Using Nasa airborne radar, Scientists have generated maps that reveal New Orleans and its surrounding areas are sinking at ‘highly variable rates’.
The highest rates were found upriver along the Mississippi near industrial areas and in Michoud – both experienced annual drops of up to two inches.
Although the study names multiple contributing, researchers found the major culprits behind the drop in elevation were groundwater pumping and dewatering.
Scientists at NASA’s Jet Propulsion Laboratory, UCLA and the Center for GeoInformatics at Louisiana State University, Baton Rouge, collaborated on the study, which covered the period from June 2009 to July 2012.
Other notable sinking was found in New Orleans’ Upper and Lower Ninth Ward in Metairie, where the measured ground movement could be related to water levels in the Mississippi.
And an annual 1.6 inch drop was observed at Bonnet Carré Spillway east of Norco, which is the area’s last line of protection against springtime river floods blowing over the levees.
Experts call this drop in evaluation ‘subsidence’, as it is when the Earth sinks as a response to geological or man-induced causes.
In the case of New Orleans, it is mostly caused by groundwater pumping and dewatering – surface water pumping to lower the water table, which eliminates standing water and soggy ground.
Other contributing factors include withdrawal of water, oil and gas, compaction of shallow sediments, faulting, sinking of Earth’s crust from the weight of deposited sediments and ongoing vertical movement of land covered by glaciers during the last ice age.
JPL scientists and lead author Cathleen Jones say the results of this research could greatly improve existing models of subsidence for the Mississippi River Delta, which could give officials the upper hand when formulating plans for future events.
‘Agencies can use these data to more effectively implement actions to remediate and reverse the effects of subsidence, improving the long-term coastal resiliency and sustainability of New Orleans,’ Jones said.
‘The more recent land elevation change rates from this study will be used to inform flood modeling and response strategies, improving public safety.’