How do you harness an epic amount of rain in a water-scarce state? Let it flood in, say scientists

(Trends Wide) — California has gone from extreme drought to extreme flooding in a matter of days. This Monday, 90% of the state’s population was on flood alert due to another round of storms. Last week, several counties in the state were experiencing the exact opposite: exceptional drought, which the US Drought Monitor considers the most severe category.

California’s parade of ultra-humid storms has not fully reversed the entrenched drought. And scientists warn it has a long way to go to erase years of unfavorable rainfall trends and overexploitation of water supplies.

But the abrupt switch from drought alerts to flood alerts highlights the dilemma facing California: how to manage an overwhelming amount of rain in a water-scarce state? Is it possible to take advantage of that water so that it is available in the dry months of summer?

Part of the solution, climate scientists explained to Trends Wide, is to remove the levees so that rivers have more room to spill their banks safely into surrounding lands.

In this image, cars are seen submerged in flood waters after heavy rains hit Windsor, California on January 9, 2023. (Credit: Justin Sullivan/Getty Images)

“We have to let our rivers flow differently, and let the rivers overflow their banks a little bit more and recharge our groundwater in the wet seasons,” Peter Gleick, a climate scientist and co-founder of Oakland’s Pacific Institute, told Trends Wide. “Instead of thinking that we can control all floods, we have to learn to live with them.”

Levees have effectively protected communities in the past, Gleick said, but they are not designed for today’s climate change challenges.

“We need a new way of thinking, we have to make that infrastructure work in a different way, we have to change some of its features,” Gleick said. “That will allow us to capture more of those flood flows, store it underground in those aquifers, and then use those groundwater resources when we need them in dry years.”

Many climate experts agree: the use of levees to prevent flooding during the wet season means less water is available to percolate into groundwater aquifers. Those aquifers are a vital source of drinking, bathing, and agricultural water throughout California’s central valley, and they are drying up.

But there’s a big catch: Giving rivers more room to overflow means entire communities would have to relocate, in a process known as controlled withdrawal.

Nicholas Pinter, a researcher and professor of Applied Geosciences at the University of California at Davis, acknowledged that controlled withdrawal is a daunting task, but noted that other countries are already doing it.

“We are behind the others,” Pinter told Trends Wide. “The Europeans started doing it in the 1990s. They invested billions of euros to roll back the dikes.”

Pinter asserted that the United States has always preferred to build infrastructure to provide protection.

“We’ve always had an engineering mindset with strong property rights,” Pinter said. “There is also intense resistance from property owners when it comes to relinquishing their property rights.”

There is also the possibility that political leaders will not support these measures, concerned about the loss of property tax revenue and the loss of building and developable land, Pinter explained.

A concept like managed retirement requires a mindset shift that will be extremely difficult to achieve, Gleick said. “These changes are absolutely easier said than done, but they have to be done.”

Both Pinter and Gleick said managed retirement is just one tool in the box when it comes to adjusting to more extreme weather. Gleick noted that there are a litany of other policies states should consider.

“We have to redesign insurance policies so we’re not rebuilding houses once they’ve been damaged in the same places they’re going to flood again,” Gleick said. “We have to design flood insurance policies to encourage people to move away from the floodplains, so that we can open up those floodplains, so that when we do have those floods, they are less damaging.”