Controls of Barrier Island Morphology

Virginia Henderson, Orrin H. Pilkey, Amy Keysworth

A study of 530 barrier islands from around the world has been made to determine broad physical and geologic controls on island occurrence and morphology. A total of 74 island chains, consisting of three or more islands each, was included in the investigation. Data for the study were derived from geologic and topographic maps and navigation charts. Environmental parameters considered include wind direction and velocity, mean significant wave height and storm-wave height, and tidal range. Island parameters include length, width, elevation, shape, volume, inlet width, tidal delta length, shoreface slope, coastal plain slope, and continental shelf slope.

Most island chains (42%) occur along Amero-trailing edges of continents. Marginal seacoasts are second in importance (32%), and 22% of all island chains are found on collision coasts. Most islands (70%) are found in microtidal (<2 m mean tide range) environments, with only 1% of individual islands occurring under macrotidal conditions (>4 m mean tide range). According to the second-order coastal classification of Inman and Nordstrom, most barrier islands are found on either mountainous (32%) or wide shelf plains (32%). Next in importance are barrier islands on deltaic coasts (15%). Tidal range does not seem to play a strong role in determining island length (or inlet frequency). Islands are mostly less than 20 km in length, regardless of tidal range, although virtually all long slands (>20 km) are found on microtidal coasts.

AAPG Search and Discovery Article #91032©1988 Mediterranean Basins Conference and Exhibition, Nice, France, 25-28 September 1988.