The Increased Risk of Flooding in Hampton Roads: On the Roles of Sea Level Rise, Storm Surges, Hurricanes, and the Gulf Stream

The impact of sea level rise on increased tidal flooding and storm surges in the Hampton Roads region is demonstrated, using similar to 90 years of water level measurements in Norfolk, Virginia. Impacts from offshore storms and variations in the Gulf Stream (GS) are discussed as well, in view of recent studies that show that weakening in the flow of the GS (daily, interannually, or decadal) is often related to elevated water levels along the U.S. East Coast. Two types of impacts from hurricanes on flooding in Hampton Roads are demonstrated here. One type is when a hurricane like Isabel (2003) makes a landfall and passes near the Chesapeake Bay, causing a large but short-term (hours to a day) storm surge. The second type is when Atlantic hurricanes like Joaquin (2015) or Matthew (2016) stay offshore for a relatively long time, disrupting the flow of the GS and leading to a longer period (several days or more) of higher water levels and tidal flooding. Analysis of the statistics of tropical storms and hurricanes since the 1970s shows that, since the 1990s, there is an increase in the number of days when intense hurricanes (Categories 3-5) are found in the subtropical western North Atlantic. The observed Florida Current transport since the 1980s often shows less transport and elevated water levels when tropical storms and hurricanes pass near the GS. Better understanding of the remote influence of the GS and offshore storms will improve future prediction of flooding and help mitigation and adaptation efforts.