrated on designated ecological features only, although the intention is to add additional ecological features, following consultation with statutory stakeholders. The following information has been collated for each of the key ecological features through extensive literature and data review:  Protected status and UK distribution.

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 General ecology e.g. life cycle, feeding requirements.  Specific habitat requirements for all life stages, including: - Substrate - Water quality - Water quantity, and  Factors known to currently affect species / community distribution and populations. For each of the Strategy wide restoration measures (e.g. tree thinning, gravel glide placement), both the positive and negative effects of implementation has been determined through an initial identification of the habitat requirements for each species and community. Following this, an assessment was made of how the habitat may alter following implementation of a river restoration measure and the resultant impact, adverse or beneficial, that this could have on species distribution and community persistence. The recommended restoration measures that were identified using the MCA are displayed in Table 6.3 along with the associated potential ecological benefits to different species and communities. These benefits will arise by ensuring that the adopted restoration measures are integrated (e.g. berms are installed to promote favourable flow over the top of installed gravel glides). Integrated measures to maintain appropriate geomorphic form and function and maximum ecological benefit will ensure resilience and persistence of the ecological communities that develop. Further details of how the measures benefit the designated species and communities can be found in Appendix C. Table 6.3 - River restoration measures and their potential ecological benefits

Restoration Measure Description & Potential Ecological Benefits Fencing constructed landward of the river bank to prevent bank erosion from the impacts of cattle grazing, with a consequent reduction in sediment ingress. Protects marginal habitat and Fencing promotes growth of emergent and marginal / aquatic plants, with associated improvement for aquatic macroinvertebrate fauna (e.g. Desmoulin's whorl snail Vertigo moulinsiana). Tree planting to cast shade over the water to control excessive macrophyte growth, provide cover for fish and to develop erosion Tree planting resistance from root reinforcement. Also provides input of leaf litter and LWD of value to macroinvertebrate fauna including white-clawed crayfish. Selective felling or lopping to provide light onto the water to encourage marginal and submerged macrophyte development and Tree thinning associated macroinvertebrates. In addition, this will generate appropriate materials for use in restoration measures, e.g. brush-fill and deflectors. Downstream pointing LWD placed and secured at the upstream side of the deflector to create flow diversity; in-filled downstream with Deflectors brush to promote silt deposition and marginal plant growth. Provides (using LWD and filled in refuge for fish fry behind structure and good flow diversity for with brush mattress) macroinvertebrates and submerged macrophytes (e.g. Ranunculion fluitantis and Callitricho-Batrachion vegetation). Removal of dredging-based informal embankments to allow out-of- bank flow across the floodplain, and back into the river. Ensures fish Lower spoil embankments that are washed out of the channel during flood can return to the river as the floodwaters recede. May also improve adjacent wetland systems through water level regime. Berm creation Horizontal lowering of bank top up to half the channel width to Unit 54 Taverham Mill to Hellesdon Mill_final for issue_V1.0.docx 89

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Restoration Measure Description & Potential Ecological Benefits increase flood flow capacity and generate arisings for bed raising where no embankments exist. Creates marginal shelf habitat for macrophytes and associated fauna plus refuges from high flows for fish fry. Improvement to instream flow conditions. Utilizing existing wet features by connecting them to the river to create essential refuge habitat for fish and other fauna. This Backchannels – measure is implemented to aid the natural recruitment of fish stocks. reconnections to IDB and existing field drains Achieved through provision of nursery habitat and refuge from high- flow events. Additional utilisation by a variety of aquatic biota, e.g. brook lamprey ammocoetes. Creating habitat where no other water bodies exist e.g. dog-leg with downstream end open and upstream end fed by percolation. This Backchannels – create measure provides refuge for fish and a place for fry to rest during new features floods, so limiting the loss of fry to reaches downstream of mill structures. Benefits all fish species through increasing recruitment potential. Creation of short lengths of full raised bed, dressed in gravel to create variation in flow and habitat for various macroinvertebrates Gravel glides and macrophytes in addition to provision of spawning substrate for fish species, e.g. trout, barbel and brook lamprey. Creation of long lengths of full width raised bed, dressed in gravel, to Bed raising reconnect channel with floodplain and create variation in flow and habitat for various fish species, macroinvertebrates and macrophytes. Full depth excavation from bank top to increase lateral variation in Channel realignment to planform, either one bank or both, using arisings to infill opposite increase river sinuosity bank. Improved geomorphological form and function beneficial to a range of associated biota.

Each of these measures has a different effect dependant on the flows in the river. Table 6.4 summarises the relationship between flow height and impact. Table 6.4 - The effect of river restoration measures according to flow condition

River Flow / Level Mill Structures Gravel Glides Deflectors New Backchannels Reconnection Backchannel Creation Berm Realignment Channel Re-sectioning Channel of Embankment Removal of Spoil Removal Tree Thinning Tree Planting Fencing Over bank I I D D D D D

Bank full D I I I D I D D D I

High flow D I I D D D D D I

Low flow D D D D I D D I Key: I=Indirect; D=Direct The effects can be direct (D), such as deflectors which will physically push flow across the river at low flows. Higher flows will go over the top of the deflector and therefore there will be no direct Unit 54 Taverham Mill to Hellesdon Mill_final for issue_V1.0.docx 90

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effects. However, the impact at low flow will have changed local silt deposition and hence vegetation patterns. The combined effect of the deflector and the vegetation will have an impact on the higher flows, but this depends on several factors such as plant growth; this effect is described as indirect (I). The combination of each of the different measures ensures that process and form of the river is impacted under all flows and so will increase the rate of change towards self-healing. From an ecological view it means that conditions within the channel vary so that biota can move to similar conditions, but in a different location, as flow increases. 6.2.3 Targeted maintenance The ‘Targeted maintenance’ option recognises that there is a need for some maintenance to be undertaken on the River Wensum due to the various pressures that limit the potential for the channel to be a totally self-cleansing and regulating system. It is also an option that can be undertaken while river restoration measures are being designed and implemented. A separate targeted maintenance protocol is being developed which sets out in more detail where, how, when and by whom maintenance will be undertaken. The protocol will allude where possible to policies such as those contained in the Broadland Rivers Catchment Flood Management Plan, specifically the reduction in maintenance of fluvial systems. In addition, the protocol will draw upon consultation with internal Environment Agency functions and other stakeholders and will have regard to current maintenance practices. The measures that are included within the ‘Targeted maintenance’ option are outlined in Sections 6.2.4 to 6.2.7. 6.2.4 Silt removal at identified ‘hotspots’ These are sections of the river where silt accumulation will have an operational impact in terms of flood risk management. Maps indicating the distribution of ‘hot spots’ on the River Wensum were received from the Water Management Alliance on behalf of the Norfolk Rivers IDB. Typically these are sections of channel upstream of mill structures where silt deposits interfere with the flow of water approaching the structure, and limit the structure’s capacity, so increasing local flood risk. Generally it is recommended that a 200m length of channel upstream of each mill is targeted for de-silting. This will also allow the character of the mill leat to remain. Without the implementation of river restoration and lowering of levels at mills, de-silted sections of river will tend to accumulate fresh deposits of silt. The de-silting operation is therefore not sustainable in the long term. It is worth noting too, that Norfolk chalk rivers have a higher sand content in the river substrate than a typical chalk river, in downstream sections, as a result of ingress of material from the drift. Restoration and targeted maintenance will not seek to remove these features and will work with them. 6.2.5 Clearance of main channel immediately downstream of identified IDB drain outfalls This is to allow the IDB drains to discharge freely, otherwise their ability to flow freely is compromised, which in turn increases siltation, and so increases the need for maintenance in areas which are often valuable as nursery habitat for fish. The inability to discharge also increases flood risk from the drain, which in some instances will significantly impact on property flooding. It is recommended that 100m downstream of confluences are regularly inspected and cleared of silt and excessive marginal vegetation if necessary. 6.2.6 Clearance or realignment of fallen trees blocking the channel Clearance of fallen trees only needs to occur if they are within the impounded section immediately upstream of the mills, or the 100m stretch downstream of IDB drain confluences, or are impacting directly on flood risk to houses, such as river blockages at bridges. Otherwise, the trees should

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be realigned to provide flow diversity, and LWD. Trees may present a problem on impounded river reaches, as they may assist a breach in a river bank where the river is a high level carrier. This is undesirable, in that the objective of the strategy is to manage change, rather than to allow unchecked natural change. 6.2.7 Strategic weed cutting This should only be carried out where there is a direct flood threat to houses caused by elevated water levels, or where freeboard is unlikely to be sufficient to receive likely rainfall. It is likely to be required in the 200m mill leat and 100m IDB drain confluence sections. As these are discrete sections, where access is reasonable, the use of weed cutting bucket equipped excavators can be used, without the need for weed boats to travel substantial lengths of the river. This removes the need for tree management to allow passage of a weedboat, or to allow cut weed to float downstream to a designated pull-out point.

6.3 Reach 01: Hellesdon Reach This section defines the preferred restoration of Reach 01 by describing key existing features; reviewing the recommended measures as stated in the RWRS; presenting the results of the MCA scoring and detailing rehabilitation measures applied to the reach. 6.3.1 Key existing features influencing proposed restoration measures Table 6.5 presents a brief description of the existing conditions of the reach as observed during the site visit conducted on 9th February 2011. The purpose of the visit was to consider the reach objectives on the ground.

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Table 6.5 - Significant features and possible measures observed for Reach 01 during site visit (February, 2011)

Noted Feature Possible Measure Lower flow control structures to improve flow The reach is significantly affected by the conditions throughout reach. The EA maintain backwater created by flow control structures weir levels based on historical management and at Hellesdon Mill (Plate 13). there is an opportunity to alter current water level management practice. Create sinuosity through installation of berms and deflectors. Option to raise bed through Channel heavily modified, straightened, gravel placement in conjunction with channel over-wide and over-deep along all of the narrowing measures, though would be reach towards Hellesdon Mill (Plate 6). dependent upon being able to lower water levels at Hellesdon. Encourage continued narrowing through tree Self narrowing evident in some parts of the felling to remove light restriction (where reach with Glyceria dominated berms appropriate) and installation of deflectors / LWD present (Plates 3 and 7). structures to improve flow variation. Lowering of dredged material embankments along TRHB to increase floodplain connectivity Substantial dredged material embankments and reduce the extent of high flow backwater along TRHB reducing floodplain connectivity from Hellesdon weirs. This will also counteract (Plates 8 and 10). potential floodplain disconnection if Hellesdon mill structures are lowered and the resultant backwater effect reduced. Improve upstream connections to maintain adjacent floodplain wetland habitats if Hellesdon weir levels are lowered. Connections will also Interconnected drainage systems along create backwater habitats for fish and potentially TRHB (Plate 11). link with the River Tud, providing a route for fish passage around Hellesdon weirs (currently impassable for fish). Over-shading by mature tree canopy along Selective thinning of tree cover to allow light some sections of the river bank. through to encourage natural berm development. Lack of tree cover along some sections of Occasional tree planting along TLHB to provide river bank (Plate 3). canopy cover, tree roots and some shading. Provided Hellesdon weir levels can be adjusted, insertion of a sequence of berms, deflectors and Flow patterns throughout reach of uniformly glides would provide local variation in flow types deep, slack flow types (Plates 3, 6, 12 and and water levels to create more natural form and 13). function. Natural encroachment of vegetation would also be encouraged.

6.3.2 Review of Reach 01 Strategy Objectives Appendix A to the RWRS (JBA, 2007) details a ‘Reach Restoration Strategy’ for each reach. These objectives have been the starting point for the consideration of rehabilitation activities. A review of these objectives is presented below in Table 6.6.

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Table 6.6 - Review of strategy objectives and recommendations for Reach 01

RWRS Objectives Atkins Comments on the RWRS Partially agree: River habitat enhancement works will be severely restricted if water levels and the backwater effect cannot be reduced within this reach. Significant improvement appears possible by changing All works must integrate with removal of sluice operation. The mill structure sill 1.1 Hellesdon Mill and associated river lowering or complete removal is probably works. detrimental as they could still provide a significant flood control mechanism for Norwich at higher water level and flow rates, once normal water levels have been reduced. Disagree: De-silting could release large quantities of silt to downstream reaches which might cause the very damage the operation was seeking to avoid. The De-silt channel just upstream of the 1.2 degree of siltation upstream of the weirs current water control structure should be investigated and, if possible, plan for natural berm development and vegetation encroachment as water levels are reduced to stabilise and trap silt on-site. Agree: This would create necessary variation in river form which has been removed by previous river works. Cost 1.3 Augment the bed using gravels. would be reduced and effectiveness increased if water levels and the backwater effect can be reduced to allow free-flowing river conditions. Partially agree: There is potential for natural narrowing processes to occur if Physical narrowing is required owing to water levels can be lowered, but some 1.4 the wide nature of the channel. artificial narrowing may be needed in some locations where it would otherwise be a slow process. Agree: Along TRHB the embankments are Remove embankments to reconnect 1.5 a major feature that disconnects adjacent river to its floodplain. wetland areas. Partially agree: This is dependent upon being able to reduce the backwater effects from Hellesdon. It could be allowed to 1.6 Develop marginal / bankside vegetation. develop naturally or augmented with artificial structures if development is slow or sporadic. Partially agree: Allow natural encroachment where possible as this Initial work required is for bed and bank provides increased stability. Vertical bank stabilisation associated with the removal 2.1 forms may need adjustment after water of Hellesdon Mill structures at the levels are lowered, although retention of the downstream end of reach structures to throttle high flows makes this type of berm development unlikely. Partially agree: Allow natural berm Appropriate measures required to accretion and vegetation encroachment 2.2 manage silt deposits upstream of the processes to trap as much silt as possible mill as water levels are lowered. Intervention to manage silt may therefore be minimal. 2.3 Augment bed on average by 0.6m using Partially agree: Some gravel augmentation

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RWRS Objectives Atkins Comments on the RWRS local gravels wherever possible and will be necessary following water level create up to 16 gravel glides or riffles in reduction, but fewer glides, and potentially the reach. at lower heights on average, than suggested in the RWRS. Partially agree: Natural berm and The channel is on average 10.7m over vegetation development should be utilised wide and physical narrowing (with wherever possible, with artificial measures associated landscaping and fencing) used to supplement this where necessary. 2.4 may have to be considered to restore Most of this reach is not subject to pressure the full functioning of the channel in this from grazing animals or public access so reach following works at the mill. fencing will not be necessary (unless new land management involves grazing). Agree: Use of targeted maintenance to Adopt / maintain maintenance regime maximise natural recovery and silt and riparian management to allow entrapment processes and to help manage 2.5 channel to create natural variations in flood flows through greater freeboard local channel width and habitat niches. created by water level lowering and flood plain connectivity. Agree: If water level reduction is possible there are likely to be large-scale changes to Post-project monitoring is required, the river habitat upstream that will need 2.6 especially in association with works at management and, where necessary, the mill structures. intervention to ensure it develops a sustainable and more natural river character. Summary Reach 01: Atkins agrees or partially agrees with the majority of the principles established by JBA for this reach. Disagreement relates to the de-silting works associated with mill structures.

6.3.3 Reach 01: Recommended restoration This section provides the details of the options and measures proposed for this reach which have been derived from the Multi-Criteria Analysis (refer to Section 5.3). A summary of the MCA results in their rank order is provided in Table 6.7 and these are further divided into importance according to how far the measure will move the reach towards achieving ‘unfavourable recovering’ or ‘favourable’ ecological condition. Table 6.7 - Recommended restoration options for Reach 01 Option Description Weighted Score Highly Important Measures 5.1m Mill structures - improve operability + protocols 13.78 Important Measures 5.14 Lower spoil embankments 10.86 5.21 Lower formal embankments 10.86 5.16 Berm creation 10.22 5.13 Deflectors 9.72 5.12 Tree thinning 9.64 5.7g Gravel glides 8.92 5.17 Backwaters – reconnections to IDB, field drains 8.22 5.11 Tree planting 7.12 Less Important Measures G3 Targeted maintenance 2.82 5.10 Fencing 1.42

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6.3.4 Targeted maintenance Following the principles established in section 6.2.2 the following measures are suggested and may form part of the targeted maintenance protocol being developed for this unit. These include: 1. Silt removal. This is recommended immediately upstream of structures, or where silt deposits will limit discharge at confluences with IDB drains or significant tributaries. Structures on this reach include Hellesdon Mill structures (Plate 15) and the River Tud automated overshot tilting gate upstream of Hellesdon Mill (Plate 2 and Plate 14). Monitoring and clearance of encroaching silt will be needed within 10m upstream and 20m downstream of each location and 10m upstream of the mill structures. This is equal to 1 channel width and 2 channel widths, respectively. 2. Clearance of main channel downstream of confluence with IDB drains. There are no IDB drain confluences in this reach. There is a requirement for inspection and clearance of encroaching marginal vegetation at connections to off-channel backwaters such as those proposed at the Costessey Pumping Station. 3. Clearance or realignment of fallen trees blocking channel. Clearance is only required where they are impacting directly on flood risk to property or the structural integrity of third party assets. Hellesdon Mill and the River Tud automated overshot tilting gate are the only significant structures in this reach, and, therefore, the same clearance distances as identified for de-silting apply at these locations. 4. Strategic weed cutting. This is only needed where there is direct threat to houses caused by elevated water levels, or where freeboard is unlikely to be sufficient to receive likely rainfall. Channel conditions downstream of confluences can impact on this, so the sections identified for silt removal need to be inspected for consideration of in-channel weed cutting.

6.3.5 Restoration Measures All of the restoration measures identified by the MCA have been incorporated into the preferred outline restoration design for Reach 01, which is shown in Figure 6.1. Of the restoration measures selected for this reach, the highly important one is: Mill structures - improve operability + protocols There are 4 controlled openings at the mill with an automatic bypass sluice immediately upstream diverting water into the River Tud (Tud Sluice). Of the 4 openings at the mill, 3 have drop boards, and these can simply have the boards removed, so simplifying the current seasonal operation. The fourth opening at the mill is controlled by a manual penstock and this can be set once the automatic level has been set for the Tud Sluice. The Tud Sluice is automatically programmed to maintain the upstream level in the Wensum as its sill level is lower than the mill openings. Initially it is suggested that the Wensum water level is lowered to the mill sill levels to allow some natural processes to start (e.g. improved development of marginal vegetation). Water levels can then be further adjusted once the river’s response to the slightly lower level has been assessed, particularly in relation to any changes in base flows.

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Figure 6.1 - Conceptual restoration plan for Reach 01 (Hellesdon Reach)

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6.4 Reach 02: Drayton Reach This section defines the preferred restoration of Reach 02 by describing key existing features; reviewing the recommended measures as stated in the RWRS; presenting the results of the MCA scoring and detailing rehabilitation measures applied to the reach. In defining the preferred restoration of Reach 02 it has been considered appropriate that the reach be divided into 2 sub-reaches to reflect the differing geomorphological character present along its 3.16km length. Field observations made in February 2011 identified this reach as longitudinally lending itself to different restoration measures and as presenting different opportunities / constraints. The 2 sub-reaches run sequentially from Costessey Mill structures to Wensum Mount Farm (Figure 6.2) and their extent and general character described in Table 6.8. A conceptual restoration plan (Figure 6.3 and Figure 6.4) and indicative cost estimate is provided for each of the 2 sub-reaches for clarity. Table 6.8 – Key characteristics of Reach 14 sub-reaches

Sub-reach Sub-reach Name Extent Character Code (km) This sub-reach is a free flowing section of river with improved habitat diversity as a result of previous restoration works at Costessey Mill to Reach 02a 0.72 Costessey Point. The confluence of Marriott’s Way Costessey Mill leat and main channel occurs in the upstream section of this sub- reach providing valuable habitat complexity. Sub-reach is affected by the backwater created at Hellesdon Mill resulting in uniform flow character. The river channel is homogenous with limited habitat diversity. Historical river works have created an over-wide channel as evidenced through vegetated marginal berm development. In places river Marriott’s Way to dredging have been formed into large Reach 02b 2.44 Wensum Mount Farm embankments isolating the river from it floodplain. Much of the sub-reach has no tree or shrub cover as it is used for intensive grazing. The floodplain is characterised by the presence of an extensive field and IDB drainage network, some of which have good connectivity to the main river and provide important backwater habitat.

6.4.1 Key existing features influencing proposed restoration measures Table 6.9 presents a brief description of the existing conditions of each sub-reach as observed during the site visit conducted on 10th February 2011. The purpose of the visit was to consider the reach objectives on the ground.

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Table 6.9 - Significant features and possible measures observed for Reach 02 during site visit (February, 2011)

Noted Feature Possible Measure Sub-reach 02a: Costessey Mill to Marriott’s Way As part of weir lowering assessments, ascertain Costessey Mill leat takes only a small potential enhancement of former mill outflow proportion of the river flow and is silted and channel with improved flows, tree thinning and over-shaded (Plate 18). silt removal. Sub-reach is not affected by Hellesdon Mill Install restoration measures to improve instream backwater and therefore free flowing habitat diversity and compliment / extend existing conditions exist. restoration works. Successful restoration works conducted along approximately 450m of sub-reach Ensure habitat connectivity between existing and below Costessey weirs, including installation any new works. of gravel glides, channel narrowing and fish refuges (Plate 22). Sub-reach 02b: Marriott’s Way to Wensum Mount Farm Lowering of water levels upstream of Hellesdon Sub-reach is affected throughout by the weirs could remove backwater effects in the backwater created at Hellesdon Mill (Plates lower section of this reach and allow for 29, 30, 33 and 35). substantial natural in-channel and marginal habitat enhancement. Improve riparian tree cover and shrub habitat along river corridor to improve cover and provide Much of the reach has no tree or shrub cover root stabilisation. Coordinate planting and as it is used for intensive grazing (Plates 24, thinning activities along this reach to provide 28, 29 and 30). variation in light and shade to influence marginal vegetation growth.

Increase channel complexity through installation The channel has been over-widened and of restoration measures such as deflectors, exhibits limited habitat diversity. gravel glides and berms.

