Several recent analyses of water level observations at NOAA tide gauges have shown that sea level rise is contributing to more frequent and longer-lasting tidal flooding than in decades past. Based on correlations between water levels at a tide gauge and reported instances of observed flooding, those thresholds are defined observationally by personnel from local National Weather Service offices during and following flooding events-rather than statistically as, for example, the 100-year flood level is. The issuance of a CFA or CFW is typically tied to a high tide that is predicted to exceed either the minor or moderate flooding threshold for an area. Moderate coastal floods today are associated with a Coastal Flood Warning (CFW) about imminent or immediate flooding that could pose a serious risk to life and property.īoth minor and moderate flooding can be detected by higher than normal water level observations at tide gauges maintained by the National Oceanic and Atmospheric Administration (NOAA). While these floods typically do not pose a direct risk to life or property, they present challenges to daily life in affected areas. National Weather Service categorizes tidal flooding that is limited in extent and duration as “minor” or “nuisance” flooding and often issues a Coastal Flood Advisory (CFA) in association with such events. In this study, we focus on tidal flooding events because they are an increasingly visible manifestation of sea level rise and one for which exposed communities are not prepared. The Northeast U.S., in particular, is a “hot spot” of rapid sea level rise, possibly caused by climate-induced weakening of the Atlantic Meridional Overturning Circulation (AMOC) and its upper branch, the Gulf Stream. The stretch of coastline from Nova Scotia to the Gulf of Mexico faced some of the world’s fastest rates of sea level rise in the twentieth century-from 2.8 mm per year in Boston to 9.1 mm per year at Grand Isle, Louisiana. Local sea level trends can differ from the global average due to factors including land subsidence, tectonics, changes in ocean circulation, gravitational or sea level fingerprinting, groundwater pumping, and dredging. This acceleration is attributed mainly to ocean warming, a quickening pace of land ice loss, and a net transfer of groundwater from the land into the sea. From 1993 to 2010, the global rate has accelerated to 3.0 +/- 0.7 mm per year. The rise in sea level is accelerating both globally and regionally in many places.

Global sea level rose by an average of 1.2–1.7 mm per year over the course of the 20 th century. Before that permanent inundation occurs, however, unprotected coastal areas could experience more frequent flooding with high tides. In the absence of coastal adaptation measures to protect against rising seas, some coastal areas could fall below the high tide line by the end of the century. With higher sea levels, local flooding thresholds can be reached more easily during average high tides. Sea level rise has the potential to inundate significant stretches of the U.S.

This does not alter our adherence to all the PLOS ONE policies on sharing data and materials as detailed online in the guide for authors. There are no competing interests, including patents, products in development or marketed products, to declare. Dahl the sole proprietor of Dahl Scientific. From these funds, the Union of Concerned Scientists provided Dahl Scientific support in the form of salaries for the first author (KAD), but did not have any additional role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript.Ĭompeting interests: Co-author Kristina A. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.ĭata Availability: All relevant data are within the paper and its Supporting Information files.įunding: The Union of Concerned Scientists received funding for this study from The Grantham Foundation, The Barr Foundation, The Energy Foundation, Mr. Received: JAccepted: OctoPublished: February 3, 2017Ĭopyright: © 2017 Dahl et al. Schumann, Bristol University/Remote Sensing Solutions Inc., UNITED STATES East and Gulf Coasts: Projections for 20. Citation: Dahl KA, Fitzpatrick MF, Spanger-Siegfried E (2017) Sea level rise drives increased tidal flooding frequency at tide gauges along the U.S.

Nc tide tables 2015