Fish Pass Design

As part of the improvements to a number of barriers owned by the Environment Agency, Fishtek Consulting worked with Hyder Consulting (now Arcadis) to produce the design (both outline and detailed) of a new bypass channel.

This channel was to replace an existing siphon weir and gravity weir, which were significant barriers to the migration of fish in the river.

The channel that was designed was of a largely natural form, with the exception of a small weir and stilling basin at the upstream end. It was determined that this feature was required for two reason:

• Shortly after coming off the old channel, the new bypass channel had to take a sharp right-angle turn in order to minimise the land take from the new channel
• The new bypass channel had to take all of the river flow, up to high flood events. The potential hydraulic force during these high flow events is significant

The channel that was designed by the Fishtek team was comprised of the new intake weir as well as a natural channel downstream comprised of a series of riffles and pools that as well as allowing the migration of fish, has created additional habitat within the river.