Effect of El Niño (1997–98) on Beaches of the Peninsular Gulf Coast of Florida

Abstract

During the winter of 1997–98, the El Niño weather pattern was a major influence on the beaches of the Gulf Coast of the Florida peninsula. Cyclonic storm patterns influenced by El Niño moved across the Gulf of Mexico from the southwest, approaching the coast of Florida from the southwest, a direction that differs from that of the usual winter frontal passage direction. The El Nino effects along the Florida Gulf Coast are in the form of subtropical, low-pressure systems including mild temperatures, frequent storms with sustained winds, high wave energy, and record amounts of rainfall. The winds and waves generated by these systems initially came from the south or west. As the storm passed over the coast, barometric pressure increased and winds shifted to the west or northwest. Ten occurrences of this weather pattern took place from late December 1997 through March 1998.An atypical south to north littoral drift was recognized in localized areas along the Florida Gulf Coast during the winter of 1997–98, instead of the typical winter pattern of north to south sediment transport. Evidence for this reversal of sediment transport is the accumulation of sediment and shoreline progradation along the southern face of coastal structures and in a concave area that is oriented northwest to south-southeast. Waves due to the El Niño winter storms approached ebb-tidal deltas at the mouth of inlets from the west or southwest. Beach shorelines on islands located adjacent to the inlets responded differently than their normal winter response as recorded in surveyed beach changes. Beaches with a north-northwest shoreline orientation (between 330 and 345 degrees) had an increased rate of shoreline erosion and volume loss. Other effects of El Niño-influenced weather included erosion at typically prograding areas, and progradation or reduced rates of erosion in typically eroding locations. Such deviations from normal patterns are important factors to include in long-term beach management plans, especially if the El Niño phenomenon continues to be a frequent occurrence.