California went from extreme drought to extreme flooding in just a few days, with 90 percent of the state’s population under a flood watch as another round of storms hit. The sudden shift underscores the dilemma facing California: How do you deal with heavy rainfall in a water-scarce state? Is it possible to use this water for use during the dry summer months?
Part of the solution, climate scientists told CNN, is to withdraw the levees, allowing more room for the river to flow safely into the surrounding land.
“We have to get our rivers to flow differently, let the rivers flood a little bit, and replenish our groundwater during the rainy season,” Peter Greck, a climate scientist and co-founder of the Pacific Research Institute in Oakland, told CNN. “Instead of thinking we can control all floods, we should learn to live with them.”
Levees have effectively protected communities in the past, but they were not designed to meet today’s climate change challenges, Gleick said.
“We need new thinking, we need to operate this infrastructure differently, we need to change some of the characteristics of that infrastructure,” Gleick said. “This will allow us to capture more of this floodwater, store it underground in these aquifers, and then use these groundwater resources when needed in dry years.”
Many climate experts agree — using dikes to prevent flooding during the rainy season means less water seeps into aquifers. These aquifers are an important source of water for drinking, bathing and agriculture throughout California’s Central Valley, and they are being depleted.
But giving rivers more room to flood is problematic. This meant that entire communities needed to be relocated; a process known as managed evacuation.
Nicholas Pinter, a researcher and professor of applied geosciences at the University of California, Davis, acknowledged that managing the retreat is a daunting task, but noted that other countries are doing it.
“We’re behind on that,” Pinter told CNN. “The Europeans in the 1990s started doing this. They made billions of euros of investment to bring back the dykes.”
The U.S. has been leaning toward building infrastructure to provide protection, Pinter said.
“We’ve always had an engineering mindset with strong property rights,” Pinter said. “There is also strong resistance from property rights owners when it comes to giving up title.”
Political leaders, concerned about lost property tax revenue and lost land for construction and development, are also likely to resist, Pinter said.
Concepts like managed retreats require a mindset shift that’s extremely difficult to pull off, Gleick said. “These changes are easier said than done, but they have to be done.”
Both Pinter and Gleick say managed retreats are just one tool in the box when it comes to acclimating to more extreme weather. States should also consider a range of other policies, Gleick noted.
“We have to redesign our insurance policies so we don’t rebuild houses where they flood again,” Gleick said. “We have to design flood insurance policies to encourage people to stay away from floodplains so we can open these floodplains so that when we get floods, they’re less destructive.”