Mapping the Storm Surge Risk

Even a Category 2 storm, given a worst-case storm track, brings the risk of 3-foot to 6-foot storm surge flooding to Boston and its suburbs (indicated by orange and yellow colors), along with a 9-foot surge risk for densely populated neighborhoods and industrial areas in towns north of the city. (Note: this “worst-case” map illustrates areas at risk, but the actual flooding would depend on the storm track and would not affect all the threatened areas during a single storm.)

A direct hit from a worst-case Category 4 hurricane would subject much of the Boston metropolitan area to the risk of 9-foot deep floodwaters and battering waves, including East Boston, Logan Airport, South Boston, Roxbury, Jamaica Plain, Brighton, Brookline, and the suburbs of Cambridge and Medford. Even a more likely lesser storm (see next frame) could flood some parts of the city and its suburbs.

Most locations in the barrier island communities near Charleston, South Carolina, are at risk of deep flood waters and battering waves in a worst-case Category 2 hurricane. A Category 5 hurricane (see next frame), though less likely, poses a far more severe risk were it to strike Charleston directly.

Very few locations in Charleston, South Carolina, and vicinity are exempt from the risk of nine-foot or greater storm-surge floodwaters in the event of a worst-case direct hit from a Category 5 hurricane. Hurricane expert Jeff Masters notes that even one foot of storm surge floodwater is enough to sweep a car off the road, while people find it hard to stand up in even six inches of storm surge flooding. Surge waters tend to move at 10 mph to 15 mph, about the speed of the hurricane’s travel.

A view of the Category 2 pane in the NHC interactive map shows a relatively moderate storm surge flood risk to Corpus Christi and surrounding areas. However, even a storm surge of less than three feet (indicated by blue on the map) poses a risk to life and to buildings.

Although nearby barrier islands and undeveloped low-lying areas near Corpus Christi, Texas, could experience 9-foot or higher water in a Category 5 hurricane storm surge, most of Corpus Christi proper would not be inundated, according to the NHC’s worst-case surge map.

Even the Maine city of Portland could experience 9-foot or higher storm surge flooding in a worst-case storm, according to the NHC’s Slosh map. However, the map does not provide detailed information on particular properties’ risk of flood (see next frame).

As this image shows, the flood risk data is not displayed on the NHC map when the user zooms down to a close view that would provide detailed information about particular streets or addresses. An NOAA spokesman said that residents should consult local authorities in the event of an actual storm. Lot-by-lot flood risk information for many U.S. coastal areas is available, for a price, from real estate analytics firm CoreLogic

The low-lying wetlands and shore surrounding Savannah, Georgia, could see extensive 9-foot storm surge floods in even a Category 2 hurricane. A major hurricane, such as Savannah has not seen in more than a century, could pose a massive inundation risk to much of the city and surrounding area (see next frame).

Savannah, Georgia, has escaped major hurricane strikes for a century and more, even as major storms have struck more northerly stretches of the coast. If a Category 5 storm were to strike the low-lying city directly, Savannah could experience widespread 9-foot inundation which could remake the face of the metropolitan area.

The NHC’s “worst-case” slosh map shows how a Category 2 storm overrunning Tampa, Florida, would likely bring 3-foot to 6-foot storm surge flooding to the Tampa Bay shoreline.

If a Category 5 storm were to strike Tampa, much of the city and vicinity could experience 9-foot or higher storm surge flooding, topped by higher waves. (Note: the red color indicates areas at risk for 9-foot or higher water in a worst-case scenario, but not all the areas in red would experience that degree of flooding in a single storm.)

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