Case study:Pearls in Peril LIFE+ GB Project - Afon Eden

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Location: 52° 52' 13", -3° 55' 37"
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Project overview

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Status In progress
Project web site
Themes Fisheries, Habitat and biodiversity, Hydromorphology, Monitoring, Water quality
Country Wales
Main contact forename Jackie
Main contact surname Webley
Main contact user ID User:Pearlsinperil
Contact organisation Scottish Natural Heritage
Contact organisation web site http://
Partner organisations Natural Resources Wales, Snowdonia National Park Authority, North and Mid Wales Trunk Road Agency
Parent multi-site project

Case_study:Pearls in Peril LIFE project

This is a parent project
encompassing the following
Pearls in Peril project logo

Project summary

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The Afon Eden is located in north Wales and is a relatively unmodified river, mainly upland in character, of approximately 10km length. The Afon Eden supports the largest population of pearl mussels in Wales. Farming and forestry have been and continue to be the main activities in the catchment. Pressures affecting the Afon Eden population include diffuse pollution from agriculture, forestry, and highway sources. NRW currently describe the Afon Eden as unfavourable.

Pearls in Peril has restored 2.4km of in-stream habitat including gravel seeding to create fish spawning habitat and the placement of boulders from historic bank protection to re-instate river bed substrate and create habitat for freshwater mussels. To address diffuse pollution from forestry activities, the project removed 2ha of conifer regeneration, blocked 12km of forestry drains, fenced 4.5km to prevent livestock access and constructed 11 settlement ponds. This work is restoring 54ha of the Brynteg forestry block to wet woodland and blanket bog and is reducing the levels of diffuse pollution entering the Afon Eden.

The project is currently working to replace two fords with bridges. The fords are heavily used by vehicles, are a source of silt and present a pollution risk to the Eden. Pearls in Peril is also working closely with project partners, North and Mid Wales Trunk Road Agency, to install drainage interceptors at strategic locations that will collect runoff from the A470 carriageway and thus improve water quality in the Eden.

Monitoring surveys and results

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Extensive monitoring work has been completed and reported. The monitoring work includes sonde analysis, water quality spot sampling, redox, macroinvertebrates, diatoms, fish and freshwater pearl mussel survey.

Redox results show a clear trend towards improved dissolved oxygen content in the substrates adjacent to and downstream of the Brynteg forestry block, indicating conservation measures at this site are having immediate positive results. Glochidial surveys indicated that trout are the preferred host fish as part of the freshwater pearl mussel lifecycle. However, electro-fishing also indicated that trout were the least abundant fish in the Afon Eden. As such, conservation measures that improve the status of the trout population would also be beneficial for freshwater pearl mussel. The on-going monitoring on the Eden has helped to focus the conservation work the project has implemented.

Lessons learnt

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Monitoring undertaken at the beginning of a project, before any physical works are implemented, is very important. This approach on the Afon Eden resulted in changes to the delivery of some project actions. Early monitoring to gather baseline information allowed the project team to focus the planning and implementation of practical conservation work at priority locations (e.g. strategic siting of settlement ponds and creating new fish spawning areas specifically suited to trout).

Image gallery

Afon Eden - PIP - In-Stream River Corridor works.jpg
Afon Eden - PIP - Catchment Interventions.jpg
Afon Eden Catchment view.jpg
WEB6 Afon-Eden FWPM-Habitat IMG-20140915-00082.jpg

Catchment and subcatchment


Name Afon Eden
WFD water body codes
WFD (national) typology
WFD water body name
Pre-project morphology
Reference morphology
Desired post project morphology
Heavily modified water body No
National/international site designation
Local/regional site designations
Protected species present No
Invasive species present No
Species of interest
Dominant hydrology
Dominant substrate
River corridor land use
Average bankfull channel width category
Average bankfull channel width (m)
Average bankfull channel depth category
Average bankfull channel depth (m)
Mean discharge category
Mean annual discharge (m3/s)
Average channel gradient category
Average channel gradient
Average unit stream power (W/m2)

Project background

Reach length directly affected (m)
Project started
Works started
Works completed
Project completed
Total cost category
Total cost (k€)
Benefit to cost ratio
Funding sources

Cost for project phases

Phase cost category cost exact (k€) Lead organisation Contact forename Contact surname
Investigation and design
Stakeholder engagement and communication
Works and works supervision
Post-project management and maintenance

Reasons for river restoration

Mitigation of a pressure Pollution incident
Other reasons for the project


Structural measures
Bank/bed modifications Introduction of spawning gravels
Floodplain / River corridor
Planform / Channel pattern
Non-structural measures
Management interventions
Social measures (incl. engagement)


Hydromorphological quality elements

Element When monitored Type of monitoring Control site used Result
Before measures After measures Qualitative Quantitative

Biological quality elements

Element When monitored Type of monitoring Control site used Result
Before measures After measures Qualitative Quantitative

Physico-chemical quality elements

Element When monitored Type of monitoring Control site used Result
Before measures After measures Qualitative Quantitative

Any other monitoring, e.g. social, economic

Element When monitored Type of monitoring Control site used Result
Before measures After measures Qualitative Quantitative

Monitoring documents

Additional documents and videos

Additional links and references

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Supplementary Information

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