Hurricane Opal Induced Changes on Natural and Nourished Beaches, West-Central Florida: Fid-Bau Portal

Hurricane Opal Induced Changes on Natural and Nourished Beaches, West-Central Florida

Davis, Richard A. / Wang, Ping

Twenty-six beach profiles were surveyed immediately after the passage of storm conditions and were compared with pre-storm situations. They include 1) eleven locations spread throughout the entire 60 km reach of the Pinellas County coast including wide, narrow, natural and nourished sites, with and without seawalls; and 2) 15 locations confined to three adjacent nourishment projects along 14 km of Sand Key.

The overall behavior of the nourished and natural beaches along the 60 km reach of coast was similar, displaying a general trend of 1) shoreline erosion ranging from 2 to 10 m, 2) upward and landward migration of the nearshore bar, and 3) backbeach accumulation and increase in the berm height. Shoreline orientation and beach sand composition played no significant role in beach performance during the storm. The technique of dry beach replenishment using a dragline and conveyer belt may contribute to the more severe shoreline erosion at the Indian Shores nourishment project as compared to the traditional pumping technique used at Indian Rocks Beach and Redington Beach.

Temporary berm accumulation and shoreline accretion were recorded at two chronically eroding locations downdrift of structures. The shoreline accretion was caused by the landward sand transport induced by the storm waves. The storm accumulation was eroded by the normal-weather longshore sediment transport within three months after the storm.

The current version of SBEACH model (Larson and Kraus 1989) failed to reproduce the Opal-induced beach changes in the surf zone. The unsuccessful prediction was attributed to the uncertainties in offshore wave measurement, and morphological and computational complications caused by the exposure of hard bottom in the nearshore region.