Providing integr water resource and er 94/216 M ftA'Anglian 2 a - 5 SOUTHERN River Deben Alleviation of Low Flows Scheme: An Environmental Appraisal Final Report May, 1994 Report No 94/3/821 Client National Rivers Authority Anglian Region Kingfisher House Goldhay Way Orton Goldhay Peterborough PE2 5ZR Southern Science Ltd Premium House Brighton Road Worthing West Sussex BN 11 2EN Tel (0903) 823328 Fax (0903) 210474 NRA Anglian River Deben ALF Environmental Appraisal CONTENTS SUMMARY 1 INTRODUCTION 1 2 ASSESSMENT OF HISTORIC AND CURRENT STATUS OF THE RIVER DEBEN - ECOLOGICAL ASSESSMENT 2 Aquatic, Riparian and Wetland Species and Habitats Associated with the River Deben 2 Sites of Nature Conservation Value in the Freshwater Deben Catchment 2 Ecological Surveys o f the River Deben 12 Macrophytes Associated with the River Deben 13 Woodland Associated with the River Deben 22 Grassland Associated with the River Deben 23 Fen Vegetation Associated with the River Deben 24 Tall Herb Vegetation Associated with the River Deben 24 BirdJife Associated with the River Deben 25 Species Diversity 25 Bird Rarity 25 Mammals Associated with the River Deben 28 National Rarity 28 County Rarity ~ 28 Fisheries of the River Deben 29 Fishing Clubs 29 NRA Fish Surveys 29 Fish Mortalities 34 Fish Health Checks 34 Chemical Water Quality of the River Deben 36 Data Used in this Study 36 Key Features o f the Water Quality Record 36 River Quality Objectives 38 Pollution Incidents 40 Channel Maintenance 40 Amenity and Recreation Associated with the River Deben 41 Public Footpaths and Bridleways 41 Wickham Market Countryside Walk 41 Ash Abbey 41 Easton Park Farm 41 Soham Nature Trail 42 Framlingham Castle 42 Southern Science Ltd 94-3-821/May 1994/NJR/63002/Final NRA Anglian River Deben ALF Environmental Appraisal Other. Sites 42 Parish Histories 42 Historic Articles and Photographs 42 Land Use and the River Deben 43 Invertebrate Records for the River Deben 45 Diversity o f Families and BMWP/ASPT Scores 45 Upstream o f Debenham STW 45 A ll 20 Road Bridge 47 Kettleburgh Bridge 47 Glevering Bridge 48 Eyke Ford 49 Summary 49 ASSESSMENT OF HISTORIC AND CURRENT STATUS OF THE RIVER DEBEN - HYDROLOGICAL AND HYDROGEOLOGICAL ASSESSMENT 56 Sources of Historical Morphological Information 56 Location of Ditches and Dykes 56 River Control Structures 56 Historical Hydrological Assessment 56 Current Hydrological Status of the River 75 Geology and Hydrogeology 85 ASSESSMENT OF IN-RIVER NEEDS 88 Aquatic Plant Communities' 88 Submerged, Narrow Leaved Plants 88 Submerged, Broad Leaved Plants 88 Rooted, Floating Leaved Plants 89 Emergent, Narrow Leaved Plants 89 Emergent, Broad Leaved Plants 89 Encroaching Plants 89 Narrow Leaved, Upright Bank Plants 90 Narrow Leaved, Straggling Bank Plants 90 Broad Leaved, Upright Bank Plants 90 Bankside Trees and Shrubs 91 General Comments 91 Riparian Wetland Sites 91 Southern Science Ltd 94-3-821/May 1994/NJRJ63002/Ftnal NRA Anglian River Deben ALF Environmental Appraisal Birdlife 93 Kingfishers 93 Bam Owl 93 Little Ringed Plover 94 Redshank 94 Shelduck 94 Teal 94 Fisheries 96 Basic Habitat Preferences 96 Specific In-River Needs of the River Deben Fishery 96 Mammals 101 Otter 101 Water Vole 102 Shrews 102 Bats 102 Channel Morphology 102 Invertebrates 103 5 CONCLUSIONS AND RECOMMENDATIONS 105 Aquatic