Climate change will bring megafloods to California

Climate change is making it a matter of time before a megaflood hits the state.

The Santa Barbara police car blocked access to the bridge, lights flashing as the thundering, swollen brown river rampaged below. The water was running so high in this Southern California county that it gushed through the railings of the bridge, and poured out onto the road.

This region is familiar with water scarcity – usually battling extreme heatwaves, wildfires, and drought. Now, Southern California is confronting an overabundance of water, in the form of torrential rain and life-threatening floods.

Earlier this week, around half a year's worth of rain was predicted to fall in Los Angeles and the surrounding areas in just one day.  

The city recorded its rainiest day ever on Monday, and it wasn't better news for the rest of California either. A state of emergency was declared and evacuation orders were issued. Mudslides hit neighbourhoods, drivers were stranded, and half a million residents lost power. About 37 million residents, or 94% of the state's population, are under flood alerts.

The already-deadly storm is caused by an atmospheric river, a corridor of water vapour in Earth's lower atmosphere which is carried along by the wind, forming long currents – a kind of sky river. The consequences can be dramatic. The precipitation that falls is comparable to the rain brought by hurricanes making landfall on the Gulf Coast.