Twentieth century storm activity and sea level rise along the United States coast and their impact on shoreline positio

Coastal storms and sea level changes play important roles in coastal landform evolution. Long records (60--90 yr) of hourly water level from tide gauges and historical shoreline position data (100--150 yr) from NOS T-sheets and vertical airphotos along the U.S. East Coast were used to investigate the temporal and geographic changes in storm activity during this century, storm impact on beaches, post-storm recovery processes, and applicability of the Bruun rule.;Three storm indices based on hourly storm surge data: count, duration, and integrated intensity (area under the storm surge curve that is above two standard deviations for the entire surge record) from 10 tide gauges along the U.S. East Coast do not show any discernible secular trend during the 20 th century. There are, however, significant interdecadal variations in storminess. There was more storm activity (number) and intensity (duration and magnitude) during the mid- to late 1950s and early 1960s, but that storminess was comparable to that experienced in the early 1930s and 1990s.;Northeaster indices exceed that of hurricanes in number, duration, and integrated intensity along the U.S. East Coast. Extratropical storms dominate the coast from Virginia northward, while the influence of hurricanes increases southward.;Beach erosion is not only related to storm severity but also to whether the storm is coincident with spring tides. A storm erosion damage index (inner product of storm surge and tide) was developed. The spatial distribution of the storm erosion damage index, including the effects of both storm tides and waves, shows that the Delmarva coast suffers the most severe storm impact; the New Jersey and Long Island, NY coasts experience considerable storm- induced erosion; the New England coast undergoes relative light storm erosion hazard; the coast from southern North Carolina to the northern Florida experiences the lightest storm impact.;Great storms cause a quantum level of beach erosion in only several days. However, beaches appear to recover to positions consistent with their long-term erosion trend regardless of storm severity. This suggests that storms have little effect on long-term beach erosion, but more pre- and post-storm data are clearly needed.;There is a significant correlation between sea level rise and long-term beach erosion at erosional areas not influenced by inlets and coastal engineering projects. The shoreline retreat rate averages about 150 times that of sea level rise. The Bruun rule is well satisfied at these areas, indicating that it is appropriate to use the Bruun rule to predict the potential beach erosion in response to sea level rise.;Most beaches along the U.S. East Coast are influenced by tidal inlets. Changes in sediment supply induced by inlet activity play a dominant role in determining long- term shoreline changes. Sea level change is only a secondary effect in these areas, and its influence cannot be discerned in areas of rapid shoreline changes because of inlets. However, beach erosion caused by sea level rise is inexorable, while down-drift erosion induced by inlets can be mitigated by natural and artificial sand by-passing. It will become ever more difficult to protect fixed coastal development as active profiles migrate landward in response to sea level rise.