Rising sea levels and the risks of moderate and severe coastal flooding

A new study from Princeton and Rutgers has found that areas along the Southeast U.S. coast, where severe flooding due to hurricanes and tropical storms is relatively frequent, may see an increase in moderate, rather than severe flooding due to sea-level rise.

On the other hand, coastal areas near Seattle, Washington, and in Southern California that normally experience very little severe flooding are likely to experience an uptick in severe and possibly historically unprecedented floods in the future due to sea-level rise.

<u>The beige and yellow colors mean little amplification of existing flooding episodes, while blue and purple colors mean hundreds to thousands of times more floods. Image courtesy of Maya Buchanan, Princeton University.</u>
<img src="https://vortex.accuweather.com/adc2004/pub/includes/columns/climatewx/2017/590x156_06080021_coasts.jpg"/>

On average, coastal flooding along the East and Gulf coasts already costs an average of 27 billion dollars annually.

This particular study, which can be found in the journal Environmental Research Letters, looked at a combination of historical data on flood heights collected at tide gauges with estimates of local sea-level changes developed earlier by Professor Robert Kopp (Rutgers), who is a co-author of this study.

<img src="https://vortex.accuweather.com/adc2004/pub/includes/columns/climatewx/2017/590x377_06080029_nj-shoreline-following-sandy-courtesy-us-dept-of-transportation---nccos.jpg"/>

Key excerpts from the study, via <a href="https://www.eurekalert.org/pub_releases/2017-06/pu-rsl060717.php" target=n>EurekAlert.....</a>

<em>The researchers calculated the "amplification factor" -- the amount by which a given rise in sea level drives the increase in the number of floods -- for numerous locations around the country. "The amount of sea-level rise that occurs will change the number of both moderate and severe floods," Buchanan said. "Climate change-driven sea-level rise is usually thought of as slow and steady, but actually a relatively small amount of increase in sea level can amplify the flood level significantly."</em>

<em>Based on the current rate increase of carbon emissions, by 2050 a moderate flood of the size that historically has occurred approximately every ten years would recur 173 times more often in Charleston but only 36 times more often in Seattle. A severe flood, defined as occurring about once every 500 years, would happen six times as often in Charleston but 273 times as often in Seattle.</em>