Fish Pass Design

Shad (Alosa sp.) used to be commonplace in the River Severn, with historical runs of these fish numbering in the hundreds of thousands in the river.

In the 1860s a series of navigation weirs and locks were constructed on the River Severn, preventing these fish from migrating further up the river than Worcester.

The Unlocking the Severn project will construct large fish passes on these weirs, enable shad to return to their historical spawning grounds.

The Fishtek team carried out all of the early optioneering for the type, location and size of fish pass to be built at each of the weirs and then produced the outline design drawings for each of the fish passes. Very large deep vertical slot passes are to be built at three of the weirs, with a large naturalised bypass channel at the final site.

CFD and physical modelling of specific elements of the vertical slot passes was commissioned and supervised by the Fishtek team and the results then used to inform the final designs. Construction of these fish passes will be complete by 2021.