Wilmslow Park Weirs, United Kingdom

Introduction

The River Bollin is a significant tributary of the River Mersey, flowing for approximately 49 km through the varied landscapes of Cheshire and Greater Manchester in North West England. It is considered one of the most actively meandering rivers in England, with a highly dynamic gravel-bed river, particularly known for rapid lateral channel shifts, significant bank erosion, and the formation of oxbow lakes.

The River Bollin is potentially the most important part of the Mersey catchment for the re-establishment of migratory salmonids (salmon and sea trout) in addition to other migratory species such as eels and lampreys (sea, river and brook). All these species would have been expected to occupy at least parts of the Bollin catchment prior to the industrialisation of the river.

The project area sits within a Local Wildlife Site, which is noted for its grassland, river, oxbow lakes and flush habitats.

Project context and opportunity

The two weirs within Wilmslow Park are blockers to the free movement of key fish species, and an overlay of mapping of its planform over hundreds of years shows that the weirs have severely impinged natural lateral movement of the river.

Outside of the impounded reach, the river is active and is creating a diverse array of morphology types including bars, cliffs and oxbows, along with diverse flow types including pools, glides and riffles.

Historically, the Mersey catchment had a very productive salmonid fishery, and its potential to support future UK salmon stocks is significant.

The River Bollin has seen significant steps towards the recovery of salmon. Following the 2004 Bollin Salmon Strategy, the five weirs downstream of Wilmslow Park have had fish passes installed, opening 31 km of river to free fish movement.

The project will look to restore natural geomorphic processes and remove blockers to fish movement.

Project aims

To achieve its aims, the project will take a vital step forward in restoring potentially the most important river within the Mersey catchment for the re-establishment of migratory salmonids, and one of the most actively meandering and varied rivers in England.

The pre-demolition phase will allow the project to achieve its goal for this stage, developing to a point of being a “shovel ready” project. This will include applying for and securing planning permission for the project, obtaining consents and licences from statutory bodies, undertaking engagement with local residents and local stakeholder groups, and engaging the delivery supply chain.

The ambition is to then submit bids to secure funding for the delivery of the removal of the weirs, which is expected to open 22.9 km of river upstream and restore natural processes at the site.