Date of Award

1976

Degree Type

Thesis

Degree Name

Master of Science in Geology

Department

Geology

First Advisor

Jon Boothroyd

Abstract

The purpose of this project was to study the relationships between dynamic nearshore processes and beach changes at Napatree Beach, Rhode Island. Beach surveys performed from December, 1974 to August, 1975 at six transects show that slight to moderate accretion of sediment occurred at all but one station. Although an overall seasonal cycle of erosion and accretion exists, erosional and accretional beach profiles are not unique to any one season. With the exception of glacial till in the vicinity of Napatree Point, sediment sampling indicated that the dominant sediment size was fine sand. There was little seasonal variation in sediment size. Negative values of skewness in most samples reflect the high energy of the nearshore environment.

A comparison of a computer model describing the littoral drift system at Napatree with empirical data indicated that some beach changes at Napatree are adequately explained by the model. The model did not accurately predict the littoral drift system associated with waves approaching from the south-southeast. A more complete understanding of the littoral drift system was obtained by considering: 1) the nature of the beach profiles in relation to existing wave regimes, 2) the magnitude and duration of coastal storms, and 3) the influence of tidal currents.

Wave refraction data indicate the strong influence that the nearshore topography has upon the local nearshore processes. Refracted waves associated with a given wave-length direction may result in littoral drift direction being both eastward and westward at the same time along various stretches of the shoreline.

Geomorphological evidence and wave refraction analysis suggest a very flight net littoral sediment flux towards the east. Although the dune line on the south side of Napatree appears to have been slowly migrating southward since 1963, the beach remains vulnerable to large storms because of its low elevation.

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