ABSTRACT

Jones, K.R. and Traykovski, P., 2019. Interaction of superimposed megaripples and dunes in a tidally energetic environment. Journal of Coastal Research, 35(5), 948–958. Coconut Creek (Florida), ISSN 0749-0208.

The superposition of smaller bedforms on larger dunes have been observed in multiple energetic tidal environments. This study analyzes the interaction of two scales of superimposed bedforms at Wasque Shoals, an ebb delta located approximately 1 km SE of Martha's Vineyard, Massachusetts. Data from a fixed rotary sidescan sonar deployed on a submerged quadpod captured the interaction of megaripples, or bedforms with wavelengths on the order of 1 m, with the lee side of a migrating dune with a wavelength of approximately 100 m. The net convergence of megaripples on the tidally dominant lee face of the dune suggests that the megaripples serve as an intermediate step between grain-scale transport processes and the large-scale dune migration. This conceptual model is quantitatively tested given observations of seabed elevation changes and dune migration rates. With this novel data set, two scales of bedforms were resolved on subtidal timescales, facilitating new insights into the dynamics of superimposed bedforms in tidal environments.

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