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Fish Passes & River Structures


Improving flood protection and fish migration on the River Windrush


By Jayne Hornsby, Land & Water


The River Windrush, Witney, Oxfordshire saw the construction of a natural fish pass, a weir and a new access bridge as part of a large construction project. Another phase of this project is included in the river restoration section on page 30.


The first part of the project centred on the fish pass which comprised a hard engineered structure at the upstream junction with the River Windrush.


A notch weir was installed using shuttering and a driven sheet piled cut off wall. Stop log groves allow for fish passage and flow control.


Boulder placement Finished inlet detailing stop log grooves Inlet shuttering


Excavation of the fish pass channel took 3 weeks, with all excavated materials being utilised on site within the landscaping works, reducing cost and environmental impact. The new river channel meanders across the flood plain to join an existing back water channel; meanders have been designed to mimic a natural channel but were left for the river to shape its own route. Riffles, stone weirs, flow deflectors and shallow scrapes were all incorporated into the design. Riffles


24 www.fadsdirectory.com


and boulder dams were constructed using locally sourced stone materials and similarly were left for the river to redistribute over time. A planting scheme was carried out to the new river channel using some 5,500 local native species.


channel under flow conditions


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