Increased high-tide flooding projected for majority of U.S. coastlines
UH News
Coastal locations around the U.S., particularly along the Atlantic coast, are experiencing recurrent flooding at high tide. The impact of high-tide flooding accumulates over numerous, seemingly minor occurrences, which can exceed the impact of rare extremes over time.
These impacts are subtle—for example, the loss of revenue
due to recurrent road and business closures—compared with the physical damage
of property and infrastructure associated with extreme storm-driven events.
“We expect the most rapid increases to be along the U.S. Pacific and Gulf of Mexico coastlines, which includes Hawaiʻi and other Pacific Islands. This is important, because this is the point at which high-tide flooding transitions from being primarily a local or regional issue and becomes a national issue affecting a majority of our nation’s coastlines,” said lead author Phil Thompson, director of the UH Sea Level Center and assistant professor of oceanography in the UH Mānoa School of Ocean and Earth Science and Technology (SOEST).
Research such as this
provides sound, science-based information on which decision makers can base
plans for adapting to sea-level rise and mitigating the impacts of local and
regional flooding.
High-tide flooding
episodes
Thompson and
researchers from around the country analyzed tide gauge data from 89 coastal
locations around the U.S., including 10 locations from Hawaiʻi and U.S.-Affiliated Pacific Islands, and
developed a novel statistical technique that combined changes in tidal range
with NOAA (National Oceanic and Atmospheric Administration) sea-level
rise scenarios for the 21st century to produce the projections of high-tide
flooding.
Continued sea-level
rise will exacerbate the issue where present, and many more locations will
begin to experience recurrent high-tide flooding in the coming decades.
Additionally, the research team found that annual cycles in tides and sea level
can combine with oceanographic anomalies to produce many high-tide flooding
episodes over a short amount of time—creating extreme months with clustered
events.
The results of the
study directly address how coastal communities could plan for the future.
“Scientists, engineers and decision-makers are accustomed to thinking about
rare high-impact events, for example, a 100-year storm, but we demonstrate that
it is important to plan for extreme months or seasons during which the number
of flooding episodes, rather than the magnitude, is exceptional,” said
Thompson.
This research is an
example of UH Mānoa’s goal of Excellence in
Research: Advancing the Research and Creative Work Enterprise (PDF), one of four goals identified in the 2015–25
Strategic Plan (PDF), updated in
December 2020.