Heightened hurricane surge risk in northwest Florida revealed from climatological‐hydrodynamic modeling and paleorecord reconstruction

Abstract

Historical tropical cyclone (TC) and storm surge records are often too limited to quantify the risk to local populations. Paleohurricane sediment records uncover long‐term TC activity, but interpreting these records can be difficult and can introduce significant uncertainties. Here we compare and combine climatological‐hydrodynamic modeling (including a method to account for storm size uncertainty), historical observations, and paleohurricane records to investigate local surge risk, using Apalachee Bay in northwest Florida as an example. The modeling reveals relatively high risk, with 100 year, 500 year, and “worst case” surges estimated to be about 6.3 m, 8.3 m, and 11.3 m, respectively, at Bald Point (a paleorecord site) and about 7.4 m, 9.7 m, and 13.3 m, respectively, at St. Marks (the head of the Bay), supporting the inference from paleorecords that Apalachee Bay has frequently suffered severe inundation for thousands of years. Both the synthetic database and paleorecords contain a much higher frequency of extreme events than the historical record; the mean return period of surges greater than 5 m is about 40 years based on synthetic modeling and paleoreconstruction, whereas it is about 400 years based on historical storm analysis. Apalachee Bay surge risk is determined by storms of broad characteristics, varies spatially over the area, and is affected by coastally trapped Kelvin waves, all of which are important features to consider when accessing the risk and interpreting paleohurricane records. In particular, neglecting size uncertainty may induce great underestimation in surge risk, as the size distribution is positively skewed. While the most extreme surges were generated by the uppermost storm intensities, medium intensity storms (categories 1–3) can produce large to extreme surges, due to their larger inner core sizes. For Apalachee Bay, the storms that induced localized barrier breaching and limited sediment transport (overwash regime; surge between 3 and 5 m) are most likely to be category 2 or 3 storms, and the storms that inundated the entire barrier and deposited significantly more coarse materials (inundation regime; surge > 5 m) are most likely to be category 3 or 4 storms.

Hurricane Sandy’s flood frequency increasing from year 1800 to 2100

“…Also, large uncertainties exist in GCM projections on both future storm activity and RSL rise, as shown in this study; future research should examine the GCMs on their capability to accurately project the key atmospheric and ocean variables that control hurricane activity and sea level dynamics. Ultimately, proxy storm records that span centuries to millennia, over various climate states, may provide critical information for evaluating model projections of both the frequency of extreme floods (31,32) and how they change with the climate (33).…”

Rapid attribution of the August 2016 flood-inducing extreme precipitation in south Louisiana to climate change

“…In particular, the climate change context of saltwater flooding must include an assessment of the regional sea level change contributions and meteorological conditions that can influence these types of events (e.g., Katsman et al, 2008;Sterl et al, 2012;Lin et al, 2012Lin et al, , 2014Little et al, 2015). While certain meteorological conditions, such as landfalling tropical cyclones, can lead to both freshwater and saltwater flooding (e.g., Lin et al, 2012;Villarini et al, 2014), the assessments and discussions presented here are only relevant to extreme rainfall events that have the potential to initiate inland flooding; we do not address changes in storm surges, nuisance flooding (Moftakhari et al, 2015) or other saltwater flooding events.…”

Parameter sensitivity and uncertainty analysis for a storm surge and wave model

“…Their research shows significant storm surges for New York with return periods of less than 500 years, which further demonstrates the potential shortcomings of relying on empirical surge and hurricane records for hazard estimation. Similarly, Lin et al (2014) propose that the Atlantic Ocean may presently be experiencing a period of reduced hurricane activity. They propose that highenergy hurricane landfalls may be more common than that estimated from the extant historical hurricane track and surge records.…”

“…As there is great uncertainty surrounding the hurricane hazard estimates for the North Atlantic region, stochastic deterministic hurricane simulations are a promising path towards developing reliable hazard estimates (Lin et al, 2012(Lin et al, , 2014. As such, we must acknowledge that numerical surge model parameter uncertainties will affect these estimates.…”