Plant Communities - 105 Conclusions of the Study 105 Recommendations 105 Riparian Wildlife Sites 107 Conclusions of the Study 107 Recommendations 107 Birdlife 108 Conclusions o f the Study 108 Recommendations 108 Fisheries 110 Conclusions o f the Study 110 Recommendations 110 Mammals 111 Conclusions o f the Study 111 Recommendations 111 Water Quality 113 Conclusions o f the Study 113 Recommendations 113 Southern Science Ltd 94-3-821/May 1994/NJR/63002/Fmal NRA Anglian River Deben ALF Environmental Appraisal Amenity, Recreation and Landscape 114 Conclusions o f the Study 114 Recommendations 114 Invertebrates 115 Conclusions o f the Study 115 Recommendations 115 The Potential Environmental Benefits and Threats from the Proposed Measures to Alleviate Low Flows on the Deben 116 Do Nothing 116 Changes or Controls on Spray Irrigation 116 Augmentation 117 River Channel Management 118 LIST OF CONSULTEES 121 REFERENCES AND BIBLIOGRAPHY 122 AUDIT TRAIL APPENDICES - Bound as a Separate Volume Southern Science Lid 94-3-821 /May 1994/NJR/63002/Final NRA Anglian River Deben ALF Environmental Appraisal CONTENTS SUMMARY 1 INTRODUCTION 1 2 ASSESSMENT OF HISTORIC AND CURRENT STATUS OF THE RIVER DEBEN - ECOLOGICAL ASSESSMENT 2 Aquatic, Riparian and Wetland Species and Habitats Associated with the River Deben 2 Sites o f Nature Conservation Value in the Freshwater Deben Catchment 2 Ecological Surveys o f the River Deben 8 Macrophytes Associated with the River Deben 9 Woodland Associated with the River Deben 15 Grassland Associated with the River Deben 16 Fen Vegetation Associated with the River Deben 17 Tall Herb Vegetation Associated with the River Deben 17 Birdlife Associated with the River Deben 18 Species Diversity 18 Bird Rarity 18 Mammals Associated with the River Deben 20 National Rarity 20 County Rarity 20 Fisheries of the River Deben 21 Fishing Clubs 21 NRA Fish Surveys 21 Fish Mortalities 25 Fish Health Checks 25 Chemical Water Quality of the River Deben 27 Data Used in this Study 27 Key Features o f the Water Quality Record 27 River Quality Objectives 28 Pollution Incidents 30 Channel Maintenance 30 Amenity and Recreation Associated with the River Deben 31 Public Footpaths and Bridleways 31 Wickham Market Countryside Walk 31 Ash Abbey * 31 Easton Park Farm 31 Soham Nature Trail 32 Framlingham Castle 32 Southern Science Ltd 94-3-821/May 1994/NJR/63002/Final NRA Anglian River Deben ALF Environmental Appraisal Other Sites 32 Parish Histories 32 Historic Articles and Photographs 32 Land Use and the River Deben 33 Invertebrate Records for the River Deben 35 Diversity o f Families and BMWP/ASPT Scores 35 Upstream o f Debenham STW 35 A1J20 Road Bridge 35 Kettleburgh Bridge 36 Glevering Bridge 37 Eyke Ford 38 Summary 38 ASSESSMENT OF HISTORIC AND CURRENT STATUS OF THE RIVER DEBEN - HYDROLOGICAL AND HYDROGEOLOGICAL ASSESSMENT 40 Sources of Historical Morphological Information 40 Location of Ditches and Dykes 40 River Control Structures 40 Historical Hydrological Assessment 40 Current Hydrological Status of the River 43 Geology and Hydrogeology 44 ASSESSMENT OF IN-RIVER NEEDS 46 Aquatic Plant Communities 46 Submerged, Narrow Leaved Plants 46 Submerged, Broad Leaved Plants 46 Rooted, Floating Leaved Plants 46 Emergent, Narrow Leaved Plants 47 Emergent, Broad Leaved Plants 47 Encroaching Plants 