A GLOBAL ASSESSMENT OF BARRIER ISLAND MORPHOLOGY AS A FUNCTION OF WAVE-TIDE REGIME

Barrier island morphology is often described by the relative influence of the local wave and tidal regime. Hayes (1979) classified islands as wave-dominated, tide-dominated, and mixed-energy. Wave-dominated islands are long, have numerous washovers, and have pronounced flood-tidal deltas. Mixed-energy islands are short, drumstick-shaped, and have large ebb-tidal deltas. This scheme was originally applied to temperate, mid-latitude coastal plains.

A recent survey of the distribution of barrier islands indicates more than 2,100 islands, covering 20,000 km, are on the world?s open ocean coasts. Approximately half are along mid-latitude coastal plains, while the other half are in the Arctic, the tropics, deserts, or along river deltas. Few models are available to describe the morphology of islands in these other settings. Analyses of Arctic (Stutz, Pilkey, and Trembanis, 1999) and deltaic barrier island morphology (Stutz and Pilkey, 2002) revealed a significant influence of grain size, sediment supply, and fluvial processes.

To test the Hayes model, each island chain identified in the survey is blindly classified using the mean wave and tide regime. Measurements of the island, inlet, shoreface, and lagoon environments of each island are obtained from maps, coastal charts, and satellite imagery. Qualitative observations, where available, are used to note the presence of specific morphologic features such as beach ridges, recurved spits, overwash, and island shape. The sensitivity of these morphologic parameters to the wave-tide classification is analyzed, allowing an assessment of the Hayes model?s usefulness across a variety of climatic and geologic settings. Additional factors such as sediment supply, wind, fluvial processes, and geologic control are proposed to explain morphologic patterns that deviate from the Hayes model.