Fish Pass Fact File: Oakenshaw

Length connected: 1.3 km

Area connected: 2.5 Ha

Completed: September 2017

Contractor: Bailey Contracts Ltd

Oakenshaw Weir before and after photograph.

Oakenshaw weir is the first of two large weirs on Hyndburn Brook, and with a 4 metre steeply sloping stone-built face the weir posed a serious barrier to fish migration. Despite the name Hyndburn Brook is, at this stage, a large main river with the potential to support a variety of wildlife.

The weir was created for the Oakenshaw Print Works, which was a large industrial site that included two large reservoirs which the weir diverted water to. One the printworks closed the reservoirs were used as landfills, before being sealed and planted with woodland. However, the weir has never been removed, in fact it has been further utilised for utilities, with a large sewage pipe passing behind the crest of the weir.

Various factors had to be taken into consideration when planning this weir removal. Not only was the presence of the sewage pipe an issue, but the weir is on a tight bend surrounded by woodland.

An appraisal concluded that a bypass channel was the best option for enabling fish passage at this weir. This bypass channel was created through the rough grassland on the inside bend of the river channel, with a whole new 90-metre-long and 3.5-metre-wide river channel being constructed through the grassland, bypassing the weir and allowing migratory fish to access the river upstream. It is thought that the route of the new bypass channel was probably the route that the river originally took before it was diverted for the mill.

In addition, a woodland planting scheme has also been created which will slow the flow of rainwater, increase shade on the river and help to control water temperatures, and increase tree cover and habitat connectivity in the area.

Overall this by pass channel has improved approximately 2.5ha or 1.3km of habitat with the associated woodland improving a further 1.2ha of habitat. Our 2017 and 2018 electrofishing results showed that the bypass channel is already being utilised by migratory fish who are making their way up Hyndburn Brook for the first time in many years.