WAVE AND CURRENT INTERACTION AT A JETTIED INLET, WELLS HARBOR, ME

Wells Inlet, located along the southern coast of Maine, has been the site of controversy since jetties were constructed there in the mid-1960's. Periodic dredging of the channel is necessary due to severe shoaling and breaking wave conditions. Causes of shoaling and general sediment circulation patterns have been studied using 19 laser survey profiles, analysis of 250 sediment samples, and examination of wave height and current velocity data obtained from three 2-week long Acoustic Current Meter deployments. Burst data collected at a frequency of 5Hz over a 5 minute period every hour allows for the examination of perturbation of the ambient current field by passing waves. Additional data averaged over 5 minute intervals 3 times per hour provide a relative tide curve and background current measurements. The jettied portion of the channel is partitioned into the thalweg region containing sediment ranging from cobbles (10 - 40 cm) to medium sand and adjacent shallow areas composed of coarse to fine sands. The channel is backed by an extensive marsh system consists of sand flats, mud flats, and isolated sandy patches of cobbles. The lack of mobile coarse-grained material in the backbarrier suggests that gravel in the jettied channel is derived from offshore sources. Mutually evasive domains of ebb and flood tidal current velocities are found in the jettied channel. Average ebb current velocities in the thalweg exceed flood velocities by as much as 16 cm/sec. Average flood current velocities in adjacent shallow portions of the channel exceed ebb velocities by as much as 17 cm/sec. Simultaneous wave height and current velocity measurements in the jettied channel show that as wave crests pass overhead they enhance flood velocities and retard ebb velocities by 10 - 25 cm/sec. Passing troughs have little or no effect on the current regime (changes of 0 - 5 cm/sec). This condition results in net landward sediment transport during high wave energy events when orbital velocities reach their maxima. These results are consistent with Solitary wave theory.