In coastal megacities around the world, the ground is sinking faster than the surrounding ocean level is rising. And, according to an article posted on DredgingToday.com, this subsidence is directly related to the over pumping of local groundwater resources.
Sections of Jakarta, Ho Chi Minh City, Bangkok, New Orleans and Dhaka have already sunk or are in danger of sinking below sea level, says Gilles Erkens, a geologist who presented the results of his study to the General Assembly of the European Geosciences Union.
A problem that costs billions
Worldwide damage attributed to subsidence is estimated to cost billions of dollars per year, and the number is expected to rise as populations and economies continue to grow.
The capital city of Indonesia, Jakarta, has sink four metres over the last 35 years, leaving it at significant risk of catastrophic flooding. The economic damage rises and the risk of more human victims is increased as the area remains under water for longer periods of time after flooding.
The city is also plagued by crumbling infrastructure (and related repair costs) as the ground shifts.
The primary cause is human activity
Groundwater extraction steadily increased over the last 3 decades to accommodate urbanization and population growth. Adding to this, coastal cities are often built on weaker soils than landlocked cities, increasing the natural rate of subsidence.
Groundwater extraction is extremely localized. So the onus is on cities to find a solution for its own subsidence.
Subsidence is a silent predator
Governments and inhabitants of these cities are mostly unaware of the urgency of this predicament.
Many governing bodies address the flooding problem, for example, by building a barrier. But as subsidence continues, the barrier will fall below sea level and no longer serve as protection to the city, but rather will hold water in.
If the extraction of groundwater is not addressed, coastal megacities will become increasingly vulnerable to catastrophic flooding. Subsidence must be included in the planning process for the medium and long term flourishing of any large, coastal city.
Find a local Heron Instruments distributor and begin your groundwater monitoring program so you can ensure subsidence doesn’t turn your city into an inland lake.
Thanks to DredgingToday.com for making us aware of this global issue.