Some IDB and field drain systems have Enhance existing backwater connections (to good connectivity to the main river and ensure they still function if water levels can be provide important backwater habitat (Plates lowered at Hellesdon) and identify where new 21 and 29). backwaters can be created. Extensive dredged river bed material has Selective removal of embankment to improve been formed into large embankments along floodplain connectivity along significant parts of the TRHB (rich in glacial gravels and shells this reach. Assess viability of re-using dredged of river molluscs) with evidence of river bed gravel within embankments for subsequent dredging maintenance works reinsertion into the channel. Locations of gravel that have formed shallower, silt-rich rich dredgings could also indicate locations of embankments along TLHB (Plates 26, 27 former riffles and glides. and 28). Where possible, narrow channel widths through River flow types are fairly uniform along this allowing natural vegetation encroachment, sub-reach except where LWD alters local artificial berm construction, selective retention of flow patterns (Plates 25 and 35). fallen trees or insertion of woody debris to act as deflectors. Large areas of floodplain are unmanaged or Enhancement of floodplain to recreate diverse form rough grassland (Plate 32). Significant wetlands, sedge beds and reedbeds wherever areas with no / limited grazing management. possible.

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6.4.2 Review of Reach 02 Strategy Objectives Appendix A to the RWRS (JBA, 2007) details a ‘Reach Restoration Strategy’ for each reach. These objectives have been the starting point for the consideration of rehabilitation activities. A review of these objectives is presented below in Table 6.10. Table 6.10 - Review of strategy objectives and recommendations for Reach 02 RWRS Objectives Atkins Comments on the RWRS Partially agree: Hellesdon Mill structures may not need to be removed to reduce the All works must integrate with removal of backwater effect. Costessey Mill structures Hellesdon Mill and lowering of structure 1.1 are complex but adjustments to water level at Costessey Mill and associated river management could improve the habitat in works. the mill channel and upstream of the weirs (Reach 03). Agree: Further restoration measures must Restoration must link with the existing 1.2 complement those already undertaken in scheme at Costessey Point. the reach to maximise habitat value. Partially agree: Natural berm development and vegetation encroachment should be encouraged and then, where appropriate, Physically narrow the channel and 1.3 install some artificial narrowing measures. augment the bed using gravels. Gravel bed augmentation will be necessary to replace the wholesale removal during past dredging works. Partially agree: Either partial or total removal of embankments would be Remove embankments along both 1.4 beneficial, but depends on feasibility: banks downstream of Marriott’s Way ground conditions and access may be significant technical constraints. Agree: Marginal vegetation is heavily Improve marginal / bankside vegetation, 1.5 grazed and few trees or shrubs are present such as tree planting. along much of the reach. In the 100 to 200m downstream of Disagree: There is the potential to create Costessey Mill and in the immediate new backwater habitats, improve flows and scour pool area of good habitat value, light levels along the mill outflow channel, 2.1 no works are required and this area and carry out works to complement should be conserved and allowed to re- restoration works already undertaken along vegetate naturally. adjoining downstream sections. Partially agree: Gravel replenishment is Augment bed on average by 0.4m using clearly necessary along this reach, though local gravel wherever possible and 2.2 not to the extent suggested in the RWRS. create up to 32 gravel glides or riffles in Glides and riffles need to be appropriately the remainder of the reach. located along the river. The channel is on average 9.8m over Agree: The adjacent land for much of the wide and physical narrowing (with reach is used for cattle grazing and fencing associated landscaping and fencing) may be necessary to reduce poaching of 2.3 may have to be considered to restore new and shallower river sections (if the full functioning of the channel in this Hellesdon backwater effects can be reach following works at the mill. reduced). Agree: Allow as much natural berm Adopt / maintain maintenance regime development and marginal vegetation and riparian management to allow 2.4 encroachment as possible, coupled with channel to create natural variations in targeted maintenance at appropriate local channel width and habitat niches. locations. Summary Reach 02: Atkins agrees or partially agrees with all but one of the principles established by JBA for this reach. The one disagreement relates to the requirement for

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RWRS Objectives Atkins Comments on the RWRS additional measures to enhance the channel immediately downstream of Costessey Mill.

6.4.3 Reach 02: Recommended restoration This section provides the details of the options and measures proposed for this reach which have been derived from the Multi-Criteria Analysis (refer to Section 5.3). A summary of the MCA results in their rank order is provided in Table 6.11 and these are further divided into importance according to how far the measure will move the reach towards achieving ‘unfavourable recovering’ or ‘favourable’ ecological condition. In addition, the suitability of each of the positive scoring measures identified by MCA for Reach 02 is presented at a sub-reach scale. The suitability of each measure has been determined by reference to existing channel and floodplain form resulting in the assignment of a rating (High, Medium, Low) for each measure at a sub-reach level (Table 6.12). This assessment is reflected in the conceptual restoration plans provided for each of the sub-reaches (Figures 6.3 and 6.4). Table 6.11 - Recommended restoration options for Reach 02 Option Description Weighted Score Highly Important Measures 5.1m Mill structures - improve operability + protocols 15.38 5.7g Gravel glides 14.24 Important Measures 5.14 Lower spoil embankments 11.38 5.13 Deflector 10.52 5.16 Berm creation 10.52 5.17 Backwaters – reconnections to IDB, field drains 10.22 5.11 Tree planting 8.92 5.12 Tree thinning 8.02 Less Important Measures G3 Targeted maintenance 7.03 5.10 Fencing 4.66

Table 6.12 – Restoration measure suitability rating for Reach 02 sub-reaches Option Description Weighted Suitability Rating for Sub-reach Score for Reach 02a 02b Mill structures - improve 5.1m 15.38 Low High operability + protocols 5.7g Gravel glides 14.24 Medium High 5.14 Lower spoil embankments 11.38 Low High 5.13 Deflector 10.52 Low High 5.16 Berm creation 10.52 Low High Backwaters – reconnections to 5.17 10.22 Medium High IDB, field drains 5.11 Tree planting 8.92 Medium High 5.12 Tree thinning 8.02 Medium Low G3 Targeted maintenance 7.03 High High 5.10 Fencing 4.66 Low Medium

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6.4.4 Targeted maintenance Following the principles established in section 6.2.2 the following measures are suggested and may form part of the targeted maintenance protocol being developed for this unit. These include: 1. Silt removal. This is recommended immediately upstream of structures, or where silt deposits will limit discharge at confluences with IDB drains or significant tributaries. There are no significant structures in this reach although three IDB drain confluences have been identified. The IDB drain confluence downstream of Costessey Mill is considered to require silt removal for free discharge. Encroaching silt removal will be needed within 10m upstream and 20m downstream of this IDB drain. This is equal to 1 channel width and 2 channel widths, respectively. 2. Clearance of main channel downstream of confluence with IDB drains. There are three IDB drain confluences in this reach; the most significant being located approximately 400m downstream of Costessey Mill. There is also a requirement for inspection and clearance of encroaching marginal vegetation at connections to off-channel backwaters, such as those proposed to the south of Bloods Dale. 3. Clearance or realignment of fallen trees blocking channel. Clearance is only required where they are impacting directly on flood risk to property or the structural integrity of third party assets. 4. Strategic weed cutting. This is only needed where there is direct threat to houses caused by elevated water levels, or where freeboard or flood plain availability is unlikely to be sufficient to receive likely rainfall. Neither is considered likely on this reach, and therefore, no inspection or works are identified.

6.4.5 Restoration Measures All the restoration measures identified by the MCA have been incorporated into the preferred outline restoration designs for Reach 02 as shown in Figure 6.3 and Figure 6.4. Of the restoration measures selected for this reach, the two highly important ones are: Mill structures - improve operability + protocols The impoundment created by the Hellesdon Mill structures extends into this reach and therefore improvements in river condition will arise from the lowering of retained water levels to create free flow. Free flowing conditions are required to facilitate the effective use of the instream restoration measures such as the berms, gravel glides and deflectors indentified for this reach and to reinstate dynamic natural hydro-morphological processes. These improvements will be most pronounced in Sub-reach 02b which currently experiences impounded conditions throughout although the reach as a whole is likely to benefit through improved habitat connectivity brought about by the facilitation of instream works in downstream sections. It is considered that only limited improvements will result if small changes in retained water level are made. Gravel glides Gravel glides have already been added to the top 1/3 of the reach with benefits to fisheries and natural form and flow function. Existing channel widths are not as excessive as seen elsewhere in this unit, which allows this form of localised bed raising to be effective. It will complement well the existing natural sections of gravel glides seen in the middle 1/3 of the reach. Similarly they will work well with the lowering of spoil embankments to manage flood flows through the reach.

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Figure 6.2 - Location of sub-reaches within Reach 02 (Drayton Reach) Unit 54 Taverham Mill to Hellesdon Mill_final for issue_V1.0.docx 103

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Figure 6.3 - Conceptual restoration plan for Reach 02a (Costessey Mill to Marriott’s Way)

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Figure 6.4 - Conceptual restoration plan for Reach 02a (Marriott’s Way to Wensum Mount Farm)

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6.5 Reach 03: Costessey Reach This section defines the preferred restoration of Reach 03 by describing key existing features; reviewing the recommended measures as stated in the RWRS; presenting the results of the MCA scoring and detailing rehabilitation measures applied to the reach. In defining the preferred restoration of Reach 03 it has been considered appropriate that the reach be divided into 2 sub-reaches to reflect the differing geomorphological character present along its 3.91km length. Field observations made in February 2011 identified this reach as longitudinally lending itself to different restoration measures and as presenting different opportunities / constraints. The 2 sub-reaches run sequentially from Taverham Mill to Costessey Mill (Figure 6.5) and their extent and general character are described in Table 6.13. A conceptual restoration plan (Figure 6.6 and Figure 6.7) and indicative cost estimate is provided for each of the 2 sub-reaches for clarity. Table 6.13 – Key characteristics of Reach 14 sub-reaches

Sub-reach Sub-reach Name Extent Character Code (km) Sub-reach is not so significantly impounded by backwater created by Costessey Mill structures as seen in the local variations in plan form and changes in cross section are Taverham Mill to Reach 03a 1.5 well developed. AWS surface water Place farm abstraction located in upstream section of reach. Floodplain storage potential reduced through presence of Costessey Pits on TRHB floodplain. Sub-reach is significantly impounded by backwater created by Costessey Mill structures and is much more uniform in plan form and cross section. Channel exhibits gross meander planform although is over- widened throughout with marginal vegetated Place Farm to Reach 03b 2.41 berm development present. Extensive field Costessey Mill drainage network on adjacent floodplain with property boundaries abutting the TRHB in lower half of reach. River channel bifurcates immediately upstream of Costessy Lane road bridge and flow is split between main channel and mill bypass.

Table 6.14 presents a brief description of the existing conditions of the reach as observed during the site visit conducted on 8th February 2011. The purpose of the visit was to consider the reach objectives on the ground.

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Table 6.14 - Significant features and possible measures observed for Reach 03 during site visit (February, 2011)

Noted Feature Possible Measure Common to both sub-reaches Reduce upstream water levels at Costessey to Reach is affected by the backwater created allow in-channel habitat enhancements where by Costessey Mill weirs (Plate 52). backwater effect is reduced. Much of the reach (especially along the left Planting of trees to enhance contrasting light and bank) has no riparian tree cover, except for shaded sections of river habitat to complement isolated trees or clumps of trees in an the wider landscape and aid variation in channel otherwise grazed landscape (Plates 41, 43, plant growth. 44, 48 and 49). Enhance connectivity to provide extensive IDB Main Drains drain the floodplain on both backwater habitats where appropriate and design banks of the river. targeted maintenance at main river confluences. Some floodplain areas are unmanaged or Assess potential for creation of new floodplain rarely grazed. wetland habitats. Sub-reach 03a: Taverham Mill to Place Farm This sub-reach is less affected by the Allow natural vegetated berm encroachment and backwater from Costessey Mill and supports natural channel narrowing processes to continue, good flow and river habitat variations, though improve bank protection from grazing and design some berm removal and bankside poaching a targeted maintenance approach to maximise still occurs (Plates 40, 41, 44 and 50). diversity. Establishment of osiers along the TRHB has Complement the habitats created by these greatly improved flow and channel diversity willows by adding to riverside tree cover and where they are now beginning to encroach enhancing associated in-channel features (e.g. into the channel (Plate 48). insertion of berms and gravel glides). Costessey public water supply intake is Assess suitability of backwater habitat creation in located in the upper section of this sub-reach adjacent drains. (Plate 45). Sub-reach 03b: Place Farm to Costessey Mill Alongside options to reduce flow impoundment This sub-reach is significantly affected by the improve bank protection from grazing and use a backwater from Costessey Mill. targeted maintenance approach to maximise diversity. Coupled with backwater reduction, installing a combination of gravel glides, artificial berms, Sub-reach has simplified flow with deep and deflectors or LWD insertion would help to slow-flowing character. establish a meandering pattern within the existing simplified channel.

Dredging works have resulted in a variety of Enhance floodplain connectivity by partial embankments and reduced floodplain embankment lowering along the reach. connectivity (Plates 50 and 52).

6.5.1 Review of Reach 03 Strategy Objectives Appendix A to the RWRS (JBA, 2007) details a ‘Reach Restoration Strategy’ for each reach. These objectives have been the starting point for the consideration of rehabilitation activities. A review of these objectives is presented below in Table 6.15.

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Table 6.15 - Review of strategy objectives and recommendations for Reach 03 RWRS Objectives Atkins Comments on the RWRS Partially agree: It may not be possible to remove Taverham Mill structures but by- passing them appears possible. Lowering All works must integrate with removal of of Costessey weirs will benefit Taverham Mill, lowering of structure at 1.1 enhancements along this reach, but may be Costessey Mill and associated river difficult without supporting legal works. agreements. Works should be designed to maximise the potential changes at these weirs. Partially agree: Depends upon degree of siltation and whether silt can remain in situ De-silt channel just upstream of to kick-start berm and marginal vegetation 1.2 Costessey Mill development following water level reduction, rather than excavating sediment out of the channel. Partially Agree: The upper sections of the reach have retained gravelly, free-flowing characteristics that do not need 1.3 Augment the bed using gravels. augmenting. The lower, dredged sections of the reach will need some degree of gravel augmentation (dependent upon water level lowering at Costessey Mill). Partially agree: Natural berm development and vegetation encroachment may be Physically narrow the channel where 1.4 possible, but some over-engineered substantially over-wide. sections may need artificial assistance to speed recovery processes. Partially agree: Partial removal to improve Reconnect river to its floodplain by 1.5 connectivity may be sufficient, rather than removing embankments. wholesale removal. Partially agree: Long sections of this reach have no tree cover or bank protection from Develop marginal / bankside vegetation root development. Many meander bends 1.6 by planting trees at meander bends. already have some tree cover, so a reach- scale approach to tree planting and thinning would be more appropriate. In the 100 to 200m downstream of Taverham Mill and in immediate scour Partially agree: Whilst the statement is pool area of good habitat value, no correct, and we agree with it, it relates to 2.1 works are required and this area should Reach 04 which is outside of the scope of be conserved and allowed to re- this report. vegetate naturally. Initial work is for bed and bank Partially agree: Allow natural stabilisation associated with lowering of encroachment where possible but vertical 2.2 Costessey Mill structures at the bank forms may need adjustment after downstream end of reach. water levels are lowered. Agree: This could involve allowing natural Appropriate measures required to channel narrowing processes and 2.3 manage silt deposits upstream of vegetation colonisation of silt deposits Costessey Mill. rather than physical removal of silt. Augment bed on average by 0.3m using Partially agree: Gravel replenishment of local gravel wherever possible and dredged sections will be necessary but not 2.4 create up to 42 gravel glides or riffles in to the extent of the number or standardised the remainder of the reach. depth of locations suggested in the RWRS. 2.5 The channel is on average 5.2m over Partially agree: Natural narrowing has Unit 54 Taverham Mill to Hellesdon Mill_final for issue_V1.0.docx 108

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RWRS Objectives Atkins Comments on the RWRS wide and physical narrowing (with already occurred along some sections, associated landscaping and fencing) whilst others remain significantly over-wide may have to be considered to restore and deep. Fencing to reduce poaching and the full functioning of the channel in this grazing would benefit marginal vegetation reach following works at the mill. development and some over-engineered sections may need adjustments to speed natural recovery processes. Adopt / maintain maintenance regime Agree: A combination of artificial and riparian management to allow enhancement works, natural encroachment 2.6 channel to create natural variations in and targeted maintenance should provide local channel width and habitat niches. the most sustainable results for this reach. Agree: Allow as much natural berm Post-project monitoring is required, development and marginal vegetation 2.7 especially in association with works at encroachment as possible, coupled with the mill structures. targeted maintenance at appropriate locations. Summary Reach 03: Atkins agrees or partially agrees with all of the principles established by JBA for this reach.

6.5.2 Reach 03: Recommended restoration This section provides the details of the options and measures proposed for this reach which have been derived from the Multi-Criteria Analysis (refer to Section 5.3). A summary of the MCA results in their rank order is provided in Table 6.16 and these are further divided into importance according to how far the measure will move the reach towards achieving ‘unfavourable recovering’ or ‘favourable’ ecological condition. In addition, the suitability of each of the positive scoring measures identified by MCA for Reach 03 is presented at a sub-reach scale. The suitability of each measure has been determined by reference to existing channel and floodplain form resulting in the assignment of a rating (High, Medium, Low) for each measure at a sub-reach level (Table 6.17). This assessment is reflected in the conceptual restoration plans provided for each of the sub-reaches (Figures 6.6 and 6.7). Table 6.16 - Recommended restoration options for Reach 03 Option Description Weighted Score Highly Important Measures None identified Important Measures 5.3m Mill structures - lower mill sills levels 10.12 5.11 Tree planting 9.73 5.10 Fencing 9.72 5.13 Deflector 9.71 5.16 Berm creation 9.71 5.7g Gravel glides 9.36 G3 Targeted maintenance 8.46 5.14 Lower spoil embankments 7.31 Less Important Measures 5.17 Backwater – reconnections to IDB, field drains 5.31 5.18 Backwater – new 4.51

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Table 6.17 – Restoration measure suitability rating for Reach 03 sub-reaches Option Description Weighted Suitability Rating for Sub-reach Score for Reach 03a 03b Mill structures - lower mill sills 5.3m 10.12 Medium High levels 5.11 Tree planting 9.73 High High 5.10 Fencing 9.72 Medium Medium 5.13 Deflector 9.71 Medium Medium 5.16 Berm creation 9.71 Medium High G3 Targeted maintenance 8.46 High High 5.7g Gravel glides 9.36 Medium Medium 5.14 Lower spoil embankments 7.31 Low High Backwater – reconnections to 5.17 5.31 Medium Low IDB, field drains 5.18 Backwater – new 4.51 Low Low

6.5.3 Targeted maintenance Following the principles established in section 6.2.2 the following measures are suggested and may form part of the targeted maintenance protocol being developed for this unit. These include: 1. Silt removal. This is recommended immediately upstream of structures, or where silt deposits will limit discharge at confluences with IDB drains or significant tributaries. Structures on this reach include Costessey Lane road bridge, Costessey Mill structures and Costessey Horseshoe Weir flow measurement site. There is one IDB drain confluence in this reach. Monitoring and clearance of encroaching silt will be needed within 10m upstream and 20m downstream of the structures. This is equal to 1 channel width and 2 channel widths, respectively. 2. Clearance of main channel downstream of confluence with IDB drains. There is one confluence with an IDB drain in the middle of the reach. There is also a requirement for inspection and clearance of encroaching marginal vegetation at connections to off-channel backwaters, either side of the IDB confluence, which aid surface water drainage from roads and properties. 3. Clearance or realignment of fallen trees blocking channel. Clearance is only required where they are impacting directly on flood risk to property or the structural integrity of third party assets. Any fallen trees upstream of aforementioned structures need to be considered on their individual merit depending on the proximity of the bridge. 4. Strategic weed cutting. This is only needed where there is direct threat to houses caused by elevated water levels, or where freeboard or floodplain availability is unlikely to be sufficient to receive likely rainfall.

6.5.4 Restoration Measures All the restoration measures identified by the MCA have been incorporated into the preferred outline restoration design for Reach 03, which is shown in Figure 6.3. This reach has no measures which are considered to be ‘Highly Important’. This reflects the relatively large standard deviation about the mean MCA score which is driven by the occurrence of two groups of high and low scoring measures. Of the restoration measures selected for this reach, the highest scoring ‘Important’ measures are listed below. It should be noted that a further four restoration measures score within only one point of the two measures highlighted below: Mill structures – lower mill sills With about half the reach affected by the backwater from Costessey Weir and sluice, lowering sill levels would have a marked effect. However, the structures form part of the Costessey Gauging

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Station which provides data on river flows for the lower part of the catchment. The gauging station also provides data for water resources planning and flood warning. This, and legal agreements relating to retained levels, will mean that changing sill levels will be practically difficult as well as technically involved due to structural stability considerations. It may be possible to lower water levels by changing the automatic sluice operation to assess the impact of change on the upstream section of river. If further lowering was assessed as being worthwhile, then the main weir could be notched to lower level, as suggested in the RWRS. Tree planting The reach is almost completely devoid of trees along the TLHB line which reduces both riparian and in-stream habitat complexity. The addition of native wetland trees along the reach will, in the long-term, improve bank stability, create a diversity of light and shade conditions and provide a potential source of large woody debris to the stream, improving physical habitat and providing cover for fish.

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Figure 6.5 - Location of sub-reaches within Reach 03 (Costessey Reach)

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Figure 6.6 - Conceptual restoration plan for Reach 03a (Taverham Mill to Place Farm)

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Figure 6.7 - Conceptual restoration plan for Reach 03b (Place Farm to Costessey Mill)

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7. Cost Estimate

This chapter covers the cost estimate for delivering the preferred restoration options/measures for each reach as outlined in Chapter 6. To set this in context, a brief background history of previous published reports and their cost estimates is summarised in Section 7.1. Current estimates for reaches 01 to 03 following the MCA analysis and concept design are presented in Section 7.2 together with the main assumptions for the estimates. Potential cost savings are presented in Section 7.3 and delivery or phasing aspects are detailed in Section 7.4 7.1 Previous cost estimates

7.1.1 Background Two previous reports, the RWRS (JBA, 2007) and Estimating Costs of Delivering the River Restoration Element of the SSSI Target (Halcrow, 2008), included some costs for restoration options on the river. The JBA RWRS report provided costs per kilometre of in-channel river works including bed raising, channel narrowing and restoring meanders. Based on these rates and the recommendations in the report for Unit 54, this equates to the costs outlined in Table 7.1. Table 7.1 - RWRS Unit 54 cost estimate (JBA, 2007)

Reach 01 02 03

Reach length: m 1645 3160 3910 Length of recommended works: 1.645 3.16 3.91 km Restoration n/a n/a n/a Narrowing <10 m 329,000 632,000 782,000 Narrowing >10 m - - - Bed raising 296,100 147,600 75,600 Landscaping 1,645 3,160 3,910 Fencing 9,870 18,960 23,460 Modification of mill - - - structures Total for reach 636,615 801,720 884,970 Total for unit 2,323,305 Note: Estimates of total river restoration and rehabilitation costs assumed from JBA 2007 Technical Report Appendix A.

