Skew Surge and Storm Tides of Tropical Storms in the Delaware and Chesapeake Bays for 1980 -2019

Abstract

Coastal flooding poses the greatest threat to human life and is often the most common source of damage from coastal storms. From 1980 to 2020, the top 6, and 17 of the top 25, costliest natural disasters in the U.S. were caused by coastal storms, most of these tropical systems. The Delaware and Chesapeake Bays, two of the largest and most densely populated estuaries in the U.S. located in the Mid-Atlantic coastal region, have been significantly impacted by strong tropical cyclones in recent decades, notably Hurricanes Isabel (2003), Irene (2011), and Sandy (2012). Current scenarios of future climate project an increase in major hurricanes and the continued rise of sea levels, amplifying coastal flooding threat. We look at all North Atlantic tropical cyclones (TC) in the International Best Track Archive for Climate Stewardship (IBTrACS) database that came within 750 km of the Delmarva Peninsula from 1980 to 2019. For each TC, skew surge and storm tide are computed at 12 NOAA tide gauges throughout the two bays. Spatial variability of the detrended and normalized skew surge is investigated through cross-correlations, regional storm rankings, and comparison to storm tracks. We find Hurricanes Sandy (2012) and Isabel (2003) had the largest surge impact on the Delaware and Chesapeake Bay, respectively. Surge response to TCs in upper and lower bay regions are more similar across bays than to the opposing region in their own bay. TCs that impacted lower bay more than upper bay regions tended to stay offshore east of Delmarva, whereas TCs that impacted upper bay regions tended to stay to the west of Delmarva. Although tropical cyclones are multi-hazard weather events, there continues to be a need to improve storm surge forecasting and implement strategies to minimize the damage of coastal flooding. Results from this analysis can provide insight on the potential regional impacts of coastal flooding from tropical cyclones in the Mid-Atlantic.

Data_Sheet_1.pdf

“…The upper Chesapeake Bay does not exhibit the same high TWL, MHHW, or surges as in the upper Delaware Bay (primarily due to the overall size, shape, and depth of the Chesapeake Bay), however, extreme skew surge RLs in both upper regions are comparable to each other. This supports results in Callahan et al (2021a), which found the upper bays were highly correlated with each other from TC-caused skew surges, more so than with their respective lower bay regions. TCs can account for close to 40-60% of the largest (top 10) coastal flooding events in the Mid-Atlantic, with smaller relative percentages over larger number of events (Booth et al, 2016;Callahan et al, 2021b).…”

“…It also essentially removes the SLR trend and minimizes inherent constituent biases when computed over long time periods, which could result from changing physiographical environmental conditions (Ross et al, 2017) or from changing seasonal weather patterns that strongly influence the Sa (solar annual) and SSa (solar semiannual) constituents (NOAA CO-OPS, 2007). More details on the computation of skew surge can be found in Callahan et al (2021a).…”

“…It represents the meteorologically-forced increase of water levels due to the net effect of winds, atmospheric pressure (i.e., inverse barometer effect), nearby river discharge, and wave setup, and is more clearly separated from the astronomically forced-tides and potential complex hydrodynamics of tidesurge interactions (Batstone et al, 2013;Mawdsley and Haigh, 2016;Williams et al, 2016;Stephens et al, 2020). Skew surge levels are consistently less than the measures of maximum NTR up to 30% (Hall et al, 2016;Callahan et al, 2021a). There have been few studies of skew surge in the Mid-Atlantic.…”

“…Mawdsley and Haigh (2016) analyzed long term trends of skew surge and Williams et al (2016) investigated tide-skew surge independence, but only a few Mid-Atlantic tide gages were included in those analyses and neither performed traditional EVA on skew surges. Callahan et al (2021a) computed skew surge at the same tide gauges as the current study but only analyzed TCs.…”

Estimation of Return Levels for Extreme Skew Surge Coastal Flooding Events in the Delaware and Chesapeake Bays for 1980–2019

“…It represents the meteorologically-forced increase of water levels due to the net effect of winds, atmospheric pressure (i.e., inverse barometer effect), nearby river discharge, and wave setup, and is more clearly separated from the astronomically forced-tides and potential complex hydrodynamics of tidesurge interactions (Batstone et al, 2013;Mawdsley and Haigh, 2016;Williams et al, 2016;Stephens et al, 2020). Skew surge levels are consistently less than the measures of maximum NTR up to 30% (Hall et al, 2016;Callahan et al, 2021a). There have been few studies of skew surge in the Mid-Atlantic.…”