Overview 

The Arklow Flood Defence Scheme is a significant flood prevention initiative implemented in the town of Arklow, located in County Wicklow, Ireland. The scheme was designed to address the persistent problem of flooding in the area and protect the town from potential risks caused by floods.

This project involved the construction of various flood defence measures, including flood walls, embankments, and river channel improvements, and relocating vulnerable businesses. The Arklow Flood Defence Scheme was carried out by the Irish government in partnership with Wicklow County Council and the Office of Public Works and was completed in 2016. The scheme has since provided essential protection to the town, reducing the risks of floods and their potentially devastating effects.

Our Role

Wicklow County Council and the OPW appointed ByrneLooby as the lead engineering consultant in a role that included hydrological studies, river and coastal modelling, preliminary design, scheme optioneering and development, and cost-benefit analyses. ByrneLooby also developed the planning stage design including the engineering drawings, prepared the Construction Environmental Management Plan and contributed to The Environmental Impact Assessment Report (EIAR).

Throughout the preliminary and planning stages, we managed site investigations and surveys, a requirement at each project phase. The Avoca River and its many tributaries drain a relatively steep catchment of 652km^2 extending from just north of the Sally Gap and flowing southwards, discharging to the Irish Sea at Arklow Town. This study addressed the flood risk of Arklow Town and required a preliminary design of appropriate flood mitigation measures. A suitable flood relief scheme for Arklow Town, based on technical, socio-economic and environmental criteria was identified.

Solution 

ByrneLooby carried out the “Avoca River (Arklow) Flood Relief Feasibility Study”. This involved establishing design return period fluvial flows and tidal levels in the Avoca River at Arklow. The design flows were obtained using gauged and ungauged flood estimation techniques. The design tide conditions were obtained from the Irish Coastal Protection Strategy Study (ICPSS) Phase II Study (DCMNR, 2006) that was funded by the Department of the Communications, Marine and Natural Resources. Hydraulic modelling was carried out using the HEC-RAS and  TeleMac2D Hydraulic Models to predict the flood profile in the study reach under a range of tidal and fluvial flood conditions for existing and proposed flood relief scenarios. The Hydraulic Modelling allowed the computation of the longitudinal Flood Profile in the reach, which provided the flood levels for preparing flood inundation maps for the various return period flood events. Flood Extent, Depth and Hazard maps were produced for the fluvial and coastal flood risk.

The scheme will protect hundreds of homes and businesses in Arklow. We coordinated with other consultants during planned phases, working simultaneously in common locations to achieve economies of scale and project savings.

The Planning Stage design is now completed, and the project was submitted to ABP for planning permission in May 2021.