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6 - Lagoons and microtidal coasts
- Edited by R. W. G. Carter, University of Ulster, C. D. Woodroffe, University of Wollongong, New South Wales
- Foreword by Orson van de Plassche
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- Book:
- Coastal Evolution
- Published online:
- 06 July 2010
- Print publication:
- 05 January 1995, pp 219-266
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- Chapter
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Summary
Introduction
This chapter deals with the evolution of lagoonal coasts. Despite being widely distributed around the globe, coastal lagoons have been studied in a fragmented manner and few co-ordinating studies have been undertaken. Lagoons exhibit many different morphologies and form under a variety of environmental conditions which determine not only the principal morphodynamic processes but also the evolutionary path which a lagoon follows. This chapter outlines various types of lagoon. It then reviews several documented examples of lagoonal evolution and assesses the main evolutionary processes. Variations between documented studies of lagoon evolution are assessed and the main controls on the evolutionary path are discussed. Existing models of lagoonal evolution are reviewed and current research deficiencies are highlighted.
Coastal lagoon distribution
Lagoons are present on many coasts of the world in a variety of environmental settings; they are most common in microtidal environments, although examples do occur in mesotidal and even macrotidal environments (Hayes, 1975). A broad range of physical and chemical characteristics consequently exists. Current estimates (Table 6.1) suggest that lagoons border between 17% (Cromwell, 1971) and 56% (Berryhill, Kendall & Holmes, 1969) of North America, and 13% of the world's coastline (Berryhill et al., 1969; Cromwell, 1971; Barnes, 1980) from the polar to tropical latitudes. The wide discrepancy in the estimates for North America highlights the difficulty in definition of a barrier lagoon. Lagoons may be even more widespread as many occur on bedrock coasts in discrete embayments, rather than linear barrier island coasts.