As extreme storms grow more frequent, what's the value of a technology that gives a warning up to five months in advance that a catastrophic flood could strike your city?
We’re guessing pretty priceless.
Scientists at the University of California, Irvine, said Monday that they have demonstrated that a NASA satellite that detects groundwater can be used to predict the potential for disasters like the Missouri River flood that devastated the Midwest of the United States in 2011.
The satellite, called GRACE (Gravity Recovery and Climate Experiment), calculates minuscule changes in the planet’s gravitational field to detect underground water basins. When a basin starts to fill up from rain or snowmelt, the area’s gravitational pull grows, which GRACE can detect. As the ground becomes more saturated, its ability to soak up water from a storm decreases and river basins subsequently overflow.
“The wetness of a watershed determines its response to precipitation,” the researchers wrote in a paper published in the journal Nature Geoscience. “We demonstrate that basin-scale estimates of water storage derived from satellite observations of time-variable gravity can be used to characterize regional flood potential and may ultimately result in longer lead times in flood warnings.”
In an email, coauthor J.T. Reager emphasized that the scientists cannot predict when a devastating flood will strike. But by determining the ground’s saturation levels, they can make accurate estimates of the potential for flooding if a big storm hits anywhere from two to five months in the future.
Warnings can then be issued far in advance, giving local authorities time to prepare to evacuate residents and secure property and infrastructure.
“Most flood forecasts are on the time frame of three to 10 days, like a weather forecast,” said Reager, who is now a research scientist at NASA’s Jet Propulsion Laboratory.
The Missouri River disaster contributed to 108 deaths and a loss of $8.4 billion from flooding between October 2010 and September 2011, according to the National Weather Service. Even absent a 500-year flood like the Missouri disaster, the weather service estimates that inland flooding causes an average of 133 deaths and $4 billion in economic losses a year.
“I think brief, extreme weather events will happen more frequently with a changing climate,” Reager said. “The type of flooding we are seeing is due to slow and steady input: continued rain and snowmelt over a long period that fills the basin gradually. Then, when a big storm comes in, it causes catastrophe because of the already saturated ground.”
Reager said the researchers wrote the paper as a proof of concept. Now it’s up to weather forecasters to put the theory into practice.