THE EFFECT OF SEAWALLS ON LONG-TERM SHORELINE CHANGE RATES FOR THE SOUTHERN VIRGINIA OCEAN COASTLINE

David R. Basco

Abstract


This paper examines the relationship between the off shore bathymetry, resulting wave climate, shore boundary conditions (i.e., seawalled versus dune/beach sections) and the shoreline response as represented by long-term shoreline change rates over 120 years for the southern Virginia ocean coastline in the United States. Along the tourist area of the City of Virginia Beach, the data supports the conclusion that a seawall's presence for over 50 years has produced no significant increase in the recession rate. The highest recession rate (3m/yr) occurs at the Sandbridge sector further south. Some now claim that the beach width is narrowing at Sandbridge as a result of recent seawall construction. This allegation completely ignores the root cause of the problem which is shown in this paper to be the steep offshore bathymetry and high wave energy in this region. If we neglect the offshore boundary conditions when making field studies of "hardfacing" versus dune/beach sections, we can reach completely erroneous results.

Keywords


seawall; shoreline change; shoreline rate of change; Virginia

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