Ebsford worked on behalf of The Scottish Environment Protection Agency (SEPA) to remove Gateside Mills Weir to improve fish passage and re-naturalise a section of the river.
Working alongside Royal HaskoningDHV, Ebsford were instrumental in the optioneering appraisal providing early involvement throughout the design process, giving them a thorough understanding of the scheme, and were perfectly placed to deliver the works.
Gateside Mill Weir is located on an incised channel of the River Eden in rural Fife, Scotland. The weir is an historic barrier to a fish passage that is no longer in use. SEPA’s Water Environment Fund provides an opportunity to restore natural fish passage at redundant weirs like this, for iconic species such as Atlantic salmon and sea trout. Upon completion of the project, Fish migration will be restored here for the first time in over 100 years.
Following minor vegetation clearance and the removal of the existing footbridge, Ebsford began excavating an area of silt in the downstream channel containing the non-native species, Himalayan balsam. This species has become one of the UK’s most invasive weed species and can leave riverbanks exposed to erosion during heavy rainfall, which can impact watercourses and increase flood risk. The seed can also survive transportation via watercourses making it a highly invasive weed, requiring careful management. Once the excavation was complete, the material was temporarily placed in a storage area before being used to fill a void and covered with clean material to prevent regrowth of the plant.
Following fish rescue in the upstream and downstream vicinity of the weir, and with sediment protection measures installed downstream to protect the watercourse from liberated silts and sediment, the weir structure was carefully dismantled. Turbidity in the water was monitored throughout the deconstruction to ensure existing wildlife would not be negatively impacted by the project. A small section of the weir was left in place on the south bank to maintain a connection with the industrial heritage of the site.
Suitable material was then reused to help construct boulder sill structures up and downstream, which create pools and riffle effects, a perfect habitat for migrating fish and a range of other native species. Re shaping of the embankments helped to realign the channel and centralise the watercourse.
Removal of this 130 year old barrier unlocked almost 18km of river channel to migratory fish species and re-started the natural river processes that would have existed prior to the weirs’ construction. Through adopting an integrated engineering and ecological approach, the health and connectivity of the river has improved significantly, providing resilience to future changes throughout the catchment and achieving challenging sustainability outcomes.
