Ecological Survey of the Grand Canal

I I ECOLOGICAL SURVEY I OF THE GRANDCANAL 1991 i I Part1 Survey Report I 1 Office Of Public Works 1992 p ii r l r I L s ECOLOGICAL SURVEY OF THE I u GRAND CANAL 1 s I J Part 1: Survey Report s I s LJ Prepared for: I The Wildlife Service and Waterways Section, s Officeof Public Works. 1992. L I r LJ By L Marie Dromey Brigid Johnston r s Sinead Keane L I E s L I El r LI s s LI s .7 U r-I r-I r-I SUMMARY 1. Part 1 contains the report of an ecological survey of LJ theGrand Canal carried out over one full growing season in 1991. The main objectives were to assess the value of the canal corridor for natureconservation, and to make r-I recommendations for the management of the canal takingthese values into account. The Circular Line, the Mainline, the rl Barrow Line and the Edenderry Branch are all fully navigable. LJ The Naas Braanch is navigable as far as Naas itself, but the section between there and the harbour at Corbally isblocked by a low bridge just outside Naas. This unnavigable stretch of canal is called the Corbally Branch in the report, to distinguish it from the navigable part of the samebranch line. The Milltown Feeder links the canal with Pollardstown L Fen, which is the main source of water for theGrand Canal system. The Kilbeggan Branch was closedto navigation in r--1 1961, and is almmost dry. The possibility of re-opening this LJ branch is being discussed at the present. 2. The habitats along the canal were assigned to the five zones into which the canal corridor was divided- boundary, boundary verge, towpath, bank verge and channel. Hedgerows arethe dominant haabitat of the boundary, but in places El where grazing did not occur scrub and small areas ofwoodland had developed. The boundary verge was dominated by grassland on the Mainline, and by scrub on the Barrow Line- suggesting .7 a difference in past management practices. The towpaath was generallygrassland dominated by trample-resistant species, i or was unvegated (a bare track, or a tarred road). The ideal r 17 bank verge includes species that are transitional between dry L and wet habitats, with grassland at the top of the bank and a I reedfringe at the water's edge. This situation is not as 17 commonalong theGrand Canal as it is on theRoyal. The channel habitats ranged from shallow-water emergents at the margins to open-waterin the centre of the canal. The L stoneworkof locks, bridges and walls provides arange of habitats ranging from wet to dry. I El 3. The vascular flora was surveyed in detail. Diversities were highest in the boundary, boundary verge and bank zones. Species occurrence in each zone was calculated inorderto L determine rare and abundant species of each and therefore of the whole canal system. The occurrence ofnationally rare species within the system was highlighted. Ecologically E interesting areas are highlighted. The BarrowLine was observed to be more woodedthan rI other sections of the system. TheMainlineitselfwas LJ observedto be uniform along its length withmuch of the scrub/wooded areas removed and replaced by grassland which is frequentlymowed. Bankrepairs werecarriedout on the u Milltown Feeder in 1990 and 1991 and the vegetation alongits i 17 E L LJ bankswas not fully established at the time of the survey. This accounts for the low terrestrial diversities there. Rare terrestrial species along the network were characteristic of habitats small in area which still survive. The Corbally Branch is not intensively managed and it is ecologically very interesting, supportinga variety of habitats each with a high speciesdiversity. This area was prposed for designation as an Area of Scientific Interest in 1991. In the channel, the greatest diversity occurs along the LJ Corbally Branch, the eastern stretch of the Mainline and the southern end of the Milltown Feeder. Theseare stretches infrequently used by boats and untreated with herbicides. The i LJ BarrowLine and the Mainline west of Edenderrysupport F extremely lowaquatic diversities due to a combination of L highboatnumbers, herbicide spraying and bankrepair. Aquatic species tolerant of eroding conditions make upthis I low diversity. F Thefindings concerning the impacts ofboating, the L effectsof herbicide, rare plants and bank type alongthe i Grand and Royal Canal networks are discussed. r L 4. Theimpacts ofmanagement on nature conservation throughout the canal system have been reviewed. Thesewere r considered underthe general headings of maintenance and L 71 recreation. Dredginganddumping of spoil can have significant impacts of the flora and fauna, as can i tree-cuttingand scrubclearance. Changingthe grazing r 17 regimemayreduce species diversity on thetowpath and L boundaryverge habitats. Miantenance of waterquality is i essential for nature conservation. Prolonged use ofaquatic herbicides has reducedthebotanical diverstiy of the L channel. M 71 5. Part 2 of the report contains gerneralguidelines for conservation management of the Grand Canal, and L recommendations for each stretch of canal. This should allow El natureconservationto be given equal prioritywith other values (in particular recreation and day-to -day maintenance) along the canal, which should allow for the existing diversty .7 of the system to be improved and not merely maintained. 