The Halcrow 2008 report covers all river SSSIs in England and includes the prevailing views of Natural England and the Environment Agency regarding appropriate measures for each unit on each river. A summary of the Halcrow costs for Unit 54 are presented in Table 7.2.

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Table7.2 - Halcrow PSA Unit 54 cost estimate

LWD

Unit 54 Fencing Structure Structure Meandering Meandering Bed Raising Modifications Modifications Cross Section Section Cross In-stream Structures Structures In-stream % length requiring 0 20 20 30 30 30 0 work Length in km 0 1.74 1.74 2.61 2.61 2.61 0 requiring work Total cost per 0 26,840 107,988 79,046 203,956 216,517 0 km/length Cost per unit per 0 46,782 188,223 206,665 533,243 566,083 0 activity £ Total for unit (£) 1,540,996

A comparison of JBA and Halcrow cost estimates is presented in Table 7.3. This shows that the cost estimates to restore Unit 54 of the River Wensum range between £1,500,000 and £2,300,000. This feasibility report has looked at all options for restoration in more detail and hence it is appropriate that the costs for the recommended options are refined further. Table7.3 - Comparison of cost estimates between JBA and Halcrow reports for Unit 54

Unit 54 LWD In-stream Structures Cross Section Modifications Bed Raising Restoration Structure Modification Totals

RWRS (£) 0 0 1,743,000 519,300 61,005 2,323,305 SSSI cost estimates 46,782 188,223 206,665 533,243 566,083 1,540,996 (£)

7.2 Present cost estimates

7.2.1 Unit 54 cost estimate Costs for implementing the recommended options and measures for the whole of SSSI Unit 54 have been estimated based on information from the RWRS (JBA, 2007), SSSI Estimated Costs Report (Halcrow, 2008) and other sources. Making use of previous cost estimates where appropriate has ensured consistency in the cost estimates so that the feasibility report provides a refined cost estimate rather than an independent one. Table 7.4 shows the revised total cost estimate for the different river restoration measures recommended for Unit 54. This estimate is based on a number of assumptions relating to sizes, quantities, materials and conditions. It also reflects current prices and costs which may have changed since the JBA and Halcrow reports were carried out. The targeted maintenance option has not been costed due to uncertainty in rates. This exclusion, along with the assumptions, will

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affect the accuracy of the final cost estimate. The full details of the costs and assumptions are given in Appendix B. Table 7.4 - Unit 54 cost estimates for various river restoration measures (February 2012)

Measure Description Quantity Rate per unit Cost (£)

5.1 Fencing (m) 8715 8 69,720 5.16 Berm creation (m) 824 90 101,520 5.12 Tree felling (m) 580 10 5,800 5.17 Backchannel – reconnection (m3) 3837 14.18 54,415 5.7g Gravel glides (m3) 8280 53 438,840 5.13 Deflector (m) 447 44 19,668 5.11 Tree planting (unit) 230 58 13,340 5.14 Lower spoil embankments volume (m3) 4556 9.83 44,786 5.21 Lower formal embankments volume (m3) 608 9.83 5,977 Option G3 Targeted maintenance Unknown Unknown Unknown Total cost: £754,066

Table 7.5 shows the cost estimates for each reach (and where applicable sub-reach) for each of the measures.

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Table 7.5 – Unit 54 cost estimates for each reach / sub-reach Sub-reach Sub- Reach 02 Sub-reach Sub-reach Reach 03 Total Cost Description Reach 01 02a reach02b (all) 03a 03b (all) (£) Fencing 13,160 5,760 19,520 25,280 12,000 19,280 31,280 69,720 Berm creation 33,570 2,880 26,100 28,980 11,160 27,810 38,970 101,520 Tree felling 2,600 500 2,700 3,200 - - - 5,800 Backchannel – reconnection 25,609 2,482 23,822 26,304 1,767 735 2,502 54,415 Gravel glides 51,940 19,504 195,040 214,544 43,089 129,267 172,356 438,840 Deflector 5,896 - 5,632 5,632 2,728 5,412 8,140 19,668 Tree planting 2,320 1,160 4,640 5,800 1,740 3,480 5,220 13,340 Lower spoil embankments 2,320 - 25,558 25,558 - 16,908 16,908 44,786 Lower formal embankments 5,977 ------5,977 Targeted maintenance Yes Yes Yes Yes Yes Yes Yes Unknown Total costs £143,392 £32,286 £303,012 £335,298 £72,484 £202,892 £275,376 £754,066

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7.3 Potential cost savings The total cost estimate of £754,066 for Unit 54 is based on a number of assumptions, in particular the materials and installation methods for the various recommended river restoration measures (see Appendix B for further details). Should alternative restoration measures be implemented, this may affect the total price outcome. Efficiency savings could be achieved by re-using, where appropriate, spoil generated as part of the restoration works to construct features that require spoil. T he following section identifies potential means of reducing costs associated with spoil disposal. Indicative savings are provided, although these may change as detailed design progresses. 7.3.1 Spoil reduction A number of the river restoration measures for Unit 54 either generate or require spoil as outlined in Table 7.6. Table 7.6 - Measures that typically generate or require spoil

Reach /Sub-reach Total 01 02a 02b 03a 03b 3 Spoil Generation (m3) (m ) Berms 890 70 657 269 672 2558 (require spoil) Backchannel reconnections 1806 175 1680 125 52 3,838 (generate spoil) Lower embankments (formal and spoil) 844 2,600 - 1,720 5,164 (generate spoil) Total surplus spoil (m3): 1,760 105 3,623 -144 1,100 6,444 Opportunity to reduce spoil Yes Yes Yes Yes Yes Yes

Table 7.6 shows there is a significant amount (around 6,500 m3) of surplus spoil that will need disposing for the whole unit. Whilst some spoil may be lost on site there are opportunities to replace gravel with spoil on some sections of reaches where this is suitable. This might include depth substitution within gravel glides (i.e. using spoil rather than gravel in constructing the lower layers of glides – see section 7.3.2 for details). Any reduction in spoil disposal will reduce the amount of trafficking on site to dispose of the material. Opportunities to reduce spoil generation and movement should be sought during the detailed planning and construction phases. This will have beneficial consequences in terms of reduced:  Land take  Cost  Carbon footprint  Grounds for landowner dissatisfaction  Need for environmental mitigation. For the channel realignment and new backchannels connections excavation lengths cannot be meaningfully reduced as they need to maintain recommended size to provide long term stability.

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7.3.2 Gravel glides The MCA identified that the most beneficial measure of reintroducing gravel to the system was in the form of gravel glides which have been recommended for all the reaches in Unit 54. Gravel glides account for 58% of the total option costs, a total estimate of around £439,000. There are two alternative methods of reducing gravel glide costs:  Replacing the gravel in the bottom 2/3 of the glide with inert fill (depth substitution), or  Replacing the downstream 2/3 with transverse hurdles to trap silt and so use deposition to create the tail of the glide (length substitution). Depth substitution: Surplus spoil has to be disposed of so could be used in part to substitute for two thirds of the gravel volume to the gravel glides. The reduction in costs comes from the reduction in volume of gravel used, as presented in Table 7.7. Table 7.7 - Gravel substitution using surplus fill

Reach Surplus No. Opportunity Volume of Gravel Volumes Totals Spoil Glides to substitute replaced by Spoil Saved Volume gravel with per glide (2/3 of (m3) excess spoil Total Glide Volume) 01 1,760 2 Yes 327 654 02a 105 1 Yes 245 105* 02b 3,623 10 Yes 245 2,453 03a -144 3 No - - - 03b 1,100 9 Yes 181 1,100* Total volume (m3) 4,312 Gravel cost £/m3 53 Spoil disposal cost £/m3 4.81

Cost for unit: £249,277 Note:*indicates where all of potential surplus spoil is used in gravel replacement.

The total achievable cost savings associated with reducing the gravel requirement through spoil utilisation in gravel glides is as follows:  A reduction in gravel costs and soil disposal costs of approximately £250,000 which represents a saving of 57% on the total gravel glide cost or 33% on the total implementation cost for Unit 54. Length substitution: Cost savings could be made by replacing some of the gravel with other material. However, substituting sections of the gravel glides with hurdles is only possible if the river bed system has some gravel. The opportunity to reduce the cost by this means will therefore need to be assessed once further information is available. Due to the historical channel dredging there is limited gravel in the existing channel so opportunities may be limited. However, during detailed design, surveys may identify the presence of gravel in the system creating gravel cost saving opportunities.

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7.3.3 Cost saving summary: There may be opportunities to make savings through replacing part of the gravel glide material through depth substitution. Should this method be implemented, this could reduce the total restoration cost to approximately £505,000. This gives a total cost saving of around 33%.

7.4 Delivery Section 7.3 provides details of the costs for physical works, but this can be influenced by how the works are carried out. The following sections explore this further. Phasing: The phasing of the excavation measures can reduce the amount of double handling needed. This has benefits in reducing the amount of physical work required, and therefore:  Unnecessary disturbance and damage to the environment.  Less disruption risk due to bad weather or poor ground conditions.  Reduction of scheme costs. It is recommended the works be phased in the order listed in Table 7.8 Table 7.8 - Recommended phasing of work

Measure Reason for Phased Order

Provides flood risk management, silt control and 1 Targeted maintenance confirms Environment Agency presence on the river. Highly important for project delivery, immediately Backwater reconnection and 2 helps with fish recruitment and flood risk, and lower embankments generates large volumes of spoil.

Must follow spoil removal to access the river banks, 3 Berm creation the two previous operations will generate the arisings with which to complete berm creation. Previous measures have improved in-channel 4 Tree thinning conditions to allow macrophyte growth, and so tree thinning is now required to remove shade.

Tree thinning and felling provides raw material for 5 Deflectors the deflectors and re-sectioning has improved channel capacity. With all previous in-channel works, and any silt release completed, smaller gravel works can be 6 Gravel glides placed in the channel at the best locations and shaped for maximum impact.

With all the in-river features in place the location for 7 Tree planting the trees can be easily seen and without further works the trees are unlikely to be damaged. If this is not done last, any further works will require 8 Fencing its removal and re-construction.

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7.4.1 Monitoring The details for river monitoring need to be agreed between Natural England and the Environment Agency before any restoration measures commence on site. Monitoring will have to commence before restoration works start to collect baseline data. Monitoring will also allow a comparison of changes to be recorded as each phase is implemented. 7.4.2 Maintenance If there are time gaps between implementing different restoration measures, then ‘Targeted maintenance’ will help manage the river appropriately until works can commence. 7.4.3 Local resources If the implementation of the works is to be phased geographically, then there is merit in including the landowners in the tendering list, as they may have the necessary resources to complete the excavation and spoil movement and spreading. This would bring unrivalled local knowledge to bear on each river reach subsection, and would open-up opportunities that other contractors would not be able to realise.

7.5 Summary Table 7.9 summarises the recommended restoration measures, in order of phasing, for Unit 54. Table 7.9 Recommended phasing of restoration measures for Unit 54

MCA Score Options Measure Phasing 01 02 03

G3 Targeted maintenance 1 2.82 7.03 8.46

5.18 Backwaters – reconnections to IDB, field drains 8.22 10.22 5.31

5.14 Lower spoil embankments 2 10.86 11.38 7.31

5.21 Lower formal embankments 10.86 n/a n/a

5.16 Berm creation 3 10.22 10.52 9.71

5.12 Tree thinning 4 9.64 8.02 n/a

5.13 Deflectors 5 9.72 10.52 9.71

5.7g Gravel glides 6 8.92 14.24 9.36

5.11 Tree planting 7 7.12 8.92 9.73

5.10 Fencing 8 1.42 4.66 9.72

Mean (all measures) 8.51 10.09 8.39

Highly important >11.94 >13.12 >11.57

Less important <5.08 <7.06 <5.22

The key points to note are:  The phasing relates to the order of installation, not to the order of importance in delivering the changes in form and process to the main river channel.

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 The scores derived from the MCA provide the method for placing each measure in relation to each other measure to give the combined final design that provides the best delivery in the long-term.  The design for each reach is related to the conditions within the unit and takes account of the changes in other reaches that have inter-reach impacts, such as mill structure backwater effects.  The phasing is independent of the length of river being worked. The cost estimate for Unit 54 is £754,066 which is considerably less than previous reports. However, although a cost saving may be achievable, this will be very much dependent on the findings at the detailed design stage once a review of additional site specific survey information (bathymetric and topographic) and utilities searches are carried out. This revised estimate is less than previous cost estimates (JBA, 2007; Halcrow, 2008) although it is difficult to compare the three estimates due to the assemblage of different components. There also needs to be allowance made for different dates of each estimate. Table 7.10 summarises the differences between the three different cost estimates. Table 7.10 - Comparison of costs between 2007, 2008 and 2011 studies Measure Halcrow (2008) JBA (2007) Atkins (Feb 2012) Length Length Length Cost (£) Cost (£) Cost (£) (km) (km) (km) Fencing* 0.00 0.00 8.72 52,290 8.72 69,720 Large woody debris 1.74 46,782 0.00 0.00 0.447 19,668 In-stream structures 1.74 188,223 0.00 0.00 1.128 101,520 Cross section 2.61 206,665 8.715 1,743,000 1.721 50,763 modifications Bed raising 2.61 533,243 4.805 519,300 0.788 438,840 Landscape** 0.00 0.00 8.715 8,715 0.81 19,140 Reconnections 0.00 0.00 0.00 0.00 2.741 54,415 Restoration 0.00 0.00 0.00 0.00 0 0 Structure modification 2.61 566,083 0.00 0.00 0 0 Totals 11.33 1,540,996 22.24 2,271,015 7.64 754,066 (excluding fencing) Overall unit rate (£/km) 176,821 260,587 86,475 Density of features 1.30 2.55 0.88 Density adjusted rate 229,867 664,616 75,765 (£/km) Notes: *Fencing length excluded from the calculation of the total length of restoration features. **Includes tree felling and tree planting.

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8. Environmental Scoping 8.1 Introduction

8.1.1 The need for Environmental Impact Assessment The types of river restoration measures identified by this feasibility study are likely to fall within the Environment Agency’s permitted development rights under Schedule 2, Part 15(b), of the Town and Country Planning (General Permitted Development) Order 1995 SI 95/418 (referred to as the GPDO) and it is anticipated that planning permission will not be required. As the details of any future schemes are developed, consultation with the relevant local planning authorities regarding the proposals will be required to confirm this view. Any works that are undertaken under Schedule 2, Part 15(b) of the GPDO fall within the remit of the Environmental Impact Assessment (Land Drainage Improvement Works) Regulations Statutory Instrument (SI) 99/1783 (as amended by SI 2005/1399 and SI 2006/618). SI99/1783 (as amended) requires that the potential for the works to give rise to significant environmental effects is considered. Where significant environmental effects are likely to occur there will be a need to undertake an EIA (Environmental Impact Assessment) of the scheme. It is considered that the works within Unit 54 are unlikely to give rise to significant environmental effects, and will therefore not require a statutory EIA. This position will be confirmed by the Environment Agency during the detailed design phase for each scheme by an internal screening exercise. In accordance with the requirements of SI 99/1783 (as amended), the intention not to produce an Environmental Statement will need to be advertised. The advertising process will be undertaken once the details of any schemes have been developed, and the relevant local planning authorities have been consulted regarding the proposals. Although a statutory EIA (with the production of an Environmental Statement) is unlikely to be required, it is Environment Agency policy to undertake EIA for its own works. Therefore, a risk- based non-statutory environmental assessment for any subsequent restoration schemes will be undertaken and this will be documented by an Environmental Report. 8.1.2 Environmental Scoping Exercise As part of this feasibility report, an environmental scoping exercise on the preferred restoration option for each reach was undertaken. The purpose of this exercise was to determine what issues will need to be considered during the Environment Agency’s non-statutory EIA for any forthcoming restoration scheme. The scoping exercise will also form part of the required documentation to gain internal approval for the scheme. The purpose of the environmental scoping exercise is to:  Provide a record of the scoping process.  Identify the methodology for undertaking and evaluating the EIA.  Identify what environmental issues will be scoped into the EIA.  Identify what environmental issues will be scoped out of the EIA.  Identify environmental constraints and opportunities that will need to be addressed at the detailed design stage.  Consult with statutory bodies and interested parties on the proposed scope. Whilst there is no formal requirement for scoping to be undertaken in the United Kingdom (IEMA, 2004), environmental scoping is a fundamental component of the EIA process because it identifies the key environmental issues and avoids progressing issues that are considered to be

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less important through to the next stage of EIA (IEMA, 2004). Figure 8.1 illustrates where environmental scoping occurs within the EIA process, and how this has been applied to Unit 54.

Environmental Scoping: Unit 54: Taverham Mill to Hellesdon Mill

SCHEME CONCEPT Understand and establish key project drivers and objectives of the Feasibility Assessment.

SCREENING Define the environmental baseline features of each reach in Unit 54. Considers a number of ‘River restoration’ and ‘Targeted maintenance’ options and measures that could be applied and implemented individually or in combination to restore Unit 54 to ‘unfavourable recovering’ or ‘favourable’ ecological condition.

CONSULTATION & RESULTS & ANALYSIS

Communicate with key statutory stakeholders and the local community to capture the ‘big’ issues, and identify the constraints and opportunities of the proposed restoration measures.

Analysing the feedback obtained from the consultation process

MULTI CRITERIA ANALYSIS (MCA) WORKSHOP Apply the MCA tool against ecology, project delivery and technical aspects that help inform the selection of appropriate measures for Unit 54.

Use results of MCA and professional judgement to select recommended option(s).

SCOPING OF THE PREFERRED OPTIONS FOR UNIT 54 Focusing on the significant environmental issues associated with the proposed restoration measures.

SCOPED IN SCOPED OUT

Request a formal scoping opinion to the planning authority to inform the project team the level of EIA required.

Undertake either a full Environmental Impact Assessment or Environmental Report for each unit

Figure 8.1 - Environmental Scoping within the EIA process

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8.2 Method of assessment The project is still at a strategic level so detailed monitoring of baseline environmental conditions have not been carried out. This means that professional judgement, in combination with the methodology explained below, was used to determine what environmental issues will be assessed in more detail at the next stage of the EIA process. The options and measures that have been detailed in Table 8.2 require scoping for potential constraints and opportunities. To carry out this level of assessment, the European Commission guidance on Screening and Scoping (2001) has been adapted to determine what type of constraints and opportunities are likely to give rise to significant effects. Table 8.1 presents the framework for classifying and evaluating the significance of potential environmental effects of the preferred river restoration option. Table 8.1 - Classifying and evaluating the significance of potential environmental effects in the scoping process (adopted from European Commission, 2001)

Key Questions Used In Environmental Scoping Measure Are the final proposed works out-of-character with the local Yes / No environment? What is the scale of the effect? Limited / Widespread Is there potential for effects on the environment outside of study Yes / No area? Are there many people affected? Yes / No

Are there protected, rare or endangered features affected? Yes / No

Is there a risk of breaching industry standards? Yes / No

Probability of occurrence Yes / No

What is the length of the effect? Short / Medium / Long

Is the effect reversible? Yes / No

Significant effect (without mitigation) Major / Moderate / Minor

8.2.1 Restoration Options and Measures Restoration options and measures outlined in Table 8.2 have been grouped to simplify the scoping process and to avoid repetition in assessing effects. The groups are:  In-channel works; berm creation; gravel glides; channel re-sectioning; deflectors; channel realignment and lowering mill sill levels.  Floodplain works; lowering spoil embankments; re-connecting to existing floodplain surface water drainage; new backwaters and tree thinning.  Other works: ‘Targeted maintenance’, tree planting and fencing. Using the information within Table 8.1 and professional judgement, the recommended restoration options and measures are assessed in terms of their significance of effect. This report has adopted the following categories to determine the significance of effect:  Potential adverse effect;  Neutral effect (or one that could be designed out); and  Potential positive effect.

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Using the results of Table 8.2, environmental issues are either scoped in or out. Issues that are scoped in will be carried through to the next stage of the EIA process. Issues scoped out are dropped from the EIA process but periodically reviewed should matters like scheme design elements change. Section 8.3 presents the results of the scoping assessment. 8.3 Results of scoping The scoping assessment was undertaken by using professional judgement and best practice literature (IEMA, 2004; and European Commission, 2001). It is considered to be in accordance with the legislation, procedure and guidance in force and with reference to international standards of EIA best practice. This section summarises the results of the scoping assessment. The scoping assessment included the opinions of public and private stakeholders captured during the initial public ‘drop-in days’ and various consultations with statutory stakeholders (refer to Chapter 4 for more information). The early consultation within the EIA process provided timely and appropriate opportunities for public and stakeholder involvement. One of the key outcomes of early engagement has been the identification for the need to implement targeted maintenance ahead of main river restoration works. The environmental scoping assessment has identified issues to be scoped in and out of the EIA process. Those issues scoped in to the assessment will require further assessment for their potential adverse or beneficial cumulative effect at the next stage of the EIA (detailed design). Table 8.2 summarises the potentially key adverse and beneficial impacts associated with the preferred restoration options for Unit 54. It provides more accurate information on exactly what data and actions are required for the next stage of the EIA assessment. Table 8.3 lists those environmental issues that were scoped into the next stage of the EIA, and Table 8.4 lists those issues that were scoped out. Information contained within Tables 8.2 to 8.4 ensures that the scope of the EIA will be focused only on key issues.

