The objective of this project was to open up 10km of habitat for salmon, trout and other fish by removing a large weir and replacing it with a‘rock ramp’ fish-pass. The 2.5m-high weir on the River Ecclesbourne at Snake Lane in Duffield, near Derby, was built in the 1970s during a flood alleviation scheme, replacing an older structure at a former corn mill. The weir was impassable to fish, but the recent appearance of Atlantic salmon, which had been spotted spawning below the weir renewed the impetus to tackle the problem. Whilst salmon often get most of the attention, it is important that other fish are able to move up and down stream too. All trout migrate up and downstream as part of their lifecycle. Small fish such as bullhead and minnows have a vital role to play in the whole river ecosystem, providing food for birds such as kingfishers, for instance. The weir was an effective barrier to wildlife, with 16 species of fish recorded below, but only 8 above.
The river here splits into two channels forming “Duck Island” (see map below, river flowing left to right), a legacy of historic milling activity. Large weirs on both channels prevented fish migration and it was necessary to preserve the original flow split between the channels, with the majority in the north channel. Because migrating fish tend to follow the main flow, the weir on the north channel was chosen for removal. The steep concrete weir was cut out with specialist equipment to avoid damage to the side walls and an adjacent bridge, and a series of rock rapids were installed to maintain upstream water levels and preserve the original flow spilt. In an ideal world, a weir removal project would restore natural water and river bed levels, removing the impounding effect and restoring natural flow patterns and habitats. This was not possible here due to the need to keep the flow split, but the rock ramp is the next best thing, providing passage for a wide range of fish species and sizes.
The work has been funded by the Environment Agency and we are working with Ace Nature on the communication aspects of this project. The menu below gives access to videos, photos and other information about the project provided by Ace Nature.
A press release about the project can be downloaded here.