Measurement of Directional Waves in Finite Water Depths

A complex wave climate is known to exist in areas of finite water depth and irregular bottom topography. A recent field study was conducted near Cape Canaveral, Florida where a large shoaling zone exists. Four wave measuring sites (two stationary and two drifting) were selected near the shoaling zone at water depths ranging from 7 to 25 meters. The data from the drifting sites were obtained using directional sensing wave buoys. During the study, a storm swept by and most of the measured wave spectra contained multiple peaks, i.e., dominant waves generated by an offshore storm with local wind generated waves superimposed. In the early stages, the offshore storm dominated the measured wave spectra. When the peak of the storm entered the area, the energy in the local wind generated sea approached the strength of the dominating energy from offshore. As the storm departed, the local wind waves faded and the offshore storm waves again dominated the measured spectra. The decaying waves gradually took on the more characteristic appearance of narrow banded swell waves. The effects of the local shoaling zone and the rotation of the storm have been used to investigate the characteristics of the measured waves.