Assessment of Fish Passage and the Ecological Impact of Migration Barriers on the River Nore Catchment
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Assessment of Fish Passage and the Ecological Impact of Migration Barriers on the River Nore Catchment ‘The Basin’ River Delour Prepared for the Nore Suir Rivers Trust Sponsored by the Office of Public Works Prepared By Alan Sullivan BSc MIFM (1st Draft) Contents Page Executive Summary 5 Acknowledgements 6 Background 7 Aim and Objectives 8 Introduction 10 Catchment Overview 10 Overview of Migration Barriers and Fish Passage 11 Introduction 11 The Legal Perspective 12 The Ecological Perspective 12 Assessing Migration Barrier Impacts 13 Barrier Impact Designation 15 Barrier Category Definition Potential Impacts 15 Temporal Barriers 15 Partial Barriers 16 Total Barriers 16 Project Justification 17 Project Description 17 Fish Presence and Habitat Information 18 Prioritisation 20 Dinan Sub-catchment 24 Site DS1: Dinan Sub-catchment 26 Site DS2a: Dinan Sub-catchment 28 Site DS2b: Dinan Sub-catchment 30 Site DS3a and DS3b: Dinan Sub-catchment 31 Site DS4: Dinan Sub-catchment 33 Site DS5: Dinan Sub-catchment 34 Site DS6: Dinan Sub-catchment 35 Site DS7: Dinan Sub-catchment 36 Site DS8: Dinan Sub-catchment 38 2 Page River Nore (main channel) 39 Site N1: River Nore Thomastown Weir 40 Site N2: River Nore Mount Juliet Estate 42 Site N3: River Nore Bennetsbridge Weir 43 Site N4: River Nore Brett’s Weir 44 Site N5: River Nore Ballyraggert Freestone Weir 45 Site N6: River Nore Castletown Weir 46 Delour River 49 Site DR1: River Delour 50 Kings River 53 Site KR1: Kings River Bradley’s Weir 54 Site KR2: Kings River Hutchinson’s Weir 56 Site KR3: Kings River Kells Mullins Mill Weir 57 Goul River 58 Site GR1: Goul River U/S of Aghmacart Bridge 58 Site GR2: Goul River Loughman’s Weir 59 Little Arrigal River 60 Site LA1: Little Arrigal River U/S Goatsbridge 60 Arrigal River 63 Site A1: Arrigal River Ballyduff 63 Discussion 64 Financial Evaluation of Mitigation Proposals 69 Cost Benefit Analysis 70 Sources of Finance 73 Recommendations and Implementation 75 References 81 Bibliography 82 3 Page List of Tables Table 1 Definition of Barrier Types and Potential Impacts (Taylor and Love, 2003). 15 Table 2 Prioritisation of Barriers Totals and Rankings based on all observed data. 67 Table 3 Prioritisation assessed on impact on Habitat and Species-Lifestage Passability only 68 Table 4 Estimated Expenditure on mitigation relative to projected post project revenue 72 Table 5 Habitat Impact Assessment 77 Table 6 Structural Condition 78 Table 7 Species and Life-stage Passability Ratings 79 Table 8 Assessment of Channel Ponding 80 List of Figures Fig:1 Lower reaches Dinan River. 24 Fig:2 The natural substrate composition of the Dinan River 24 Fig:3 This extensive landslide is one of a number of such events identified in the 25 Dinan sub-catchment in 2007. Fig:4 The Dinan River immediately downstream of the Metal Bridge site. 25 Fig:5 The Metal Bridge. 26 Fig:6 The stepped sill 27 Fig:7 The bridge sill near Coan. 28 Fig:8 The fish pass is blocked with cobble. 29 Fig:9 View downstream from Coan Bridge 29 Fig:10 The bridge sill at Coan on a tributary of the Dinan River. 30 Fig:11 Castlecomer Weir 31 Fig:12 The bridge sill at Castlecomer Bridge 32 Fig:13 Ormonde Bridge (N78) an imposing and total barrier to indigenous fish 33 Fig:14 Doonane Bridge. 34 Fig:15 Drumgoole Weir 35 Fig:16:Massford Bridge in low flow 36 Fig:17 Massford Bridge site during an adult salmonid migration discharge 37 Fig:18 Clogh Bridge 38 Fig:19 Thomastown Weir looking downstream from the apex crest 40 Fig:20 Spawning area of P.marinus (sea lamprey) immediately d/s of Thomastown Weir. 41 Fig:21 Thomastown weir is in an advanced state of structural decay 41 Fig:22 The weir at Mount Juliet. 42 Fig:23 Bennetsbridge Weir 43 Fig:24 Brett’s Weir May 2007 44 Fig:25 Ballyraggert Weir 45 Fig:26 Ponding of channel upstream of Ballyraggert Weir 45 Fig:27 Castletown Weir in low April flow 46 Fig:28 Castletown weir. River flow rates suitable for the migration of adult salmon. 47 Fig:29 This was the only outlet for the downstream migration of smolts in April 2007. 48 Fig:30 The Delour River above Anatrim Bridge. 49 Fig:31 ‘The Basin’ Impoundment; 50 Fig:32 The confluence of the River Delour with the River Nore 51 Fig:33 The fish pass at the Basin 51 Fig:34 The Kings River above Stoneyford 53 Fig:35 Bradley’s weir February 2007, 54 Fig:36 Bradley’s Weir April 2007 55 Fig:37 Hutchinson’s Weir (Kings River) 56 Fig:38 Mullins Weir. (Kings River) 57 Fig:39 Goul River, u/s of Aghmacart Bridge 58 Fig:40 Goul River, Loughman’s Weir 59 Fig:41 The water diversion structure to Gerard Kerwan’s Goatsbridge fish farm. 61 Fig:42 Over-spill attracts fish to un-passable sections of barrier. 62 Fig:43 The entrance to the pool pass at Goatsbridge. 