A Study of Geologic and Hydraulic Processes at East Pass, Destin, Florida. Volume 1. Main Text and Appendices A and B
1992
Morang, Andrew
From 1983 to 1991, the Coastal Engineering Research Center and US Army Engineer District, Mobile, monitored waves, currents, tidal elevations, bathymetry, and shoreline changes at East Pass Inlet, Destin, FL. Based on these data and on historical records, a three-phase model has been developed that describes the inlet's behavior during the last 120 years: (a) Phase 1 (pre-1928), spit development and breaching, covering the period when the inlet was oriented northwest-southeast between Choctawhatchee Bay and the Gulf of Mexico. (b) Phase 2 (1928-1968), stable throat position but main ebb channel that migrated over a developing ebb-tidal shoal. This phase covers the time after the inlet breached Santa Rosa Island in a north-south direction and then migrated eastward. (c) Phase 3 (1968-present), after rubble-mound jetties were built, the throat and main ebb channel were stabilized, while ebb-tidal shoal grew. Despite the jetties, East Pass has continued to try to move eastward. The driving forces of the eastward migration are hypothesized to be (a) wave forces--the predominant wave direction measured in 10-m water depth is from the southwest, while the shore trends east-west; (b) backbay tidal channel and flood-tidal shoal geometry direct ebb currents towards the eastern shore of the inlet; (c) because of freshwater inputs, the ebb flow is longer in duration and higher in velocity than the flood. Maximum measured ebb currents in the inlet are over 5.0 ft/sec (1.5 m/sec), producing a discharge of about 90,000 cu ft/sec 500 cu m/sec .
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