A sinking feeling
Jakarta, Indonesia has launched a 40-year program that will include constructing a chain of 17 islands to enclose Jakarta Bay.
IMAGE COURTESY OF WITTEVEEN+BOS
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.”
“With land subsidence, the city itself is the cause, so it can try to mitigate it.”
—Gilles Erkens, PhD, Deltares Research Institute, Utrecht, the Netherlands
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 infrastructure programs.
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 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, Indonesia for the Netherlands-based engineering firm Witteveen+Bos. His organization developed the Jakarta plan and is now helping the Indonesian government strengthen the seawall and relocate the people who live there. “That's one of the most sensitive issues in the project,” Mr. Coenen says. “We have to relocate at least 6,000 families.”
(3.3 feet) Expected maximum rise in global sea levels by 2100
Number of Chinese residents vulnerable to flooding due to rising sea levels
Cost of Jakarta, Indonesia's 40-year risk management program
The long-term challenges, he says, involve securing reliable contracts to ensure a financially feasible program. The key will be establishing a single project authority with sound project management practices. The initiative's decades-long timeline also means project plans must include strong financial foresight. The outer seawall project will take 15 years to execute while the islands, which project leaders hope will function as a separate city, will be complete in 40 years. The plan is for new island real estate to ultimately pay for the project, with international loans bridging the financial gaps.
These 10 countries are at the greatest risk for flooding due to rising sea levels.
|1. China||50.5 million|
|2. Vietnam||23.4 million|
|3. Japan||12.8 million|
|4. India||12.6 million|
|5. Bangladesh||10.23 million|
|6. Indonesia||10.15 million|
|7. Thailand||8.2 million|
|8. The Netherlands||7.8 million|
|9. The Philippines||6.2 million|
|10. Myanmar||4.7 million|
|Source: Climate Central|
To weather the storms that come with changing political tides—and government administrations— the project plan must be flexible, Mr. Coenen says. He recommends that project teams re-evaluate the program every two to three years.
“You cannot plan ahead 25 to 40 years from now, not with such a complicated, interrelated plan,” he says. “You must be very flexible and make contingency plans that can withstand delays or changes.”
Ho Chi Minh City, Vietnam is learning from a country renowned for its flood mitigation projects: the Netherlands. The Netherlands’ approach is to allow some floodwater to flow in, rather than try to keep all of it out.
The Dutch city of Rotterdam is helping Ho Chi Minh City officials attack the problem from two sides: bolstering protections against the water while creating spaces for it to enter. The city is pursuing 30 projects worth over US$190 million that focus on water resources, energy, and waste and land management. To slow subsidence, the city will build 30 large reservoirs that store tens of millions of cubic meters of water, helping to significantly reduce the amount of water pumped from aquifers.
As the Ho Chi Minh mitigation projects get underway, team members are learning from Dutch flood-management professionals. But knowledge is being transferred in the other direction as well. “They're learning from us about storm-surge barriers and dikes,” Alexandra van Huffelen, Rotterdam's vice-mayor for sustainability, told The Guardian, “and we're learning from them [that] you need to…let nature help you protect the coastline.” —Novid Parsi
MAY 2015 PM NETWORK
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