ANOMALOUS ACCRETION ALONG OUTER CAPE COD SHORELINE POSSIBLY LINKED WITH AEOLIAN TRANSPORT ASSOCIATED WITH PARABOLIC DUNE FIELD

The bluffs of unconsolidated glacial deposits on outer Cape Cod, Massachusetts, have been subjected to wave action throughout the Holocene transgression. Eroding coastal deposits have supplied sediment for construction of spits and barrier beaches to the north and south. The construction of those landforms has not been contemporaneous because the rates and direction of sediment transport have varied with sea level. Recent study indicates that the bluff section of Outer Cape Cod retreats at rates of approximately 0.5 m/yr at the north end and 1.0 m/yr at the south end.

This study examines current and past measurements of outer Cape Cod coastal features to identify trends affecting these landforms. Historical coastal profile measurements were analyzed along with newly acquired data for quantitative comparisons, both on and off shore. Current locations of shoreline features obtained by lidar and differential GPS were analyzed along with original 19th century and mid 20th century survey data to provide quantitative descriptions of the three major coastal landform systems on outer Cape Cod: the Nauset-Monomoy barrier system, mid-Cape bluffs and Provincetown Hook. GIS was utilized to manage and visualize these different data sources.

Within the Provincetown Hook system, a striking accretional anomaly was recognized upon initial analysis of the data. When plotted on aerial photographs the anomalous accretion appeared to be associated with a major parabolic dune field near the Provincetown – Truro boundary. A working hypothesis was developed that the accretion

is the result of the northeast flank of the parabolic dune field encroaching onto the beach producing a cross-shore sediment flux.