HOLOCENE HISTORY OF CATASTROPHIC HURRICANES AND FIRES ALONG THE U.S. GULF COAST

Hurricanes and wildfires are two of the most important natural hazards in the U.S. Gulf Coast region. Recent developments in paleotempestology have suggested that for any given place along the Gulf coast, the return period of a direct hit by a catastrophic hurricane (defined as Saffir-Simpson category 4 or 5) is in the order of 300 years, or a landfall probability of 0.33% per year. Sedimentary records from a series of coastal lakes and marshes show that over the past 5000 years, each Gulf coast site was struck by catastrophic hurricanes at least 9-12 times, with a hyperactive period during 3400-1000 yr BP. Detailed proxy records of catastrophic wildfires are still lacking for the Gulf coast region, but a paleotempestological record based on a study of overwash sand layers, fossil pollen, and microscopic charcoal from Little Lake provides a rare opportunity to reconstruct a history of intense hurricane strikes and wildfires in coastal Alabama during the last 1300 years. The data suggest that coastal Alabama was directly struck by intense hurricanes (category 3-5) seven times during the past 1300 years. Remarkably, three of the four charcoal concentration peaks occur immediately above the more distinct overwash sand layers, implying that catastrophic fires are likely to occur shortly after an intense hurricane strike. It has been hypothesized that fire hazard increases significantly after an intense hurricane strike due to increased fuel accumulation and drier microclimatic conditions. Our data from Little Lake and other coastal sites seem to support the notion of a hurricane-fire interaction in the maritime pine-oak forests of the Gulf coast region.