Assessment of physical habitat condition and development of restoration actions for the River Wye SAC in Wales S. Thomas, J.A. Constantine, I. Durance, S.W. Griffiths, M. Munday, S.J. Ormerod, N. Small & I.P. Vaughan Cardiff University NRW Evidence Report No. 51 Date www.naturalresourceswales.gov.uk About Natural Resources Wales Natural Resources Wales is the organisation responsible for the work carried out by the three former organisations, the Countryside Council for Wales, Environment Agency Wales and Forestry Commission Wales. It is also responsible for some functions previously undertaken by Welsh Government. Our purpose is to ensure that the natural resources of Wales are sustainably maintained, used and enhanced, now and in the future. We work for the communities of Wales to protect people and their homes as much as possible from environmental incidents like flooding and pollution. We provide opportunities for people to learn, use and benefit from Wales' natural resources. We work to support Wales' economy by enabling the sustainable use of natural resources to support jobs and enterprise. We help businesses and developers to understand and consider environmental limits when they make important decisions. We work to maintain and improve the quality of the environment for everyone and we work towards making the environment and our natural resources more resilient to climate change and other pressures. www.naturalresourceswales.gov.uk Page 1 Evidence at Natural Resources Wales Natural Resources Wales is an evidence based organisation. We seek to ensure that our strategy, decisions, operations and advice to Welsh Government and others are underpinned by sound and quality-assured evidence. We recognise that it is critically important to have a good understanding of our changing environment. We will realise this vision by: Maintaining and developing the technical specialist skills of our staff; Securing our data and information; Having a well resourced proactive programme of evidence work; Continuing to review and add to our evidence to ensure it is fit for the challenges facing us; and Communicating our evidence in an open and transparent way. This Evidence Report series serves as a record of work carried out or commissioned by Natural Resources Wales. It also helps us to share and promote use of our evidence by others and develop future collaborations. However, the views and recommendations presented in this report are not necessarily those of NRW and should, therefore, not be attributed to NRW. www.naturalresourceswales.gov.uk Page 2 Report series: NRW Evidence Report Report number: 51 Publication date: December 2014 Contract number: NRW 13 002334 Contractor: Cardiff University Contract Manager: Dyson CD Title: Assessment of physical habitat condition and development of restoration actions for the River Wye SAC in Wales Author(s): Thomas S, Constantine JA, Durance I, Griffiths SW, Munday M, Ormerod SJ, Small N, Vaughan IP Technical Editor: Vaughan IP Peer Reviewer(s) N/A Approved By: Dyson CD Series editor(s): N/A Restrictions: None Distribution List (core) NRW Library, Bangor 2 National Library of Wales 1 British Library 1 Welsh Government Library 1 Scottish Natural Heritage Library 1 Natural England Library (Electronic Only) 1 Distribution List (others) JNCC, Peterborough 1 Environment Agency, Bristol 1 Wye and Usk Foundation, Brecon 1 River Restoration Centre, Cranfield 1 Chris Bromley, SEPA 1 Jonathan Gibson, EA 1 Chris Mainstone, NE 1 Jenny Wheeldon, NE/EA 1 Recommended citation for this volume: Thomas S, Constantine JA, Durance I, Griffiths SW, Munday M, Ormerod SJ, Small N, Vaughan IP. 2015. Assessment of physical habitat condition and development of restoration actions for the River Wye SAC in Wales. NRW Evidence Report No: 51, 137pp, Natural Resources Wales, Cardiff. www.naturalresourceswales.gov.uk Page 3 Contents Crynodeb Gweithredol ......................................................................................................... 7 Executive Summary ........................................................................................................... 10 SAC condition assessment ............................................................................................ 10 Devising restoration options ........................................................................................... 11 WFD assessment ........................................................................................................... 11 Multi-criteria analysis ...................................................................................................... 11 1. Introduction .................................................................................................................... 13 Overall objectives and scope ......................................................................................... 14 Spatial scale/level of reporting ....................................................................................... 15 2. SAC condition assessment ............................................................................................ 16 Overall rationale/outline method ..................................................................................... 16 Comparison of the observed hydromorphology to un-modified conditions and other rivers in Wales and England .................................................................................................... 16 Sampling scheme ........................................................................................................... 18 Data collection and assessment criteria ......................................................................... 20 Assessment results ........................................................................................................ 32 3. WFD assessment........................................................................................................... 38 Outline results ................................................................................................................ 46 4. Devising restoration options ........................................................................................... 48 Restoration options ........................................................................................................ 51 5. Cost-benefit/multi-criteria analysis ................................................................................. 94 Multi-criteria analysis of restoration options ................................................................. 102 Approach ...................................................................................................................... 103 References ...................................................................................................................... 122 Appendix 1. Data collection in RHS format from Fluvial Audit and aerial photographs. ... 125 Appendix 2: Potential consequences of hydromorphological modifications for SAC target species. ............................................................................................................................ 132 www.naturalresourceswales.gov.uk Page 4 List of Figures Figure 1. The overall process followed in this report, leading from waterbody-level assessment to management recommendations. ............................................................... 14 Figure 2. Extent and data availability: (a) SAC river network, (b) extent of the Fluvial Audit, (c) complete set of 500m reaches sampled from Fluvial Audit and/or aerial photographs (n=560), and (d) WFD river network showing all RHS data from 2006 onward (n=38). ..... 15 Figure 3. Example of nearest neighbour analysis for a location on the upper Ithon. .......... 19 Figure 4. A small section of the Mithil Brook with aerial photography, 50m ‘spot-check’ markers and the Fluvial Audit bank protection layer.. ........................................................ 19 Figure 5. Results of the SAC assessment plotted for WFD waterbodies. .......................... 36 Figure 6. Catchments passing the <10% artificial or intensive land cover rule based on LCM2007.. ......................................................................................................................... 47 Figure 7. Four general approaches to river restoration, with the seven broad categories of modification seen in the Wye mapped onto them. ............................................................. 48 www.naturalresourceswales.gov.uk Page 5 List of Tables Table 1. CSM guidelines (JNCC, 2014) and the extent to which they could be assessed in the Wye, based on current data. ........................................................................................ 17 Table 2. Generic assessment of channel modifications found in the Upper Wye: their potential impacts upon geomorphic processes, symptoms that may be observed and variables from Fluvial Audit or RHS that may help to identify the impacts. ........................ 23 Table 3. Hypothesised changes among Fluvial Audit reaches that could indicate hydromorphological impacts (‘symptoms of impact’) of channel re-alignment, embankments and bank protection. ................................................................................... 29 Table 4. RHS variables, derived from Fluvial Audit data, used to predict HMS. ................ 30 Table 5. Summary of the results of SAC assessments based on WFD waterbodies. ........ 34 Table 6. Summary of the results of SAC assessments