Over time dams, weirs and other river obstructions have become larger and more common obstructing the migration of fish.
Recent European and UK legislation places greater obligations on the owners of river structures to take account of fish passage. The building of fish passes is now restoring rivers to a pre-industrial richness of bio-diversity.
On the River Medway in Kent Halcrow was lead consultant and designer on an innovative pilot project to build a combined fish and canoe pass using sustainable solutions. The pass allows canoes to traverse Porters Lock without the need to remove the canoe from the river whilst allowing fish passage up and over the lock structure.
The University of Kassel in Germany had developed special brushes, experimenting with their size, length, shape and configuration to control water flow in flumes. Halcrow utilised this development work to design a pass which met the Environment Agency’s requirements. The brushes were key to allowing the very different needs of the canoes and fish to be met. They needed to be strong enough to arrest the flow to a speed safe for canoeists yet suitable for fish passage and flexible enough to bend as canoes pass over the top of them.
The Medway now has an innovative new kind of structure, the first of its kind in the UK, providing a true environmental enhancement to the river and its users.