Assessing decadal-scale changes to a giant sand wave field in eastern Long Island Sound

Three digital precision bathymetric data sets spanning 16.1 yr enabled a long-term analysis of the geometric, migration, and volumetric changes to large bedforms in a 1 k[m.sup.2] region of eastern Long Island Sound. Whereas a 1 yr study of sand wave mechanics during 1987 provided indirect evidence of long-term southwestward transport, this study adds a June 2003 data set and conclusively demonstrates a basinward (southwestward) progression of sand waves between 7 and 17 m in height. In addition, the modus operandi of sand wave migration during various temporal scales involves crestal flexing, crestal rotation, and differential migration along the crest. A volumetric analysis suggests that the sand waves are in a waning phase of migration and early stage of preservation as sea level rises into the basin and flood-dominant tidal currents decrease in strength. Keywords: sand waves, dunes, migration, morphology, subtidal environment, tidal currents, GIS.