Atmospheric rivers are relatively narrow bands of moisture that ferry precipitation across the Pacific Ocean to the West Coast and are key to California’s water supply.

When people think of natural disasters in California, they typically think about earthquakes. Yet the natural disaster that residents are most likely to face involves flooding, not fault lines. In fact, all 58 counties in the state have declared a state of emergency from flooding at least three times since 1950. And the state’s capital, Sacramento, is considered one of the nation’s most flood-prone cities. Floods also affect every Californian because flood management projects and damages are paid with public funds.