EPA - Ireland's Environment, An Integrated Assessment - 2020

Ireland’s Environment – An Integrated Assessment 2020 Topic Box 8.3  Sea Level Rise: Coastal Protection and Managed Realignment Projections for the influence of climate change in Ireland include the effects of sea level rise, coastal erosion and flooding. Supported by the Local Authority Climate Action Regional Offices, several local authorities have recently released climate adaptation and mitigation plans (Chapter 2). These have considered areas identified to be at risk by the ICPSS to formulate policy and planning solutions to tackle storm surges and sea level rise. Solutions can include coastal defences (sea walls, beach groynes, beach supplementation), zoning to restrict further development in flood risk areas and nature-based solutions. The Office of Public Works provides funding to local authorities to carry out minor coastal protection projects. In 2018, ten projects were approved, with just under half of these being flood risk management studies and the other half relating to the construction or repair of hard engineering coastal defences, such as rock revetments and sea walls. However, the cost of installing or maintaining these defences must be balanced against the value of the land that is being protected (Nottage and Robertson, 2005). In addition, it could result in coastal habitat loss or ‘coastal squeeze’, where intertidal habitats are lost because the high-water mark is fixed by a defensive structure such as a sea wall and the low water mark moves landwards towards this structure in response to sea level rise. One nature-based solution to projected sea level rise and flooding is managed realignment. This allows previously reclaimed land in coastal areas and estuaries to be surrendered back to natural tidal processes. This can improve coastal protection while at the same time providing intertidal habitats for protected species. The recent EPA-funded SAMPHIRES (Saltmarsh Function and Human Impacts in Relation to Ecological Status) project has reviewed a number of systems in Ireland where managed and unmanaged (or unplanned) realignment has occurred (Perrin et al. , 2020). One such example is Harper’s Island in Cork. This system was managed as farmland until its abandonment in 2006 (Figure 8.8). Following this, a subsurface breach in a levee allowed saline waters to enter and saltmarsh vegetation rapidly established itself on the island. Cork County Council now own and manage the island as a bird reserve in partnership with Birdwatch Ireland and Glounthaune Community Association. Other examples of managed and unmanaged realignment include projects carried out in Kilmacleague West Wetlands (Co. Waterford), Ballymacoda (Co. Cork), Rogerstown Estuary (Co. Dublin) and Tramore Strand (Co. Waterford). Managed realignment may result in the creation or movement inland of saltmarshes, mudflats or lagoons, all of which are habitats protected under the Habitats Directive Annex 1. Indeed, modelling studies suggest that, in future sea level rise scenarios, managed realignment and long-term planning will be necessary to ensure conservation in terms of both species present and habitat extent (Perrin et al. , 2020). Although Ireland has yet to adopt managed realignment as a mainstream coastal engineering option, evidence from other EU countries suggests that this could be a proactive and cost-effective management option to adapt to, and protect from, climate-driven coastal flooding (Esteves and Williams, 2017). Figure 8.8  Aerial images of the site at Harper’s Island from 2003 (left) and 2017 (right), before and after the unmanaged realignment of the system, respectively (Source: Google Earth from Perrin et al. , 2020) 212