Catchment Fluvial Geomorphological Audit of the Axe Catchment Detailed Geomorphological Survey (Report B)
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Catchment Fluvial Geomorphological Audit of the Axe Catchment Detailed Geomorphological Survey (Report B) October 2004 ENVIRONMENT AGENCY ENVIRONMENT AGENCY Catchment Fluvial Geomorphological Audit of the Axe Catchment Document review and issue history Report Title: Catchment Fluvial Geomorphological Auditof the Axe Catchment Detailed Geomorphological Survey (Report B) Attachments: CD containing · Electronic Copy of this Report · Reach-by-Reach Geomorphological Database · Web-Based Photo Viewer · Geomorphological GIS Data BBR Project Number 0013499 Revision Status Issued to Date Author Reviewed by number R01 First draft Dave Bartram 29th Oct 2004 D Wishart R Traynor J Brookes A01 Final report Dave Bartram 7th Dec 2004 D Wishart R Traynor J Brookes Environment Agency Client: South West Region Agency Project Manager: David Bartram Consultants: Babtie Brown & Root iii BBR No: BWA 0013499 Rev R01 October 2004 ENVIRONMENT AGENCY Catchment Fluvial Geomorphological Audit of the Axe Catchment Contents 1.0 Introduction .................................................................................................................2 1.1 Background .................................................................................................................... 3 1.2 Aims and Objectives....................................................................................................... 3 1.3 Detailed Geomorphological Survey - User Guide ............................................................ 4 2.0 Consultation ................................................................................................................9 2.1 Introduction .................................................................................................................. 10 2.2 Issues raised ................................................................................................................ 11 3.0 Catchment Overview.................................................................................................13 3.1 Topography .................................................................................................................. 14 3.2 Geology, Soil and Hydrogeology................................................................................... 14 3.3 Hydrology and Water Resources .................................................................................. 17 3.4 Land use ...................................................................................................................... 18 3.5 Fauna and Flora ........................................................................................................... 20 3.6 Human Beings.............................................................................................................. 22 3.7 Catchment Initiatives .................................................................................................... 23 4.0 Geomorphological History .......................................................................................26 4.1 Introduction .................................................................................................................. 27 4.2 Catchment Changes..................................................................................................... 27 4.3 Channel Changes......................................................................................................... 34 5.0 Characterisation of Watercourses ...........................................................................38 5.1 Introduction .................................................................................................................. 39 5.2 Watercourse Summary Sheets ..................................................................................... 39 6.0 Catchment-Scale Geomorphology...........................................................................50 6.1 Introduction .................................................................................................................. 51 6.2 The Sediment Regime.................................................................................................. 51 6.3 External Controls.......................................................................................................... 59 6.4 Internal Controls........................................................................................................... 64 7.0 Summary ...................................................................................................................70 7.1 Catchment Influences................................................................................................... 71 7.2 Geomorphological Processes ....................................................................................... 71 7.3 Key Issues.................................................................................................................... 73 8.0 References.................................................................................................................74 iv BBR No: BWA 0013499 Rev R01 October 2004 ENVIRONMENT AGENCY Catchment Fluvial Geomorphological Audit of the Axe Catchment v BBR No: BWA 0013499 Rev R01 October 2004 ENVIRONMENT AGENCY Catchment Fluvial Geomorphological Audit of the Axe Catchment 1.0 Introduction 2 BBR No: BWA 0013499 Rev R01 October 2004 ENVIRONMENT AGENCY Catchment Fluvial Geomorphological Audit of the Axe Catchment 1.1 Background The decline in habitat and water quality of the River Axe has become an issue of increasing concern in recent years. The following problems have been identified by the Environment Agency, South West Region: · Point source and diffuse pollution from nutrients · Unrestricted livestock access to the river · Increased cultivation of maize · Soil erosion · Bankside erosion · Waste management The Environment Agency South West Region are undertaking work to tackle these issues as part of the wider Cycleau Project, to develop and apply innovative best farming practices and deliver sustainable land management in the Axe and Char catchments. Cycleau is a trans- national project involving the rivers of South West England, Western France and Ireland funded by the EU North West Europe INTERREG IIIB programme – further information can be found at the project website http://www.cycleau.com (www1). As part of the Axe and Char project, Babtie Brown and Root (BBR) have been commissioned by the Environment Agency to undertake geomorphological studies of the Axe catchment and a section of the River Char downstream of the A35 roadbridge to the river mouth at Charmouth. The outputs from this geomorphological work are as follows: Catchment Fluvial Geomorphological Audit of the River Axe Report A – Method Description Report B – Detailed Geomorphological Survey of the Axe Catchment (this report) Report C – Catchment Geomorphological Action Plan Geomorphological Assessment of the River Char River Char Geomorphological Assessment This report (Report B - Detailed Geomorphological Survey of the Axe Catchment) is a technically based report aimed at rivers and fisheries managers with an appreciation of geomorphological issues. It is intended to provide detailed technical information regarding the findings of the Catchment Fluvial Geomorphological Audit. 1.2 Aims and Objectives The Catchment Fluvial Geomorphological Assessment of the Rivers Axe is intended to assist in the achievement of some key objectives of the Cycleau Project, which include: · To deliver Best Farming Practices · To ensure that the River Axe SAC meets favourable conservation status · To protect and improve habitats, species, landscape, archaeology and historic environment · To ensure appropriate management of bankside erosion within the catchment. BBR No: BWA 0013499 3 Rev R01 October 2004 ENVIRONMENT AGENCY Catchment Fluvial Geomorphological Audit of the Axe Catchment The specific objectives of this project are: 1. To provide a baseline data set, identifying the major geomorphological processes and features occurring along selected watercourses in the River Axe catchment. 2. To identify and report on the key areas of geomorphological activity, determine any important factors affecting this activity and to provide guidance on appropriate methods of control or management. 3. To identify any areas where restoring the natural geomorphology may improve the potential for habitat creation whilst reducing bankside erosion. 4. To provide information to inform the control of the development of in-river works such as outfalls, weirs, and flood defence structures, to ensure potentially adverse effects of these on the geomorphological processes are either avoided or minimised. In addition to informing the Cycleau Project, improved geomorphological baseline datasets will be of particular relevance to ecological appraisal, water resources and development control. Geomorphological information can be used to foster closer links between geomorphology and deliverance of a suitable flow regime through the Catchment Abstraction Management Strategy (CAMS) process. The data can also be used to inform the control of the development of in-river works such as outfalls, weirs and flood defence structures to ensure that potentially adverse effects on geomorphological processes are either avoided or minimised. 1.3 Detailed Geomorphological Survey - User Guide The detailed geomorphological survey is intended to achieve objective 1) and the first part of objective 2) of the “Catchment Fluvial Geomorphological Audit of