The New Year has started in a bit of a rush at Fishtek. We are very busy with a wide range of fisheries work, despite the weather’s best efforts to turn the entire UK into one giant pond! An exciting project which we have been working on over the last few months is the Tidal Gate Damper, or TGD.
Tidal gates present significant barriers to eel migration and have likely contributed to the reduction of the European eel (Anguilla anguilla) in our rivers. There are currently few options available to improve eel passage at tidal gates and existing devices are often expensive, require frequent maintenance and can be prone to theft. The tidal gate damper was originally developed by Fishtek Consulting and Royal Haskoning DHV as an effective solution to improve eel passage at tidal gates and was awarded the Sturgeons Lair prize for innovation (a European Competition for environmental innovation) in 2013.
The Damper is made from a compressible Co-Polyester Elastomer and easily retrofitted to existing tidal gates. It has a consistent damping performance over a wide temperature range and a long operating life up to 1 million cycles, equating to many years of typical use. Maintenance requirements are minimal and it can generally be retro – fitted to existing gates within a day.
The first Tidal Gate Damper was installed at Royal Drift Tidal Flap on the River Severn in October 2013. A bespoke monitoring station was developed by Fishtek that simultaneously monitors gate aperture, upstream and downstream water levels and salinity. The station is being used to evaluate the effectiveness of the damper. Initial findings demonstrate that the damper is an effective solution to improve eel passage at tidal gates by reducing the speed at which the gate closes on an incoming tide and increasing the head differential required for the gate to close. With the damper disengaged, the gate closes with a negative head differential (higher head on the river side) and there is therefore no ingress potential. Conversely, when the damper is engaged the gate closes with a positive head differential (higher head on the tidal side), creating an ingress potential for eels approaching the gate on the incoming tide. Glass eels are very thin (~ 2 mm) and providing there is some ingress potential they can pass the gate.
The data from the monitoring will be used to calibrate the current performance expectations of the damper to allow us to produce bespoke dampers to meet specific site requirements, including head differential, aperture size and ingress potential.
