EOF ANALYSIS OF SHORELINE CHANGES FOLLOWING AN ALTERNATIVE BEACH FILL WITHIN A GROIN FIELD

Laura Lemke, Jon K. Miller, Alicia Mahon, Elizabeth Livermont

Abstract


The evolution of a beach nourishment project constructed in Long Branch, NJ was investigated using the method of empirical orthogonal functions (EOF). Most applications of EOFs on beach fill projects have focused on traditional linear fills on relatively long, straight, uninterrupted coastlines. The Long Branch project was somewhat unique in that it was designed as a feeder beach and was constructed within a groin field. EOFs were used to analyze shoreline positions and nearshore beach slopes at the site. The first three modes, determined from the shoreline position data set, explain more than ninety percent of the variation from the mean. Mode 1 and Mode 3 illustrate variations of the fill’s spreading as material moved in the direction of the net littoral drift, where several shore-perpendicular structures intercepted it. One of these structures was a large outfall pipe, which was shown to have a dominant influence over the shoreline evolution. The second mode was related to seasonal or storm impacts. The EOF analysis of the beach slope data also identified modes related to the spreading of the fill (Mode 2) and seasonal impacts (Mode 1). Overall, the eigenfunctions determined from both data sets reflect the morphological changes which were observed during the field surveys.

Keywords


EOF analysis, beach nourishment, groin

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References


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DOI: https://doi.org/10.9753/icce.v34.sediment.83