RAPID: Understanding Hurricane Ian's Storm Surge Inundation and Sediment Transport in Order to Advance the Field of Paleotempestology

Hurricane Ian made landfall in Southwest Florida on September 28, 2022, generating extensive flooding. The change to the coastline was substantial and was accompanied by loss of human life and extreme infrastructure damage. Hurricane Ian is considered a rare, high loss event also known as a “tail-risk event.” Tail-risk hurricanes are a serious threat for coastal communities, such as the South Florida coastline, where the past few decades have seen rapid population growth.

Estimating future hurricane risk relies upon knowledge of past events, but most hurricane records only extend back ~170-years. Scientists can use the geologic record to find evidence of past hurricanes over thousands of years. These records help to uncover long-term patterns in hurricane activity and explore the causes of hurricanes like Hurricane Ian.

Hurricane Ian provides an excellent opportunity to study the geologic evidence of a tail-risk hurricane to estimate how often these events have occurred. This project will analyze sediment samples and measure elevation in areas impacted by the storm. These analyses will provide a key for what evidence is left behind in the geologic record from tail-risk hurricanes.

Further work will apply these characteristics back in time in the geologic record to determine storm frequency. The results of this study will be used to support improvement of models, hurricane risk assessment, planning, and development. This work will better inform insurance and re-insurance industries, coastal managers, federal disaster agencies, and local communities about rare tail-risk hurricanes. The data produced during this study will be widely disseminated to the public.

Several paleotempestology reconstructions have already been developed for the Southwest Florida coastline and have extended our knowledge of hurricane activity in the area back more than 1000-years. However, well documented modern analogs are needed to help interpret these long-term records. The landfall of Hurricane Ian along the Southwest Florida coast provides an opportunity to investigate the character of overwash deposits associated with a strong category 4 hurricane (150 mph winds).

Studies of modern storms, such as the deposits left behind by tail-risk hurricanes like Ian, are essential for being able to accurately interpret the sediment record. This research aims to examine post Hurricane Ian sedimentological and geomorphologic change at six previously studied back-barrier field sites from as far south as the Fakahatchee, Ten Thousand Islands, to as far north as Bokeelia, Pine Island.

Sediment cores will be taken to determine the character and nature of Hurricane Ian storm surge driven overwash deposits. The cores will be examined for grain size, event-bed deposition, and clast composition. The character and nature of the overwash deposits will be compared to nearby high-water marks and Hurricane Ian SLOSH model output runs.

In addition, an in-depth study of the barrier island geomorphologic change will be carried out utilizing pre- and post-hurricane landfall LiDAR data. This project will advance the field of paleotempestology through a better understanding of tail-risk hurricane deposition, which will ultimately lead to better reconstructions of such events down-core.

Therefore, this research will increase understanding of tail-risk hurricane return periods. This research will also help to determine the response of vulnerable barrier islands to tail-risk storm events. The generated hurricane data sets will be later used in computer models.

This information will aid in the better understanding of the long-term climate drivers that control the formation, intensity, and track of hurricanes, which is critically important for hurricane risk assessment and coastal management decision-making. In addition, the geomorphologic study will inform coastal managers on the importance of barrier islands in blocking and/or reducing storm surge/overwash.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.