SCIENCE
TECH
DIY
COVID-19
NEWSLETTER SIGN-UP "
REVIEWS
&
" # $ '
!
___
make your piggy bank happy
Humans are altering Earth’s tides,
and not just through climate
change
Shipping is a surprisingly major driver.
BY PHILIP KIEFER MARCH 08, 2021
ENVIRONMENT
UNSPLASH
"(%#
SHARE
I
f you’d been standing in just the right Miami Beach parking garage in 2016, you would have been
visited by an octopus, washed in on an especially high tide. In Boston, you might have needed to
wade to work in the past year. Across the country, sunny day floods, which occur because of high tide,
rather than storms, are becoming increasingly common—they’re the leading edge of sea level rise, as
tides reach further and further into coastal cities.
But climate change is just one way that humans are driving sunny day flooding. New research,
published Friday in the journal Science Advances, finds that coastal development has increased the
intensity of the tides themselves. At 18 sites across the US, projects on coasts amplified the effects of sea
Meet Tucker Carlson's Wife
level rise on local flooding, to the point that by 2019, a quarter of all nuisance flood days in those
Tucker Carlson's wife is getting a lot of
attention and for all the right reasons
locations were related to local changes in tide.
sponsored by: HealthyGeorge
READ MORE
The research builds on increasing recognition that humans can shape tides, says Thomas Wahl, an
engineer at the University of Central Florida who studies coastlines and climate change, and is an
author on the paper. “For a long time, oceanographers operated under the premise that tides are
stationary, they’re driven by the relationship between the sun, moon, and Earth, and the system doesn’t
change.”
But over the last few years, Wahl says that there’s been a growing body of research that shows that tides
in bays, estuaries, and even along the open coastline can be reshaped by human hands.
That can happen in many different ways. Hard seawalls reflect high water, and land creation can
influence currents in unpredictable ways. But “number one, of course, is dredging,” says Wahl. Most
American ports rely on massive channels dug into the muddy bottoms of harbors to allow the passage
of oceangoing ships.
Cargo ships have grown physically larger over the last 100 years, so shipping channels have too,
changing the local tides. “We basically have marine highways that are going into our shallow water
harbors,” says Stefan Talke, an environmental engineer at California Polytechnic State University and
another study author.
“If you dredge, you have deeper water,” says Wahl. “If you have deeper water, you have less friction, so
the tidal waves can enter the system more quickly, and leave more quickly.” And when it rushes in
faster, it can slosh up higher on land.
Digitized “marigrams” from Astoria, OR. With permission from Stefan Talke
Still, knowing that humans can change tides doesn’t necessarily mean understanding how
developments have played out along the American coastline. To get that information, Talke has been
digging through federal records to understand how tides looked hundreds of years ago.
“The US government has been measuring tides since at least the 1840s,” Talke says. Surveying
waterways was key to the country’s economic and colonial ambitions, which depended on the shipping
industry. “They needed to make maps, they needed to know when high tide was.”
But many of the records, kept on long, well-preserved scrolls, have disappeared into the National
Archives. (Some were destroyed entirely, including those for Charleston, South Carolina, which were
stored in a customs house attic and eaten by “vermin,” Talke says.) Talke and his students have spent
years digitizing what records they can find.
In half of the locations where long-term data was available, tidal gauges showed intensifying highs and
lows over the last 100 years. The changes were more pronounced in cities located in slightly inland
estuaries, where a dredge channel deepens the waterway most dramatically. Wilmington, North
Carolina, which was flooded for almost a quarter of 2016, was particularly affected, though
Philadelphia and New York City saw similar trends.
switch, save and shop
On their own, the more intense tides wouldn’t necessarily have led to increased flooding. But the higher
overall oceans and more intense tides have compounded, leading to more days where water spills onto
streets.
And because the research focused only on the 40 locations with a hundred years of tidal records, Wahl
thinks the findings are only part of the picture. “There are probably many other places where the same
thing is going on, but we don’t know, because we don’t have that same amount of data.”
A few inches of water might not be as catastrophic or deadly as a storm surge, Wahl says, but over time
they can have bigger economic consequences. “At some point, it has an impact on infrastructure.
People can’t go to work. Businesses can’t open.”
But understanding the role of infrastructure in high tides might help guide sea level adaptation. The
Army Corps already uses data on catastrophic flooding risk when it evaluates new dredging projects,
since it’s well-known that shipping channels can intensify storm surge during hurricanes. One such
passage was implicated in the deadliest flooding of Hurricane Katrina.
But, Wahl says, “we haven’t really attempted to study how [shipping channels] could affect just the tide,
and how that would affect nuisance flooding.”
This research, he says, provides the first steps towards asking those questions. “We may have to ask
ourselves if we are aiming for bigger ships, or less flooding.”
Correction 3/18/21: The article previously misspelled a source’s name in one spot and left a word out of
an affiliation.
CLIMATE CHANGE
FLOODS
GLOBAL WARMING
SHIPPING
TIDES
SPONSORED CONTENT
Recognize This Former Male Star? See
Her Before Her Transition!"
BY WOAHWORLD
MORE TO READ
RELATED
Why wildfires are suddenly ravaging the Southeast
Get used to fires in the Great Smoky Mountains
READ NOW
RELATED
RELATED
This Is Exactly How Important Soil Is To
Life On Earth
How California is saving rainwater for a
sunny day
Scientists put an exact number on soil
biodiversity's...
Meet Helen Dahlke, a water banker
Popular in the Community
AdChoices
Sponsored
Conversation
Your voice matters. Conversations are moderated for civility. Read the community guidelines here.
Log In
Be the !rst to comment...
Powered by
Terms | Privacy | Feedback
Like science, tech, and DIY projects?
Sign up to receive Popular Science's emails and get the highlights.
LET'S GO
LINKS
Home
Newsletter Sign-up
Contact
Privacy Policy
Terms of Use
Masthead
Sitemap
DepositPhotos
Top Articles
Do Not Sell My Personal Information
by Popular Science
FOLLOW US
!
"
#
$
%
READ MORE
DISCLAIMER(S)
We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.
Registration on or use of this site constitutes acceptance of our Terms of Service.
READ MORE
© 2021 Camden Media. All rights reserved.
X