Nigel Holmes Report
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Environmental Quality Appraisal of the River Ems A Report to EA, Sussex Area, Worthing June 2007 Dr Nigel T H Holmes ALCONBURY ENVIRONMENTAL CONSULTANTS The Almonds, 57 Ramsey Road, Warboys, Huntingdon PE28 2RW, UK Tel: 01487 822020; Mobile: 07957 424887 EMAIL: [email protected] Ems Environmental Quality Appraisal – Holmes 2007 1 Executive Summary The Environment Agency (EA) identified the Ems in 2003 as being potentially over-licensed for groundwater abstraction and potentially at risk of ecological damage. Being a chalk stream bestows greater status regarding its ecological importance because such systems are Biodiversity Action Plan (BAP) priority habitats. Continual development pressure also puts further strains on the environment and requires the EA to be able to protect the best, and enhance the rest, wherever possible. The prime driver for this investigative project was therefore to obtain as much information as possible to help the EA in this task. For each of the four reaches in the catchment, an assessment of the present-day ecological status was carried out alongside a review of contemporary and historic factors that could influence the ecological health of the river. This report presents the findings of the study. A key conclusion from the study was that there has probably been significant degradation of ecological quality, but paucity of data makes totally objective conclusions on the ‘cause’ and ‘effect’, and the severity of them, virtually impossible. Therefore it has to be accepted that conclusions drawn are not always supported by firm facts, but have been derived from many disparate sources that, taken together, do provide very important evidence of ‘damage’. In brief summary, the report has concluded the following. ! Natural Flow Characteristics are very different in the four reaches assessed, and this is still the key determinant of the assemblage of plants and animals found within the majority of the catchment. ! Historic changes to alter the channel form are considered to be a very influential anthropogenic factor impacting what would be ‘natural’ plant and animal communities in the catchment, but these have occurred over centuries and communities will have changed, and possibly become more diverse, as a result of these changes. ! Routine Flood Defence Management is only considered to have significant impacts on ecology in the middle and lower catchment where measures, in the past, have aimed at creating over-large, clean channels with limited structural diversity. ! Siltation is a problem that affects ecology greatly, especially fish and invertebrates, and in the permanently flowing reaches of the catchment is perceived to be a problem that may be on the increase. ! Concerns relating to abstraction-induced low flows has been one of the drivers for the study, and is considered to have impacted the plant and animal communities in the river, especially fish. ! Present/recent water quality - from reviewing data, it would appear that poor water quality is not an issue today, and no catastrophic pollution events have been reported to have affected the catchment in the past. ! Alien species are only implicated in impacting water voles, and the fragmented population remains on a knife- edge and vulnerable to re-appearance of this predator in the future. ! Barriers to migration is primarily an issue for fish; these have serious implications for sea trout, a species with a long history associated with the river and one that could be greatly enhanced by improved migration potential through the river Based on the review of available information, the report makes a series of recommendations for actions. These include: ! Getting an objective resolution of the impacts of abstraction on flow [discharge] (already in hand by EA proposals, but may take 3 years) - without a clearer understanding of the effects the major abstractions have in causing flow to depart from naturalness, it will be difficult to objectively determine if, and where, most environmental gain could be achieved through changes to resource management. ! In parallel with the above, there is a need to determine more objectively how effective the present augmentation is in protecting both river landscape and ecology downstream of its inflow. Emergency measures are recommended for dry periods when the augmentation flow is not reaching its intended target. ! A Water Level Management Plan is deemed essential to enable sea trout to migrate into the system and maximize potential for increasing channel habitat diversity and decreasing flood risk. ! Modified river management measures (historical flood defence practices) are recommended; these have been presented to EA flood defence personnel for consideration