Inverse modeling of storm intensity based on grain-size analysis of hurricane-induced event beds

Abstract:

As the coastal population continues to grow in size and wealth, increased hurricane frequency and intensity present a growing threat of property damage and loss of life. Recent reconstructions of past intense-hurricane landfalls from sediment cores in southeastern New England identify a series of active intervals over the past 2,000 years, with the last few centuries among the most quiescent intervals. The frequency of intense-hurricane landfalls in southeastern New England is well constrained, but the intensity of these storms, particularly prehistoric events, is not. This study analyzes the grain sizes of major storm event beds along a transect of sediment cores in Salt Pond, Falmouth, MA. Several prehistoric events contain more coarse material than any of the deposits from the historical interval, suggesting that landfalling hurricanes in the northeastern United States may have been more intense than the historically encountered category 2 and 3 storms. The intensity of major storm events is estimated using grain-size analysis with a digital image processing, size, and shape analyzer. Since event deposits in Salt Pond result from a combination of coastal inundation and wave action, a large population of both historical and synthetic storms is used to assess the storm characteristics that could result in the wave heights inversely modeled from grain size trends. Intense-hurricane activity may be closely tied to warming in sea surface temperature. As such, the prehistoric intervals of increased frequency and intensity provide potential analogs for current and future hurricane risk in the northeastern United States.