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Table 8.2- Environmental scoping assessment for recommended restoration options Legend Potential adverse effect Neutral effect Potential positive effect

In-channel works Floodplain works Other works

Individual Environmental Scoped Environmental Phase Aspect of Proposed Works Giving Rise to Potential Impact Group In? Features m r Be Gravel Glide Channel Re- sectioning Deflectors to Connect Channels Channel Realignment Sill Mill Lower Levels Spoil Lower Embankments Re-connect to Floodplain Drains New Backwaters / Tree Felling Thinning Targeted Maintenance Fencing Tree Planting Construction activities include additional vehicle movements. The number of Heavy Goods Vehicles (HGVs) needed to transport the required gravel is low and transport will be Construction X undertaken over a short period of time. Therefore, adverse impacts to local ambient air Air quality quality are unlikely to be significant.

Operation No effects are anticipated for the operational phase. X

Restoration schemes have the potential to result in the release of atmospheric carbon. Air and Climate However, schemes will be designed to minimise the use of synthetic and imported Construction materials. Where possible, materials used will be from within the site or imported from a  local source to minimise carbon emissions associated with transportation. Waste will be Climate change minimised, and arisings will be reused on site wherever possible. The restoration measures proposed will be designed to adapt to future uncertainty. Tree planting has the potential to become a natural carbon sink, therefore offsetting the impacts Operation X of tree felling. However, the restoration is unlikely to have a significant impact on climate change and is therefore scoped out.

Construction works are likely to have a temporary negative effect on the local landscape. Tree felling and pollarding to improve river biodiversity and to provide woody debris for in- Construction channel works are likely to impact locally on landscape and visual amenity. However, the magnitude of these works is low, and tree planting within the floodplain will offset tree Landscape Landscape and removal in the long term. character & visual  visual amenity amenity Restoration of the river through introducing greater sinuosity or improvements to the riparian habitats should return the target reaches to a more natural state. Once Operation established, these works would be expected to improve the visual amenity value of the reaches through softening the “man-made” feel of certain sections of the river, especially those where the channel has been canalised and sinuosity has been significantly reduced.

Physical works to the banks (e.g. re-profiling, construction of berms, reduction in spoil banks to source gravels and reconnect to floodplain) as well as tree management and Construction  access and plant movements, have the potential to result in disturbance and/or damage to Protected species protected species and their habitats, such as water voles, otters, bats and badgers.

Ecological improvement of the river is the key objective of the project. Completed schemes Operation  are expected to result in long-term benefits for protected species. Works including bank re-profiling and bed-level raising have the potential to disturb in-situ Flora & Fauna sensitive aquatic species. Increasing the number and range of riffles, glides, runs, pools Construction and flow types will have adverse impacts on fish and aquatic populations during  construction but will provide significant long term improvements to the habitats available for Fisheries, a wide range of macro-invertebrates. invertebrates and Ecological improvement of the river is the key objective of the project. The works are likely flora to result in long term improved habitat for key aquatic fauna. This may include Desmoulin’s whorl-snail (Vertigo moulinsiana), bullhead (Cottus gobio), white-clawed crayfish Operation  (Austropotamobius pallipes) and brook lamprey (Lampetra planeri). One of the key PSA targets is the improvement of the Ranunculion fluitantis and Callitricho-Batrachion vegetation community which is characteristic of the river type.

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In-channel works Floodplain works Other works

Individual Environmental Scoped Environmental Phase Aspect of Proposed Works Giving Rise to Potential Impact Group In? Features m r Be Glide Gravel Channel Re- sectioning Deflectors to Connect Channels Channel Realignment Sill Lower Mill Levels Lower Spoil Embankments Re-connect to Floodplain Drains New Backwaters / Tree Felling Thinning Targeted Maintenance Fencing Tree Planting Construction of some restoration options may leave open areas of bare ground which may give rise to opportunistic invasive plants. Good construction and site management, Construction  including plant maintenance (e.g. vehicle cleaning) will be necessary to prevent the spread of such invasive species. Reconnection to floodplain features (e.g. gravel pits, existing field drains and wetland pools) Invasive and non- has the potential to spread invasive species such as Crassula, Azolla and signal crayfish. native species Any reconnections considered as part of the restoration will require a site specific Operation assessment of existing constraints and control options. Invasive species recorded in this  reach include Canadian pondweed, Elodea Canadensis and the naturalised shrimp, Crangonyx pseudogracalis. Azolla is known to be present in connected ditches in Reach 03. There may be tree thinning and felling, during construction, to improve habitat diversity. Construction This has the potential to impact on visual amenity/landscape character. Trees Planting of additional trees will, in time, provide submerged roots for colonisation by  Operation numerous macro-invertebrate species, from caddis flies to crayfish. The surrounding landscape will also benefit from additional tree planting. Short-term, physical changes to hydrology due to temporary works in the channel are not Construction likely to cause significant effects. Geomorphology Physical changes through excavations, bank re-profiling, bed-raising and infilling, works to  Operation improve sinuosity and channel narrowing. Improvements in field surface water drains through re-connecting the main river to these drains will improve surface water drainage. Construction Short-term increases in flood risk may occur due to temporary works in the channel.

Drainage and flood River restoration measures such as lowering mill sill levels, lowering spoil embankments,  risk channel re-sectioning and installing gravel glides all have the potential to change flood risk Operation Water and floodplain water levels, both locally and further afield. This will need assessment at the detailed design stage. Such changes could be negative or positive in terms of flood risk.

In-channel construction will disturb bank and bed sediments and result in the release of sediment to the river and temporarily reduce water quality. There is also a risk of Construction chemicals, oils or fuels being accidentally released into the environment during Water quality construction. 

Bed raising with gravels and the creation of new pool, riffle and glide sequences all have Operation the potential to improve existing water quality in the long-term.

Construction works are likely to have temporary impacts on public and private access to Construction  affected land, including angling access and footpaths.

The rehabilitation works would provide significant opportunities to improve river angling. Humans Canoeing: Whilst there are no statutory navigation rights on the fluvial River Wensum, where there is agreed access for canoeists, impacts and opportunities will be assessed. Human Operation  Where there is no agreed access for canoeists, this will be treated like a normal constraint. Environment Reduction in retained water levels upstream of Costessey Mill will change the appearance of the river for householders whose gardens abut the Wensum.

There may be temporary loss of land use for activities such as grazing, due to construction Land use Construction works. This is unlikely to result in significant environmental effects but will require careful  management with landowners to enable construction.

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In-channel works Floodplain works Other works

Individual Environmental Scoped Environmental Phase Aspect of Proposed Works Giving Rise to Potential Impact Group In? Features m r Be Glide Gravel Channel Re- sectioning Deflectors to Connect Channels Channel Realignment Sill Lower Mill Levels Lower Spoil Embankments Re-connect to Floodplain Drains New Backwaters / Tree Felling Thinning Targeted Maintenance Fencing Tree Planting Rehabilitation works may involve minor realignments of the river channel which may result in the permanent loss of a small amount of grazing land immediately adjacent to the river. The lowering of river banks and / or reconnection of the river to adjacent field drains may result in more frequent small scale flooding of the functional floodplain. However, the floodplain of the River Wensum is within the Broads ESA scheme so as to support Operation  extensive and traditional management regimes. Although the ESA scheme is closed to further entrants, the River Wensum is a target area with regard to Higher Level Stewardship. If changes in hydrological regime were to impact the feasibility of management prescriptions under existing schemes, then schemes would need to be modified.

Noise is expected to be created by construction works but this will be minimised through Construction mitigation and best practice construction techniques. There will be no operational noise X Noise & vibration associated with the development.

Operation No effects are anticipated for the operational phase. X

It is expected there will be a short term increase in traffic through local villages during Construction  construction as a result of importing materials to site. Traffic & transport Operation No effects are anticipated for the operational phase. X

Construction works are expected to have short-term adverse effects on local landscape Construction quality. However, construction related impacts will be short term and the visual amenity is X expected to improve in the medium to long-term. Landscape and Local landscape visual amenity character There may be long-term changes to the landscape character that will need to be assessed on a case by case basis. It is anticipated that naturalisation of the river will be an Operation  improvement. However, there may be instances where there are significant changes to existing landscapes of local or national significance.

Earthworks and construction may give rise to adverse effects on the historic environment. Construction Excavation of banks for channel realignment and the lowering of raised spoil embankments  Historic Cultural heritage may have adverse effects on unknown items of historic significance. environment Engineering works may have long-term adverse effects on mill buildings which are of Operation  historical and cultural importance.

There is potential for restoration works to result in large volumes of soil being removed or imported to site. An attempt will be made to balance cut and fill wherever possible to reduce soil demand and wastage. Demand for soil will be met by using local sources Construction  where practicable. Surplus soil (e.g. through the creation of berms and channel re- Soils sectioning) will be disposed of on the landholding where practicable and, if not, off-site as a form of waste.

Operation No effects are anticipated for the operational phase. X

Construction X The recommended restoration works are not likely to give rise to either adverse or positive Soils & Geology Geology effects on existing drift geology or deep geology. Operation X

Historical contamination: Desktop investigations have not revealed any significant historical industrial land use along the river margins other than that associated with mills. However, various samples taken at mills along the Wensum have failed to meet the waste Construction  Ground acceptance criteria required for landfill due to contaminants that are not covered by the Soil contamination Guidance Values. Further checks prior to construction would need to be made on the contaminants not covered by the Soil Guidance Values. No effects are anticipated for the operational phase. Operation X

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In-channel works Floodplain works Other works

Individual Environmental Scoped Environmental Phase Aspect of Proposed Works Giving Rise to Potential Impact Group In? Features m r Be Glide Gravel Channel Re- sectioning Deflectors to Connect Channels Channel Realignment Sill Lower Mill Levels Lower Spoil Embankments Re-connect to Floodplain Drains New Backwaters / Tree Felling Thinning Targeted Maintenance Fencing Tree Planting There is potential for restoration works to require waste materials to be removed from site. A Site Waste Management Plan will be implemented as part of the Environment Agency’s Construction X best practice approach to waste management. This will be produced separately to the EIA Waste Waste and therefore this issue is scoped out of the EIA. No effects are anticipated for the operational phase. Operation X

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Table 8.3 - Issues scoped into the EIA process

Environmental Individual Justification Group Environmental Features Air and climate Climate change The carbon impact of restoration measures will be considered in the design process and the assessment of different options will be reported in the EIA if considered to be significant. A carbon calculator will be maintained throughout the development and implementation of restoration measures. Construction work has the potential to adversely affect Protected species protected species such as water vole, otter, bats and badger. Fisheries, The key impacts of restoration works on these species invertebrates and during construction and operation will need to be flora identified and assessed. Invasive species represent a threat to the structural Flora and fauna integrity of works, a risk to human health for both construction workers and the wider public, and also to Invasive and non- the natural environment by taking over habitats to the native species detriment of native plant and animal species. It can be very expensive to remove invasive species through removal and disposal of surrounding soil. Damage to trees may be caused by direct removal or Trees by changes in the soil character upon spoil removal or deposition. Physical changes from excavations on geomorphology Geomorphology need to be investigated in more detail at the next stage of the EIA. The impacts of local restoration schemes on flood risk Drainage and flood Water will need to be assessed, during both construction and risk environment once the project is operational. Construction in or near to water risks water quality being adversely affected by the mobilisation of silts or Water quality the accidental release of contaminants. The EIA will consider how these risks will be managed. There may be short term disruption to public and or private access during construction. The rehabilitation works may provide opportunities to improve river Humans angling. Whilst there are no statutory navigation rights on the fluvial River Wensum, where there is agreed access for canoeists, impacts and opportunities will be Human assessed. environment There may be temporary and permanent changes in land Land use use, including impacts on ESA agreements and other agri-environment schemes. It is expected that there will be a short-term increase in Traffic & transport traffic on the local road network during construction as a result of importing materials to site. Cultural heritage Historic The key construction and operational effects on cultural and archaeology environment heritage and archaeology need to be identified. The key construction and operational effects of the Landscape Local landscape restoration works on the landscape character and character and character visual amenity of the Wensum valley need to be visual amenity identified and assessed. The recommended restoration works are not likely to Soils & geology Soils give rise to either adverse or positive effects on existing soils. However, there may be issues relating to

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Environmental Individual Justification Group Environmental Features balancing quantities of supply (cut) and demand (fill) which have environmental implications. There are risks of encountering contaminated material Ground in all earthworks. This risk will need to be assessed contamination during the design phase.

Table 8.4 - Issues scoped out of the EIA process

Environmental Individual Justification Group Environmental Features There will be short-term, localised impacts on air quality during construction. These impacts are considered to be temporary and not significant enough to warrant further Air and climate Air quality investigation. Standard best practice approaches to be adopted during construction should be adequate to manage these impacts and therefore air quality will not be considered further in the EIA. Noise is expected to be created by construction works, Human but this will be minimised through mitigation and best Noise & vibration environment practice construction techniques. There will be no operational noise associated with the completed works. The restoration works are not likely to give rise to either Soils & geology Geology adverse or positive effects on existing drift geology or deep geology. It is unlikely that the proposed works will generate waste Waste n/a that will have to be managed through a waste exemption licence or be taken off-site.

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9. Consents

A number of consents and permissions are likely to be required in order to implement the recommended river restoration options and measures for Unit 54. These are listed in Table 9.1, together with the organisations that are responsible for granting them and a summary of the action needed as the EIA progresses. Table 9.1 - Likely planning consents and permissions

Likely Organisation Comment Consent

The Environment Agency has permitted development rights under the Land Drainage Act 1991 and Water Resources Act 1991 to carry out necessary restoration works within main rivers. The River Wensum is a main river so works within the channel Environment Agency do not require planning consent. The permissive rights extend to 9m either side of the main channel. Planning Local planning authorities will be consulted to permission determine if any aspects of proposed river restoration schemes require planning permission.

Planning permission will be obtained from the local authority if any works are not covered as ‘Permitted Local Planning Authority Development’ under Part 14, Schedule 2 of the Town & Country Planning (General Permitted Development) Order 1995.

The Environment Agency will screen individual Environmental restoration projects for their environmental risk. Impact In accordance with Works are not likely to require a full EIA Assessment Environment Agency EIA (Environmental Statement) but as best practice the (statutory / non policy. Environment Agency will carry out an appropriate statutory) level of environmental assessment.

If any of the works (particularly the mill works) involve alterations to listed buildings or structures, consultation with the relevant Conservation Officers Listed building from the local authorities will be required. A separate Local planning authority consent Listed Building Consent may be required from the local authority for works affecting listed buildings or structures. This should not affect permitted development rights.

Development and Flood Risk Team has been consulted and a Flood Defence Consent will be Flood Defence Environment Agency required. This may include the need for a formal Consent Flood Risk Assessment if planning permission is required.

Consent will be required from the Internal Drainage Norfolk Rivers Internal IDB Consent Board for any works to watercourses for which they Drainage Board have responsibility as the drainage authority.

Natural England will need to give their written assent Assent under for any works to be carried out within or affecting the Section 28 of River Wensum Site of Special Scientific Interest. The the Countryside Natural England proposals will be developed in partnership with and Rights of Natural England, and assent will be obtained prior to Way Act any works starting on the SSSI.

Consideration of An assessment will be required under Regulation 61 need for Natural England of the Conservation of Habitats and Species Habitats Regulations 2010 due to the designation of the River

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Likely Organisation Comment Consent Regulations Wensum as a Special Area of Conservation (SAC). It Assessment is anticipated at this stage that the works will be “directly connected with or necessary to the management of the site” and therefore a detailed assessment under the regulations (i.e. an appropriate assessment) will not be required This will be confirmed in writing with Natural England.

Natural England is actively working with the project team to assent the proposed works and ensure that the mitigation measures outlined below will not adversely affect protected species or their habitats. A consent letter from Natural England is needed before Protected any works can begin. species and Natural England Otters, water voles, bats and badgers are known to associated be present along the River Wensum. Since these are licences protected species, there will be a requirement to implement some mitigation measures as part of the proposed river restoration scheme. Consent from Natural England will be required to carry out mitigation activities if these require trapping or destructive search for water voles, for example.

Waste The requirement for a Waste Management Licence Management Environment Agency will be reviewed once detailed designs are available. Licence

Landowner Various landowners We need to continue liaison with landowners. consents

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10. Project Risks

A number of key project risks may delay the delivery of the recommended option for Unit 54 and these include: 1. Uncertainty of availability of funding to implement recommended option.

2. Timing and magnitude of water resources sustainability reductions (reductions in public water supply abstraction downstream of Taverham).

3. Protected species survey and mitigation.

4. Inappropriate maintenance both prior to and post restoration.

5. Obtaining landowner consents to undertake enhancement works on private land, as well as other permissions and consents (e.g. Flood Defence Consent).

6. Cost associated with the implementation of detailed designs especially in relation to mill structure alteration.

7. Changes in UK or European environmental legislation.

8. Extreme weather conditions and / or flooding.

9. Gate lowering trials conducted as Hellesdon (Atkins, 2011) have highlighted potential risks associated with reduced river levels impacting floodplain lake systems and water dependant SSSI land parcels.

10. Uncertainty over relationship between water level adjustment at Hellesdon, sustainability reductions, floodplain water levels and changes to backwater extent in Reaches 01 and 02 still exist. Further river flow and ground water level modelling may be required to determine risks specific risks and inform instream restoration measure design.

To manage these risks it is recommended that there is ongoing communication with key stakeholders including landowners, Anglian Water, local planning authorities, NCC, internal Environment Agency functions, the Norfolk Rivers IDB, Natural England and the local communities within Unit 54 (Table 10.1).

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Table 10.1 – Key project risks that may delay the delivery of the recommended options for Unit 54 Risk Proposed Mitigation Level of risk Availability of funding for Raise profile of project nationally and seek early High scheme. identification of external sources of funds. Uncertainty over timing and Maintain open dialogue between EA WR / EA FRM / magnitude of water NE / AWS. Monitoring of pilot restoration trials to High resource sustainability better establish results of larger restoration activity. reduction. Ongoing and open discussion with landowners and other stakeholders to inform them of the potential for Landowners not giving ecological improvements through enhancement permission for Medium works. Listen to landowners’ concerns and work enhancement works. collaboratively to identify alternative methods or materials for proposed works. The need to mitigate and Measures to prevent this will be undertaken in plan around protected accordance with the Environmental Good Practice Medium species. Site Guide and Planning Policy Statement 23. Work collaboratively with the Environment Agency Operations Delivery Team and the IDB to identify and Inappropriate maintenance agree an appropriate maintenance protocol within the Medium prior and post restoration. context of the Targeted Maintenance option. Ensure that no inappropriate maintenance or other work is undertaken by riparian landowners. Uncertainty over change in backwater length Undertake modelling and a trial to assess extent of Medium achievable through backwater reduction. operational changes. The cost of each restoration option will vary according to technical constraints such as access and scale of Uncertainty regarding costs. Low project. Cost will need to be revised during the detailed design stage. Lack of forward momentum Ongoing consultations and discussions with the local to keep the scheme residents and key stakeholders. Provide regular Low progressing to achieve updates in the form of a newsletter. benefits in the river. Change in UK or European Keep abreast of proposed changes in legislation so environmental legislation any changes in detailed design can be informed at an Low (e.g. fisheries legislation). early stage. Monitor weather conditions and ensure new and part built features are secured at the end of each working Extreme weather conditions day to prevent them being damaged by extreme Low and / or flooding. weather or flood events. Allow contingency to cover the eventuality of adverse weather.

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11. Conclusions and Recommendations 11.1 Conclusions This report identifies river restoration options and measures that could be implemented to restore Unit 54 (Taverham Mill to Hellesdon Mill) of the River Wensum Site of Special Scientific Interest (SSSI) to ‘unfavourable recovering’ or ‘favourable’ ecological condition. If river alterations are not delivered there remains a risk that the Government Public Service Agreement (PSA) target for SSSI condition will not be met and the condition of the river will not be improved. The physical modifications that have been identified, if implemented, will also help to return the river to Good Ecological Potential under the Water Framework Directive. Consideration has been given to terrestrial SSSI units on the functional floodplain where there is the prospect of improving any hydrological linkage with the river. Multi-Criteria Analysis A MCA was applied across a range of potential restoration options. This allowed options to be assessed individually and against each other in terms of technical, economic and environmental constraints or opportunities. The MCA is a powerful tool for appraising all options and associated measures in a consistent, replicable and transparent way. It can be used to identify those options that will move the SSSI unit towards ‘unfavourable recovering’ or ‘favourable’ ecological condition and those that do not. It also provides an indication of the relative importance of the options and their measures in improving ecological condition for a particular reach. How those options and measures are applied to a reach is a case of professional judgement. The results of the MCA show that the recommended option for Unit 54 is a combination of minor in-channel restoration measures including berm, deflector and gravel glide installation, combined with backwater reconnection and changing the operational procedure around existing mill infrastructure to reduce backwater effects. Costs The estimated cost of the recommended option for the unit is £324,000 (to the nearest thousand) which is less than previous estimates. This is partly a reflection of the restoration design philosophy used which is to provide features that the river cannot restore itself (i.e. back channels, and gravel glides) and to provide features that will ‘kick start’ a wider recovery process (i.e. deflectors, berms in key locations, channel re-sectioning and realignment). It is also a reflection of a detailed cost estimate exercise based on a more in-depth understanding of the restoration requirements for this unit. Environmental issues This feasibility report has also provided baseline data for a range of environmental criteria. This, and the information contained within Chapters 4 to 8, has allowed environmental issues to be scoped in or out of the environmental assessment that will be required to accompany the detailed design of restoration schemes. Consultation Ongoing consultation with landowners and local interest group is strongly recommended given the sensitivity of the issues relating to water resources sustainability reductions in this unit. Both the amount of surface water abstraction and the extent of river restoration will impact on preferred water levels through the unit. Any changes in the existing regime will need to be carefully explained and managed.

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11.2 Recommendations To keep up the momentum for this project, there are a number of recommendations as follows: 1. To improve the likelihood of delivery of restoration schemes it is important that the project team continues to consult on a regular basis with key stakeholders, including, but not limited to:

 Anglian Water Services  Landowners  District and County Council planning authorities to determine the level of EIA required and any supporting planning consents  Internal Environment Agency functions  Natural England  Norfolk Rivers Internal Drainage Board.

