Evaluation of criteria for predicting erosion and accretion on an estuarine sand beach, Delaware Bay, Jew Jersey |
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| Authors: | Nancy L Jackson |
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| Institution: | 1. Center for Policy Studies, New Jersey Institute of Technology, 07102, Newark, New Jersey
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| Abstract: | Predicting erosion and accretion of sand beaches in estuaries is important to managing shoreline development and identifying
potential relationships between biological productivity and beach change. Wave, sediment and profile data, gathered over twenty-nine
days on an estuarine sand beach in Delaware Bay, New Jersey, were used to evaluate the performance of four criteria that predict
beach erosion and accretion due to wave-induced cross-shore sediment movement (Dean 1973; Sunamura and Horikawa 1974; Hattori
and Kawamata 1980; Kraus et al. 1991). Each criterion defines a relation, between a wave and sediment parameter, and includes
a coefficient that discriminates beach erosion and accretion events. Relations, based on small-scale laboratory and field
data, were evaluated for predicting erosion or accretion at the study site. Significant wave heights at the study site, monitored
near high water, ranged from 0.08 to 0.52 m with periods of 2.4 to 12.8 s. Median grain sizes of sediments on the beach foreshore,
gathered at low water, ranged from 0.33 to 0.73 mm. All four criteria showed a clustering of erosion and accretion events.
Relations derived from small-scale laboratory data were better predictors of erosion on the profile at the field site than
those derived from field data gathered on exposed ocean environments. The planar profile and dominance of incident waves of
low height and short period are similar to laboratory conditions characterized by initial planar beach slopes and monochromatic
waves. Decreasing the value of the empirical coefficient to account for the differences in the magnitude of wave energy and
grain size increases the performance of the criteria tested to predict erosion of the profile. |
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