Space Daily via NASA: One morning in 2008, research scientist Cathleen Jones of NASA's Jet Propulsion Laboratory in Pasadena, Calif., was flying over the San Andreas fault near San Francisco, testing a new radar instrument built at JPL. As the plane banked to make a turn, she looked down to see the Sacramento River delta, a patchwork of low-lying lands crisscrossed by levees.Jones was using an instrument that can measure tiny movements of the ground on the scale of less than half an inch (less than a centimeter). It's called the Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR).
"It struck me that this new instrument might be perfect for monitoring movement of levees," said Jones. Checking the scientific literature, she found that nothing like that had been attempted before in the delta. She reported her idea to water managers at the California Department of Water Resources (DWR). She didn't know it, but she was at the beginning of a long-lived initiative to refine NASA technology for use in safeguarding the delta levees.
In the Sacramento River delta north of San Francisco Bay, islands, agricultural lands and communities below sea level are protected from surrounding water channels by more than 1,100 miles (1,800 kilometers) of dirt levees, many of which date back to the California Gold Rush. About two-thirds of all Californians and more than 4 million acres of irrigated farmland rely on the delta for water.
If a levee gives way, the results can be disastrous. A single 2004 levee failure created $90 million of damage and threatened the water supply to Southern California. However, the first warning that a levee is developing a structural problem can be a tiny soil deformation -- too small to be noticed by a visual inspection....
FEMA photo of a levee near Bombay Beach, California
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