47 Narrow Leaved, Upright Bank Plants 48 Narrow Leaved, Straggling Bank Plants 48 Broad Leaved, Upright Bank Plants 48 Bankside Trees and Shrubs 49 General Comments ‘ 49 Riparian Wetland Sites 49 Southern Science Ltd 94-3-821/May 1994/NJR/63002/Final NRA Anglian River Deben ALF Environmental Appraisal Birdlife 51 Kingfishers 51 Bam Owl 51 Little Ringed Plover 52 Redshank 52 Shelduck 52 Teal 53 Fisheries 54 Basic Habitat Preferences 54 Specific In-River Needs o f the River Deben Fishery 54 Mammals 59 Otter 59 Water Vole 60 Shrews 60 Bats * 60 Channel Morphology 60 Invertebrates 61 5 CONCLUSIONS AND RECOMMENDATIONS 63 Aquatic Plant Communities 63 Conclusions o f the Study 63 Recommendations 63 Riparian Wildlife Sites 65 Conclusions o f the Study 65 Recommendations 65 Birdlife 66 Conclusions o f the Study 66 Recommendations 66 Fisheries 68 Conclusions o f the Study 68 Recommendations 68 Mammals 69 Conclusions o f the Study 69 Recommendations 69 Water Quality 71 Conclusions o f the Study 71 Recommendations 71 Southern Science Ltd 94-3-821/May 1994/NJR/63002/Final NRA Anglian River Deben ALF Environmental Appraisal Amenity, Recreation and Landscape 72 Conclusions o f the Study 72 Recommendations 72 Invertebrates 73 Conclusions o f the Study Recommendations The Potential Environmental Benefits and Threats from the Proposed Measures to Alleviate Low Flows on the Deben 74 Do Nothing 74 Changes or Controls on Spray Irrigation 74 Augmentation 74 River Channel Management 74 LIST OF CONSULTEES REFERENCES AND BIBLIOGRAPHY 79 AUDIT TRAIL APPENDICES - Bound as a Separate Volume Southern Science Ltd 94-2-821/May I994/NJRJ63002/Final NRA Anglian River Deben ALF Environmental Appraisal SUMMARY ^ Introduction ^Lr^ .,<N , y f ^ V<*K * The River Deben is a rural river flowing through a boulder clay coy^red Chalk catchment to the Deben estuary near Woodbridge in Suffolk, Figure 1. It was identified by the National Rivers Authority (NRA) in 1993 on a priority list of 40 rivers where low flows, due to authorised abstraction, were considered a potential problem. In 1959 and 1973 the river through Wickham Market is reported as having dried up • for several days although flows, due to groundwater baseflow, were still measurable downstream at Naunton Hall (AWA, 1975). During 1976 the river upstream of Debenham STW is reported to have dried up (AWA, 1983) and undated newspaper ^ reports suggest this reoccured in either 1989 or 1990. ^ pr- As part of a NRA (Anglian) appraisal of the feasibility and cost/benefit of possible solutions to low flows in the Deben, Southern Science were commissioned to collate and review available baseline ecological data for the freshwater reach of the river and its adjacent riparian habitat, and to identify the in-river needs of key species or habitats present. A variety of data sources were approached for information including Suffolk Wildlife Trust, English Nature, Suffolk County Council, The Otter Trust, MAFF, local studies libraries and the NRA itself. 5 Key species and habitats were selected because of their rarity, or because they were considered to be characteristic of the river. For each of these species or habitats their in-river needs were assessed with particular attention paid to the impacts of flow, channel maintenance, important habitat features and water quality.