2. ‘Targeted maintenance’ should be implemented as soon as possible to demonstrate a commitment to continued management of the river where this can be justified. This will also drive further action to implement the remaining recommended restoration options.

The environmental issues that have been scoped into the next stage of environmental assessment should be considered as part of a best practice Environmental Report.

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12. References

1. @One Alliance (2007) River Wensum Aquatic Macrophyte Survey: AMP4 Water Resources Environment Programme: Habitats Directive Review of Consents. 2. APEM (2009) An Investigation into the Spawning and Recruitment Success of Barbel in the River Wensum. Scientific Report EA 4010776. 3. Atkins (2010a) River Wensum Restoration Strategy, Mill Operating Protocol. Draft report to Eastern Area, Anglian Region, Environment Agency. 4. Atkins (2010b) River Wensum Restoration Strategy. Implementation River Unit 53 Lenwade to Taverham Mill. Feasibility & Environmental Scoping Assessment. January 2010. Report to Eastern Area, Anglian Region, Environment Agency. 5. Atkins (2011). River Wensum Restoration Strategy, Hellesdon Sluice Lowering Trial. Technical report for the Environment Agency 6. Babtie Brown & Root (2003) Upper River Wensum Strategy Study: Strategy Study Report. Report to Eastern Area, Anglian Region, Environment Agency. 7. Broadland Landscape Character Assessment (1999) Chris Blandford Associates for Broadland District Council. 11107301R Final Report_EC_02-05-08. [Online document: http://www.broadland.gov.uk/housing_and_planning/618.asp - last accessed 26th April 2011] 8. Broadland District Council (May 2006) Broadland District Local Plan (Replacement) – to update following Joint Core Strategy Adoption (March 2011) [Online document: http://www.broadland.gov.uk/housing_and_planning/561.asp - last accessed 26th April 2011] 9. Centre for Aquatic Plant Management (CAPM) (2002) Macrophyte Survey on the River Wensum. 10. Econ (1999) River rehabilitation feasibility study of the River Wensum (Norfolk)-Phase 2. Report to Eastern Area, Anglian Region, Environment Agency, Norwich, UK, 153pp. Perrow, M.R. & Newson, M.D. 11. English Nature (1993) Notification of SSSI Status: River Wensum, Norfolk. 12. Entec (2010) Habitats Directive Review of Consents - Stage 4 Options Appraisal: River Wensum SAC. Report for the Environment Agency. 13. Environment Agency (1995) River Corridor Survey of the River Wensum (Anglian Region, Eastern Area). 14. Environment Agency (1999) River Wensum Water Level Management Plan. Environment Agency (Anglian Region, Eastern Area). 15. Environment Agency / Natural England (2004) The state of England’s chalk rivers: Summary report by the UK Biodiversity Action Plan Steering Group for Chalk River. [Online: http://www.freshwaterlife.org/servlet/BinaryDownloaderServlet?filename=1152695564918_chalk_ riv_summary_834762_1_.pdf. Accessed November 2009. 16. Environment Agency (2005) Crayfish Distribution in the River Wensum – Results & Observations from the 2003 Ecological Appraisal Fisheries Sampling Programme. EA, Anglian Region, Eastern Area. 17. Environment Agency (2007a) The River Wensum Water Level Management Plan. Report produced by Entec UK Ltd. 18. Environment Agency (2007b) Factors affecting roach Rutilus rutilus (L.) recruitment and survival in the River Wensum, Norfolk. EA, Anglian Region, Eastern Area. 19. Environment Agency (2007c) Assessing the natural recruitment and sustainability of barbel Barbus barbus (L.) populations in the River Wensum, Norfolk. EA, Anglian Region, Eastern Area. 20. Environment Agency (2009a) Position statement on hydropower. [Online: http://www.environment- agency.gov.uk/static/documents/Research/Hydropower_position_statement_FINAL_English.pdf. Accessed August 2009].

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21. Environment Agency (2009b) Good practice guidelines annex to the Environment Agency hydropower handbook: The environmental assessment of proposed low-head hydro power developments. [Online: http://www.environment- agency.gov.uk/static/documents/Business/Low_Head_Hydropower_August_2009.pdf. Accessed August 2009]. 22. Environment Agency (2009c) Water Resources GIS. October 2009 version. 23. Environment Agency (2010a) River Wensum SAC – Site Action Plan. 24. Environment Agency (2010b). What’s in your backyard. [Online: http://www.environment- agency.gov.uk/homeandleisure/37811.aspx. Accessed August 2010]. 25. Environment Agency (2011) Web-based Flood Mapping: http://maps.environment- agency.gov.uk/wiyby/wiybyController?x=531500.0&y=181500.0&topic=floodmap&ep=map&scale =3&location=London,%20City%20of%20London&lang=_e&layerGroups=default&textonly=off 26. European Commission (2001) Guidance on EIA Scoping. Environmental Resources Management. 27. Gillian, S; Boyd, K; Hoistma, T and Kauffman, M (2005) Challenges in developing and implementing ecological standards for geomorphic river restoration projects: a practitioner’s response to Palmer et al. Journal of Applied Ecology. 28. Halcrow (2008) Estimating costs of delivering the river restoration element of the SSSI PSA target. Final report prepared for the Environment Agency. 29. Heritage Gateway Website: http://www.heritagegateway.org.uk/gateway/advanced_search.aspx. 30. IEMA (2004) Guidelines for Environmental Impact Assessment. 31. JBA Consulting (November 2007) River Wensum Restoration Strategy, Supporting Technical Report for Natural England. 32. JNCC (2002) Standard Data Form DoE SPA, SCI and SAC: River Wensum. Version 2.1, Natura 2000 Data Form. 33. JNCC (2007) Second Report by the UK under Article 17 on the implementation of the Habitats Directive from January 2001 to December 2006. Peterborough: JNCC. Available from: www.jncc.gov.uk/article17. 34. Mant, J. & Fellick, A. (2007) The River Wensum, Norfolk: An assessment of the current approaches to river restoration along the River Wensum and their potential to support chalk stream habitat requirements. A report to Natural England (prepared by the River Restoration Centre, Bedfordshire). 35. Multi-Agency Geographic Information for the Countryside (MAGIC) Website address: http://www.magic.gov.uk/. 36. National Biodiversity Network Gateway Website: http://www.nbn.org.uk/ 37. Natural England (2007) Conservation Objectives and definitions of favourable condition for designated features of interest: River Wensum SSSI. Consultation Draft, Norfolk and Suffolk Team. 38. Natural England (2010) SSSI Condition Assessment – River Wensum SSSI [Online: http://www.sssi.naturalengland.org.uk/Special/sssi/reportAction.cfm?report=sdrt13&category=S&r eference=1006328 Accessed September 2010). 39. Norfolk Rivers Internal Drainage Board (2007) Standard Maintenance Operations for rivers. 40. Sear, D.A., Newson, M., Old, J & Hill, C. (2006) Geomorphological Appraisal of the River Wensum Special Area of Conservation. English Nature Research Reports, No 685, by GeoData, University of Southampton. 41. South Norfolk Landscape Character Assessment (June 2001) South Norfolk Council. [Online documents: http://www.south-norfolk.gov.uk/planning/3143.asp - last accessed 26th April 2011] 42. Stansfield, J., Adams, C., Whiting, C., Markwell, H. & Brown, R. (2001) River Wensum Invertebrate survey and ecological assessment 2001. Environment Agency, Fisheries, Recreation & Biodiversity: Ecological Appraisal Team, Ipswich.

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43. Wensum Valley Project (1994) Wensum Valley Strategy, Norfolk. Produced by the Joint Advisory Panel of the Wensum Valley Project. 44. Wild Frontier Ecology Limited (2007) Water Vole Monitoring Report – River Wensum and Tributaries. River Wensum Mink Control Project. Report produced by John Harris for Norfolk County Council.

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Appendices

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Appendix A - Multi-Criteria Analysis technical note

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A.1 MCA Criteria & Options / Measures Feedback from the MCA workshop with the Environment Agency and Natural England confirms the need for greater clarification of the MCA process and in particular how the criteria and options/measures are defined. This technical note is to address those queries. Within the criteria definitions, explanation is given of the 5 point scoring to which the weightings are applied. Typical scoring considerations for each criterion have been given to provide greater consistency of scoring. A.1.1 Criteria and criteria group definitions The criteria are divided into 3 major groups:  Ecology  Project Delivery  Technical. The ecology is the main driver for the project and so has to have the highest weighting, which is 1. The project objectives do not stand alone. Not only does the project have to succeed, but it must also be seen and felt to succeed. Therefore the aspirations of the stakeholders in the project also have to be recognized. This is nearly as important so the weighting for this is 0.9. To make a difference to the ecology the RWRS has to be implemented. An assessment of the choices implementation generates needs to be made. We have called this group technical criteria. There has to be a consideration of the practical delivery of the project in the real world as it is generally true that technical complexity generates cost, and impacts on quality and time. The weighting needs to be reasonably high, but not as high as the previous items, so 0.8 is used. Each of the three criteria groups is made up of a number of related criteria, which in turn have relative importance and hence need different weightings. These are explained by group. A.1.2 Ecology The primary objective of the project is to improve the ecology of the River Wensum. This falls into two parts: legally protected ecology and the rest. So, as a crude split the ecology needs to be divided into at least 2 sub groups. However, the legal protection is variable and progressive, with some species and habitats afforded greater protection than others. To demonstrate compliance with the law the criteria analysis needs to reflect the progressive nature of the legal protection. We have therefore divided the legally protected ecology into 3 sections to reflect the levels of importance:  International: SAC  National: SSSI  Regional: BAP. To this we add the non-protected ecology. This has to be included so as to satisfy the Environment Agency’s broader legal duty to consider and further conservation. This gives a fourth sub-group as follows:  Local: Contribution to overall ecology. In terms of RWRS these 4 items are not equal. The definitions and weightings are explored below.

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A.1.3 Compliance with National Designation: SSSI The primary drivers for the RWRS are the Defra PSA target based on SSSI condition (95% of SSSIs by area to be in favourable or unfavourable recovering condition by December 2010) and the requirement for the river to achieve ‘Good Ecological Potential’ under the Water Framework Directive. The SSSI covers the following: Table A.1 - SSSI designation targets

Statutory / Non Statutory Conservation Targets Drivers SSSI designation  Flow: Flow regime should be characteristic of the river. Levels of abstraction should not exceed the generic thresholds laid down for moderately sensitive SSSI rivers by national guidance.  Water quality: Biological GQA Class B; Chemical GQA Class B; No unnaturally high loads of suspended solids.  Phosphate: An annual average phosphate concentration of 0.05mg/l from the upstream limits of the SSSI to the confluence of the River Wensum with the White Water (the tributary that drains from East ), and 0.1mg/l from that confluence to the downstream limit of the SSSI.  Siltation: No excessive siltation. Channels should contain characteristic levels of fine sediment for the river type.  Channel form: should be generally characteristic of river type, with predominantly unmodified planform and profile. Bank and riparian zone vegetation structure should be near-natural.

So from a project perspective the national protection has to have the highest weighting. Thus, it is allocated the highest weighting which is 1. With regard to scoring the following applies (Table A.2): Table A.2 - SSSI scoring

Compliance with National Designation: SSSI Score Description Typical Effect +2 High relevance Direct immediate improvement in designated item. +1 Low relevance Moving towards favourable condition. 0 Neutral No change. -1 Low Detriment Moving away from favourable condition. -2 High Detriment Permanent adverse changes.

A.1.4 Compliance with International Designation (SAC): The SAC covers the following:

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Table A.3 – SAC designation targets (Natural England, 2007)

Statutory / Non Statutory Conservation Targets Drivers SAC Designation The conservation objectives for the European interest features on the SSSI are:

to maintain*, in favourable condition, the:

 Watercourses of plain to montane levels with the Ranunculion fluitantis and Callitricho-Batrachion vegetation

to maintain*, in favourable condition, the habitats for the population of:

 Bullhead (Cottus gobio)  Brook lamprey (Lampetra planeri)  White-clawed crayfish (Austropotamobius pallipes)  Desmoulin’s whorl snail (Vertigo moulinsiana)

*maintenance implies restoration, if the feature is not in favourable condition.

PDFs of English Nature publications on the ecology and monitoring of the five European features can be downloaded from the publications catalogue on the Natural England website (www.naturalengland.org.uk).

The international protection must also rank highly, but from a project perspective, not as highly as the national importance; a weighting of 0.8 was used. With regard to scoring, Table A.4 outlines how SAC targets have been scored. Table A.4 –SAC scoring

Compliance with International Designation (SAC) Score Description Typical Effect +2 High relevance Direct immediate improvement in designated item. +1 Low relevance Moving towards favourable condition. 0 Neutral No change. -1 Low Detriment Moving away from favourable condition. -2 High Detriment Permanent adverse changes.

A.1.5 Compliance with Regional Designation (BAP): The biodiversity action plan most relevant to the River Wensum is the chalk rivers action plan. There are a number of additional species and habitat action plans that may be affected by river restoration on the Wensum. These are summarised in Table A.5. This criterion is also intended to cover protected species issues (e.g. those covered by the Wildlife and Countryside Act).

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Table A.5 – Biodiversity Action Plan targets

Statutory / Non Statutory Conservation Targets Drivers UK Biodiversity Action Plan The objectives of the UK National Chalk Rivers Habitat Action Plan are:

 Maintain the characteristic plants and animals of chalk rivers, including their winterbourne stretches.  Restore all rivers notified as SSSI to favourable condition.  Restore important non-SSSI rivers to favourable condition.

There are a large number of other national/Norfolk Habitat and Species Action Plans relevant to the Wensum, including floodplain and coastal grazing marsh, reed-bed, fen, otter, water vole, Desmoulin’s whorl snail, white-clawed crayfish and bat species. All these SAP/HAPs have targets and objectives (www.norfolkbiodiversity.org)

Bearing in mind that both the national and international importance will provide a good level of protection for BAP species and habitats, from a project perspective, this was not felt to be as important to the project, but still needed to be included, so the weight is correspondingly lower. The value of 0.6 was used. Table A.6 lists how UK BAP targets were scored. Table A.6 – UK Biodiversity Action Plan scoring

Compliance with Regional Designation (BAP) Score Description Typical Effect +2 High relevance Direct immediate improvement in designated item. +1 Low relevance Moving towards favourable condition. 0 Neutral No change. -1 Low Detriment Moving away from favourable condition. -2 High Detriment Permanent adverse changes.

A.1.6 Contribution to overall ecology: The non-protected ecology needs to be included to address the Agency’s duty to further conservation. Table A.7 lists those issues/drivers that have been identified as being important to improving overall ecology in the Wensum.

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Table A.7 – Issues identified in this study as being important drivers for restoration

Statutory / Non Statutory Conservation Targets Drivers North Norfolk Natural  Identify and promote flows necessary to sustain Area Profile geomorphological and ecological interest of the system.

 Identify, maintain, enhance, and restore both natural and man- made riverine features which provide ecological and conservation interest.  Ensure protection, enhancement and restoration of habitat features during the design and implementation of flood defence schemes.  Restore arable land adjacent to rivers back to pasture to reduce silt loading and improve habitats.  Manage associated dyke systems on a regular but not intensive regime. Environment Agency  To sustain and where appropriate enhance or restore the habitat diversity within the water environment.  To provide an environmental assessment and recommendations to ensure the maintenance and enhancement of conservation interest to flood defence.  Develop Water Level Management Plans to protect the ecology of sensitive wetlands.  Fisheries Action Plan for the Wensum. European Water  Take appropriate measures to ensure water bodies attain Framework Directive Good Ecological Status/Potential by 2027.

 Establish a Programme of Measures to ensure water bodies attain Good Ecological Status/Potential. European Habitats  Monitor, assess and enhance favourable condition of SAC Directive rivers.

 Review of consents under Regulation 50 of the Habitats Regulations is another major driver for the Environment Agency and other competent authorities.

UK Gov Public Service  95% of SSSIs by area in favourable or unfavourable Agreement (PSA) recovering condition by December 2010. Targets

Planning Policy  PPS9 sets out the Government’s national policies on Statement 9: protection of biodiversity and geological conservation through Biodiversity and the planning system. Geological Conservation  Plan policies on the form and location of development should take a strategic approach to the conservation, enhancement and restoration of biodiversity and geology. Environmental Higher Level Stewardship applications for environmentally Stewardship Targeting - sensitive farming practice: Mid Norfolk  Maintain or enhance Sites of Special Scientific Interest (SSSIs).  Improvement of water quality through reduction of soil erosion (priority: River Wensum catchment) and leaching of nutrients. Unit 54 Taverham Mill to Hellesdon Mill_final for issue_V1.0.docx 150

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Statutory / Non Statutory Conservation Targets Drivers  Conservation of landscape and wildlife associated with arable farming; in particular maintaining locally distinctive landscapes and reversing the decline in farmland birds.  Protection of historic and archaeological sites.  Access – provide further recreational facilities, to promote greater appreciation of the countryside.  Maintenance and restoration of BAP priority habitats.  Conservation of BAP priority and locally important species.

However, again from a project perspective this is not as important so is weighted lower at 0.5. Scoring of this criterion is shown in Table A.8. Table A.8 – Contribution to overall ecology scoring

Contribution to Overall Ecology Score Description Typical Effect +2 High relevance Direct immediate improvement in designated item. +1 Low relevance Moving towards favourable condition. 0 Neutral No change. -1 Low Detriment Moving away from favourable condition. -2 High Detriment Permanent adverse changes.

A.1.7 Project delivery To deliver the project the RWRS objectives need to be met, and the stakeholders they impact on need to support and promote those objectives. Thus, the criteria within this group can be subdivided into:  RWRS objectives,  Stakeholders The stakeholders for this project naturally fall into 2 groups:  Statutory stakeholders, and  Non-statutory stakeholders. The definition of statutory stakeholders is straight forward: it is those statutory bodies that are either funding the works or have a legal right to control the outcomes (for example: Environment Agency). Non-statutory stakeholders are those outside of the government bodies who have a legal right to comment and so influence the outcomes (for example: landowners). The outcomes of the RWRS do not stand in isolation because besides impacting on the people in the valley they impact on the wider environment and its use. This is the non ecological environment of the valley which is predominantly of interest to people, so we have termed it:  Human Environment. This gives 4 sub-criteria, and again, in terms of the RWRS these are not equal. The definitions and weightings are explored below.

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A.1.8 Compliance with strategy objectives This whole project is about delivering the objectives of the RWRS. This comprises of 2 parts:  The general objectives of the project, as covered in the RWRS Recommendations.  The specific restoration measures for individual reaches as covered in RWRS Appendix A. Clearly this is the most important criterion and so has to have the maximum weighting of 1. Scoring of this criterion is shown in Table A.9. Table A.9 – Compliance with strategy objective scoring

Contribution to Overall Ecology Score Description Typical Effect Immediate and/or full delivery of easily identified +2 High relevance RWRS objective. Enabling or partial delivery of identifiable RWRS +1 Low relevance objective. 0 Neutral No change. Temporary or low level interference with RWRS -1 Low Detriment objective. Immediate and/or full interference of easily identified -2 High Detriment RWRS objective.

A.1.9 Compliance with statutory stakeholders This covers the views of those statutory bodies that have a legal and/or financial stake in the success of the project. In probable order of priority, this includes:  Environment Agency  Natural England  Norfolk Rivers IDB  Local authority  Norfolk CC  English Heritage. For the project to be supported to fruition, with the objectives carried forward into the future, the statutory stakeholders will have to feel that the project is a success. This will have to consider views from the wider organisation where there is consultation. Without the support of the statutory bodies the full delivery of RWRS reach objectives will be difficult. This is nearly as important as compliance with the RWRS itself, and so has a weighting of 0.9. Scoring of this criterion is shown in Table A.10.

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Table A.10 – Stakeholder scoring

Compliance with Statutory Stakeholders Score Description Typical Effect +2 High relevance Large majority with favourable view. +1 Low relevance Small majority with favourable view. 0 Neutral No issues. -1 Low Detriment Small majority with concerns. -2 High Detriment Large majority with concerns.

A.1.10 Agreement with non-statutory stakeholders Non-statutory stakeholders are those outside of the government bodies who have a legal right to comment and so influence the outcomes. This covers, in probable order of importance:  Landowners  Agricultural tenants  Fishery tenants  Householders  Commercial interests. Although the statutory bodies have the ability to impose some aspects of the strategy on the valley, without support of those who own or occupy the land and river the process of implementation would be:  Slow and expensive, due to legal process.  Lacking in richness due to lack of local knowledge informing designs.  Viewed as a failure and so lack long term viability.  Impact on long term relationships with the statutory bodies in everything they do.

This is of importance to the project delivery and so is weighted at 0.9. Scoring of this criterion is shown in Table A.11. Table A.11 – Non-statutory stakeholder scoring

Compliance with Non-statutory Stakeholders Score Description Typical Effect +2 High relevance Large majority with favourable view. +1 Low relevance Small majority with favourable view. 0 Neutral No issues. -1 Low Detriment Small majority with concerns. -2 High Detriment Large majority with concerns.

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A.1.11 Contribution to human environment This covers both non-river statutory designations such as:  Archaeology  Town & Country Planning as well as human usage of the river and valley such as:  Angling  Canoeing  Walking & footpaths  Landscape and wider amenity. Although this is the non ecological environment of the valley, it is predominantly of interest to people, so it must be included in the criteria. It is important, but not central to the delivery of the project and so has been given a weighting of 0.4. Scoring of this criterion is shown in Table A.12. Table A.12 – Human environment scoring

Human Environment Score Description Typical Effect +2 High relevance Widespread support. +1 Low relevance Some support. 0 Neutral Indifferent. Some general concern or local concern about small -1 Low Detriment issue. Wide scale concern or strong concern over specific -2 High Detriment local issue.

A.1.12 Technical This criteria group concentrates on the delivery of the RWRS objectives. It is broken down into 4 sub-criteria areas:  Technical feasibility & practicality  Geomorphic form & function  Flood risk  Climate change & sustainability. Each of these deals with particular risks that will vary by reach and by the selected restoration solutions applied at particular locations.

