Title

Field results and physical modeling of the sediment dynamics of a channeled, peritidal coastal system in southwest Florida

Date of Award

2007

Availability

Article

Degree Name

Doctor of Philosophy (Ph.D.)

Department

Marine Geology and Geophysics

First Committee Member

Eugene C. Rankey, Committee Chair

Second Committee Member

Harold R. Wanless, Committee Member

Abstract

The fundamental question that this dissertation attempts to evaluate is "How do sedimentologic processes build or modify geomorphology." To answer this question, this dissertation explores the dynamic behavior of a subtropical, carbonate/organic, channeled peritidal system in southwest Florida, in the area of Cape Sable. One particular component of the peritidal system, i.e. tidal creeks and the networks they form, is studied outside the subtropical setting of Florida as an experimental model in a fluid-sediment laboratory.The field study concentrates on investigating the hydrologic, sedimentologic and geomorphic patterns and linkages created by interactions of various components (e.g. tidal creeks, mudflats, marshes) within the system. Remote sensing data (aerial photographs and high-resolution satellite images) are integrated with sedimentologic observations from sediment cores and reference markers, and hydrodynamic time series measurements (water level, current velocity, discharge, suspended sediment concentration, salinity, wind speed). Geochemical analyses of sediments and calculation of suspended sediment fluxes further document the complex pattern of sediment sources and sinks.The results suggest that geomorphic shifts on Cape Sable (e.g. tidal inlet instability, accelerated accumulation rates, irreversible marsh collapse) are driven by a change in external forcing mechanisms such as human interference, hurricanes, and most importantly, accelerated relative sea level rise over the past 80 years. The relative contribution of day-to-day and winter storm processes on the overall sedimentologic changes appears equal. The recycling of organic-rich carbonate muds during the latest rapid rise of relative sea level results in a shallowing-upwards succession of tidal deposits and a spatial reorganization of facies.Exploration of experimental tidal channel geometry through space and time reveals distinct trends and empirical relationships between channel attributes, such as length, width, depth, width/depth ratio, and sinuosity. The laboratory experiments also demonstrate that despite constant external boundary conditions during one lab run (no change in sea level or sediment supply), tidal creeks grow with short pulses of headward channel extension followed by long periods of stasis or slow growth. Autogenic processes (e.g. delta lobe switching) play an important role in triggering the upstream channel extensions (the bursts of growth). The importance of these observations lies in the fact that rapid geomorphic changes or in general, dynamic coastal behavior, can occur without external forcing.**This dissertation is a compound document (contains both a paper copy and a CD as part of the dissertation). The CD requires the following system requirements: Adobe Acrobat; Windows MediaPlayer or RealPlayer.

Keywords

Geology

Link to Full Text

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