Seawall and Revetment Stability Study, Cape Hatteras Lighthouse, North Carolina

It is anticipated that erosion and gradual shoreline retreat will eventually diminish the beach fronting the Cape Hatteras Lighthouse. The US Army Engineer District, Wilmington, (SAW), is proving design expertise to NPS for the development of coastal protection works to safeguard the lighthouse. The plan of protection selected by NPS consists of encircling the lighthouse with a wave-reflecting seawall fronted by a stone revetment. The model study was conducted to determine the adequacy of the proposed seawall and revetment design and, if necessary, to develop alternate designs from which an optimum plan for stability and economy could be determined. The specific purposes of this investigation were to determine: a) The most severe wave conditions relative to stability of the seawall and stone revetment within the limits of still-water levels (sw1's) and wave periods that could be expected to occur in the area of the Cape Hatteras Lighthouse, b) The stability and optimum stone size of the rubble stone revetment under worst breaking wave conditions, c) The distribution of wave forces on the gravity seawall so that it could be designed to withstand their resultant forces and ensure stability against overturning and sliding, d) A seawall curvature that would prevent overtopping and minimize the resultant wave forces on the seawall itself; and e) The combined stability of the seawall and revetment resulting from the hydraulic interaction of the two components. Keywords: Hydraulic models; Stapods; Water waves; Wave pressure.