Coastal erosion Ireland
The Irish coast
Ireland has coastline of approximately 7400 km (+/-5%) (8). Topography, together with linked geological controls, has resulted in extensive (3000 km) rock-dominated coasts. This is particularly so for the southwestern, western and northern regions of Ireland. In contrast, the eastern and south-eastern regions are composed of unconsolidated Quaternary glacigenic sediments and fewer rock exposures. Glacial and fluvial actions have also created major sedimentary areas on the western coasts in the form of large bays and estuaries. Within the different coastal settings, significant coastal systems include those of cliffs, beaches, and barriers (sand and gravel types); lagoons; dunes and machair (sand ‘‘plains’’); and salt marshes, mudflats and other wetlands (7).
Variation in the late Quaternary ice loading of Ireland has led to a north-to-south gradient in isostatic crustal movements, resulting in predominantly emergent coasts in northern areas and changing southwards to coastal environments that are submergent to ‘‘apparently stable’’. Relative sea level for Ireland is rising 1 mm/y on average, although there are significant regional variations (7). At present, there are no apparent effects of climate warming on SLR and coastal changes (9).
Tidal regimes are primarily meso- to macrotidal (spring tidal range is 2 m to more than 4 m) but also include microtidal areas (spring tidal range is below 2 m) for south-east and central northern coasts. This varied tidal background is further influenced in height by major storm activity. Coasts, particularly those of western Ireland, are exposed to the full effects of eastwards-moving cyclones and swell wave energy from the North Atlantic. The predicted changes in North Atlantic storminess as part of climate warming are likely to cause Ireland’s coastal wetlands and other soft-sedimentary systems to be among the first in Europe to respond to storm-led SLR (7).
Vulnerabilities - the current situation
Most of the Irish Sea coast is experiencing long-term recession, beaches and dunes are retreating. The rate of recession is highly variable in time and space (1). The vulnerability of Ireland to sea level rise is relatively low (7).
Coastal defences and other infrastructure are often old, and less than 4% of the coastline is protected by shoreline defences (12). In many rural areas, structures now serving as defences were originally built as property or agricultural boundaries (e.g., walls and dikes). Existing structures frequently have their origin in the 19th century and have been modified subsequently on a piecemeal, needs-must basis. These structures are unlikely to be able to cope with future SLR and linked changes (7).
Until the 1990s, the extent of coastal defence works was small in relation to the length of the coast: in the Republic of Ireland 3.8% (2). Since the ‘Celtic Tiger’ economy, the extent of coastal development has increased dramatically and so has the extent of coastal defence works (1).
Sediment deficit and ‘‘coastal squeeze’’ (13) are noticeable on Ireland’s coasts. The transfer of ‘‘new’’ sediments to most coasts from offshore–shelf sources has almost ceased (14). In the late Holocene, coastal barriers became stranded against the uplands and landwards-rising hard-rock surfaces. Consequently, beach-barrier sediments are being lost through reworking alongshore and diffused into other coastal environments. This leaves a regionally to locally varied and often-limited capacity for the further onshore movement and adjustment of soft-sedimentary coasts to SLR impacts (1,7).
Coastal erosion rates upon ‘‘soft’’ (sediment-dominated) coasts (e.g., sandy systems and glacial sediments) reach average values of 0.2–0.5 m/y, commonly rising to 1–2 m/y on southern and eastern coasts (10). Retreat rates for rocky shorelines are not well known (11). Current total rates of land loss for Ireland from erosion and flooding have been estimated to be approximately 1.6 km2/y, concentrated in about 300 sites (12).
Vulnerabilities - the future situation
Modelling shows increased winter storms into the 21st century, especially for north-west to northern coasts, and calmer summers. Analyses of wind variations for south-east and eastern coasts may also suggest an increased occurrence of easterly winds and associated storminess in these regions. Coastal erosion will increase (7).
The effect of a sea level rise on estuaries will tend to enlarge their vertical and horizontal extent, resulting in the penetration of tides further upstream. The outflow from rivers would be impeded as a consequence. These changes in estuary morphology would also diminish sediment supply to the coastal zone as the sediment would be retained within the confines of the estuary. This has important implications for the coastal zone as off-shore sediment supply has almost ceased requiring reworking of existing sediment within the coastal zone. Studies conducted on the east coast of Britain predicted that estuaries could migrate landwards at a rate of 10 m per year, assuming a sea level rise of 6 mm per year, while open coast landforms could migrate longshore at 50 m per year (7).