A.1.13 Technical feasibility & practicality This item covers:  Feasibility assessment  Engineering design  Construction process  Commercial risk

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 Maintenance liabilities.

This is the most important aspect regarding the management of risk in the project, and so is an important technical factor within the technical criteria group. A weighting of 1 has been used. Scoring of this criterion applies and is shown in Table A.13. Table A.13 – Technical scoring

Technical Feasibility & Practicality Score Description Typical Effect +2 High relevance Large benefit with little risk. +1 Low relevance Small overall benefit or lack of difficulty 0 Neutral Average. -1 Low Detriment Some difficulty. -2 High Detriment Little benefit with large risk.

A.1.14 Geomorphic form & function The shape of the river and the flow processes are important for 2 reasons:  The environmental designations specifically mention them, and  it is necessary to understand the processes and the resulting river shape to be able to design any of the restoration options/measures to produce predictable results that sustain into the future. This is therefore important regarding the management of risk in the project, and so has to be an important technical factor within the technical criteria group. A weighting of 1 has been used. Scoring of this criterion is shown in Table A.14. Table A.14 – Geomorphic scoring

Geomorphic Form & Function Score Description Typical Effect Immediately delivers full form and/or mature +2 High relevance processes. +1 Low relevance Kick starts process or provides some form. 0 Neutral No change. Reinforces existing lack of processing at a local -1 Low Detriment scale. Reinforces existing lack of processing or creates -2 High Detriment inappropriate processing anywhere.

A.1.15 Flood risk Flood risk management is one of the Environment Agency’s primary responsibilities, therefore project outcomes cannot increase flood risk to people or properties. This is particularly important on the Wensum as there are 44 properties at risk of flooding, and there are routine maintenance activities to control existing flood risk.

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Any proposals that impact on water level or flow on statutory Main River require Flood Defence Consent from the Environment Agency, the primary objective of which is to demonstrate no detrimental effects on flood risk. This is a significant factor within the technical criteria group and so has a weighting of 1. Scoring of this criterion is shown in Table A.15. Table A.15 - Flood risk scoring

Flood Risk Score Description Typical Effect +2 High relevance Good risk reduction locally and/or elsewhere. +1 Low relevance Some reduction in flood risk anywhere. 0 Neutral No change. -1 Low Detriment Some increase in flood risk anywhere. -2 High Detriment Significant increase in local flood risk.

A.1.16 Climate change & sustainability This has been included to ensure that project proposals remain fit for purpose into the future. Current UK guidance on the impacts of climate change on fluvial flooding from the government’s Foresight Report, which has fed into Planning Policy Supplement Note 25 (PPS 25), recommends that an allowance of an extra peak flow of 20% is made, which covers the impact on flood risk change to 2050. Project proposals are viewed against their ability to withstand increased flows without detriment to themselves, the habitat created by them, or flood risk. Clearly a lack of robustness is not very sustainable in its own right. However, given wider concerns, a view on the carbon footprint of proposals is also appropriate. Whilst it is a useful criterion it is not the most important, so a weighting of 0.8 is used. Scoring of this criterion is shown in Table A.16. Table A.16 – Climate change scoring

Climate Change & Sustainability Score Description Typical Effect +2 High relevance Is stable in the short and long term. Is stable in the short term or provides a pre-cursor to +1 Low relevance later works. 0 Neutral No change. -1 Low Detriment Is unstable in the short term or prevents later works. -2 High Detriment Is unstable in the short and long term.

A.1.17 MCA options 6 major option groups have been identified:  Do nothing  Do minimum  Targeted maintenance  Continue as present Unit 54 Taverham Mill to Hellesdon Mill_final for issue_V1.0.docx 156

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 River restoration  Alternative options. These are in rough order of increasing intervention with the natural processes. They are briefly described below:

A.1.18 Do nothing As the objective of the strategy is to improve the ecology of the river, which is predicated on the return of natural form and process, this option means:  No maintenance to main river or IDB channels  No restoration to any channels or floodplain  No operational activity A.1.19 Do minimum This is from the view of the RWRS and so means:  Opportunistic restoration, eg. o Securing fallen trees as LWD, o Re-shaping shoals where growth occurs after floods o Re-shaping bank profiles to create berms when bank collapse occurs  No maintenance  No operational activity A.1.20 Targeted maintenance This covers:  Reduced maintenance: reactive in selected critical areas.  Mitigation for activity in form of small scale restoration.  Operational activity; sluice management for high flows. A.1.21 Continue as present This covers existing arrangements:  Planned maintenance: assessed LWD & CWD removal; selected weed cutting and silt removal.  Opportunistic small scale restoration.  Operational activity: sluice management for high flows. A.1.22 River restoration This covers 20 different restoration measures that have been identified for the river. Each of these is assessed for its use on the particular reach being scored. A.1.23 Alternative options There are 3 options that have been considered:  Increased main river maintenance. This includes: - Increased in-channel clearance of silt.

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- Increased frequency of weed cutting. - Return of channel to “design” dimensions. - Maintained timber clearance. - Bank repairs.  Increased main river and IDB channels maintenance. This includes: - As above, plus, - Integrated programme for main river and IDB channels. - Inclusion of IDB channel main river confluences for regular maintenance.  Mills re-use for hydro-power. This includes: - Overall generation of energy through harnessing the kinetic energy of water. - Operational reinstatement of all water level control structures. - Operating protocols for all structures. - Regular channel maintenance around control structures. These options were derived from comments picked up at the ‘drop in’ sessions and represent broad aspirations.

A.2 Use of MCA Scorings The use of MCA and the resultant reach scores represents a key part of the design process. The overall process is shown in Table A.17 as follows: Table - A.17 - SSSI Designation targets

A Constructing the MCA Tool 1 Identification of options/measures. 2 Selection of success criteria. 3 Ranking of success criteria using weightings. 4 Setting up the MCA table. B Applying the MCA Tool (Spreadsheet) to Specific Reaches 1 Is the option/measure applicable to the reach? If no, discard. 2 Work through each criterion by option/measure. 3 Apply weighting and determine total weighted score (TWS) 4 Discard all options/measures with zero or negative scores. 5 Mill structure measures: Apply the best scoring measure. Other measures: Undertake statistical analysis and discard measures scoring 6 below lower limit. Other measures: Apply remaining measures in order of highest to lowest 7 scoring. 8 Gravel works: Apply best scoring measure.

A.2.1 Note on statistical approach The options need to be checked for importance to see which ones are truly important and which ones are not. This has been determined by calculating which options have a TWS outside of one standard deviation either side of the mean. This was chosen as it is a standard measure of dispersion. Those with a value greater than the sum of the mean plus the standard deviation are

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of high importance: those with a value less than the sum of the mean minus the standard deviation are of low importance. Those of low importance represent those options that could easily turn negative were only a few criteria to get more harshly re-appraised: those of high importance are those that are very robust, and so represent the minimum options that should be carried out on any reach.

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Appendix B - Costings

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B.1 COST DETAILS To generate the cost estimate for Unit 54, a certain number of assumptions have been made:  General assumptions that apply to all measures.  Specific assumptions that apply to particular measures. B.1.1 General assumptions The following costs have not been taken into account: 1. Significant works to address site access issues (haul roads, tracks etc). 2. Works relating to unforeseen ground conditions and ground investigation costs. 3. Allowances for landowner compensation or accommodation works. 4. Phase I habitat surveys and ecological mitigation works. 5. Utility searches. 6. Contractors general Items/Insurances. 7. Detailed design. 8. Permissions, consents and consultation related costs. 9. Project specific risks. 10. Costs have not been inflated using latest price indices but are believed to be representative of current market conditions. The cost estimates has been derived using assumptions appropriate for the level of detail necessary for concept design. These estimates allow comparison of costs between other conceptual designs undertaken for individual river units.

B.1.2 Specific Assumptions Fencing Fencing costs are summarised in Table B.1 below. The following assumptions apply: 1. The fencing used is assumed to be simple livestock fencing: - 100mm diameter tanalized timber posts driven at 3m centres, - 3 barbed wires at 1.2m, 0.8m and 0.4m. 2. Fencing lengths vary depending on the reach. Fencing is installed where necessary to protect the river edge from poaching that could be caused by grazing. This is to satisfy landowner requirements and bank protection needs.

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Table B.1 - Total estimated costs for fencing in Unit 54

Reach Reach Length (m) Assumed Fencing Length (m) 01 1645 1645 02 3160 3160 03 3910 3910 Total Length: 8715 Rate for supply and installation £/m 8 Total for unit: £69,720

Berm creation Berm costs are summarised in Table B.2 below. The following assumptions apply: 1. Low level berms will be constructed below 1/2 bank height, on the inside of existing bends, to increase sinuosity of the channel. 2. A total of 35 berms are recommended each of which are assumed to be two times the erodible bank width in length. 3. Construction activities consist of removing vegetation for re-use; staking the new alignment with hardwood posts at 0.75 m centres; placing double height coir rolls against the stakes; backfilling with local material to blend height to local berm heights; replace vegetation. 4. The bioengineering revetment is to be cut back into the existing bank material to stop outflanking.

Table B.2 Total estimated costs for berm creation for Unit 54

Reach No. Berms Erodible Width Berm Length (m) Total Length (m) (m) 01 11 16.95 33.9 373 02a 1 16.1 32.2 32 02b 9 16.1 32.2 290 03a 4 15.45 30.9 124 03b 10 15.45 30.9 309 Unit total (m) 824 Rate (£/m) 90 Total for unit: £101,520

Tree felling Tree felling costs are summarised in Table B.3 below. The following assumptions apply: 1. Qualified arborists can typically trim, control and fell 4 riverside trees (approximately 50 years old) over 50 m of river, in a day. 2. Tree felling is required along the banks of 530 m (rounded to the nearest ten) of river. 3. Cost per day for a team of two qualified arborists to trim, control fell is assumed to be £500. This assumes 4 trees (approximately 50 years old) over a distance of 50m can be felled in one day. Costs include cording the wood for log piles, or trimming and cutting trunks for re-use. Costs do not include any transport or movement of timber once felled. Tree felling costs are taken as £10/m of river.

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Table B.3 - Total estimated costs associated with tree felling for Unit 54

Reach Length (m) 01 260 02a 50 02b 270 03a 0 03b 0 Length in unit: 580 Rate (£/m) 10 Total for unit: £5,800

Backchannel reconnection Backchannel reconnections and new backwaters have been costed the same. The costs are summarised in Table B.4 below. The following assumptions apply: 1. Backchannel reconnection assumes simple excavation to connect existing channels with the river excavating a total of 2741m with no bank or bed protection. 2. The target depth has been assumed to be half of resistant bank depth. 3. Backchannel reconnection works would also need to include appropriate works to re-form the backchannel to enhance stability and habitat delivery. Typically this could consist of re-sectioning and removing encroaching silt and vegetation within the channel. 4. Reconnection at the downstream end will be excavation down to river bed level; reconnection at the upstream end will be by excavation down to the backchannel bed level, post any clearance / re-forming works. 5. Bank protection works beyond re-placing vegetation turfs are not taken into account in the rates. Any further works will be dependent on local conditions found during detailed design investigations.

Table B.4 - Total estimated costs associated with backchannel reconnection for Unit 54

Reach Exc. Length River Depth Nom. Section Volume Cost 2 (m) (m) (m ) (m3) (£)

01 1290 0.845 1.4 1806 25,609 02a 125 0.83 1.4 175 2,482 02b 1200 0.83 1.4 1680 23,822 03a 89 0.79 1.4 124.6 1,767 03b 37 0.79 1.4 51.8 735 Unit rate of excavation (£/m3) 9.83 Dispose of spoil 100m from excavation (£/m3) 4.35 Total for unit: £54,415

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Gravel glides Gravel glide costs are summarised in Table B.5 below. The following assumptions apply: 1. Cost is directly dependant on volume placed. 2. Gravel glides dimensions vary according to location as indicated in the Table B.5 below. 3. Gravel glides have been dimensioned using channel size dimensions provided in the 2007 JBA report. Width of channel used has been taken as the ‘erodible bank width’ as it is representative of the realistic width of erosion, and therefore needs protection. The depth of gravel used is the amount identified as needed to raise the bed. The length of the glide is taken as 3 times the resistant bank width to ensure that ‘edge effects’ are controlled, so that these artificial glides more closely match those observed, and will realistically fit between the existing bends. 4. The long section through the glide assumes a 1:1 slope at the upstream and downstream ends to give some stability. This has been allowed for in the volume per glide. 5. The rate for supply and placement of gravel is based on a material supply cost of £27/tonne for 20-50mm gravel rejects and a placement cost of £4.85/m3. At 1.78t/m3 the gravel supply rate equates to £48.06/m3, which combined with the placement rate gives an overall rate of £53/m3.

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Table B.5 Total estimated costs associated with installing gravel glides for Unit 54

Reach Number of Bed Erodible Resistant Length Volume Volume Glides Raising Width (m) Width (R) per Glide* per Reach (m) 3 x R (m) Required (m3) (m) 01 2 0.84 16.95 11.2 33.6 490 980 02a 1 0.7 16.1 10.65 31.95 368 368 02b 10 0.7 16.1 10.65 31.95 368 3680 03a 3 0.56 15.45 10.25 30.75 271 813 03b 9 0.56 15.45 10.25 30.75 271 2439 Volume for unit: (m3) 8280 Rate for supply and placement (£/m3) 53 Total for unit: £438,840

Deflector Deflector costs are summarised in Table B.6 below. The following assumptions apply: 1. It is assumed that these are created from large woody debris (LWD) won locally and where possible from tree felling activities. 2. A deflector group consists of 3 deflectors pointing upstream; spaced at natural channel width along the bank to affect an area equivalent to 3 times natural channel width. The length of the deflector is determined locally so as to mobilize silts and suit channel width. 3. The deflectors consist of clean timber tree trunks alternately staked and wired to hardwood stakes at 1m centres. The butt end is embedded into the bank by 2m or one third length whichever is the shortest. The trunks are to be laid on shorter faggot bedding. 4. Deflector height to be no higher than high summer water level so that it can drown out under higher flows. 5. Deflectors are recommended for 14 locations in this unit.

Table B.6 - Total estimated costs associated with implementing deflectors for Unit 54

Reach No. of Groups Length per Reach (m) 01 4 134 02a 0 n/a 02b 4 128 03a 2 62 03b 4 123 Total for unit: 447 Rate (£/m) 44 Total for unit: £19,668

Tree planting Tree planting costs are summarised in Table B.7 and B.8 below. The following assumptions apply:

1. Tree species are assumed to be appropriate native riverside species such as: alder, black poplar, and willow. The black poplar needs to be from a certified source (and of Norfolk provenance) as they hybridize readily.

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2. Tree planting consists of a group of 10 individual trees at specific locations to create shade and bank reinforcement. Tree group planting is recommended in 23 locations. Planting areas to run on average for 10m along the bank length. 3. Planting costs include: supply of 2-3m standard; planting; tube, stake and tie and deer proof enclosure. Total costs estimated cost per tree is £58. 4. Cost for planting a tree is estimated on team of two (£500/day) capable of planting 3 trees per hour over 7 hours.

Table B.7 - Estimated tree costs

Item Cost (£) Supply 2-3m standard tree 10 Plant tree 23 Supply & install: tube, stake, ties 1 Deer proof enclosure 24 Total cost per tree 58

Table B.8 - Estimated costs for new tree planting for Unit 54

Reach No. of Locations No. Trees 01 4 40 02a 2 20 02b 8 80 03a 3 30 03b 6 60 Total 230 Rate (£/tree) 58 Total for unit: £13,340

Other restoration measures Other restoration measures in Unit 54 refer to lowering both spoil and formal embankments. Construction costs for these measures are summarised in Table B.9 and B10 below, respectively.

Table B.9 - Estimated costs for lowering spoil embankments in Unit 54

Max height Reach volume Reach Length (m) Max width (m) (m) (m3)

01 59 3 1 236 02a 0 - - n/a 02b 650 4 1 2600 03a 0 - - n/a 03b 860 4 0.5 1720 Volume for unit: (m3) 4556 Earth movements cost (£) 9.83 Total for unit: £44,786

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Table B.10 – Estimated costs for lowering formal embankments in Unit 54

Max height Reach volume Reach Length (m) Max width (m) (m) (m3) 01 152 4 1 608 02 0 - - n/a 03 0 - - n/a Volume for unit: (m3) 608 Earth movements cost (£) 9.83 Total for unit: £5,977

B.1.3 Summary costs for recommended restoration measures for Unit 54 Table B.11 - Unit 54 cost estimates for various river restoration measures (February 2012)

Measure Description Quantity Rate per unit Cost (£)

5.1 Fencing (m) 8715 8 69,720 5.16 Berm creation (m) 824 90 101,520 5.12 Tree felling (m) 580 10 5,800 5.17 Backchannel – reconnection (m3) 3837 14.18 54,414 5.7g Gravel glides (m3) 8280 53 438,840 5.13 Deflector (m) 447 44 19,668 5.11 Tree planting (unit) 230 58 13,340 Other Lower spoil embankments volume (m3) 4556 9.83 44,786 Other Lower formal embankments volume (m3) 608 9.83 5,977 Option G3 Targeted maintenance Unknown Unknown Unknown Total cost: £754,065

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Appendix C – Ecology tables

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C.1 River Wensum SSSI/SAC: Status, ecology and habitat requirements of European interest features

Species / community Designations and status General ecology Habitat requirements Habitat requirements (continued)

Brook lamprey Listed in annexes IIa and Va of the Habitats Brook lamprey have both a sedentary larval Ammocoete larvae Adult lamprey (Lampetra planeri) Directive, Appendix III of the Bern (ammocoete) stage and an adult dispersal Substrate Adult spawning grounds Convention, and as a Long List Species in phase, during which spawning takes place. Ammocoetes occur in suitable silt beds, mainly in running water but Spawning grounds are located in areas of the UK Biodiversity Action Plan. They do not feed as adults and hence spawning sometimes in large numbers in silt banks in lakes. Preferred small stones and gravel in flowing water, is generally considered to be preceded by a substrate varies in depth from a few cm to 30 cm and is generally with spawning often occurring at lower The most common of the 3 British relatively short migration to the spawning areas. composed of mud, silt, or silt and sand with a high organic content ends of pools. The spawning gravels are lampreys, occurring over much of the Brook lamprey tend to undertake small upstream (optimum particle size 80–380 μm). Larval nursery beds are often composed of stones up to 3 in. with good British Isles. Absent from much of Scotland migrations prior to spawning during which time located at the edges of streams and rivers, well away from the main permeability, although smaller north of the Great Glen. they continue to burrow like ammocoetes or hide current in flowing backwater sections. consolidating particles are required. under stones during the day. The extent of the Stones embedded in fine sands or silts migration depends on stream gradient which Water quantity and quality which form a hard bed are often avoided. may also impact upon the distance ammocoetes Flow rates of 0.5 m s-1 at the water surface, and 0.4 m s-1 at a The nest, which may be constructed by up drift downstream during development, as well as depth of 25 cm have been observed above nursery beds and flows to a dozen or more adults, is normally an spawning habitat availability. After spawning has of 8–10 cm s-1 have been recorded over Lampetra burrows. oval depression about 20–40 cm across occurred, newly hatched larvae leave the nest and 2–10 cm deep. and distribute themselves by drifting Water quantity and quality downstream and burrowing in suitable areas of The brook lamprey is regarded as being silty sand. sensitive to pollution requiring at least UK Water Quality Class B (EA classification) Life-cycle in all parts of any river where brook Metamorphosis July to September lamprey life stages occur. At spawning Spawning migration November to February sites flow velocities of 30–50 cm s-1 have Spawning March to April (10-11oC) been noted. Bullhead (Cottus In the UK the native range of Cottus gobio Common species of the headwaters of many Bullhead habitat requirements are dependent on life stages. Coarse Substrate gobio) is restricted to England and Wales, types of upland and lowland river where it is benthic substrates with large stones are required for breeding and Benthic gravel and stones substrates are although some introduced populations are associated with stony benthic habitats with shallow riffles and glides are utilised by YOY (young of year) fish. a vital habitat requirement for bullheads established in Scotland. moderate flow. Also occasionally found in lakes. Adults appear to prefer sheltered sections created by woody debris, as they provide both spawning habitats Listed in annexes IIa and Va of the Habitats Benthic macroinvertebrates such as Gammarus tree roots, leaf litter, macrophyte cover or large stones and all life and refuges against flow and predators. Directive, Appendix III of the Bern and Asellus, together with aquatic fly larvae are stages require slack-water refuges during spate flows. Bullheads will also utilise macrophytes as Convention. the dominant prey items. Habitat H3260 ‘Rivers refuges from predators and flows if large with Ranunculion fluitantis and Callitricho- Water quantity stones are a limiting factor. If gravel and batrachion vegetation’ is a key habitat for this Water depth is not critical providing it is >5 cm and flow is stone substrates are not limiting within the species in the UK. adequate. High temperatures or low dissolved oxygen may be fatal stream, bullheads will also associate with in shallow water, because temperature fluctuations are greater. depositional habitats such as pools Spawning occurs from February to July with the Typically, bullhead are found in depths of 20 to 40cm. containing woody debris. male excavating a nest under a suitable large stone to attract a female. Bullheads may use Water quality Channel structure other media such as woody debris or tree roots. Some tolerance to organic pollution (ammonia) and heavy metals is Natural channel forms exhibiting riffle/pool The female lays a batch of up to 400 eggs (2– exhibited where oxygen saturation remains high. The bullhead’s sequences provide appropriate substrate 2.5 mm in diameter), which adhere to the sympatric occurrence with brown trout indicates a requirement for and flow character for bullhead, as a underside of the stone. The male defends the oxygen concentration of 40% saturation and critical thermal limits of result supporting higher densities than brood against predators and maintains water – 4.2 and 27.7°C have been described. heavily modified channels. circulation by fanning the eggs. Eggs hatch after Filamentous algal growth resulting from eutrophication is Riparian trees are known to provide 20 to 30 days and after 10 days the fry (9 mm in detrimental where algae cover the favoured coarse, hard substrate shade and shelter as well as valuable length) disperse, colonising newly available (see below) and influence food-web dynamics. input of woody debris and leaf litter. habitat downstream including temporary channels, and floodplain lakes.

