FORMS OF EROSION AND ACCRETION ON CAPE COD BEACHES

Abstract

Frequent measurements of beach profiles have been made at sixteen areas between Maine and Long Island since September 1965 by members of the Coastal Research Center of the University of Massachusetts. This research effort has resulted in the accumulation of approximately 2000 beach profiles along the New England coastline. The detailed analysis of profiles from Monomoy Island and Nauset Spit on Cape Cod has revealed the following erosion-accretion characteristics: 1. The most active areas of the beach profile in terms of sand transport are at the low-tide, neap high-tide, and spring high-tide zones. The center of the beach face is relatively inactive. 2. An exception to this behavior occurs during severe storms when large volumes of sand are removed from the entire beach face, producing a concave upward profile shape. 3. During periods of relatively low wave activity there is much interaction in terms of sand movement between these three zones, resulting in the formation of distinctive profile shapes. 4. These profile shapes tend to maintain themselves through sand movements which cause the berm to migrate back and forth along the profile. 5. This activity is often accomplished with little or no net sand erosion or accretion to the total profile. These conclusions, combined with additional analyses, indicate that the traditional measurements of total beach width and high tide beach width (i.e., to the berm) are not a reliable indication of sand volume changes on beaches.