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1. Introduction 2. European Economic Policies and Ireland Frank Convery, University College Dublin 3. Partition, Politics and Social Conflict Dennis Pringle, St Patrick's College, Maynooth 4. Irish Population Problems John Coward, University of Ulster, Coleraine 5. Crime in Geographical Perspective David Rottman, Economic and Social Research Institute, Dublin 6. The Historical Legacy in Modern Ireland Stephen A. Royle, The Queen's University, Belfast 7. The Problems of Rural Ireland Mary Cawley, University College, Galway 8. Agricultural Development Desmond A. Gillmor, Trinity College, Dublin 9. The New Industrialisation of Ireland Barry Brunt, University College, Cork 10. The Changing Nature of Irish Retailing Tony Parker, University College, Dublin 11. Transportation James Killen, Trinity College, Dublin and Austin Smyth, Strategic Planning Consultant with Northern Ireland Railways 12. Patterns in Irish Tourism John Pollard, University of Ulster, Coleraine 13. Irish Energy: Problems and Prospects Palmer Newbould, University of Ulster, Coleraine 14. Water Resource Management David Wilcock, University of Ulster 15. Resources and Management of Irish Coastal Waters and Adjacent Coasts Bill Carter, University of Ulster, Coleraine 16. Air Pollution Problems in Ireland John Sweeney, St. Patrick's College, Maynooth 17. Regional Development Strategies James A. Walsh, St Patrick's College, Maynooth.

An exploratory approach to coarse clastic barrier development is based on a conceptual outline of shoreline processes around drumlin islands and likely interaction among them. The case study is the eroding drumlin archipelago at Clew Bay, western Ireland. Sediment released by an erosional front is forming beach ridges, spits, and transient linkages. Transfer of sediment is significant for barrier form and control of coastal change. Linking of adjacent drumlins affects dispersal of material within the barrier system. IN this article we advocate an exploratory approach to the problems of coastal barrier development. Emphasis is placed initially on the spatial variability of wave processes and the resultant patterns of sediment mobility and dispersal into barriers that are formed between relatively fixed headlands as represented by drumlin islands. We then exemplify some of these ideas with evidence from a drumlin archipelago in western Ireland that is undergoing erosion and deposition by Atlantic Ocean waves. Understanding dynamics of spatial and temporal processes has been a key goal in many recent investigations of sequential barrier development. Many recent and valuable reconstructions of Holocene barrier evolution (Kraft, Allen, and Maurmeyer 1978; Rampino and Sanders 1981; Thom, Bowman, and Roy 1981; Boyd and Penland 1984) have difficulties in explaining the environmental changes that must have occurred to justify their interpretations about structural barrier changes. A pertinent example of disputed structural change is the problem of whether barriers migrate continuously shoreward in step with a rising sea level or are drowned by rising sea level. Dillon (1970) suggested that for the latter to occur there would have to be an insufficient expansion in sediment supply, geometrical or power related, that could match the demands of a linear increase in barrier height necessary to resist crestal overtopping that accompanies sea-level rise. Failure of sediment supply in combination with a rapid rise of sea level could allow the swash zone to plane off the barrier crest and spatially to jump to the landward side of the back-barrier lagoon, with resultant drowning of the original barrier. Rampino and Sanders (1980, 1981) make considerable use of the concept of barrier drowning to explain the origin of offshore relict deposits along the Long Island shelf. Not surprisingly, this concept is criticized because of lack of support in terms of process (Swift and Moslow 1982; Leatherman 1983), but, to be fair, it is difficult to make detailed or precise statements * We thank the University of Ulster and Queen's University for financial aid in this project. * Department of Environmental Studies, University of Ulster, Coleraine, Northern Ireland BT52 1SA. t Department of Geography, Queen's University, Belfast, Northern Ireland BT7 1NN. This content downloaded from 157.55.39.105 on Sun, 15 Jan 2017 02:55:07 UTC All use subject to http://about.jstor.org/terms THE GEOGRAPHICAL REVIEW about process variability on a scale more sophisticated than is justified by field evidence. Another source of difficulty is the use of sequential-stage models to explain barrier evolution (Penland, Suter, and Boyd 1985), where each stage reflects a principal structural change in genesis and development of morpho-sedimentary units that form the barrier sequence. The initial conceptual attraction of this type of model must be balanced against the need both to explain how and why stage transitions may occur and to assess the range and variety of morpho-sedimentary facies that are present in each stage. With these issues as background, we propose a different perspective on the problem of coarse clastic barrier evolution. Firstly, we consider how an isolated sediment source undergoing wave attack could develop a range of shoreline depositional morphologies. Secondly, we examine how interaction of two or more such sediment sources could contribute to barrier genesis. Thirdly, we apply our conceptual findings to an example of multiple coarse clastic sediment sources (drumlins), on the basis of our experiences on the paraglacial coasts of Ireland and eastern Canada. Drumlins are depositional landforms of glacigenic origin, characterized by ellipsoid-shaped hills tens of meters in height and to a maximum of a kilometer in length. They are usually found in groups or swarms (Price 1973: 79-81). The attraction of drumlin islands for coastal geomorphological research is that they provide rapidly eroding, finite sources of sediments, although they often occur on coasts subject to rapid sea-level change. At the western Ireland case study, Clew Bay, County Mayo, drumlin-island development has a context of stationary sea level or, at most, minimal sea-level rise. This use of drumlin examples should not preclude extension of our comments to other morphologically similar coasts, for example, on coral atolls (Hopley 1971) and volcanic islands (Norrman 1980), where finite sediment sources are also found. SINGLE DRUMLIN ISLANDS A single drumlin perturbs the incident-wave field (Fig. 1A) through refraction, reflection, and diffraction of incident waves (Arthur 1947; Jonnson, Skovgaard, and Brink-Kjaer 1976). In essence a drumlin acts to capture wave energy and forms an energy sink within the wave field. The dimensions of this sink depend on both wave parameters and local bathymetry. Secondary, trapped-wave interactions may also occur around drumlin islands (LonguetHiggins 1967). Behind an island, crossing of wave crests indicates a shadow zone to form part of a wave caustic. The idealized drumlin shoreline presents a somewhat unusual convex configuration or ellipsoid form to incoming waves that contrasts markedly with the usual equilibrium concave planform of headland-bay coasts. Some lateral variations in wave parameters that exist along one edge of a drumlin, points 1 to 8 on Figure 1A, are sketched in Figure 1B. The two most funda222 This content downloaded from 157.55.39.105 on Sun, 15 Jan 2017 02:55:07 UTC All use subject to http://about.jstor.org/terms