NASA has just confirmed the sum of all fears for many native Southerners. Along with its surrounding areas, New Orleans is sinking at a higher rate than previous estimates imagined. Through the use of airborne radar mapping the rate that the ground sunk over the last few years, NASA was able to document the precise regions at the highest risk. This will allow them to monitor what requires planning and building.
Earth’s surface sinks due to a culmination between both natural and man-made causes. Deposited sediment’s weight ultimately causes subsidence which moves glaciers causing the compaction of shallow sediments. As humans, we too can influence the process when we pump out oil or gas via water withdrawal.
As groundwater is extracted dewatering the region, surface water is subsequently removed to prevent standing water from causing sinking. Unfortunately, constructing the levees has exasperated this problem because they have prevented the natural build-up of counteractive sediment.
The areas where the issue has become most apparent include upriver along the Mississippi River, areas of Norco and Michoud and more. In these places, the ground is sinking at an average of 2 inches each year. Areas of greater concern such as New Orleans and its Lower 9th Ward have a subsidence coinciding with the water levels of the Mississippi River. Ground level changes around the levees made to prevent flooding are actually sinking by 1.6 inches annually.
NASA’s data will be utilized for map building while they track differences in elevation on our planet’s surface down to the difference of a centimeter. Since these factors alone can’t inform the team of researchers just what is causing the drastic change in ground level, scientists will need to study all prospective causes in order to operate within the various time and space scales.
Though the knowledge of this region’s sinking is not exactly new, NASA has highlighted the degree of its occurrence seems to be much faster and greater than previously determined. It could also place particular regions at an even greater risk of flooding than before. They hope that this newfound data will help to reduce or reverse the subsidence in the hardest hit areas while assisting in the strategic choices for the future.
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