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Species / community Designations and status General ecology Habitat requirements Habitat requirements (continued)

Desmoulin’s whorl Desmoulin’s whorl snail is listed under Desmoulin’s whorl snail lives in permanently Water level requirements snail (Vertigo Annex II of the European Union Habitats wet, usually calcareous, swamps, fens and Hydrology is a factor determining the distribution of the Desmoulin’s moulinsiana) and Species Directive. It is a priority marshes, bordering rivers, lakes and ponds, or whorl snail with high groundwater levels throughout the year being species in the UK Biodiversity Action Plan in river floodplains. It is most often found in open one of the most important factors. Maximum snail densities are (HMSO 1996) and is listed in the British situations associated with the following often located where water levels are continuously above the ground Red Data Book (Bratton 1991) as an RDB3 vegetation: surface throughout the year, and where mean annual water levels (Rare) species. • Reed sweet grass (Glyceria maxima) are more than 0.25 m above the surface. • Sedges (Carex riparia, C. acutiformis, C. Annual fluctuations of between about 0 m and 0.6 m above ground Scattered sites across southern England paniculata, C. elata) level provide optimum conditions with summer water level critical from Norfolk to Dorset, with isolated • Saw sedge (Cladium mariscus) thresholds estimated to be at 0.5 m below surface ground level. populations elsewhere. Southern chalk • Reed (Phragmites australis) streams have been shown to be as • Reedmace (Typha latifolia and T. angustifolia) Humidity important as the East Anglian fens as • Branched bur reed (Sparganium erectum) Humidity is important since the snail spends much of the year strongholds for this species. • Iris (Iris pseudacorus) climbing in the canopy of the vegetation well away from the ground. • Reed canary grass (Phalaris arundinacea) Humidity regimes are likely to be influenced by vegetation structure, Adjacent to rivers, its presence/absence and which is clearly affected by management. population density are largely determined by the structure and topography of the banks and the nature of the riparian management. The most suitable riparian habitats comprise a relatively broad strip where Glyceria or Sparganium spp. form dense floating rafts on gently sloping banks. Steeper banks as a result of canalisation, impounding, channel dredging, and weed cutting reduces habitat development often resulting in the absence of the snail. 3260 Water courses of Sub-type 1 rivers on chalk substrates. The Characterised by the abundance of water- Ranunculus follows a four phase cycle of biomass development: plain to montane levels community is characterised by pond water- crowfoots Ranunculus spp., subgenus • Regrowth phase in autumn triggered by the seasonal increase in with the Ranunculion crowfoot Ranunculus peltatus in spring-fed Batrachium (Ranunculus fluitans, R. penicillatus flow. fluitantis and headwater streams (winterbournes), stream ssp. penicillatus, R. penicillatus ssp. • Extension phase over winter to April. Rapid increase in biomass Callitricho-Batrachion water-crowfoot R. penicillatus ssp. pseudofluitans, and R. peltatus and its hybrids). with the development of long streamers in spring. vegetation pseudofluitans in the middle reaches, and They may modify water flow, promote fine • Consolidation and flowering phase over late spring to summer. river water-crowfoot R. fluitans in the sediment deposition, and provide shelter and • Biomass production increases then slows as energy is invested in downstream sections. Ranunculus is food for fish and invertebrate animals. flowers and seeds. typically associated in the upper and middle Ranunculus communities are associated with • Decline phase over late summer to autumn. reaches with Callitriche obtusangula and C. assemblages of other aquatic plants e.g. platycarpa. Rorippa nasturtium-aquaticum, Callitriche spp., Sium latifolium and Berula erecta, Myriophyllum Flow Sub-type 2: This variant is found on other spp. and Myosotis scorpioides. The cover of Velocity and discharge are prime factors due to the high substrates, ranging from lime-rich these species may exceed that of Ranunculus photosynthetic rate of Ranunculus: fast flows are required to deliver substrates such as oolite, through soft species. Three main sub-types are defined by oxygen and carbon to the plant. Velocity also acts indirectly to sandstone and clay to more mesotrophic substrate and the dominant species within the remove potentially competitive or shading algae, and clearing silt and oligotrophic rocks. Ranunculus community. from gravels. 0.3 – 0.5 ms-1 optimal summer velocity band. It is recognised that Sub-type 3: This variant is a mesotrophic to Ranunculus growth can occur above the threshold of 0.5 ms-1 but oligotrophic community found on hard rocks is subject to mechanical stresses. in the north and west. Substrate Clean gravel river beds encourage Ranunculus root development and prevent the development of other algal growth which is given an advantage on soft, silty substrates.

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Species / community Designations and status General ecology Habitat requirements Habitat requirements (continued)

White-clawed crayfish Listed under annexes II and V of the EU Crayfish distribution is influenced by geology, Water quality (Austropotamobius Habitats Directive and Appendix II of the requiring relatively hard, mineral-rich waters of The majority of records for the white-clawed crayfish occur in UK pallipes) Bern Convention. Protected under calcareous catchments. The species occurs in a Environment Agency General Quality Assessment Class A and B Schedule 5 of the variety of habitats including canals, streams, waters, an indication of their association with unpolluted fluvial Wildlife and Countryside Act (1981). Priority rivers, lakes, reservoirs and water-filled quarries. systems. The white-clawed crayfish is principally found in alkaline species under the UK Biodiversity Action waters for which calcium and pH requirements are: Plan with its own Species Action Plan. It is typically found in watercourses of 0.75 m to • calcium (5 mg l-1 minimum) 1.25 m deep, but is also found in small streams • pH (6.5–9.0) Austropotamobius pallipes is widespread in (about 5 cm of water) and in deeper, slow- most parts of England and is common in flowing rivers (2.5 m). In flowing water the BOD parts of eastern Wales. It is present in white-clawed crayfish may be found associated The white-clawed crayfish is particularly susceptible to acute south-west Northern Ireland. A significant with: pollution incidents caused by spills of organic material with a high part of the EU resource is found in the UK, biochemical oxygen demand (BOD), such as cattle slurry or silage. but the species is now seriously threatened • Undermined, overhanging banks. over most of its range in Britain. • Sections exhibiting heterogeneous flow Turbidity and siltation patterns with refuges. Gills are easily clogged by sediment and this may cause physico- • Under cobbles (juveniles) and rocks in riffles, pathological changes in the long term. White-clawed crayfish tend and under larger rocks in pools. to avoid substrates covered in mud or silt unless they are actively • Among roots of woody vegetation, foraging for food. accumulations of fallen leaves and boulder weirs. Vegetation • Under water-saturated logs. White-clawed crayfish utilise aquatic macrophyte vegetation for cover and food. They may be found amongst Cladophora spp; The white-clawed crayfish is primarily Fontinalis spp.; or vascular plants such as water crowfoot and carnivorous, feeding on aquatic watercress. Their association with such vegetation may be due to macroinvertebrates and carrion. In addition, their foraging and is particularly important in shallow water habitats allochthonous material in the form of dead as they provide protection from predation and high flows. leaves may provide an important source of food.

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C.2 Potential impacts of mill modification on European interest features of the River Wensum SSSI/SAC

Mill structures Species / community Improve operability + Remove flow control Lower mill sill levels Bypass channels Fish passes Remove all protocols mechanisms

Brook lamprey Due to the range of options Due to the range of options Due to the range of Positive Positive Positive (Lampetra planeri) available under this measure available under this measure options available under Reduction of habitat Reduction of habitat Reduction of habitat severance and increase in assessment of the potential assessment of the potential this measure assessment severance and increase in severance and increase in available habitat for existing lamprey populations. positive/negative effects on positive/negative effects on the of the potential available habitat for existing available habitat for existing Reduction in vulnerability of populations to the ecological feature cannot ecological feature cannot be positive/negative effects lamprey populations. lamprey populations. anthropogenic disturbance through increase in extent be commented on at this commented on at this point. on the ecological feature Reduction in vulnerability of Reduction in vulnerability of of available habitat. point. cannot be commented on populations to populations to anthropogenic Improved ammocoete dispersal and adult migration Review of effects to be at this point. anthropogenic disturbance disturbance through increase through removal of potential barriers. Review of effects to be determined on a site-by-site through increase in extent in extent of available habitat. Increase in available habitat for all life stages. determined on a site-by-site basis following establishment Review of effects to be of available habitat. Improved ammocoete basis following establishment of options and resultant determined on a site-by- Improved ammocoete dispersal and adult migration Negative of options and resultant changes to physical habitat site basis following dispersal and adult through removal of potential Removal of barrier previously preventing colonisation changes to physical habitat e.g. flow, sediment dynamics. establishment of options migration through removal barriers. by competitive/damaging species. e.g. flow, sediment and resultant changes to of potential barriers. Increase in available habitat dynamics. physical habitat e.g. flow, Increase in available for all life stages. Design recommendations sediment dynamics. habitat for all life stages. Provision of appropriate flow velocities to ensure Negative passage is not limited to more active swimming Negative Increased connectivity species. Increased connectivity allowing colonisation of allowing colonisation of reaches by reaches by competitive/damaging competitive/damaging species. species. Design recommendations Design recommendations Provision of appropriate flow Provision of appropriate velocities to ensure passage flow velocities to ensure is not limited to more active passage is not limited to swimming species. more active swimming species.

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Species / community Improve operability + Remove flow control Lower mill sill levels Bypass channels Fish passes Remove all protocols mechanisms

Bullhead (Cottus Due to the range of options Due to the range of options Due to the range of Positive Positive Positive gobio) available under this measure available under this measure options available under Reduction of habitat Reduction of habitat Reduction of habitat severance and increase in assessment of the potential assessment of the potential this measure assessment severance and increase in severance and increase in available habitat for existing bullhead populations. positive/negative effects on positive/negative effects on the of the potential available habitat for existing available habitat for existing Reduction in vulnerability of populations to the ecological feature cannot ecological feature cannot be positive/negative effects bullhead populations. bullhead populations. anthropogenic disturbance through increase in extent be commented on at this commented on at this point. on the ecological feature Reduction in vulnerability of Reduction in vulnerability of of available habitat. point. cannot be commented on populations to populations to anthropogenic Improved dispersal and adult migration through Review of effects to be at this point. anthropogenic disturbance disturbance through increase removal of potential barriers. Review of effects to be determined on a site-by-site through increase in extent in extent of available habitat. Increase in available habitat for all life stages. determined on a site-by-site basis following establishment Review of effects to be of available habitat. Improved dispersal and adult basis following establishment of options and resultant determined on a site-by- Improved dispersal and migration through removal of Negative of options and resultant changes to physical habitat site basis following adult migration through potential barriers. Removal of barrier previously preventing colonisation changes to physical habitat e.g. flow, sediment dynamics. establishment of options removal of potential Increase in available habitat by competitive / damaging species. e.g. flow, sediment and resultant changes to barriers. for all life stages. dynamics. physical habitat e.g. flow, Increase in available Design recommendations sediment dynamics. habitat for all life stages. Negative Provision of appropriate flow velocities to ensure Increased connectivity passage is not limited to more active swimming Negative allowing colonisation of species. Increased connectivity reaches by allowing colonisation of competitive/damaging reaches by species. competitive/damaging species. Design recommendations Provision of appropriate flow Design recommendations velocities to ensure passage Provision of appropriate is not limited to more active flow velocities to ensure swimming species. passage is not limited to more active swimming species.

Desmoulin’s whorl Due to the range of options Due to the range of options Due to the range of n/a n/a Review of effects to be determined on a site-by-site snail (Vertigo available under this measure available under this measure options available under basis following establishment of options and resultant moulinsiana) assessment of the potential assessment of the potential this measure assessment changes to physical habitat e.g. flow, sediment positive/negative effects on positive/negative effects on the of the potential dynamics. the ecological feature cannot ecological feature can be positive/negative effects be commented on at this commented on at this point. on the ecological feature point. can be commented on at Review of effects to be this point. Review of effects to be determined on a site-by-site determined on a site-by-site basis following establishment Review of effects to be basis following establishment of options and resultant determined on a site-by- of options and resultant changes to physical habitat site basis following changes to physical habitat e.g. flow, sediment dynamics. establishment of options e.g. flow, sediment and resultant changes to dynamics. physical habitat e.g. flow, sediment dynamics.

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Species / community Improve operability + Remove flow control Lower mill sill levels Bypass channels Fish passes Remove all protocols mechanisms

3260 Water courses of Reduction in impoundment Reduction in impoundment will Reduction in Reduction in impoundment n/a Reduction in impoundment will result in improved plain to montane levels will result in improved flow result in improved flow regime impoundment will result in will result in improved flow flow regime for Ranunculus communities. Review of with the Ranunculion regime for Ranunculus for Ranunculus communities. improved flow regime for regime for Ranunculus effects to be determined on a site-by-site basis fluitantis and communities. Review of Review of effects to be Ranunculus communities. communities. Review of following establishment of options and resultant Callitricho-Batrachion effects to be determined on a determined on a site-by-site Review of effects to be effects to be determined on changes to physical habitat e.g. flow, sediment vegetation site-by-site basis following basis following establishment determined on a site-by- a site-by-site basis dynamics. establishment of options and of options and resultant site basis following following establishment of resultant changes to physical changes to physical habitat establishment of options options and resultant habitat e.g. flow, sediment e.g. flow, sediment dynamics. and resultant changes to changes to physical habitat dynamics. physical habitat e.g. flow, e.g. flow, sediment sediment dynamics. dynamics.

White-clawed crayfish Due to the range of options Due to the range of options Due to the range of Positive Positive Positive (Austropotamobius available under this measure available under this measure options available under Reduction of habitat Reduction of habitat Reduction of habitat severance and increase in pallipes) assessment of the potential assessment of the potential this measure assessment severance and increase in severance and increase in available habitat for existing white-clawed crayfish positive/negative effects on positive/negative effects on the of the potential available habitat for existing available habitat for existing populations. the ecological feature cannot ecological feature cannot be positive/negative effects white-clawed crayfish white-clawed crayfish Reduction in vulnerability of populations to be commented on at this commented on at this point. on the ecological feature populations. populations. anthropogenic disturbance. point. cannot be commented on Reduction in vulnerability of Reduction in vulnerability of Improved dispersal through removal of potential Review of effects to be at this point. populations to populations to anthropogenic barriers. Review of effects to be determined on a site-by-site anthropogenic disturbance. disturbance. Increase in available habitat for all life stages. determined on a site-by-site basis following establishment Review of effects to be Improved dispersal through Improved dispersal through basis following establishment of options and resultant determined on a site-by- removal of potential removal of potential barriers. Negative of options and resultant changes to physical habitat site basis following barriers. Increase in available habitat Removal of barrier previously preventing colonisation changes to physical habitat e.g. flow, sediment dynamics. establishment of options Increase in available for all life stages. of reaches by competitive and damaging species e.g. e.g. flow, sediment and resultant changes to habitat for all life stages. signal crayfish. dynamics. physical habitat e.g. flow, Negative sediment dynamics. Negative Removal of barrier previously Removal of barrier preventing colonisation of previously preventing reaches by competitive and colonisation of reaches by damaging species e.g. signal competitive and damaging crayfish. species e.g. signal crayfish.

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C.3 Potential impacts of gravel works on European features of the River Wensum SSSI/SAC

Gravel works Species / Gravel glides Gravel glides + transverse hurdles Bed raising (large scale) community

Brook lamprey Positive Positive Positive (Lampetra planeri) Provision of suitable spawning habitat for adult brook lamprey. Provision of suitable spawning habitat for adult brook lamprey as a Significant increase in the extent of suitable spawning habitat for adult brook Improvement to local water quality through turbulent flow and result of gravel installation. lamprey. resultant increase in DO concentration. Hurdle construction will promote deposition of fine sediment Improvement to local water quality through turbulent flow and resultant DO favouring ammocoete life stages. concentration. Negative Improvement to local water quality through turbulent flow and Small scale loss of silt bed areas suitable for ammocoete resultant DO concentration. Negative development. Potential for large scale loss of silt bed areas suitable for ammocoete Potential to cause damage to existing populations during gravel Negative development. placement. Small scale loss of silt bed areas suitable for ammocoete Potential to cause damage to existing populations during installation of bed development at site of gravel placement. raising measures. Design recommendations Potential to cause damage to existing populations during gravel Provision of suitably sized spawning substrate. placement. Design recommendations Glide depth and morphology to provide appropriate flow velocities Provision of suitably sized spawning substrate. that reduce fine sediment deposition. Design recommendations Glide depth and morphology to provide appropriate flow velocities that reduce Maximise flow heterogeneity through the creation of diverse bed Provision of suitably sized spawning substrate. fine sediment deposition. topography. Glide depth and morphology to provide appropriate flow velocities Maximise flow heterogeneity through the creation of diverse bed topography. that reduce fine sediment deposition. Maximise flow heterogeneity through the creation of diverse bed topography. Bullhead (Cottus Positive Positive Positive gobio) Provision of vital habitat for bullhead spawning and adult and Provision of vital habitat for bullhead spawning and adult and YOY Provision of vital habitat for bullhead spawning and adult and YOY (young of YOY (young of year) fish life stages. (young of year) fish life stages. year) fish life stages. Improvement to local water quality through turbulent flow and Diversification of instream flow character. Diversification of instream flow character. resultant increase in DO concentration. Improvement to local water quality through turbulent flow and Provision of suitable habitat for macroinvertebrate prey items and macrophyte Diversification of instream flow character. resultant DO concentration. cover e.g. Ranunculus. Provision of suitable habitat for macroinvertebrate prey items and Provision of suitable habitat for macroinvertebrate prey items and Improved depth through bed raising. macrophyte cover e.g. Ranunculus. macrophyte cover e.g. Ranunculus. Improved depth through bed raising. Negative Negative Potential to cause damage to existing populations during installation of bed Potential to cause damage to existing populations during gravel Negative raising measures. placement. Potential to cause damage to existing populations during gravel placement. Design recommendations Design recommendations Habitat value can be further increased through addition of larger Habitat value can be further increased through addition of larger Design recommendations stone/boulder substrates within gravel glide. stone/boulder substrates within gravel glide. Habitat value can be further increased through addition of larger Maximise flow heterogeneity through the creation of diverse bed topography. Maximise flow heterogeneity through the creation of diverse bed stone/boulder substrates within gravel glide. topography. Maximise flow heterogeneity through the creation of diverse bed topography.

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Species / Gravel glides Gravel glides + transverse hurdles Bed raising (large scale) community

Desmoulin’s whorl n/a n/a Positive snail (Vertigo Potential to improve local water level regime through more frequent moulinsiana) inundation of marginal habitats.

Design recommendations Incorporate measures such as lowering embankments and berm creation.

3260 Water Positive Positive Positive courses of plain to Provision of suitable rooting habitat for Ranunculus community Provision of suitable rooting habitat for Ranunculus community Provision of suitable rooting habitat for Ranunculus community vegetation. montane levels vegetation. vegetation. Provision of favourable flow and depth conditions for development of with the Provision of favourable flow and depth conditions for Provision of favourable flow and depth conditions for development Ranunculus vegetation. Ranunculion development of Ranunculus vegetation. of Ranunculus vegetation. fluitantis and Negative Callitricho- Negative Negative Batrachion Design recommendations vegetation Design recommendations Design recommendations Provide varied glide depth and morphology to maximise flow diversity. Provide varied glide depth and morphology to maximise flow Provide varied glide depth and morphology to maximise flow Consideration given to translocation of existing plants to encourage diversity. diversity. establishment. Consideration given to translocation of existing plants to Consideration given to translocation of existing plants to encourage encourage establishment. establishment.

White-clawed Positive Positive Positive crayfish Provision of suitable habitat and foraging area for white-clawed Provision of suitable habitat and foraging area for white-clawed Provision of suitable habitat and foraging area for white-clawed crayfish. (Austropotamobius crayfish. crayfish. Improvement to local water quality through turbulent flow and resultant pallipes) Improvement to local water quality through turbulent flow and Improvement to local water quality through turbulent flow and increase in DO concentration. resultant increase in DO concentration. resultant increase in DO concentration. Negative Negative Negative Potential to cause damage to existing populations during gravel placement. Potential to cause damage to existing populations during gravel Potential to cause damage to existing populations during gravel placement. placement. Design recommendations Glide depth and morphology to provide appropriate flow velocities that reduce Design recommendations Design recommendations fine sediment deposition. Glide depth and morphology to provide appropriate flow velocities Glide depth and morphology to provide appropriate flow velocities Maximise flow heterogeneity through the creation of diverse bed topography. that reduce fine sediment deposition. that reduce fine sediment deposition. Habitat value can be further increased through addition of larger Maximise flow heterogeneity through the creation of diverse bed Maximise flow heterogeneity through the creation of diverse bed stone/boulder substrates within gravel glide. topography. topography. Habitat value can be further increased through addition of larger Habitat value can be further increased through addition of larger stone/boulder substrates within gravel glide. stone/boulder substrates within gravel glide.

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C.4 Potential impacts of other river restoration measures on the European features of the River Wensum SSSI/SAC

Other

Species / Fencing Tree planting on Tree felling Deflector (using LWD Lower spoil Channel re- Berm creation Backwaters – Backwaters – new Channel realignment Changing Lower community embankment and filled in with brush embankments sectioning reconnections to primary and embankments mattress) IDB, field drains secondary channels n/a Positive Positive Positive Positive Positive Positive Positive Positive Positive Positive Positive Localised shading General Improvement of flow General improvement General improvement Berm creation will Increase in the Increase in the extent Promotion of more Potential to General improvement may inhibit improvement to conditions adjacent to to channel form and to channel form and increase flow velocities extent of habitat of available marginal natural flow character improve the extent to channel form and development of instream habitat deflector which will act process through process through (most effective during available for ammocoete habitat. and sediment regime of suitable process through algae, improving through to improve spawning increase in duration of increase in duration of low flow periods) and utilisation by Provision of refuge favouring habitat spawning and/or increase in duration spawning habitat encouragement of gravels through silt channel forming flows. channel forming flows. reduce local fine spawning adult or areas during high flow development for both larval habitat. of channel forming ) quality. natural narrowing removal. Increased connectivity sediment deposition larval ammocoete events. adult and larval life flows. process. Associated fine with floodplain Negative improving spawning life stages. stages. Negative Increased Design sediment deposition will features that provide Potential to cause habitat if gravels are Design Potential to reduce connectivity with recommendations Negative provide ammocoete shelter and refuge for damage to existing present. recommendations Negative habitat quality for floodplain features Incorporate Reduced shade habitat. lamprey. populations during Ensure sweetening Potential to cause ammocoete life that provide shelter additional measures may encourage implementation of Negative flow is maintained to damage to existing stages where and refuge for such as fencing to development of Negative Design measure. Potential to cause reduce risk of silting populations during primary channel lamprey. Lampetra planeri remove algae reducing Potential to cause recommendations damage to existing up of backwater implementation of provides extensive grazing/trampling spawning habitat damage to existing Incorporate with populations during features. measure. silt beds for larval pressure. quality at a local populations during additional measures implementation of development. Design scale. placement of deflectort. such as gravel measure. Potential to affect recommendations placement. existing population Incorporate with Design Design Design through changes additional measures

Brook lamprey ( recommendations recommendations recommendations in water such as gravel Adopt selective Incorporate with Incorporate additional availability. placement. felling to ensure additional measures measures such as some tree cover such as gravel gravel placement and remains of varied placement. deflectors. age structure.

