Classification of Fetch Limited Dunes in the Lower Chesapeake Bay: Evidence of Morphologic Equilibrium

Abstract

As part of a comprehensive assessment of dunes and beaches in the Virginia portion of the Chesapeake Bay, U.S.A., we developed a classification system for dunes that incorporates historical shoreline dynamics, shoreline reach setting, local geomorphologic situation, and shoreline use. Our classification system demonstrates the broad diversity of sandy shorelines in the lower Bay; however, we present a geomorphologic relationship between dunes and beaches that appears to act independently of geologic diversity. Cross-shore profiles revealed that the height of the primary dune crest above mean low water relates to the lateral distance between the point of mean low water and the normal line through the dune crest (termed the estuarine dune index [EDI]) in a 1 : 10 ratio. Mean EDIs showed no statistically significant differences between shoreline classes, which provides firm evidence of an equilibrium condition for fetch limited dunes (termed the point-one rule) and promises to be useful for shoreline assessments and the sustainable engineering of nourished shorelines.