Project Background

The last three decades have seen an increase in global awareness of the need for fish species to migrate to fulfil life cycles. The necessity for free movement fish in rivers is now readily acknowledged. Since 1992, three pieces of European Union legislation have forced the focus of fisheries management and fish protection to expand beyond the commercially relevant salmonids to include all fishes, namely (a) the Habitats Directive (92/43/EEC), (b) the Water Framework Directive (2000/60/EC), and (c) the Regulation establishing measures for the recovery of the stock of European eel (EC/1100/2007).

Furthermore, the European Commission agreed in 2020 the EU Biodiversity Strategy for 2030 “Bringing nature back into our lives” which also calls for removal or adjustment of barriers to fish, restoration of rivers into free-flowing rivers and re-establishment of fish spawning and nursery areas in European rivers. Improving river connectivity is a key target of the EU Nature Restoration Regulation, a key element of the EU Biodiversity Strategy, which requires EU member states to identify and remove obsolete barriers that prevent the connectivity of surface waters, so that at least 25 000 km of rivers are restored to a free- flowing state across the EU by 2030.

As part of nationwide investigations, Inland Fisheries Ireland (IFI) carried out a fish migration barrier assessment on the River Liffey in 2022. Although the river is subject to various anthropogenic pressures, the Liffey still supports several resident and migratory fish species, notably salmon, and retains considerable ecological potential. Unfortunately, most fish survey sites in the Liffey catchment are failing to achieve Water Framework Directive (WFD) requirements for fish ecological status. This is because the River Liffey is significantly fragmented, which impacts on its WFD status and its ecological health. The barrier study found that historical weirs pose a barrier to upstream and downstream migration of various fish species such as salmon and eel on the Liffey. These weirs are located on the main river channel downstream of the dam at Leixlip:

1. Island Bridge Weir, Islandbridge, Dubin 8

2. Chapelizod Weir, Chapelizod, Dublin 20

3. Palmerstown Weir, Palmerstown Lower, Dublin 20

4. Wrens Nest Weir, Lower Road, Dublin 20

5. Anna Liffey Weir, Lucan, Co. Dublin

6. Lucan Weir, Lucan, Co. Dublin

7. Lucan West Weir, Lucan, Co. Dublin

“The assessment undertaken by IFI coincided with community-initiated consultations with the local authorities and the River Basin Management Service (formerly the Local Authority Waters Programme or LAWPRO) regarding improving water quality in the river and improving salmon stocks. This project is therefore a collaborative initiative between Fingal County Council, Dublin City Council, South Dublin County Council and Inland Fisheries Ireland, with support from the River Basin Management Service, the Liffey Rivers Trust and the Liffey Salmon Project.”

Project Objectives

The Liffey Salmon Migration Barrier Project seeks to develop and implement a river continuity process by mitigating the impact to fish migration at the seven weirs by developing improved fish passage facilities at each weir with full consultation with all stakeholders. The habitat requirements of the following fish species have to be considered for the design of improved fish passage facility at each weir:

  • Atlantic Salmon

  • Sea Trout

  • Sea & River Lamprey

  • European Eel

  • Twite & Allis shad

The project objectives are:

  • To improve fish passage at the seven weirs on the Liffey

  • To improve river continuity and the environmental and water quality status of the River Liffey in line with the objectives of the Water Framework Directive

  • Final design shall have no impact on bridges upstream or downstream

  • Final design shall cause no increase in flooding or flood risk

  • To repair remaining historic structures and recorded monuments at the weirs

The following options will be considered at each weir:

A. Complete weir removal

B. Removal of a section of a weir (i.e. partial removal)

C. Refurbishment of existing fish ladder (which cater for salmon only)

D. Lowering of the existing weir in conjunction with other fish passes

E. Installation of rock ramp fish pass downstream of the weir

F. Construction of an upstream rock ramp

G. Bypass channel

H. Any other feasible options considered by the consultant

I. Do nothing

Acting as the lead Local Authority to undertake stage 1 and stage 2 of this project, Fingal County Council has appointed a team of consultants which comprises:

  • MKO – Planning, Ecology, Landscape, and Environmental Consultants

  • CDM Smith – Civil and Environmental Engineers

  • Molloy Associates – Conservation Architects

  • IAC Archaeology – Archaeologists

  • CORA – Conservation Engineers

  • Dr Fred Hamond – Industrial Heritage

  • ADCO – Underwater Archaeologists