Analysis of Short-Term Variations in Beach Morphology (and Concurrent Dynamic Processes) for Summer and Winter Periods, 1971-72, Plum Island, Massachusetts
beach morphology, beach profiles, breakers, meteorological variables, morphology, Plum Island, waves, Massachusetts, Gradient, offshore
Misc. Report No. 77-5
An analysis of the relationship between wave and meteorological variables and beach morphology was undertaken during the summer and winter periods, 1971-1972, on Plum Island, Massachusetts. Variables were measured or computed bihourly, 24 hours per day, throughout both study periods. The variables were wave period, wave height, breaker type, breaker angle, longshore current velocity, wave steepness, breaker power, wind speed and direction, barometric pressure, air and water temperature, and ground water elevation. Daily topographic maps of the intertidal zone were constructed for 12 beach profiles spaced at 60-meter intervals. Variations in beach process variables, during both the summer and winter periods, were directly related to the passage of high- and low-pressure systems and to the proximity of the system to Plum Island. With an increase in breaker power and breaker steepness, the high tide beach-face gradient increased. Increases in breaker power also resulted in a rise to the level of the ground water surface. Although most process variables were similar for the summer and winter periods, strong offshore winds and extreme low temperatures that accompany polar high-pressure systems are unique to the winter period. Difference in bach morphology within a small area appear to reflect the state of recovery of the beach profiles after a storm. Adjacent profiles at different stages of maturity are controlled by the proximity of the nearshore bar. The closer the bar is to shore, the faster the sediment is returned to the beach zone.