and in-principle support for their implementation was indicated. ! Channel enhancements/restoration could be carried out at several locations; one opportunity has already been acted upon and there is fulsome landowner support for the major opportunities elsewhere. ! Targeted surveys in areas identified as potentially of very high, yet unconfirmed, conservation interest have been made, as have recommendations for controlling aliens and the possible introduction of crayfish to the catchment. Ems Environmental Quality Appraisal – Holmes 2007 2 Contents 1. Introduction 5 2. Approach 10 3. Background Information on the Character of the Ems Catchment 15 3.1 Introduction 3.2 Discharge, and the Key Factors Influencing it 3.2.1 General Catchment Considerations 3.2.2 Abstractions 21 3.2.3 Discharges 24 3.2.4 Summary 3.3 Water Quality 29 3.4 Channel Form, Flood Risk and River Management 33 3.4.1 General Considerations 3.4.2 Land Drainage, River Management & Flood Risk Management 34 3.4.3 Present-day Channel Form – Habitat Character 36 3.5 Other Key Factors Affecting Ecology 37 4. Information Used for Assessment of Current and Past Ecological Status 39 4.1 Introduction 4.2 Mammals 4.3 Fish 4.4 Invertebrates 43 4.5 Macrophytes 46 4.6 Habitats 48 4.7 Biodiversity Action Plan and Red Data Book Species 49 5. Reach Characterisation and Environmental Quality Assessment of the Ems 51 5.1 Introduction 5.2 Ems Reach 1 – Source to Broadwash 5.3 Ems Reach 2 – Broadwash to Watersmeet 58 5.4 Reach 3 – Aldsworth Arm 66 5.5 Ems Reach 4 – Watersmeet (Westbourne Mill Pond) to Harbour 71 6. Summary of Key Factors Affecting the Ecological Status of the Ems Catchment 78 7. Recommended Short- and Medium-Term Actions (including Key Data Gathering needs) 80 References, Glossary of abbreviations & Acknowledgements 85 Ems Environmental Quality Appraisal – Holmes 2007 3 Appendices & Annexes – Bound as Separate Volume Appendix 1 Maps of reaches and site locations Appendix 2 Maps showing locations of major data sources Appendix 3 Illustrated River Rehabilitation Case Example Appendix 4 River Management Annex 1 Channel Characterisation Annex 2 MTR and macrophyte data from 2005-7 Annex 3 Summary of resume of some key reference documents and data ! 3A Ecology ! 3B Flow, Abstraction & Hydrology ! 3C Physical Channel Character, Flood Defence, River Management ! 3D Miscellaneous/Other – e.g. LEAP, WFD Annex 4 Summaries of key information in files, and records of meetings/interviews ! 4A Ecology ! 4B Flow, Abstraction & Hydrology ! 4C Physical Channel Character, Flood Defence, River Management ! 4D Local Personnel Annex 5 Photographs taken during study – electronic only, on CD Ems Environmental Quality Appraisal – Holmes 2007 4 1. Introduction This report has been prepared for the Fisheries, Recreation & Biodiversity (FRB) team of the Sussex Area of the Environment Agency (EA). The study reported on here is a review of the environmental state of the River Ems historically, and at present, and draws together information on environmental factors that influence ecology. Together, this information provides a basis for determining what are the key factors influencing ecological status today, and what may be required to restore it to its historical health. The study has developed from, and is intended to draw together, several initiatives that began around 2000. The Fisheries, Recreation and Biodiversity (FRB) team initiated a ‘Sussex Chalk Rivers Project’ primarily because little-known rivers such as the Ems and Lavant were increasingly under threat from development, despite being priority BAP habitat (chalk stream). At the same time, the Catchment Abstraction Management Strategy (CAMS) for the area identified that the rivers were ‘over-licensed’ (EA; 2003) and possibly impacted by abstraction, but the latter could not be quantified. It was also of great concern to ecologists that the CAMS process did not adequately cater for winterbourne (intermittently flowing) reaches; the same such reaches that were under threat from developers, often because they did not realize their ecological importance. These areas of concern for, and responsibility of, the EA provided a catalyst for different functions to work together to raise the profile of the streams and combine forces to undertake work to help understand them better so that actions could be brought to help ‘protect the best and enhance the rest’. The Water Framework Directive (WFD) has, in recent years, also become increasingly important as implications of its implementation become clearer. Rivers so physically altered as the Ems are designated ‘heavily modified waterbodies (HMWBs)’, but despite this the Directive requires measures to be put in place to help them achieve ‘Maximum Ecological Potential (MEP)’ or ‘Good Ecological Potential (GEP)’ through