DYNAMIC EQUILIBRIUM BEACH PROFILES: FORCES OF OFFSHORE SEDIMENT TRANSPORT IN MARYLAND’S CHESAPEAKE BAY
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Abstract
To examine the impact of shoreline erosion on the near shore environment, it is necessary
to estimate the quantity and quality of yearly sediment mass that is likely to be added by
erosion. Data were collected in 2008 at ten sites along the Maryland shoreline of the
Chesapeake Bay and compared to both empirical and theoretical models of offshore
profiles. The data collected at each site included a series of three-dimensional
bathymetric profiles from offshore transects run at each site, as well as a series of
sediment core data that were acquired along each transect. Relationships between grain
size, beach type, sediment composition, and strength of eroding sediments were also
explored. The results showed that sands dominated offshore surficial sediments at most
locations, even though the source sediments were mixtures of sands and muds. The
observed offshore profiles were consistent with expectation from ocean beach profile
paradigms, with the exception that the steepness proportionality factor was not related to
sediment grain size. An adjusted form of the classic Bruun relationship for predicting
shoreline retreat was in approximate agreement with long-term observations.