High tides, caused by the effects of the sun’s and moon’s gravitational pulls on the Earth, are no new phenomenon. But coastal flooding from such high tides is becoming more and more of a problem. As global warming worsens and sea levels rise, high-tide flooding is affecting coastal communities more than ever before.
A new website shows users, via multiple maps of the U.S., the estimated number of days of high-tide flooding that could occur per year up to 2100. As someone looks at the maps, they can drag a bar to change the year, in one-year increments, and observe the severity of flooding in 99 different coastal cities across the country. Different colors represent greater danger, and users can zoom in and click on a specific city to see the number of flooding days there.
Six maps represent six different scenarios, ranging from low to extreme, based on estimated mean sea-level rise (which could vary from 0.3 meters to 2.5 meters). Ultimately, how those scenarios will actually play out depends on how seriously we take climate change. “What this app is showing is what all the potential scenarios are, for either our lack of change or if we make drastic changes,” says Dan Pisut, environment content lead at ArcGIS Living Atlas of the World, a collection of maps and geographic information. Esri, which developed the site, makes the ArcGIS cloud-based mapping software that allows for data analysis through geographic and spatial visualizations.
Some coastal communities will be more vulnerable than others. According to Esri’s analysis, in the intermediate scenario (where the mean sea-level rise is at 1 meter), the number of flooding days in Atlantic City, New Jersey, will increase from 25 a year to 55 a year between 2021 and 2031; and in Sewell’s Point, a peninsula in Norfolk, Virginia, from 22 to 52. Galveston, Texas, is not yet among the top ten spots with the most flooding days, but annual flooding days are predicted to rise there from 16 to 58, a 263% increase; and in Grand Isle, Louisiana, from 7 to 54, a 671% increase. By 2050, Grand Isle would have 324 flooding days under the intermediate scenario—and in the extreme scenario, 365 days of flooding a year.
City planners and municipal and state leaders already use Esri’s tools for making impact scenario assessments, and the company hopes they’ll be able to make strategic decisions about coastal management using these maps. Flood water is affecting roads, rail, and property near coastlines and causing stress to the stormwater pumping systems already set up to mitigate problems. Miami and Charleston have been able to build seawalls, but they may not be protective enough very soon if levels keep increasing at the same rate.
Esri hopes people will use the free app to see the alarming prospects of global warming and take it more seriously. “We have done a pretty good job at minimizing these impacts with engineering efforts,” says Keith VanGraafeiland, the ocean curator for the Living Atlas team. “But there’s going to be a certain point in time when those efforts are going to be outweighed by what Mother Nature is doing.”
This post has been updated to clarify that ArcGIS is the software made by the company Esri.