Meyers, S.D., M. E. Arias, M. Kramer, and M. E. Luther. 2025. Final Report to The Tampa Bay Estuary Program, Oct. 25, 2025. https://drive.google.com/file/d/1_xrxiM9TVqpv9meVR3ZpdJ7vElPC7tLe/view
Summary: Erosion of the shoreline around MacDill Air Force Base presents a long-term threat to the
sustainability of base operations. The primary mechanism behind this erosion is generally
understood to be ocean waves and the strong, erratic currents they generate. These waves can be
generated by winds or large ships transiting the nearby shipping channel. Designing effective
protective measures for the shoreline requires specialized understanding of these waves such as
their height, period, and duration, but there has never been a quantitative study of the wave
environment in the vicinity of the base. The primary objective of this study was to reduce this
knowledge gap by deploying wave-measuring devices off the southeast shore of the base. These
instruments measured the water level (yielding wave height and frequency) and the speed and
direction of the currents. The instruments operated in a fixed position about 150 m (492 ft)
offshore for a few weeks. The water was deep enough that the instruments were always
submerged even at low tide, so the water level sensors were always functioning. Wake statistics
along with estimates of the erosion generated by tides, wind waves, and wakes were computed
based on these measurements. Information on the nearby vessel traffic was obtained from the
Automatic Identification System and correlated with the wave measurements.
Significant findings from analysis of the data from these instruments include:
- The average duration of a ship wake was a little over 1 hr
- Large wakes often led to wave breaking that greatly elevated turbulence in the water and
enhanced erosion - Living shorelines to be installed must be able to withstand this turbulent environment
- Wave-induced currents were much more erosive than tidal currents and almost 50% more
erosive than typical wind-driven waves - As the waves move onshore from the study site they will tend to increase in height, and
generate more wave breaking, turbulence, and erosion - Most of the ships moving in and out of port were large (> 100 m or 330 ft)
- Cargo, cruise liner, and tanker vessels were most frequently associated with large wakes
- The large wakes were generated by these ships displacing a significant fraction of water
out of the channel - Adaption and protection rather than regulation appeared to be the method most likely to
protect the shoreline around MacDill - Future studies should include direct measurements of sediment resuspension
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