Extreme Wave Heights Along the Atlantic Coast Of the United States

Abstract

This paper discusses storm-generated waves in Georges Bank, Baltimore Canyon, and Georgia Embayment. Waves were hindcast for all severe hurricanes affecting those areas during 1900-75 and were used to determine statistics for hurricane-generated waves. The extreme-wave statistics were found to be less severe than results presented elsewhere. Introduction Three areas on the outer continental shelf (OCS) along the U.S. Atlantic Coast - Georges Bank, Baltimore Canyon, and Georgia Embayment (Fig. 1) - are promising future sources of hydrocarbons. To develop safe, promising future sources of hydrocarbons. To develop safe, economical designs for the offshore structures required to develop and produce these potential sources, descriptions of oceanographic and meteorological conditions must be available. Storm-generated wave conditions are of particular concern because storm waves are of major particular concern because storm waves are of major importance in determining the maximum loads that these structures must withstand. This paper discusses extreme wave conditions in each area.Extreme wave conditions reflect rare occurrences and, thus, must be determined from a data base spanning a long enough time to form a representative or statistically significant sample of storm-generated waves. Hindcasting procedures can provide such a data base. Measured wave data only recently have been obtained from the Atlantic OCS. Measured data are useful when calibrating or verifying hindcasting methods. However, it is impractical to obtain a measured-wave data base with a sufficiently long time span to be used directly when estimating reliably the extremes associated with long return periods. Wave data available from ship observations span a longer period of time, but are subject to observational errors period of time, but are subject to observational errors (particularly in storm seas) and to the so-called "fair weather bias" resulting from ships that avoid storms when possible. Scope The required storm-wave data for this study were obtained by hindcasting procedures.' We included examination of historical storms that affected the areas, hindcasting of deep-water waves generated by a number of the more severe storms, and determination of the statistics for extreme wave conditions from the hindcast data.Both hurricanes (tropical cyclones) and winter storms (extratropical cyclones) affect the Atlantic OCS. Accordingly, waves generated by each type of storm must be considered when developing extreme-wave statistics. Hurricane-generated waves are obviously important in each area. Winter storm-generated waves are generally more severe in Georges Bank and Baltimore Canyon than in Georgia Embayment.Hurricanes were a major focus in this study. Wave data were hindcast for the most severe historical hurricanes and were used to determine hurricane-wave statistics in each area. Three severe winter storms affecting the mid-Atlantic coast also were hindcast. While these data were insufficient to determine winter storm-wave statistics, they did measure the relative severity and importance of winter storms vs hurricane waves for Baltimore Canyon. Data available from other sources were used to determine wave statistics for winter storms in Baltimore Canyon and Georges Bank.Lastly, a description of the over-all wave statistics for all storms, which jointly considered both hurricane and winter storms, was developed for Georges Bank and Baltimore Canyon. JPT P. 1697