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Sinking Cities in Indonesia Caused by Groundwater and Gas Extraction

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MIAMI – Jakarta and several other major Indonesia cities are sinking at alarming rates of up to 22 cm per year, according to a new study by scientists at the University of Miami (UM) Rosenstiel School of Marine and Atmospheric Science. This rapid land subsidence of major cities, due to extraction of groundwater for industrial use, is likely to put the densely populated coastal regions below sea level in less than two decades.

"Our study shows that some parts of Jakarta, and elsewhere in Indonesia, will be below sea level in less than 20 years if they don't stop pumping groundwater," said Rosenstiel School Professor Falk Amelung, a co-author of the study.

Rosenstiel School geophysicist Estelle Chaussard and Amelung used Interferometric Synthetic Aperture Radar (InSAR), a satellite-based technique, to produce high-resolution maps of the land subsidence in Indonesia and isolate its causes. Previous scientific field studies had documented rapid land subsidence in only three Indonesian cities.

"We did not expect to detect so many other sinking cities," said Chaussard.

The researchers attributed this rapid land subsidence to groundwater extraction in four major urban areas, including in the capital and largest city of Jakarta (population: 9.5 million), Bandung (population: 2.4 million), Pekalongan (population: 200,000), and Semarang (population: 1.5 million). Indonesia's municipal water supply serves only 25% of its more than 240 million people therefore the majority of the population and industries rely heavily on groundwater extraction for water. Land subsidence from gas field exploitation was also shown to occur near the Indonesian cities of Lhokseumawe and in the Sidoarjo regency.

Unlike Venice, which is sinking at a rate of 2 to 3 millimeters per year, heavily developed regions of Indonesia, including in Jakarta and five other major cities are sinking at rates of tens of centimeters per year.

"Since these cities are close to sea level and because the subsidence is extremely rapid, the societal impacts could be huge, both in terms of water resources and sinking of the land relative to the ocean," said Chaussard. "Understanding of the processes involved and continuing the monitoring are thus critical for mitigation purposes."

The island nation is highly susceptible to climate change impacts such as sea-level rise and coastal flooding from monsoons. Identification of the locations and cause of the land sinking is a necessary first step in the development of hazard mitigation plans, according to the study's authors.

The study was published in the early online edition of the journal Remote Sensing of Environment. The study's authors are Chaussard, Amelung, Hasanudin Abidin from the Institute of Technology in Bandung Indonesia, and Sang–Hoon Hong from the Korea Aerospace Research Institute in the Republic of Korea.

About the University of Miami's Rosenstiel School
The University of Miami's mission is to educate and nurture students, to create knowledge, and to provide service to our community and beyond. Committed to excellence and proud of the diversity of our University family, we strive to develop future leaders of our nation and the world. Founded in the 1940's, the Rosenstiel School of Marine & Atmospheric Science has grown into one of the world's premier marine and atmospheric research institutions. Offering dynamic interdisciplinary academics, the Rosenstiel School is dedicated to helping communities to better understand the planet, participating in the establishment of environmental policies, and aiding in the improvement of society and quality of life. For more information, please visit www.rsmas.miami.edu.


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