Integrated Coastal Zone Management
Neither Ireland nor Northern Ireland has yet adopted a strategic approach to shoreline management. Responsibility for coastal erosion management remains fragmented and practice-led. The emphasis still appears to remain on protection schemes but with an anticipated increased reliance on beach nourishment in Ireland (6). At present, there are no specific national (or islandwide) policies in place to manage the effects of SLR under global warming (7).
Awareness of climate-warming issues and flood risk has led many local authorities and the Environmental Protection Agency in the Republic of Ireland (responsible for implementing environmental impact assessments, or EIAs) to prohibit developments in the coastal zone below 3-m msl and close to vulnerable dune and eroding coastal areas. EIAs for large-scale coastal developments are now required. However, politics and money ‘‘speak’’, and planning guidelines are increasingly becoming infringed in the absence of clear ICZM policy and linked legislation (7).
In essence, Ireland’s coastal vulnerability lies more with the attitudes of the people towards Integrated Coastal Zone Management than in any physical susceptibility of the coast for response to climate changes. Integrated Coastal Zone Management should be strengthened by (7):
- implementing recommendations for a more integrated coastal zone authority structure (possibly an islandwide;
- coastal authority crossing political divides). The establishment of a dedicated and fully resourced authority able to deal rapidly and practically with coastal environmental problems as they start to arise through the 21st century might be desirable;
- empowering stakeholder involvement. In essence, the development of flexible and culturally appropriate bottom-up approaches to the solution of practical coastal-use problems and the generation of local–regional scale policy planning is ideal;
- providing adequate resources, systems, and structures for the collection of high-quality information about the coastal zone and for its continued monitoring. The linking of these activities to the process of management would facilitate informed decision making and planning;
- education and adaptability.
A quantitative and regular environmental audit of Ireland’s coasts ahould be made, incorporating scenario building to allow for the possible effects of climate warming and SLR on these coasts. ... This audit should become a part of the coastal local government authorities’ required 5-year review of structured environmental planning. Coastal trouble spots should be identified and planning and remedial approaches should be devised, with resourcing strategies implemented to meet the needs (7).
The potential for planned adaptation exists through the development of both accommodation- and retreat-type strategies (15), including those of coastal setback or even of shoreline realignment and managed retreat (16). However, cultural attitudes and historically important land holding rights may offset this potential advantage of apparently long, ‘‘unfixed’’ shorelines (7).
Site-specific control measures
Great pressure on coastal authorities exists to provide site-specific control measures to deal with erosion or related problems of coastal dynamics. Attitudes focused upon coastal defence are still common. Small site schemes of riprap, gabions, seawall construction and sand-fixing, or beach nourishment measures occur widely (7).
Shoreline armouring is the dominant response to coastal erosion. The National Trust (the single biggest coastal landowner in Northern Ireland) has recently adopted a policy of non-interference in coastal processes (17). Sea defences will not be built or maintained and some of its beach infrastructure has been constructed in such a way as to render it demountable and movable should it be threatened by future coastal erosion. Soft engineering in the form of beach nourishment is uncommon in Ireland (1).
The references below are cited in full in a separate map 'References'. Please click here if you are looking for the full references for Ireland.
- Salman et al. (2004)
- Carter and Oxford (1988), in: Cooper (2013)
- Environmental Protection Agency (2003)
- Pethick (2001), in: Environmental Protection Agency (2003)
- Department of the Environment, Heritage and Local Government
- Casey (2009), in: Cooper (2013)
- Devoy (2008)
- Marine Institute STAFF (1996), in: Devoy (2008)
- Devoy (2000a, 2000b), in: Devoy (2008)
- Carter and Bartlett (1990); National Coastal Erosion Committe Staff (1992), both in: Devoy (2008)
- McKenna et al. (1992), in: Devoy (2008)
- Carter (1991a), in: Devoy (2008)
- Pethick (1993); Pye and Allen (2000), both in: Devoy (2008)
- Carter et al. (1987); Carter and Wilson (1993), both in: Devoy (2008)
- Parry (2000); Smit et al. (1999), both in: Devoy (2008)
- Pethick (1993), in: Devoy (2008)
- National Trust (2006), in: Cooper (2013)