Building on lessons learnt from the former East Germany, we have built a fish pass on the River Medway Navigation in Kent that combines safe passage for fish and canoeists alike.
This is the first pass of this type in a British river and from start to finish the project took just five months and cost 94,000 GBP funded by Environment Agency Waterways and Recreation departments. It involved the use of an 80 tonne crane to lift an 8 tonne excavator onto the lock island.
The combined pass consists of a 1.5 metre wide steel trough 70cm deep, 17 metres in length with a gradient of approximately 1 in 12 (8%). The key element to the successful operation of the channel is the installation of artificial plastic reeds referred to as “fish brushes”. These fish brushes slow the water flow down and create eddies and back currents to enable fish to swim up the pass. Secondly, the softness and flexibility of the individual brush strands allow canoeists to safely pass without injury to themselves or damage to their canoes.
Porters Lock on the River Medway was the chosen site for this pilot project as an existing concrete channel with a fixed crest weir had suitable dimensions to suit the pass criteria.
The Project Manager, Phil Munslow said ‘The success of this innovative project was due to good cross team working between Waterways and Fisheries, and the dedication, expertise and flexibility of the construction team. Thanks also must go to our German colleagues who provided good and free design advice.
We faced many challenges in getting the project to site as well as the complex engineering works to fabricate and install the pass itself.
This structure is a further string in the bow of what the River Medway has to offer for canoeists, but fundamentally it aids the migration of all fish species at this location - which to date has been impossible for them’.