Improving an urban district’s flood resilience in Ireland

Ennis South Flood Relief Scheme

The urban district of Ennis South includes several flood prone areas including St. Flannan’s/ Toberteascáin, Ballybeg, and properties adjoining the Clareabbey floodplain, which include Quin Road Business Park and Abbeyville Housing Estate. Flood risk in Ennis South is complex, combining two sinking streams, urban drainage, karst hydrogeology, river flooding, and tidal estuary conditions. The presence of such extremely poor ground conditions, the protected status of the Lower River Shannon Special Area of Conservation Natura 2000 site, and the prevailing flood risk from the River Fergus posed significant challenges to any scheme implemented.

Clare County Council formed a steering group, which included the Office of Public Works as the funding authority, to deliver a flood relief scheme for the area. The Council then employed our engineering and environmental team to develop a scheme for Ennis South.

We were responsible for managing investigation contracts, hydrological and hydraulic analyses, and topographical and environmental surveys. Our team undertook options appraisal and costing, scheme development and design, and engagement with relevant parties as well as prepared a Natura Impact Statement and Environmental Impact Assessment Screening. We delivered the scheme through the planning process, contract documentation preparation, tender process, construction, and handover stages and fulfilled the statutory role of Project Supervisor Design Process (PSDP).

The scheme consists of two large urban culverts, which alleviate flood waters at St. Flannan’s/ Toberteascáin and Ballybeg, more efficiently diverting them into the Clareabbey floodplain. We reinforced the old earthen embankments bordering the floodplain with a steel sheet piled flood wall driven through the deep and extremely soft alluvial soils—extending 30 metres (100 feet) depth in places. A flood water pumping station helps to regulate flood levels while also allowing the floodplain to retain its pre-scheme hydrological function alongside the River Fergus.

With the new flood mitigating infrastructure in place, Clare County Council can now plan for sustainable development of Ennis South well into the future.