It took around 100 years for some parts of Houston to sink ten feet. Then Hurricane Harvey nailed the city and it only took a matter of days for Houston to sink even more.
According to Chris Milliner with the Jet Propulsion Laboratory at Caltech, the weight of Hurricane Harvey's floodwaters is so massive that the water flexed the Earth's crust and pushed Houston down by approximately two centimeters.
"We believe that the loading of water from flooding has acted to elastically deform the crust downwards," says Milliner, who analyzed Global Positioning System data to arrive at his astonishing conclusion.
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As the Press has previously reported, natural and unnatural subsidence has caused regions of Harris, Fort Bend, Montgomery, Brazoria and Galveston counties to drop anywhere from one to ten feet. Because the area's soil is predominantly clay, the ground has been more prone to sinking compared to a robust surface like bedrock. Add to that the removal of groundwater for oil and gas production, and the sprawling city has sunk at a disconcerting rate.
The floodwaters are causing an altogether different sinking effect, one that's probably reversible. Milliner believes that once the water makes its way downstream to the Houston Ship Channel, Houston will bounce back up.
"As the water slowly recedes over the coming days/weeks and unloads the crust, we should expect uplift as the crust recovers elastically," says Milliner. "The crust's elastic response to loading and unloading is similar to if you were to jump on and off your mattress."