RENEE MONTAGNE, HOST:

 

The U.S. has done a lot to prepare for things like tornadoes and hurricanes. But what about more extreme events? A major tsunami or a large asteroid hurtling toward Earth? NPR's Jon Hamilton reports on what scientists are saying about those mega-disasters.

 

JON HAMILTON, BYLINE: In the winter of 1861 and 1862, California endured a flood that's often described as biblical.

 

LUCY JONES: It rained for 45 days straight.

 

HAMILTON: Lucy Jones from the U.S. Geological Survey says the rain created a lake in the central valleys that stretched for 300 miles. She says the flood also transformed California.

 

JONES: It bankrupted the state, destroyed the ranching industry, drowned 200,000 head of cattle, changed California from a ranching economy to a farming economy.

 

HAMILTON: It was a classic mega-disaster. Jones told scientists at an American Geophysical Union conference in Washington, D.C. that she's been studying the event to prepare for the next big flood. She says the California deluge was caused by an atmospheric river, a ribbon of concentrated water vapor that can produce extreme storms.

 

JONES: They have the rain potential of hurricanes, or even more so because they go on for weeks. But they don't have as much wind, and they don't have the reputation that hurricanes have.

 

HAMILTON: Jones says meteorologists have learned to detect these atmospheric rivers. And she says California now has an extensive system of dams and flood control channels that didn't exist in the 1860s. So she says it should be possible to start releasing water before the system gets overwhelmed.

 

JONES: There's always something you can do to make it less of a disaster than it might otherwise be, if you've got enough information.

 

HAMILTON: Another threat from the skies comes in the form of asteroids and comets. An asteroid several miles across probably wiped out the dinosaurs 66 million years ago. But Lindley Johnson of NASA says an asteroid just half a mile across could create a global dust cloud.

 

LINDLEY JOHNSON: Causing the Earth's atmosphere to become opaque, and blocking out the sun and things like that.

 

HAMILTON: So Johnson says NASA has a simple strategy for big asteroids.

 

JOHNSON: Well, you find them before they find us, and that's the real driver behind NASA's current work.

 

HAMILTON: NASA has found more than 10,000 near-Earth objects. And Johnson says the agency has a plan to fend off any big object headed our way.

 

JOHNSON: Hit it with something really hard and fast, and the change in velocity then would change the orbit enough so that it would not hit the Earth.

 

HAMILTON: The ocean can also produce mega-disasters. In 2004, a tsunami in the Indian Ocean killed more than 230,000 people. In 2011, another tsunami killed more than 15,000 people in Japan. Eddie Bernard of the National Oceanic and Atmospheric Administration says even Japan was overwhelmed by the damage.

 

EDDIE BERNARD: That exceeded their capacity to recover, because in many cases, the entire city was washed away. Tens of thousands are still living in government housing two years after the fact.

 

HAMILTON: Bernard says the result would been much worse in the U.S.

 

BERNARD: Japan was much better prepared, and they're recovering much easier than perhaps we would, because they've thought this thing through. For example, they restored their roads in a matter of weeks. For the communities that survived, they restored electricity within 10 days.

 

HAMILTON: A government study found that if a similar tsunami struck Oregon, some areas would lose electricity for months, and water for more than a year. Bernard says that's too long. People will leave, and businesses will fail unless communities find a way to minimize damage and restore services more quickly.

 

BERNARD: The communities that do something will survive, and the ones that don't will be ghost towns. It's that simple.

 

HAMILTON: The Oregon Legislature has been holding hearings this summer on how to make communities more resilient. Jon Hamilton, NPR News.