A validated tropical-extratropical flood hazard assessment for New York Harbor

Abstract

Recent studies of flood risk at New York Harbor (NYH) have shown disparate results for the 100 year storm tide, providing an uncertain foundation for the flood mitigation response after Hurricane Sandy. Here we present a flood hazard assessment that improves confidence in our understanding of the region's present‐day potential for flooding, by separately including the contribution of tropical cyclones (TCs) and extratropical cyclones (ETCs), and validating our modeling study at multiple stages against historical observations. The TC assessment is based on a climatology of 606 synthetic storms developed from a statistical‐stochastic model of North Atlantic TCs. The ETC assessment is based on simulations of historical storms with many random tide scenarios. Synthetic TC landfall rates and the final TC and ETC flood exceedance curves are all shown to be consistent with curves computed using historical data, within 95% confidence ranges. Combining the ETC and TC results together, the 100 year return period storm tide at NYH is 2.70 m (2.51–2.92 at 95% confidence), and Hurricane Sandy's storm tide of 3.38 m was a 260 year (170–420) storm tide. Deeper analyses of historical flood reports from estimated Category‐3 hurricanes in 1788 and 1821 lead to new estimates and reduced uncertainties for their floods and show that Sandy's storm tide was the largest at NYH back to at least 1700. The flood exceedance curves for ETCs and TCs have sharply different slopes due to their differing meteorology and frequency, warranting separate treatment in hazard assessments.

Atmospheric Research Over the Western North Atlantic Ocean Region and North American East Coast: A Review of Past Work and Challenges Ahead

“…ETC winds can on occasion reach hurricane force and cause damaging coastal storm surges. Orton et al () found that in the New York City area, ETCs are a dominant cause of surge events that have an annual probability greater than 1%. The National Oceanic and Atmospheric Administration (NOAA) National Climatic Data Center (NCDC) estimated that from 1980 to 2016, major ETC events caused more than $1 billion in damage for each event (https://www.ncdc.noaa.gov/billions/summary-stats).…”

Numerical Modeling of Historical Storm Tides and Waves and Their Interactions Along the U.S. East and Gulf Coasts

“…To date, most of the historical storm surge and wave modeling studies for the U.S. East and Gulf Coasts have focused on individual TCs in a specific region (e.g., Bilskie et al, ; Bunya et al, ; Dietrich et al, ; Hope et al, ; Kennedy et al, ; Lin et al, ; Marsooli et al, ; Orton et al, ; Shen et al, ; Sheng et al, ; Westerink et al, ). In addition to historical surge and wave modeling, probabilistic flood hazard assessment studies also usually focus on a specific region (e.g., Lin & Emanuel ; Lin et al, ; Orton et al, ). Despite the appreciable number of storm‐specific and region‐specific studies, storm surge and wave conditions over the entire basin (of the U.S. Atlantic Coast) are rarely studied.…”

SynthETC: A Statistical Model for Severe Winter Storm Hazard on Eastern North America

“…ETC winds sometimes reach hurricane force and drive 35 damaging coastal storm surge. Orton et al (2016) found that in the New York City 36 area, ETCs are the dominant cause of surge events that have annual probability 37 greater than 1%. NOAA's NCDC estimated $40.9 billion in insured and uninsured 38 losses due to ETC events from 1980 to 2016 that caused more than one billion 39 dollars in damage each (www.ncdc.noaa.gov/billions/summary-stats; see also Smith 40 and Katz, 2013).…”