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Delta Subsidence: An Imminent Threat to Coastal Populations.

Schmidt CW - Environ. Health Perspect. (2015)

View Article: PubMed Central - PubMed

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In 2009 Syvitski reported that increasing compaction and reduced aggradation had put many of the world’s deltas in danger, more than half of them in Asia. “All trends point to ever-increasing areas of deltas sinking below sea level,” he wrote. “And it remains alarming how often deltas flood, whether from land or from sea, and the trends seem to be worsening. ” The biggest threat, Syvitski says, is that a delta will tip toward a collapsed state, meaning that it likely will never be restored to anything remotely similar to its natural condition... Yet it can take much longer—decades or more—for the salt levels in contaminated freshwater aquifers to decline once extraction has ceased... That’s because compared with the pumping pressure that draws saltwater up, the gravity that pulls it down is a much weaker force, Oude Essink explains... As Japan’s economy came back to life, groundwater use picked back up, and by 1968 subsidence in some places peaked at 24 cm per year... The Tokyo Metropolitan Government imposed strict regulations on groundwater consumption, and by 2006 subsidence once again had been reduced, reaching about 1 cm per year in areas that previously had been most affected... In 1985, with foundering infrastructure, worsening floods, and skyrocketing costs of pumping storm water into the sea, the government raised groundwater taxes sharply, according to Oranuj Lorphensri, director of the Bureau of Groundwater Control in Bangkok... She says groundwater use has since fallen to 0.8 million m per day, and subsidence has been reduced to 1–2 cm per year... The trend is especially pronounced in northwest Jakarta, where subsidence can reach 20 cm per year... At the Rise and Fall project’s kickoff meeting, some officials were skeptical that groundwater exploitation is what drives subsidence in the Mekong Delta. “People just say ‘groundwater is causing this,’ but we have no data to prove it,” says Bui Tran Vuong, deputy director general of the Division of Water Resources, Planning, and Investigation for South Vietnam... Syvitski warns it could have unpredictable consequences. “Even if you could do it, roads and buildings would buckle as the land rises. ” Oude Essink disagrees, saying that MAR projects around the world show it to be a potentially worthy approach for reducing the groundwater declines, and therefore subsidence... It’s hard to notice a drop in land elevation of a few centimeters per year until its consequences materialize in a catastrophic event, such as a devastating flood... Yet over time, these declines become significant... Although sea-level rise gets most of the attention, for vast numbers of people worldwide, subsidence is by far the more immediate problem... But because subsidence is a local problem, local solutions are needed to keep it bay.

No MeSH data available.


Related in: MedlinePlus

Along the Ganges–Brahmaputra Delta, earthen and concrete embankments surround low-lying agricultural areas known as polders. These embankments protect the land within, but they also block the deposition of new sediments during the rainy season. Consequently, the polders subside. When Cyclone Aila hit Bangladesh in May 2009, floodwaters crested over the embankments, turning sections of the polders to lakes. These residents are hauling mud to help build up an embankment after the cyclone, which did have one benefit—it left the area inundated with a long-overdue deposition of fresh silt, in some areas reaching 70 cm thick.© Espen Rasmussen/Panos Pictures
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d35e167: Along the Ganges–Brahmaputra Delta, earthen and concrete embankments surround low-lying agricultural areas known as polders. These embankments protect the land within, but they also block the deposition of new sediments during the rainy season. Consequently, the polders subside. When Cyclone Aila hit Bangladesh in May 2009, floodwaters crested over the embankments, turning sections of the polders to lakes. These residents are hauling mud to help build up an embankment after the cyclone, which did have one benefit—it left the area inundated with a long-overdue deposition of fresh silt, in some areas reaching 70 cm thick.© Espen Rasmussen/Panos Pictures


Delta Subsidence: An Imminent Threat to Coastal Populations.

Schmidt CW - Environ. Health Perspect. (2015)

Along the Ganges–Brahmaputra Delta, earthen and concrete embankments surround low-lying agricultural areas known as polders. These embankments protect the land within, but they also block the deposition of new sediments during the rainy season. Consequently, the polders subside. When Cyclone Aila hit Bangladesh in May 2009, floodwaters crested over the embankments, turning sections of the polders to lakes. These residents are hauling mud to help build up an embankment after the cyclone, which did have one benefit—it left the area inundated with a long-overdue deposition of fresh silt, in some areas reaching 70 cm thick.© Espen Rasmussen/Panos Pictures
© Copyright Policy - public-domain
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4528996&req=5

d35e167: Along the Ganges–Brahmaputra Delta, earthen and concrete embankments surround low-lying agricultural areas known as polders. These embankments protect the land within, but they also block the deposition of new sediments during the rainy season. Consequently, the polders subside. When Cyclone Aila hit Bangladesh in May 2009, floodwaters crested over the embankments, turning sections of the polders to lakes. These residents are hauling mud to help build up an embankment after the cyclone, which did have one benefit—it left the area inundated with a long-overdue deposition of fresh silt, in some areas reaching 70 cm thick.© Espen Rasmussen/Panos Pictures

View Article: PubMed Central - PubMed

AUTOMATICALLY GENERATED EXCERPT
Please rate it.

In 2009 Syvitski reported that increasing compaction and reduced aggradation had put many of the world’s deltas in danger, more than half of them in Asia. “All trends point to ever-increasing areas of deltas sinking below sea level,” he wrote. “And it remains alarming how often deltas flood, whether from land or from sea, and the trends seem to be worsening. ” The biggest threat, Syvitski says, is that a delta will tip toward a collapsed state, meaning that it likely will never be restored to anything remotely similar to its natural condition... Yet it can take much longer—decades or more—for the salt levels in contaminated freshwater aquifers to decline once extraction has ceased... That’s because compared with the pumping pressure that draws saltwater up, the gravity that pulls it down is a much weaker force, Oude Essink explains... As Japan’s economy came back to life, groundwater use picked back up, and by 1968 subsidence in some places peaked at 24 cm per year... The Tokyo Metropolitan Government imposed strict regulations on groundwater consumption, and by 2006 subsidence once again had been reduced, reaching about 1 cm per year in areas that previously had been most affected... In 1985, with foundering infrastructure, worsening floods, and skyrocketing costs of pumping storm water into the sea, the government raised groundwater taxes sharply, according to Oranuj Lorphensri, director of the Bureau of Groundwater Control in Bangkok... She says groundwater use has since fallen to 0.8 million m per day, and subsidence has been reduced to 1–2 cm per year... The trend is especially pronounced in northwest Jakarta, where subsidence can reach 20 cm per year... At the Rise and Fall project’s kickoff meeting, some officials were skeptical that groundwater exploitation is what drives subsidence in the Mekong Delta. “People just say ‘groundwater is causing this,’ but we have no data to prove it,” says Bui Tran Vuong, deputy director general of the Division of Water Resources, Planning, and Investigation for South Vietnam... Syvitski warns it could have unpredictable consequences. “Even if you could do it, roads and buildings would buckle as the land rises. ” Oude Essink disagrees, saying that MAR projects around the world show it to be a potentially worthy approach for reducing the groundwater declines, and therefore subsidence... It’s hard to notice a drop in land elevation of a few centimeters per year until its consequences materialize in a catastrophic event, such as a devastating flood... Yet over time, these declines become significant... Although sea-level rise gets most of the attention, for vast numbers of people worldwide, subsidence is by far the more immediate problem... But because subsidence is a local problem, local solutions are needed to keep it bay.

No MeSH data available.


Related in: MedlinePlus