Waves in Western Long Island Sound: A Fetch-Limited Coastal Basin

This paper summarizes the statistics of observations of wind and surface gravity waves in Long Island Sound, a large estuarine embayment in southern New England. We examine the relationship between significant wave height and wind speed and direction and show that the significant wave height and dominant period in western Long Island Sound have an asymmetric response to the wind direction. Waves are larger and have longer periods when the wind is from the east than when the same stress is directed from the west. The data are consistent with the predictions of empirical parameterizations of fetch limited wave growth when the wind is from the west. However, for easterly winds, the westward narrowing of the Sound limits wave growth and requires that an effective fetch of approximately 30 km be used in the empirical formulae. An examination of the extreme values in the time series shows that previous estimates based on simulations significantly underestimates the occurrence of large waves with the important consequence that design guidance for shore protection structures may underestimate wave heights during severe storms. We speculate that earlier work has not adequately represented the consequences of fetch asymmetry on wave growth.

Automated summary

This paper summarizes observations of wind and surface gravity waves in Long Island Sound and explores the relationship between significant wave height and wind speed and direction. It shows that waves respond asymmetrically to wind direction, being larger and having longer periods when the wind is from the east compared to the west. The data support fetch limited wave growth predictions for westerly winds, but suggest that an effective fetch of approximately 30 km is needed for easterly winds.