Project Details - Rock Ramp Fish Pass

Client: Ribble Rivers Trust, Wade Group Contractors

Categories: Detailed Design, Geomorphology

When: March-April 2020

Location: River Darwen, Lancashire, UK

Edenvale Young were appointed by the Wade Group to undertake the design of a rock ramp fish pass to bypass the existing weir on the River Darwen, as part of a design and build contract for the Ribble Rivers’ Trust.

The site lies just upstream of the confluence between the Rivers Ribble and Darwen with fish migration prevented by a 4m high masonry weir.

The key project requirements;

The objective of the work was to facilitate the migration of fish upstream on the river through the provision of a bypass rock ramp fish pass.

The scope of works included hydraulic modelling using both 1D and 2D approaches to the modelling of the existing and proposed arrangements to achieve flow depths and velocities within the pass to allow target species of fish to move through the fish pass.

2d Hydraulic Modelling

The fish pass comprises a series of riffle pool features running down the pass. The structure is primarily formed in rock using local gritstone with a concrete inlet weir.

Plan View of the 2D Hydraulic Model

Riffle Pools under construction

Edenvale Young produced detailed design drawings for the construction of the works with Wade Construction completing construction in September 2020.

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