Designing flood relief for communities along Ireland’s largest river

Carrick on Shannon Flood Relief Scheme

Carrick on Shannon and Cortober have a history of flooding from the River Shannon, the largest river in Ireland, and its tributaries. Leitrim County Council, collaborating with Roscommon County Council and the Office of Public Works (OPW), engaged our team to provide engineering and environmental consulting services to develop a flood relief scheme for the area.

We created a hydraulic model that extends from Lough Allen, at the top of the Shannon catchment, downstream past Athlone Town, covering an area of 4,600 square kilometres (1,776 square miles) and a total model length of over 150 kilometres (93 miles). This reach of the Shannon also contains numerous manmade controls, which impact the river’s flow. The design standard for the scheme is the 1-in-100-year flood, and it’s designed to be adapted for climate change in the future. Elements of the scheme will be delivered for the mid-range future climate change. Our team has modelled this hydrologically complex system in Flood Modeller Pro, with urban floodplains modelled using TUFLOW. scenario.

Ground conditions in the vicinity of Cortober are particularly poor, creating challenges in the development of engineering solutions. Together with our geotechnical specialists GDG, we developed solutions to the technical, environmental, and economic constraints involved. Our team also led three separate public participation and engagement events to refine the solutions.

The left bank of the River Shannon is more notable for its public spaces, historic buildings, and structures. Stitching a flood defence into the charming urban waterfront of Carrick on Shannon presented its own unique challenges to preserve these features. We gathered a multidisciplinary team of engineers, landscape architects, ecologists, built heritage specialists, and archaeologists to develop the optimum solution for our client.

To the north of the Town Centre, we developed a solution to use playing fields to store river and stormwater from a local tributary of the River Shannon. This reduces the requirement for flood defences and develop the natural flood plains along the stream banks.

Currently moving through the approvals stage associated with the Public Spending Code, the scheme is due to proceed to planning in the spring of 2026.