Microtidal Coasts

Excerpt

Coasts where the tidal range (difference between successive high and low tide levels) does not exceed 2 m are commonly referred to as microtidal (Hayes, 1979; Davies, 1980; Cooper, 1994). Such coasts may be composed of a variety of materials and occur in all latitudinal zones and in a variety of energy settings. Their common characteristics are derived from the fact that their small tidal range focuses marine action (via waves and tidal currents) into a relatively narrow vertical range. Hayes (1979) identified a generalized link between tidal range and coastal morphology. Microtidal coasts were characterized by long, narrow barriers with abundant washover features, well-developed floodtidal deltas, and small ebb-tidal deltas. These characteristics have often led to application of the term “wave-dominated” to such coastlines, although Davis and Hayes (1984) demonstrated that this is not universally true. Some microtidal coasts do exhibit dominance of tidal currents over waves and some macrotidal coasts exhibit wave-dominance. The west peninsular coast of Florida is a good example of a microtidal coast on which wave energy (and sediment supply) is low and yet large tidal deltas develop that are more characteristic of tide-dominated conditions (Davis and Hayes, 1984). Microtidal coasts are widespread in oceanic areas (most Indo-Pacific islands), in some semi-enclosed seas (Mediterranean, Baltic, Gulf of Mexico), on parts of continental margins (S.W. Africa, S. Australia, central Brazil, Antarctica) and on lake shorelines (US Great lakes, African Rift lakes). …