March 2020, ScientificAmerican.com 29VENTURES
THE BUSINESS OF INNOVATIONWade Roush is the host and producer of Soonish, a podcast
about technology, culture, curiosity and the future. He
is a co-founder of the podcast collective Hub & Spoke and
a freelance reporter for print, online and radio outlets,
such as MIT Technology Review, Xconomy, WBUR and WHYY.Ocean water expands as it soaks up heat from a warming
atmosphere. Add in water from melting glaciers and ice sheets,
and the global mean sea level will most likely rise by anywhere
from 1.4 to 2.8 feet (43 to 84 centimeters) by 2100, according to
the Intergovernmental Panel on Climate Change.
This gradual swelling will stress coastal cities, which are
already seeing more sunny-day “nuisance flooding” at high
tide. But the bigger threat is from waves and storm surges,
which are amplified by higher sea levels. If greenhouse gas
emissions go unchecked, by 2100 this combination will produce
peak sea levels that are, on average, 1.9 to 5.6 feet higher than
today’s mean sea level. As soon as 2050, the kind of extreme
coastal flooding we currently expect every 100 years will occur
every year at tropical latitudes and every 10 years in many U.S.
coastal cities. By 2100 annual flood damage could amount to
9.3 percent of the global gross domestic product, or tens of tril-
lions of dollars a year.
Most nations are not living up to their Paris Agreement com-
mitments to curb greenhouse gases, but even if they were, some
sea-level rise would be inevitable. So there is really no choice
but to try to defend our coasts.
The question is, How? Would it be smarter to build big, ex -
pens ive surge barriers that protect entire harbors or to imple-
ment smaller-scale changes along the shoreline?
Not surprisingly, many city planners are attracted to the sec-
ond, less costly option. In my hometown of Boston, which has a
47-mile shoreline, Mayor Marty Walsh’s “Resilient Boston Har-
bor” plan envisions a city buffered by restored marshes and by
elevated parks, walkways and roads. Researchers at the Univer-
sity of Massachusetts Boston endorsed that approach in a 2018
preliminary study, concluding that such land-based resiliency
measures would be more cost-effective than a barrier across the
harbor’s mouth.
But the reality, I suspect, is that we will have to do both. Let’s
say Boston elevated its frequently flooded Long Wharf and Sea-
port districts by three feet or so. That would fend off extra-high
king tides, which occur when Earth, the moon and the sun
align. But it would not help much against storm surges.
“Even though sea-level rise and storm surge are related, they
are separate, distinct phenomena, and it’s important to address
them with separate engineering and technology responses,”
says William Golden, who filed the 1982 lawsuit that led to the
cleanup of Boston Harbor and who later founded the National
Institute for Coastal and Harbor Infrastructure, a Boston-based
nonprofit. “What we feel is often possible and justifiable in
urbanized areas is to focus on the concept of a layered defense:
a land-based system on the perimeter to address sea-level rise
integrated with a regional system of sea gates designed to pre-
vent inundation from storm surge.”
The UMass researchers estimated the cost of Boston’s pro-
posed Outer Harbor Barrier at $8 billion to $12 billion. Two
huge “floating sector gates,” modeled on the mammoth Maes-
lant kering storm-surge barrier in the Netherlands, accounted
for two thirds of that price tag. But there are cheaper options for
sea gates, such as the $550-million floating barge that would
close off the “Ike Dike” proposed for Texas’s Galveston Harbor.
And even at $12 billion, a barrier might be a good investment.
According to the U.K.’s Tyndall Center for Climate Change
Research, a 100-year storm coming on top of a hypothetical 1.6-
foot rise in sea level would threaten $460 billion in assets in the
Boston area alone.
At his nonprofit, Golden is working to gather Boston com-
munity leaders in a push for a more thorough study of the Out-
er Harbor Barrier that could help qualify the project for federal
funding. “What we need now is to have an in-depth additional
cost-benefit analysis, so that we make sure our public policy
isn’t based on a preliminary study,” Golden says. “This is going
to affect the city forever.”Dollars for Dikes
Massive storm-surge barriers
may be worth the cost
By Wade Roush
Illustration by Jay Bendt
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