Seasonal drivers of storm tides and flood impacts along the US Atlantic Coast

Densely populated coastal areas face increasing flood risk as rising sea levels combine with storm surges and high tides. Much of the U.S. East Coast experiences extratropical cyclones (ETCs) more frequently than tropical cyclones (TCs), yet many studies on extreme flood risk focus primarily on TCs or exclude ETCs altogether. ETCs occur primarily during November to April (henceforth, cool-season), while TCs occur primarily during May to October (henceforth, warm-season). This study performs a quasi-nonstationary skew surge joint probability (qn-SSJPM) analysis of storm tide exceedance distributions for cool and warm season from 23 tide gauges along the U.S. east coast to assess seasonal contributions to extreme water levels. From Boston, MA northward, cool-season extreme storm tides predominate, while south of Wilmington, NC, warm-season storm tides predominate. Using a property damage curve for New York City, we show that cool- and warm-season storms cause comparable amounts of economic damage each year. These findings highlight the importance of treating cool- and warm-season storms as statistically separate to improve flood risk analysis and coastal protection.