Beach Erosion and Accretion at Virginia Beach, Virginia, and Vicinity.

摘要

Eighteen profile lines from Fort Story south to the Virginia-North Carolina State line were surveyed monthly for 27 months (Sep 74 to Dec 76). Net volume changes were moderate, with maximum rates of accretion at the north and south ends of the study area. A statistical analysis using earlier surveys going back to Nov 56 confirms the pattern of accretion in the north and south separated by erosion in the middle. Maximum annualized accretion rate during the 27-month study was 18.9 cubic meters/meter of beach front/year at Fort Story, and maximum erosion rate 11.6 cubic meters per meter per year at Sandbridge. Under present conditions, rates of erosion and accretion are independent of the 4 types of shore usage defined for this area--commercial, natural, military, and residential. The narrow, erosional beaches are located at the center of the study area in Back Bay National Wildlife Refuge (natural area), Dam Neck (military), and Sandbridge (residential); the wide, accretional beaches are located at the north and south ends in Fort Story (military) and False Cape State Park (natural). Instead of beach usage, it is suggested that the observed differences result from a nodal zone of diverging longshore transport in the middle of the study area (approximately Dam Neck to Back Bay). North of this zone, net transport is to the north, and south of this zone, it is hypothesized that net transport is to the south.