62 Fig:44: Ballyduff Weir. Water diversion structure to Gerard Kerwan’s Ballyduff fish farm. 63 Fig 45 Overview of migration barriers and geographical influence on Nore catchment 66 4 Executive Summary It is envisaged that the preliminary results of this working document will assist in formulating a strategic plan to provide a process for improving passage for anadromous and non-anadromous salmonids and indigenous fish species at barriers within the River Nore system. Critical components considered necessary for creating a catchment reduced and/or free of impediments to passage have been delineated and described. Components covered within this planning document include: ecological impacts of barriers and fish migration on the River Nore catchment; description, classification and prioritisation of barriers, mitigation prioritisation process, barrier mitigation alternatives, outline of project engineering and construction options, project funding options. The study has been designed to form the framework of an annual work plan and project work plans incorporating all components. When assessing the ecological impact from a catchment perspective, the reality of the scale of influence of the barriers is quite profound. It is estimated that over 30% of the catchment is negatively influenced. It has been calculated that in excess of 150,000 metres of channel on the River Nore catchment is directly impacted by barriers to migration or loss of habitat through ponding of river channel. The removal or the mitigation of the barriers highlighted in the report will have a profoundly positive impact on the entire ecology of the Nore catchment, directly benefiting all indigenous fish species and peripherally benefiting many species such as dippers, kingfishers, otters, freshwater pearl mussel, crayfish and invertebrates. Within the context of the report, the barriers on the main channel of the River Nore constitute perhaps the most contentious, expensive (in terms of mitigation) and limiting (in terms of their over-all effect on the ecology of the Nore catchment). It is envisaged that delineating a course of action through consultation may be a complicated and protracted procedure as many of the socio-economic issues will be deep rooted and highly emotional. It will be vital to conduct an outreach programme to discuss the ecological, social and economic issues within stakeholders and the community. A number of barriers identified in this report have structural damage and have a high risk of failure and would be of concern to the statutory organisations involved in the management of the Nore catchment. However, the primary purpose of this prioritisation is to identify sites needing fish passage remediation; thus, more weight was put on the biological criteria to identify crossings which are serious impediments to migration and that have significant reaches with suitable upstream habitat. 5 Acknowledgements It would be difficult to thank everyone that has in some way participated in this report without leaving someone out so I am not going to mention any persons by name. The support from the representatives of the Nore Suir Rivers Trust without whose ability this study would not have got off the ground, the OPW for the financial support in funding the report, and the angling clubs and their representatives on the River Nore catchment from Mountrath to Durrow and Freshford to Kells and Kilkenny to Thomastown to name a few. I would like to extend my appreciation to the riparian land owners and the management/owners of the weirs/bridge sills for permitting access and supplying valuable historical evidence. Finally, I would like to thank representatives of the CFB, SRFB, DCMNR, EPA, Parks and Wildlife, and the Heritage Council, for their professional advice and information. Definition of Conservation Based on the 1980 United Nations Environment Program: “That aspect of renewable resource management which ensures that utilisation is sustainable and which safeguards ecological processes and genetic diversity for the maintenance of the resource concerned. Conservation ensures that the fullest sustainable advantage is derived from the resource base and that facilities are so located and conducted that the resource base is maintained”. 6 Background In 1994 Dr Martin O’Grady (CFB) and Mr. Tom Sullivan (SRFB) published a baseline fishery survey and development plan for the River Nore catchment. A major component of the report focused on channel ponding and physical impoundments to the migration of fish; it stated; ‘‘a number of impassable man- made physical barriers were either prohibiting or severely limiting salmon access to a number of potentially productive spawning and nursery zones’’. The report also states; ‘‘the number of physical impediments to the upstream movement of anadromous and non-anadromous salmonids is unusually high in the Nore catchment relative to Irish standards’’.