The RRC would like to thank the sponsors of the RRC Annual Conference 2015 who support discounted places

Transcription

1 16 TH ANNUAL NETWORK CONFERENCE Tweet us using #RRC2015 People and Process-Based River Management: Restoring River Processes; Natural Flood Management; Healthy Catchments The RRC would like to thank the sponsors of the RRC Annual Conference 2015 who support discounted places

2 16 th RRC Annual Network Conference PEARLS IN PERIL LIFE + NATURE IMPROVING FRESHWATER PEARL MUSSEL HABITAT THROUGH RESTORATION OF NATURAL PROCESSES Kenneth MacDougall Hannah Barker EnviroCentre Ltd. Stephen Addy Susan Cooksley The James Hutton Institute

3 Photos: Doug Blease, EnviroCentre Project to safeguard the future of the freshwater pearl mussel Funded through EU LIFE + Nature programme and 22 organisations across Scotland, England & Wales

4 Project Sites River South Esk, Angus Aboyne, Sluie and Banchory, River Dee, Aberdeenshire Special Areas of Conservation (SAC) for freshwater pearl mussel and Atlantic salmon Freshwater pearl mussel population unfavourable due to a range of pressures including diffuse pollution and damage caused by engineering works Previous studies identified engineered structures impacting physical river processes and habitats

5 Project Aims Prioritise restoration on the basis of benefits to freshwater pearl mussels and restoration of natural processes through: Assessment of baseline hydromorphology (including impacts of pressures) and habitat Identification of restoration measures and prediction of impacts (channel, habitat and flood risk) Prioritise, design and cost restoration measures Outline effective monitoring methods to evaluate success of restoration work Stakeholder engagement and consultation throughout co-ordinated by wider project team

6 River South Esk Large rock armour bank protection to reduce channel movement and sediment input Constrained morphological freedom and created unnatural channel morphologies Physical changes and altered habitats o Simplified channel complexity o Increased velocities and sediment transport, and coarsening of substrate o Reduced input of bank sediment (sands and gravels)

7 Predicted Effects of Structure Removal Hydromorphological Short term bank erosion and sediment input Longer term restoration of natural processes and forms Habitats Increased diversity of morphology in existing channel Finer riffle substrate more suitable for spawning salmonids Bank undercutting and block input providing cover for fish Input of coarser bank sediment for sustaining freshwater pearl mussel habitats downstream

8 River Dee Long history of constructing croys, mainly to improve fishing conditions by creating pools Many constructed from naturally occurring boulders found on the riverbed 2D hydrodynamic model of channel conditions to predict impact on hydraulics and sediment patterns

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10 Paired Croys Both photos taken in 1996

11 Bankside Works Pre-works (unknown year) 1996

12 2D Hydrodynamic Modelling (River2D) Detailed bathymetric survey using Z-boat Model calibration using field measurements Baseline scenario and post-restoration scenario modelled Spatial predictions of hydraulic conditions in the vicinity of each croy (e.g. water depth, velocity, Froude number) Provided input data for spatial predictions of sediment transport processes Froude number used to predict hydraulic habitats

13 2D Hydrodynamic Modelling depth Depth at Q 75

14 2D Hydrodynamic Modelling velocity Velocity spatial plot and vectors

15 2D Hydrodynamic Modelling Outputs Velocity residuals comparing pre- and postrestoration scenarios at different flow conditions

16 2D Hydrodynamic Modelling Outputs Shields stress comparing pre- and post- restoration scenarios at QMED

17 Distribution of freshwater pearl mussels Photos: Doug Blease, EnviroCentre

18 Aboyne croys removed 2014 Photos: River Dee District Salmon Fishery Board / River Dee Trust

19 Summary Works programmed for later in 2015 followed by monitoring Detailed baseline assessment and predictions of response informed by modelling Distribution of freshwater pearl mussel habitats analysed Linking predicted hydraulic/sediment change to habitat preference Case studies for future works Photos: Doug Blease, EnviroCentre