6. Part 3 of the report contains the base-linemaps LJ producedin the field - each showing lkm of the canal, with the botanical features maked on it in some detail. L 17 EJ 17 El J CONTENTS PAGE F-1 LJ LIST OF PHOTOGRAPHS iii It LIST OF FIGURES iii LIST OF TABLES iv LIST OF APPENDICES v J ACKNOWLEDGEMENTS vi LJ SOME DEFINITIONS AND ABBREVIATIONS vi u MANAGEMENT OBJECTIVES 1 GENERAL GUIDELINES FOR CONSERVATION MANAGEMENT 1 LJ PHOTOGRAPHS 7 EJ CHAPTER 1. INTRODUCTION 40 1.1 History of the Grand Canal 40 EJ 1.2 Ecological surveys 43 1.3 Grand Canal Ecological Survey 43 1.4 Study Area 44 EJ CHAPTER 2. HABITATS 49 ri LJ 2.1 Introduction 49 2.2 Woodland 49 2.3 Scrub 50 2.4 Hedgerow 50 2.5 Fen 51 2.6 Bog 51 El 2.7 Ditches and Drains 51 2.8 Grassland 52 2.9 Bare Ground 53 El 2.10 Bank 53 2.11 Aquatic Habitats 53 2.12 Stonework 54 l__1 CHAPTER 3. FLORA OF THE GRAND CANAL 55 EJ 3.1 Introduction 55 3.2 Methodology 55 3.3 Results 56 s 3.4 Discussion 61 3.5 Comparison of Grand and Royal Canals 64 5 3.6 Areas of High Ecological Interest 66 3.7 Conclusions 70 5 rJ Ej rl LJ PAGE CHAPTER 4. IMPACTS OF MANAGEMENT 82 4.1 Maintenance 82 4.2 Recreation 103 CHAPTER S. CONCLUSIONS 112 El 5.1 Nature Conservation and Management 112 112 E] 5.2 Canal A.S.I.s BIBLIOGRAPHY 114 El APPENDICES 118 v n LJ Ll C LJ C LJ n E E] G LIST OF PHOTOGRAPHS 17 PHOTOGRAPHS CANAL PAGE L1 1-33 Mainline 7 34-40 Barrow Line 24 LJ 41 Edenderry Branch 28 42-47 Naas Branch 29 48-49 Milltown Feeder 32 El 50-55 Kilbeggan Branch 33 56-60 Barrow Line 36 .7 LIST OF FIGURES LJ FIGURE NO. PAGE r t 1.1 Inland Waterways of Ireland 41 1.2 Kilometre Sections and ASIs along the Grand Canal Mainline 46 El 1.3 Kilometre Sections and ASIs along the Grand Canal Branches 47 4.1 Channel Orientation and Planting for El Shade 90 4.2 Manipulation of Shading 91 4.3 The Impacts of Recreation (excluding E1 management) on animals 104 4.4 The Impacts of Boats on Plants 105 El v'-1 E1 .7 u u ur1 Hl EJ El El U LIST OF TABLES TABLE NO. PAGE 1.1 Summary of the Grand Canal System 42 1.2 Areas of Scientific Interest along the r1 Grand Canal 48 3.1 Grand Canal - High and Low Diversity in the Boundary Zone 71 3.2 Grand Canal - High and Low Diversity in the Boundary Verge Zone 71 3.3 Grand Canal - High and Low Diversity in the Towpath Zone 72 3.4 Grand Canal - High and Low Diversity in the Bank Zone 72 3.5 Grand Canal - High and Low Diversity in the Channel 73 3.6 High and Low % Occurrence of Species in L the Boundary Zone of the Grand Canal 74 3.7 High and Low % Occurrence of Species in I the Boundary Verge Zone of the Grand Canal 76 C 3.8 High and Low % Occurrence of Species in I the Towpath Zone of the Grand Canal 78 r 3.9 High and Low % Occurrence of Species in L - the Bank Zone of the Grand Canal 79 I 3.10 High and Low % Occurrence of Species in the Channel of the Grand Canal 80 L 3.11 High and Low % Occurrence of species on the Locks and Bridges of the Grand I rj Canal 81 u 4.1 Hedgerow Shrubs and Trees 82 4.2 Native Trees and Shrubs suitable for Planting 85 r 4.3 Target Spectra of Selected Herbicides 92 L 4.4 Susceptibility of Aquatic Plants to Dichlobenil 93 4.5 Susceptibility of Aquatic Plant Species to Casoron (Dichlobenil) and Clarosan (Terbutryne) based on Trials Conducted in Ireland and the U.R. 95 4.6 The Susceptibility of Aquatic plants to Erosion. 106 n EJ I t/ El u LIST OF APPENDICES APPENDIX n PAGE LJ Appendix 1 Plants of the Boundary Zone of the Mainline 118 r-, LJ Appendix 2 Plants of the Boundary Verge Zone of the Mainline 125 L Appendix 3 Plants of the Towpathof the Mainline 134 Appendix 4 Plants of the Bank along the Mainline 139 E) Appendix 5 Plants of the Channel of the Mainline 148 s Appendix 6 Plants of the Locks and Bridges along the Mainline 151 El Appendix 7 Plants of the Boundary Zone of the Grand Canal Branches 156 s Appendix 8 Plants of the Boundary Verge Zone of the Grand Canal Branches 161 s Appendix 9 Plants of the Towpathof the Grand Canal Branches 167 r 17 Appendix 10 Plants of the Bank along the Grand Canal Branches 170 El Appendix 11 Plants of the Channel of the Grand Canal Branches 176 l LJ Appendix 12 Plants of the Locks and Bridges along the Branches of the Grand Canal 179 s Appendix 13 Species Diversity of all Zones along each sample area along the Mainline and Branches of the Grand Canal 183 s r1 LJ U E U El 0 El y Ll r r--1 tl L r ACKNOWLEDGEMENTS I L] r This survey was supervised by Jim Ryan of the OPW Parksand Wildlife Service who provided helpful comments.

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