Date of Award

1999

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Geography and Anthropology

First Advisor

Keith G. Henderson

Abstract

The north-facing, estuarine shores of barrier islands along the northern Gulf of Mexico are experiencing severe shoreline erosion. This erosion process is related to storm events that occur when cold fronts pass along the coast. These cold fronts are associated with the migration of extratropical (mid-latitude) cyclones and anticyclones across the region in winter. Wind data collected by a NOAA weather buoy over the period 1981--1997 were used, in conjunction with daily weather maps, to evaluate winter storm activity. Seven synoptic weather patterns that produced extratropical storm events along the northern Gulf Coast were identified. Statistics were computed for the mean and maximum speeds of the "northerly" winds produced by the 506 storms identified in the study. Similar statistics were computed for the northwesterly and northeasterly winds. The data indicate that northeasterly winds prevail over northwesterly winds by a margin of approximately 2:1 between September and May, which may be used to infer that the predominant direction of sediment transport is westward. This finding was attributed to the clockwise wind rotation pattern of anticyclones that dominate wind flow patterns in the region after cold fronts pass along the coast. Oceanographic data collected during 3 storm events showed that low tide levels reduced water depth across the shallow, nearshore platform which resulted in waves expending their energy on the platform before reaching the foreshore. High tide levels allowed waves to traverse the nearshore platform and expend their energy on the foreshore. Thus, sediment transport occurs along the platform during low-tide periods and along the foreshore during high tide periods. Variations in tides, therefore, may influence the predominant direction of sediment transport along the foreshore and the nearshore platform during storms in which the wind shifts from northwest to northeast, which occurred in approximately 70% of the storms. Tropical Storm Josephine (October, 1996) disrupted the beach response study; however, a noteworthy response was observed. The storm increased the width of the beach by transporting sediment from the backshore to the foreshore. Extratropical storm impacts re-stored the beach to its original morphology by the end of the winter storm season.

ISBN

9780599252271

Pages

211

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