Positive Positive Positive Positive Positive Positive Positive Positive Positive Positive Positive Positive Encourage Riparian tree General Improvement of flow Increased connectivity Return of natural Localised channel Improved Provision of new Promotion of more Potential to General improvement riparian tree development will improvement to conditions through with floodplain channel form and narrowing may promote connectivity to habitats natural flow character improve the extent to channel form and establishment to provide shade and instream habitat deflector installation features that provide function will promote increased flow additional habitats forcolonisation by and sediment regime of available process through supply shade and shelter as well as through combined with marginal shelter and refuge for conditions that will velocities, improving suitable for bullhead. favouring habitat habitat. increase in duration shelter as well as valuable input of encouragement of facilitation of fine bullhead. favour species and physical habitat colonisation by Provision of refuge development for both of channel forming valuable input of woody debris and natural narrowing sediment deposition. General improvement potentially improve conditions for bullhead. bullhead. areas during high flow adult and juvenile life Negative flows. woody debris and leaf litter. process. to channel form and densities and standing Increase in the events. stages. Potential to affect Increased leaf litter. Reduction in Negative process through crop. Negative extent of habitat existing population connectivity with Improved bank localised sediment Negative Potential to cause increase in duration of Potential to cause available for Negative through changes floodplain features stability and input through Localised removal damage to existing channel forming flows. Negative damage to existing utilisation by Design Potential to cause in water that provide shelter reduced sediment improved bank of shade and populations during Potential to cause populations during bullhead for shelter recommendations damage to existing availability. and refuge for input. stability. shelter plus gravel placement. damage to existing implementation of from high flow Ensure sweetening populations during bullhead. reduction in populations during measure. events and/or flow is maintained to implementation of ) valuable supply of implementation of additional reduce risk of silting measure. Design Design woody debris and measure. Design spawning habitat up of backwater Design recommendations recommendations leaf litter. recommendations and nursery features. recommendations Incorporate Incorporate Reduced shade Design Incorporate additional grounds. Incorporate with planting of native additional measures may encourage recommendations design measures such additional measures

Cottus gobio deciduous such as fencing to development of Incorporate additional as gravel placement such as gravel species that will remove algae reducing measures such as and deflectors. placement. provide seasonal grazing/trampling spawning habitat gravel placement. input of leaf litter. pressure. quality at a local

Bullhead ( Planting of native scale. deciduous species that will provide Design seasonal input of leaf recommendations litter. Adopt selective felling to ensure some tree cover remains of varied age structure.

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Species / Fencing Tree planting on Tree felling Deflector (using LWD Lower spoil Channel re- Berm creation Backwaters – Backwaters – new Channel realignment Changing Lower community embankment and filled in with brush embankments sectioning reconnections to primary and embankments mattress) IDB, field drains secondary channels Positive Positive Positive Positive Positive Positive Positive Positive Positive Positive Positive Positive Exclusion of Reduced shading Potential for Improve connectivity Re-sectioning may Berm creation may Increase in the Backwater areas may Potential to improve Improvement of Lowering of grazing pressure Negative of wetland plant establishment of between river and favour growth of favour growth of extent of habitat improve the extent of marginal habitat water level embankments may from marginal Increased shading of communities and marginal wetland marginal habitats. If marginal plants and marginal plants and available for area available for quality. regimes in improve the extent of areas and wetland plant reduction in local vegetation on lateral silt suitable water level provided suitable provided suitable water colonisation by colonisation by adjacent floodplain area available for encouragement of communities water demand. berms. regimes are water level regimes level regimes are wetland plants. marginal plants and, Negative area through colonisation by ) marginal plant associated with snail maintained snail are maintained snail maintained snail Potential to provided suitable Potential to cause increase in ground marginal plants and, development. populations. populations may populations may populations may improve water water levels are damage to existing water levels. provided suitable Reduction in Local effects on Design benefit. benefit. benefit. levels adjacent to maintained, snail populations during water levels are poaching of water availability recommendations Improve dispersal of main river. populations may implementation of Negative maintained, snail marginal habitats. through tree uptake. Encourage species through Negative Negative benefit. measure. Potential to affect populations may vegetation improved connectivity Potential to cause Potential to cause existing population benefit. Negative Design establishment on in river corridor. damage to existing damage to existing Negative Design through changes May eventually recommendations silt berms through populations during populations during Potential to cause recommendations in water Negative Vertigo moulinsiana result in Ensure planting does transplantation of Negative implementation of implementation of damage to existing Promote suitable availability. development of not create a appropriate Potential to cause measure. measure. populations during water level regimes in Design marginal tree significant shading wetland plants. damage to existing implementation of marginal areas recommendations cover and hence impact on existing populations during Design Design measure. through appropriate Incorporate with loss of suitable suitable snail habitat. implementation of recommendations recommendations channel design. additional measures habitat. measure. Encourage marginal Encourage marginal Design such as gravel vegetation vegetation recommendations placement. Design establishment through establishment through Encourage marginal recommendations transplantation of transplantation of vegetation Encourage marginal appropriate wetland appropriate wetland establishment through

Desmoulin’s whorl snail ( vegetation plants in treated plants in treated areas. transplantation of establishment through areas. appropriate wetland transplantation of plants in treated appropriate wetland areas. plants in treated areas.

Positive Negative Positive Positive Positive Positive Positive n/a n/a Positive Positive Positive Improved bank Gradual increase in Reduction of local Improvement of flow General improvement General improvement General improvement to Promotion of natural Potential to General improvement stability may shading will, over shading will conditions favouring to channel form and to channel form and channel form and flow and sediment provide more to channel form and reduce localised time, favour more promote Ranunculus growth process through process. process. regime conducive to appropriate flow process through sediment input. shade tolerant Ranunculus downstream of flow increase in duration of Ranunculus conditions for increase in duration species. growth. Selective deflector. channel forming flows. Negative Negative communities. Ranunculus of channel forming Negative tree felling Potential to cause Potential to cause development. This flows. Development of Design encouraged rather Negative Negative damage to existing damage to existing Negative potential is

Callitricho-Batrachion riparian recommendations than widespread Potential to cause vegetation stands vegetation stands Potential to cause improved if Negative vegetation will Provide varied shade removal to provide damage to existing Design during implementation during implementation damage to existing secondary channel

and increase shading pattern through a mosaic of shade vegetation stands during recommendations of measure. of measure. communities during contains more Design increasing selective planting and light habitats. implementation of Incorporate with implementation of appropriate recommendations competition from locations. measure. additional measures Design Design measure. substrate e.g. Incorporate with more shade Negative such as gravel recommendations recommendations areas of gravel. additional measures tolerant species. Potential to Design placement. Incorporate with Incorporate with such as gravel increase the recommendations additional measures additional measures Negative placement. development of Incorporate with such as gravel such as gravel Potential to affect competitive algal additional measures placement. placement. existing stands of

Ranunculion fluitantis species e.g. such as gravel vegetation through epiphytes. placement. changes in water availability.

Design recommendations Incorporate with additional measures such as gravel placement.

3260 Water courses of plain to montane levels with plain levels with courses of the montane to 3260 Water vegetation

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Species / Fencing Tree planting on Tree felling Deflector (using LWD Lower spoil Channel re- Berm creation Backwaters – Backwaters – new Channel realignment Changing Lower community embankment and filled in with brush embankments sectioning reconnections to primary and embankments mattress) IDB, field drains secondary channels Positive Positive Positive Positive Positive Positive Positive Positive Positive Positive Positive Positive Encourages Riparian tree Reduction of local Improvement of flow General improvement Return of natural Localised channel Increase in Increase in available Promotion of more Potential to General improvement riparian tree development will shading will conditions adjacent to to channel form and channel form and narrowing may promote available habitat habitat and dispersal natural flow character improve the extent to channel form and establishment to provide shade and promote increased deflector which will act process through function will promote increased flow velocities and dispersal for for existing white- and sediment regime of available process through supply shade and shelter as well as instream to improve habitat increase in duration of conditions that will improving physical existing white- clawed crayfish favouring habitat habitat. increase in duration ) shelter as well as valuable input of productivity, quality for white-clawed channel forming flows. favour this species. habitat conditions for clawed crayfish populations. development for of channel forming valuable input of woody debris and potentially crayfish. white-clawed crayfish. populations. Reduced vulnerability white-clawed crayfish. Negative flows. woody debris and leaf litter. increasing Negative Reduced to anthropogenic Potential to affect leaf litter. Reduction in availability of food Negative Design Potential to cause Negative vulnerability to disturbance. Negative existing population A. pallipes Improved bank localised sediment items. Potential to cause recommendations damage to existing Potential to cause anthropogenic Potential to cause through changes Design stability and input through damage to existing Incorporate with populations during damage to existing disturbance. damage to existing in water recommendations reduced sediment improved bank populations during additional measures implementation of populations during populations during availability. Incorporate with input. stability. gravel placement. such as gravel measure. implementation of Negative implementation of additional measures placement. measure. Removal of barrier measure. such as gravel Design Design previously placement. Design Design recommendations recommendations Design preventing recommendations recommendations Incorporate with Incorporate additional recommendations colonisation of Incorporate Planting of native additional measures measures such as Incorporate additional reaches by planting of native deciduous species such as gravel gravel placement. design measures such competitive and White-clawed crayfish ( deciduous that will provide placement. as gravel placement damaging species species that will seasonal input of leaf and deflectors. e.g. signal crayfish. provide seasonal litter. input of leaf litter.

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River Wensum Restoration Strategy Implementation SSSI Unit 54: Feasibility and Environmental Scoping Report

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River Wensum Restoration Strategy Implementation SSSI Unit 54: Feasibility and Environmental Scoping Report

Appendix D – Terrestrial SSSI unit links to River Wensum SSSI units

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Appendix D – Links between terrestrial and riverine units of the River Wensum SSSI units

Terrestrial SSSI Riverine RWRS Details of Terrestrial SSSI unit Natural England comments on Action units SSSI reach / linkage between terrestrial and units reaches riverine SSSI units Name: Costessey Common South Foster  No information provided. Conceptual design proposes: 38 (Full SSSI ID 54 03 and Mann 1023143)  Backwater reconnection on Location: TG 165 121 southern border of SSSI unit. Area: 2.03ha  Instream restoration

measures include glide, Type: Neutral grassland – lowland berm and deflector

installation. Condition Assessment: Unfavourable recovering (assessed November 2010)

Management: This is a grassland unit adjacent to the River Wensum. The grassland is an indeterminate community that best fits MG11 Festuca rubra-Agrostis stolonifera-Potentilla anserina (this is not a notified feature of this SSSI). Indicator species include Galium palustre, Juncus acutiflorus, Mentha aquatica, Persicaria amphibia, Rhinanthus minor and Filipendula ulmaria. The grassland forms a mosaic with large patches of Iris pseudacorus, Filipendula ulmaria, Lythrum salicaria, Glyceria maxima and Juncus effusus. The unit has not been grazed for 2 years and does require a grazing regime to be re-established. ‘Weed species’ also need to be closely monitored; a patch, approximately 10m x 5m, of creeping thistle (Cirsium arvense) and nettle (Urtica dioica) was recorded (TG16620 12129). In addition, Himalayan Balsam (Impatiens gladulifera) is growing adjacent to the stream on the southern edge and is spreading into the unit. There is no fence between unit 38 & 39 and they can be managed as one block. Name: Costessey Common South  No information provided. Conceptual design proposes: 39 (Full SSSI ID 54 03 Costessey Parochial Trust 1023144)  Backwater reconnection on

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Terrestrial SSSI Riverine RWRS Details of Terrestrial SSSI unit Natural England comments on Action units SSSI reach / linkage between terrestrial and units reaches riverine SSSI units Location: TG 165 120 eastern border of SSSI unit.  Instream restoration Area: 2.39ha measures include glide, berm and deflector Type: Neutral grassland – lowland installation.

Condition Assessment: Unfavourable recovering (assessed November 2010)

Management: This is a grassland unit that best fits MG8 Cynosurus cristatus-Caltha palustris. Indicator species include Briza media, Filipendula ulmaria, Galium palustre, Lychnis flos-cuculi, Ranunculus flammula, Carex sp., Trifolium pratense, Rhinanthus minor and Orchidaceae sp. The grassland forms a mosaic with large patches of Iris pseudacorus, Filipendula ulmaria, Lythrum salicaria, Glyceria maxima and Juncus effusus. Himalayan Balsam (Impatiens gladulifera) is growing along the stream that forms the southern boundary of the unit and is invading the field. The grassland on the northern edge of the unit is more typical of MG1 Arrhenatherum elatius and species recorded include Dactylis glomerata, Arrhenatherum elatius, Phleum bertolonii, Achillea millefolium , Heracleum sphondylium, Urtica dioica, Agropyron repens, Torilis japonica, Rumex obtusifolius, Cirsium arvense, Holcus lanatus, Agrostis tenuis and Lolium perenne. Mature alders (Alnus glutinosa) 10m x 20m are growing in what appears to be a former pond. Other species recorded here include Filipendula ulmaria, Iris pseudacorus, Cirsium palustre, Rumex hydrolapathum, Phalaris arundinacea and Stachys palustris, with alder seedlings/saplings growing around the periphery. A large patch of nettle (Urtica dioica), creeping thistle (Cirsium arvense),

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Terrestrial SSSI Riverine RWRS Details of Terrestrial SSSI unit Natural England comments on Action units SSSI reach / linkage between terrestrial and units reaches riverine SSSI units greater burdock (Arctium lappa) and broad- leaved dock (Rumex obtusifolius) is growing near the gate and is likely to be a former dung heap from the adjacent stables (TG 16443 12029). Oak seedlings were growing throughout the sward. The unit has not been grazed for 2 years and does require a grazing regime to be re-established. There is no fence between units 38 and 39 and for management purposes they can be treated as one block. Top soil has been removed from some areas near to the gate. Name: Rogers Farm Joyhold Ltd  Unit 40 lies immediately adjacent Conceptual design proposes: 40 (Full SSSI ID 54 01 to the River Wensum, which is 1023145) Location: TG 193 114 embanked and impounded.  Reconnection of floodplain  The unit is hydrologically drainage infrastructure to Area: 1.94ha disconnected from the river, and main channel to maintain is drained through the network of flow through SSSI network. Type: Neutral grassland – lowland internal drains and IDB drains.  Lowering of embankments to

 A feasibility study for River Unit 54 improve floodplain Condition Assessment: Unfavourable is required in order to identify the connectivity. recovering (assessed January 2010) most appropriate restoration of  Instream works include

the river unit, and hence glide, berm and deflector Management: Vegetation semi-natural and connectivity between river and installation. dominated by floodplain and grazing marsh floodplain. habitats. A very low intensity summer cattle  If hydrological regime between grazing regime has been established, but river and floodplain is restored beasts hardly venture onto the floodplain tall then there may be opportunities to herb fens. Regime compatible with the make this unit more appropriate special interest of the river. Current grazing for Desmoulin’s whorl snail. regime favours appropriate conditions for Desmoulin’s whorl snail. Name: Rogers Farm The Great Hospital  Unit 41 lies immediately adjacent Conceptual design proposes: 41 (Full SSSI ID 54 01 to the River Wensum, which is 1023146) Location: TG 195 112 embanked and impounded.  Reconnection of floodplain  The unit is hydrologically drainage infrastructure to Area: 4.32ha disconnected from the river, and main channel to maintain is drained through the network of flow through SSSI network. Type: Neutral grassland – lowland internal drains and IDB drains.  Lowering of embankments to  A feasibility study for River Unit 54 Condition Assessment : Unfavourable improve floodplain is required in order to identify the recovering (assessed January 2010) connectivity.

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Terrestrial SSSI Riverine RWRS Details of Terrestrial SSSI unit Natural England comments on Action units SSSI reach / linkage between terrestrial and units reaches riverine SSSI units most appropriate restoration of  Instream restoration Management: Vegetation semi-natural and the river unit, and hence measures include glide, dominated by floodplain and grazing marsh connectivity between river and berm and deflector habitats. A very low intensity summer cattle floodplain. installation. grazing regime has been established, but  If hydrological regime between beasts hardly venture onto the floodplain tall river and floodplain is restored herb fens. Regime compatible with the then there may be opportunities to special interest of the river. Current grazing make this unit more appropriate regime favours appropriate conditions for for Desmoulin’s whorl snail. Desmoulin’s whorl snail. Name: Rogers Farm NRA  Unit 42 lies immediately adjacent Conceptual design proposes: 42 (Full SSSI ID 54 01 to the River Wensum, which is 1023147) Location: TG 196 110 embanked and impounded.  Reconnection of floodplain  The unit is hydrologically drainage infrastructure to Area: 4.44ha disconnected from the river, and main channel to maintain is drained through the network of flow through SSSI network. Type: Neutral grassland – lowland internal drains and IDB drains.  Lowering of embankments to  A feasibility study for River Unit 54 Condition Assessment : Unfavourable improve floodplain is required in order to identify the recovering (assessed January 2010) connectivity. most appropriate restoration of  Instream restoration the river unit, and hence Management: Vegetation semi-natural and measures include glide, connectivity between river and dominated by floodplain and grazing marsh berm and deflector floodplain. habitats. A very low intensity summer cattle installation.  If hydrological regime between grazing regime has been established, but river and floodplain is restored beasts hardly venture onto the floodplain tall then there may be opportunities to herb fens. Regime compatible with the make this unit more appropriate special interest of the river. Current grazing for Desmoulin’s whorl snail. regime favours appropriate conditions for Desmoulin’s whorl snail. Name: Rogers Farm Mallett  Unit 43 lies immediately adjacent Conceptual design proposes: 43 (Full SSSI ID 54 01 to the River Wensum, which is 1023148) Location: TG 194 109 embanked and impounded.  Reconnection of floodplain  The unit is hydrologically drainage infrastructure to Area: 4.18ha disconnected from the river, and main channel to maintain is drained through the network of flow through SSSI network. Type: Neutral grassland – lowland internal drains and IDB drains.  Lowering of embankments to

 A feasibility study for River Unit 54 improve floodplain Condition Assessment : Unfavourable is required in order to identify the connectivity. recovering (assessed January 2010) most appropriate restoration of  Instream restoration

the river unit, and hence measures include glide,

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Terrestrial SSSI Riverine RWRS Details of Terrestrial SSSI unit Natural England comments on Action units SSSI reach / linkage between terrestrial and units reaches riverine SSSI units Management: Vegetation semi-natural and connectivity between river and berm and deflector dominated by floodplain and grazing marsh floodplain. installation. habitats. A very low intensity summer cattle  If hydrological regime between grazing regime has been established, but river and floodplain is restored beasts hardly venture onto the floodplain tall then there may be opportunities to herb fens. Regime compatible with the make this unit more appropriate special interest of the river. Current grazing for Desmoulin’s whorl snail. regime favours appropriate conditions for Desmoulin’s whorl snail. Name: Riverside Close Hellesdon Jefferys  Unit 44 lies immediately adjacent Conceptual design proposes: 44 (Full SSSI ID 54 01 to the River Wensum, which is 1023163) Location: TG 197 107 embanked and impounded.  Reconnection of floodplain  The unit is hydrologically drainage infrastructure to Area: 3.17ha disconnected from the river, and main channel to maintain is drained through the network of flow through SSSI network. Type: Neutral grassland – lowland internal drains and IDB drains.  Lowering of embankments to

 A feasibility study for River Unit 54 improve floodplain Condition Assessment : Unfavourable is required in order to identify the connectivity. recovering (assessed February 2010) most appropriate restoration of  Instream restoration

the river unit, and hence measures include glide, Management: An assessment of this unit connectivity between river and berm and deflector was carried out based upon the conclusions floodplain. installation. of the River Wensum Restoration Strategy, and upon discussions with the site owner. Vegetation semi-natural and dominated by floodplain and grazing marsh habitats. No grazing regime. Regime compatible with the special interest of the river. Himalayan balsam present on margins of river, and may be present on network of drains on this unit.

Notes – 1. ‘Terrestrial SSSI units’ refers to non-riverine units of the River Wensum SSSI (e.g. SSSI ID 1023157). 2. ‘Riverine SSSI units’ refers to those units of the River Wensum SSSI that comprise sections of river channel (e.g. Unit 54). 3. ‘RWRS reaches’ refers to reaches of river channel as defined in the River Wensum Restoration Strategy (e.g. Reach 01, Hellesdon Reach). 4. ‘Details of terrestrial SSSI unit’ are taken from Nature on the Map: http://www.natureonthemap.org.uk/ 5. ‘Natural England comments on linkage between terrestrial and riverine SSSI units’ are those from an emerging condition assessment of terrestrial SSSI units undertaken by Natural England. The condition assessment is thus far incomplete and in draft form. 6. ‘Action’ refers to those proposed options/measures in the conceptual design undertaken by Atkins.

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7. Changes in river / floodplain hydrology will be considered at detailed design stage as modelling will be required to determine the extent of the relationship. It is inappropriate at this stage due to the potential complexity of this relationship. Reasons stated for “unfavourable condition” of individual SSSI units will be included in the drivers for the design.

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