California: California is facing a potentially multi-billion-dollar flood threat as El Nino gathers strength in the Pacific Ocean, with the heaviest rains expected during the winter months.
The warming El Nino phenomenon can unleash powerful Pacific storms, including atmospheric rivers, some of which are known as the “Pineapple Express” when they originate near Hawaii.
Disaster modelers at Climate X, a risk analytics firm backed by Google Ventures, estimate El Nino could cause $2 billion to $3 billion in statewide losses from flooding and mudslides through the winter, based on damage from past events. California averages about $500 million in annual flood damage, according to nonprofit Climate Central.
An emerging threat is a pulse of Kelvin waves that can raise sea levels across the Pacific, said Michael McPhaden, a senior scientist affiliated with the University of Washington’s Cooperative Institute for Climate, Ocean and Ecosystem Studies. The underwater waves, caused by changing winds during El Nino, can worsen coastal flooding when storms and high winds hit California.
The next significant wave is expected to reach California by early October, according to McPhaden. Kelvin waves have already raised sea levels by up to 16 inches (40 centimeters), said Paul Roundy, an El Nino researcher and atmospheric science professor at the University at Albany.
California has already faced coastal impacts since El Nino developed in June. In early September, remnants of storm Marie hit Southern California, severely damaging more than a dozen oceanfront homes in Orange County and nearly erasing some beaches and seawalls. At least one home was marked for demolition.
These early bursts of “substantial” beach erosion months ahead of El Nino’s peak “raise the potential for more severe coastal flooding, erosion, and infrastructure damage,” said Adam Smith, a Climate Central disaster researcher.
Coastal erosion risk across California tends to rise by more than two-thirds during extreme El Nino events, according to Climate X.
Governor Gavin Newsom declared a statewide emergency on September 22, directing transportation officials to assess vulnerable infrastructure and allowing expedited levee repairs, channel-widening projects and bridge protections.
In Malibu, officials are planning community workshops from September 29 to prepare residents for the “unique risks” of an El Nino winter.
“We’ve mapped it out and the worst-case scenario is not good,” said Susan Duenas, Malibu’s public safety director.
Rock slides and “mud floods” could cut off roads, potentially leaving residents stranded after heavy rains. “We tell people to have enough food for a couple weeks,” Duenas said.
Homes and infrastructure near wildfire burn scars are especially vulnerable, said Erik Larson, a Climate X scientist. “Anytime you have wildfire, especially on slopes, you’re way more at risk of landslides,” Larson said. “The removal of vegetation like that is going to cause a lot more water to flow over the surface, so it increases your risk of flash floods.”
