Managing Flood Risk on the River Shannon

The national Catchment Flood Risk Assessment and Management (CFRAM) Programme was undertaken by the OPW in partnership with its consultants, Local Authorities and other stakeholders. It involved a study of 80% of Ireland’s major source of flooding across 300 communities across the country.  It was the most comprehensive study of flood risk ever undertaken by the State. The country was divided into 6 regional study areas based on river basin districts.  This included a study on the Shannon River Basin District.

The findings from the CFRAM Programme are set out in 29 FRMPs which identify and describe the flood risk assessed in each of the 29 river basins and set out the proposed measures, both non-structural and structural, to address that flood risk. The approach to the CFRAM Programme was strategic.  It recognised the need, in line with international best practice, to move to a more sustainable, planned and risk-based approach to dealing with significant risks of flooding. 

The Shannon River Basin District (RBD) includes the entire catchment of the River Shannon and its estuary, covering some 17,800km² and 20% of the island of Ireland. The RBD covers parts of 17 counties: Limerick, Clare, Tipperary, Offaly, Westmeath, Longford, Roscommon, Kerry, Galway, Leitrim, Cavan, Sligo, Mayo, Cork, Laois, Meath and Fermanagh.

The Catchment Flood Risk Assessment and Management (CFRAM) Programme focussed on the areas at significant flood risk and its impact, that were identified through an assessment of areas known to have experienced flooding in the past and areas that may be subject to significant flooding in the future. A total of 67 communities in the Shannon RBD were assessed as part of this study. 

The Flood Risk Management Plans for the Shannon include 34 new flood relief schemes to protect communities in the Shannon River Basin District. Of these, work has commenced on 22 schemes which are currently at various stages of development. The remaining schemes will be advanced during the second phase of implementation of the Flood Risk Management Plans. The work of the Group is informed by the Flood Risk Management Plans and is focussed on adding to the proposed flood protection measures.

Yes. There was extensive public consultation during the process to develop the Flood Risk Management Plans for the Shannon RBD.  This involved 144 Public Consultation Days where members of the public had opportunities to engage with the process and to discuss past floods and the accuracy of the maps.  This consultation resulted in 156 submissions that were received by the OPW from stakeholders comprising members of the public, elected representatives, Local Authorities and various organisations.  Observations were considered and the Flood Risk Management Plans were amended accordingly, as appropriate.

The Department of Public Expenditure and Reform carried out an independent review of the strategic level environmental assessments on the Flood Risk Management Plans and the final Plans were formally submitted to the Minister for Public Expenditure and Reform for approval, in accordance with statutory requirements. 

The Flood Risk Management Plans are available to the public at www.floodinfo.ie

Maintenance of rivers and other watercourses has some benefit in preventing the deterioration of channel conveyance capacity. While maintenance on its own cannot protect properties and has no beneficial effect on extreme flood events such as that witnessed along the Shannon during the Winter of 2015, it is recognised that maintenance can play a positive role in mitigating against the effects of less severe flood events and summer flooding.

Some of the State Agencies involved with the River Shannon carry out extensive maintenance works each year. Details of this work is set out in the Group’s annual work programmes which can be viewed here.

In 2017, the Group developed a short-term targeted programme of maintenance activities for the River Shannon. Consent was received from the National Parks Wildlife Service to carry out proposed activities at seven locations identified that would benefit from maintenance. Work involving tree cutting and the removal of silt and emergent vegetation has been completed in five of these locations. This work was undertaken to enhance the conveyance capacity and to halt further deterioration of the river.

On completion of the targeted maintenance programme, the Group agreed on an assessment to examine the potential scope and scale of a strategic programme of maintenance for the River Shannon. Based on the outcome of this assessment, the Group took a decision to progress a strategic programme of maintenance activities to halt the deterioration of the River Shannon to improve the conveyance capacity of the channel. The nature of this work mainly involves tree and vegetation management and silt removal.

Between 1945 and 1995 the OPW completed 34 Arterial Drainage Schemes on river catchments together with 5 Estuarine Embankment Schemes. The primary purpose of all of these schemes was to provide agricultural land with flood alleviation and outfall for land drainage, over 260,000Ha (650,000 acres) of land benefited. OPW have a maintenance responsibility for over 11,500 Km of channel, over 750Km of embankments and associated bridges, sluices, weirs, pumping stations and other structures on these schemes. The OPW spend over €18m per year maintaining these and other Flood Relief Schemes constructed under the 1995 Amendment Act which have transferred to maintenance.

Maintenance of channels is carried out using suitably rigged excavators that remove silt and vegetation from the channel bed restoring it to its original conveyance capacity. It does not involve deepening or widening of the existing channel. The OPW maintenance operations are carried out in accordance with OPW Environmental Management Protocols and Standard Operating Procedures.

Outside of the major flood relief schemes, local flooding issues are being addressed by local authorities with support from the OPW under the Minor Flood Mitigation Works and Coastal Protection Scheme. This scheme provides funding for minor flood mitigation works or studies, costing less than €750,000 each, to address localised flooding and coastal protection problems. To date, the OPW has approved funding of €35m for over 600 projects for the Shannon River Basin District. Two thirds of these projects are outside of the areas studied by the CFRAM Study.

In 2019, the Group has agreed to a hydro-geomorphological assessment of the Lower Shannon to identify the cause, rate and degree of restriction over time due to sedimentation and subsequent vegetative growth. This study was completed in 2020 and further work is underway to explore the various options, potential benefits and indicative costs of each option.

A decision was taken by the Group in 2016 to trial the lowering of the lake levels in Lough Allen to help mitigate potential flood risk during the Winter period.

An analysis has shown that this may have a small positive impact on the extent of certain flood events that might occur during any given Winter. A protocol was developed between the ESB, Waterways Ireland and the OPW for the operation of the Bellantra Sluices at the outlet of Lough Allen to reduce the levels in the Lough by approximately 0.7m, subject to favourable weather conditions. The Group has agreed to the continued operation of the trial, on temporary basis, pending the completion of a flood relief scheme for Carrick on Shannon.