Revitalising River Alt: A feasibility study for weir removal, England

Introduction

The River Alt flows 45 km from Huyton in Merseyside into Liverpool Bay at Hightown. The river’s lower reaches from the Estuary to the Dam at Aintree, Liverpool, have always been important in draining the low-lying agricultural areas. The Dam site is located on the edge of the urban area, next to agricultural land and the M57 motorway.

The lower reaches of the River Alt have a good population of fish, Eels and associated wildlife, including recent Otter sightings. Several important wildlife sites are along the river, such as Lunt Meadows, Alt Meadows, Croxteth Park and the M57 Nature Improvement Area (NIA).

Project context and opportunity

Along the River Alt, the lower reaches and their tributaries are important for several fish species like protected European freshwater eel and otters. These lower sections are also popular for recreational fishing and walking, providing an important resource for local communities.

Above the dam, there seems to be a much lower fish population with limited opportunities for local communities to enjoy the river. The upper reaches are subjected to higher levels of urban diffuse pollution, and several initiatives are currently looking to mitigate this pollution.

The dam presents a clear barrier to fish and eel movement. The removal of the dam will open up approximately 29 km of the main river and over 30km of tributaries allowing free movement around most of the river catchment for migratory fish and eels and increase the viability of the habitat for protected species such as otters.

Removal of the barrier, combined with other planned initiatives, will increase the ecological value of the upper reaches of the River Alt and open up areas of the river for local communities to enjoy.

Project aims

The project aims to assess the feasibility of removing the largest barrier along the River Alt. This will be an important step towards improving the river’s ecological value and allowing greater accessibility to river corridors for local communities.

The project’s main goals are:

• Remove the weir on the River Alt and open up the river system for free movement of aquatic species.
• Increase public awareness of issues like water quality, biodiversity and recreation along the River Alt.
• Engage relevant stakeholders and use this project as a starting point to develop further initiatives to continue ecological improvements along the River Alt.

Project achievements

The feasibility study for removing the Alt Weir was conducted between January and September 2023. The key achievements and outcomes of the project are as follows:

• Feasibility Assessment: Successfully assessed the feasibility of removing the weir on the River Alt, located between the Leeds/Liverpool Canal aqueduct bridge and Bull Bridge road crossing.
• Stakeholder Engagement: Gathered all relevant existing data and consulted with stakeholders, including the regulatory authority (Environment Agency) and the weir owners (United Utilities), who expressed full support and agreement to the weir’s removal if the feasibility report was favourable.
• Riparian Landowners: Contacted and informed riparian landowners about the proposed weir removal.
• Ecological Surveys: Completed comprehensive ecological surveys based on advice from Environment Agency ecologists. Conducted a full e-DNA fish survey in July 2023, which revealed significant fish populations, including freshwater eels, below the weir. The data showed that the weir obstructs fish and eel migration, indicating that its removal would enhance species movement and improve the ecological status of the River Alt.
• Habitat Assessment: Indicated that the good riparian habitats would remain unaffected by the weir removal, and the successful removal of the weir and its structures would further enhance these habitats.
• Breeding Bird Survey: Demonstrated a healthy assemblage of breeding birds using the riparian habitats, which the weir removal would not impact.
• Specialist Consultancy: Engaged JBA consultants to work on the feasibility and design of the weir removal. They assessed the structure of the weir, potential impacts on the river corridor and surrounding infrastructure, and methods for removal, including bank and river-bed restoration.
• Positive Conclusion: JBA concluded that removing the weir structure presents a significant opportunity to improve river function and fish passage without increasing flood or erosion risk.

The project team received a follow on demolition grant from the programme in 2026.