Coastal cities around the world are sinking.
By 2100, sea levels are expected to rise by up to
1 meter ( 3. 3 feet), causing billions of dollars in
annual damage. And extracting excess groundwater
triggers a sinking effect known as subsidence.
“Land subsidence in many coastal cities is a major
issue because it enhances flood risk,” says Gilles
Erkens, PhD, senior geologist, Deltares Research
Institute, Utrecht, the Netherlands.
In some cities, the ground is
going down 10 times faster
than the water is going up.
While the impact can be devastating, the right project can
help city governments confront
the problem head-on. “It’s difficult for a city to try to mitigate sea level rise because it’s
a global problem,” Dr. Erkens
says. “With land subsidence,
the city itself is the cause, so it
can try to mitigate it.”
Down, But Not Out
To stay above water, some
cities have launched mega-
projects spanning years—or
even decades. Jakarta, Indonesia—one of the world’s
fastest-growing cities and its fastest-sinking city—is
also the site of one of the world’s largest infrastruc-
Home to 28 million people, the Jakarta metropolitan region has sunk 13 feet ( 4 meters) due to
subsidence during the past 35 years, according
to Deltares. That’s why, in October 2014, Jakarta
O S launched the first phase of a 40-year, US$40 billion risk management program.
The near-term measures include bolstering 32 kilometers ( 20 miles) of existing
seawalls, while long-term solutions include the creation of drainage systems,
pumping stations, an outer seawall and a chain of 17 artificial islands that will
enclose Jakarta Bay. The enclosure will effectively create a large reservoir that
can act as a storage pool for surging water.
“In this densely populated city, we proposed going offshore because that’s
where you have the space,” says Victor Coenen, a project manager in Jakarta,
the city itself
is the cause,
so it can try to
—Gilles Erkens, PhD,
Deltares Research Institute,
Utrecht, the Netherlands
Jakarta, Indonesia has launched a
40-year program that will include
constructing a chain of 17 islands to
enclose Jakarta Bay.