Environment Agency the Middle and Lower Stour and Moors River Ecological Vision and Restoration Measures
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Environment Agency The Middle and Lower Stour and Moors River Ecological Vision and Restoration Measures Hyder Consulting (UK) Limited 2212959 The Mill Brimscombe Port Stroud Glos GL5 2QG United Kingdom Tel: +44 (0)1453 423 100 Fax: +44 (0)1453 887 979 www.hyderconsulting.com Environment Agency The Lower and Middle Stour and Moors River Ecological Vision and Restoration Measures Author Mark Lang Checker Bruce Lascelles Approver Bruce Lascelles Report No 002-GL-UA004077-03 Date 26th September 2012 This report has been prepared for the Environment Agency and Natural England in accordance with the terms and conditions of appointment for Broad Ecological Vision and Restoration Measures dated 26/10/2011. Hyder Consulting (UK) Limited (2212959) cannot accept any responsibility for any use of or reliance on the contents of this report by any third party. The Lower Stour and Moors River —Broad Ecological Vision and Restoration Measures Hyder Consulting (UK) Limited-2212959 CONTENTS SUMMARY ..................................................................................................... 2 Part A 4 1 Introduction ........................................................................................... 4 1.1 Survey area .......................................................................................... 4 1.2 What is meant by an ecological ‘vision’ ................................................ 6 1.3 Key Legislative and Policy Drivers ........................................................ 6 1.4 Survey Methodology ............................................................................. 9 PART B ......................................................................................................... 12 2 Introduction to the Middle and Lower Stour ....................................... 13 2.1 Geology and soils ............................................................................... 13 2.2 Geomorphology .................................................................................. 13 2.3 Catchment land use ............................................................................ 14 2.4 Habitats and species .......................................................................... 15 2.5 Water quality ....................................................................................... 16 2.6 Landscape and recreation .................................................................. 16 2.7 Fisheries ............................................................................................. 16 2.8 Physical modifications ........................................................................ 17 2.9 Long term ecological vision for the Middle and Lower Stour .............. 29 2.10 Conclusions from the ecological vision ............................................... 38 PART C ......................................................................................................... 39 3 Introduction to the Moors River System ............................................. 40 3.1 Introduction ......................................................................................... 40 3.2 Geology and Soils .............................................................................. 40 3.3 Geomorphology .................................................................................. 40 3.4 Catchment land use ............................................................................ 43 3.5 Habitats and species .......................................................................... 43 3.6 Water Quality and resources .............................................................. 46 3.7 Landscape and recreation .................................................................. 46 3.8 Fisheries ............................................................................................. 46 3.9 Physical Modifications ........................................................................ 46 3.10 Long term ecological vision for the Moors River System .................... 51 3.11 Description of the Moors system once the ecological vision is implemented ....................................................................................... 61 3.12 Conclusions from the ecological vision ............................................... 62 The Lower Stour and Moors River —Broad Ecological Vision and Restoration Measures Hyder Consulting (UK) Limited-2212959 Page i 4 References ......................................................................................... 63 The Lower Stour and Moors River —Broad Ecological Vision and Restoration Measures Hyder Consulting (UK) Limited-2212959 Page ii SUMMARY Hyder were contracted by the Environment Agency to undertake a study of the Middle and Lower River Stour (the Main River only) and Moors River system in Dorset. In order to inform the study a survey was carried out which involved walking the banks of both rivers, recording key geomorphological features, the extent of physical modification that each river has been subject to and providing recommendations for enhancement measures to restore each river to a more natural state and allow the expression of the characteristic habitat form and function for the benefit of the flora and fauna characteristic of the river type. The main driver for this work is the onus on the Environment Agency to seek improvement to rivers and watercourses under the Water Framework Directive (WFD), in addition to other statutory drivers. The walkover study identified that the Middle and Lower Stour has been subject to significant historical artificial modifications, including dredging and channel realignment for flood defence and other purposes. In addition, there are a number of weir structures causing impoundment to flows. This has resulted in large sections of the channel being relatively uniform (wide and often deep), with the channel form lacking a diverse morphology. By contrast, The Moors River System is essentially a natural system exhibiting an exceptionally diverse range of aquatic and wetland vegetation. On a local scale the river has, in the past, been modified to provide water for mills, trout lakes and for watercress cultivation. In the southern reaches of the river, below Verwood, discrete lengths have been dredged and realigned for agriculture, flood alleviation and urban drainage. In addition, until recently, weed cutting in the channel took place to increase drainage capacity. Following the completion of the survey an ecological vision was drawn up for each river. The ecological vision aims to present a definition of what good ecological status on both rivers should look like, the objective being for each river to exhibit the biological, chemical and structural characteristics that would be expected under nearly undisturbed conditions (i.e. in a natural, unmodified state what should both rivers look like, and what habitats, species and geomorphology would be expected). It is beyond the remit of this report to comment in detail on the potential effects of climate change. However, it is worth noting that the restoration measures proposed have the potential to increase the resilience of the River Stour and Moors River to the effects of climate change, as well as providing a number of additional benefits. Restoration suggestions for the Stour have focused on the removal of structures such as weirs, where possible, and physical intervention to restore diversity to the channel and improve connectivity with the surrounding floodplain. For the Moors River, restoration measures have focused more on management of adjacent habitats rather than extensive physical restoration of the channel itself. Although both rivers would benefit from the implementation of restoration measures, it was apparent that both currently support a diverse range of wildlife. The measures proposed aim to build on the wealth of biodiversity that already exists. This report presents the survey methodology and the broad ecological vision for the Middle and Lower Stour and the Moors River. The report has been divided into three sections: . Part A Introduction and generic information applicable to both rivers . Part B Introduction to and ecological vision for the Middle and Lower Stour . Part C Introduction to and ecological vision for the Moors River System The Lower Stour and Moors River —Broad Ecological Vision and Restoration Measures Hyder Consulting (UK) Limited-2212959 Page 2 Following on from this report, detailed reach by reach restoration plans have been produced for each river. These plans are the subject of a separate report. The Lower Stour and Moors River —Broad Ecological Vision and Restoration Measures Hyder Consulting (UK) Limited-2212959 Page 3 Part A 1 Introduction 1.1 Survey area This report presents the results of a geomorphological and ecological survey of the Middle and Lower Stour and the Moors River System in Dorset. This report presents a broad overview of the main physical habitat modifications that each river has been subject to, the impact of these on the ecology of the rivers and a broad overview of actions that could be undertaken to improve the habitat condition of each river. Following the production of this report, a series of reach by reach restoration measures will be identified, together with a high level consideration of the potential flood risk implications. This will be set out in a separate report. The section of the River Stour that this report is concerned with is from the confluence of the River Lydden, upstream of Sturminster