Search

Airborne bathymetric lidar surveys taken in Florida before and after the severe 2004 and 2005 hurricane seasons show infilling of seventeen dredged nearshore borrow pits. During these seasons, groups of pits captured volumes that were the equivalent of up to four years of net longshore transport, even though only one of the seventeen pits studied was inside the presumed depth of closure. Unsurprisingly, dimensionless infilling increased strongly with the ratio of wave height to pit depth. For open coast pits with large alongshore lengths, cross-shore infilling appeared to dominate over longshore infilling but both processes may be of comparable importance in shorter pits. Infilling of three borrow pits adjacent to ebb shoals was found to be considerably larger than on open coasts. Bathymetric changes in borrow pits occurred at greater depths than on nearby undisturbed profiles. Crude estimates of the long term infilling rates from tropical cyclones indicate that annual infilling volumes may be equivalent to more than one quarter of the expected net longshore transport at some locations. However, the episodic nature of hurricanes means that infilling events will be highly irregular. [ABSTRACT FROM AUTHOR]

There are increasing demands for reliable engineering tools for sediment modeling and water resources management. The Lake Okeechobee environmental model (LOEM), which was calibrated and verified to simulate sediment resuspension and transport in Lake Okeechobee, Florida, is a dependable tool to meet those demands. The LOEM contains 2,126 horizontal grid cells and 5 vertical layers. The primary hydrodynamic and sediment transport driving forces are wind waves, surface wind stresses, and inflows/outflows. The LOEM was calibrated and verified, using two sets of observed data from May 16 to June 13, 1989 and January 17 to March 3, 2000, respectively. The model results indicate that sediment solids are resuspended primarily by wind–wave action and transported by lake circulation. The strong relationship between significant wave height and suspended sediment concentration in the lake indicates that sediment resuspension is primarily driven by wind-induced waves. To simulate this sediment resuspension, the processes of wind–wave- and current-induced bottom shear stresses on the lake bed were added to the LOEM. Once resuspended, the suspended sediment is transported to different areas of the lake by wind-induced currents. The importance of wind-wave, currents, and their interactions to sediment transport is included and discussed. By using the comprehensive data set for model calibration and verification, the LOEM model is proven to be a useful tool to water sources management in the lake. [ABSTRACT FROM AUTHOR]

Presents information on a study which measured the total longshore sediment transport rate in the surf zone by impoundment at a temporary groin installed at Indian Rocks Beach in Florida. Methods for field measurements of the longshore transport rate and their technical difficulties; Study area and methodology; Results; Conclusions.

Field data from Perdido Key, Florida, describing the response of an evolving beach nourishment project and the causative forces are analyzed in terms of sediment-transport rates and gradients. Numerical models for planform and profile evolution are applied and tested against the field data. Commonly applied concepts within the coastal engineering community regarding the “depth of closure,” profile “equilibration,” and the best-choice coefficient for use in a predictive equation for longshore sediment transport rate are discussed. The results indicate that the beach planform may be described qualitatively by an analytical solution, and a one-line numerical model gives a reasonable quantitative description of the longshore gradient of longshore sediment transport. The depth to which longshore sediment transport gradients affect the profile appears to be much less than the depth to which profile changes are observed, illustrating the importance of cross-shore sediment transport. An existing profile-response model, slightly modified, yielded good results immediately following nourishment, but poorer results as the beach profile approached a more natural configuration. [ABSTRACT FROM AUTHOR]