It is always nice seeing a project through to completion, particularly one that has been worked on for a while. We have been heavily involved in the design and construction of a fish pass on the River Gwash, in East Anglia. The pass is a natural bypass channel that is also the new river channel, as the previous route by which water passed downstream (over a weir or through a siphon) is to be completed blocked off, sending all of the water down the new bypass.
Working with Arcadis, we were responsible for the outline design and detailed civil construction design of the bypass channel, which included a new weir (with a low head-drop across it and deep streaming-flow notch), large intake structure, natural channel with riffles and pools and a large ‘off-line’ pool for additional fish habitat. Everything was then built by Jackson.
The vegetation hasn’t grown back yet, so the works still look a bit ‘raw’, however we think that the overall look of the finished pass is pretty good. As well as providing fish passage at a point in the river where previously there was an impassable weir, the new weir and bypass channel will accommodate flows up to the highest ever recorded in the river – essential from a flood risk perspective.