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Age, drought, rodents and neglect weaken California levees and increase flood danger

The levee breach that left an entire California city under water this weekend is highlighting how the state’s vital flood control infrastructure is being weakened by age, drought, climate change, rodents and neglect, leaving dozens of communities at risk.

On Friday night, the rising Pajaro River burst through the frayed levee, inundating the entire town of Pajaro and sending its approximately 3,000 residents into what authorities now estimate will be months-long exile. A second offense was reported Monday.

For decades, the federal government ignored the levee, which never achieved the status of a project worthy of repair, despite repeated pleas, violations, flooding, and even two deaths.

“Yeah, the money wasn’t there because the prioritization wasn’t there,” said Mark Strudley, executive director of the Pajaro Regional Flood Management Agency.

And as communities and local government agencies pleaded for help and funding, the levee aged, eroded and, in some places, collapsed.

The situation is not exclusive to Pájaro. Experts say similar weaknesses plague levee systems in California and the nation.

As climate change threatens to intensify and exacerbate extreme weather events, such as floods and even droughts, the concern and despair of residents and first responders in communities near these crumbling systems is growing.

“We all know that there are many economically disadvantaged communities being built in areas prone to natural disasters,” Strudley said. “That is the very unfortunate way the planning and development process has worked for the last 100 years or more in the United States.”

Throughout Northern California, the Central Valley, and the Sacramento-San Joaquin River Delta, there are more than 13,000 miles of levees designed to protect dry land from flooding, supply drinking water, and protect homes, businesses, and agriculture from flooding.

According to the work of Farhid Vahedifard, a professor of civil engineering at the University of Mississippi, settlers built a large percentage in the mid to late 19th century to protect farmland from flooding.

“And they’ve worn out, just like anything else,” Strudley said. “They have a limited lifespan.”

In most cases, Strudley and Vahedifard said, the levees were built with unengineered and poorly compacted mixtures of sandy, clay and organic soils, material “that was scraped from the river bed and used as fill to build the levees.” said Strudley.

In addition, they have suffered the wear and tear of time, rodents, seismic events, and drought.

“These things seep in long before they overflow,” Strudley said, noting that one of the biggest problems is burrowing animals.

In 2011, the California Department of Water Resources surveyed the Northern California levee system. The assessment considered about 1,800 miles of earthworks along the Sacramento and San Joaquin river basins and found that more than half of the levees were what they considered “high hazard,” indicating they were in jeopardy. fail during an earthquake or flood.

And that was before the megadrought, which dried up the soils inside and below the levees, causing structures to weaken and lose strength, Vahedifard said.

The drought also accelerated subsidence as water districts and users drew water from underground aquifers, depressing and subsiding the land above.

But until recently, the federal government and the US Army Corps of Engineers did not view these systems as a priority, especially if they were located in underserved or economically disadvantaged communities.

“The federal funding system for levees and other life-saving systems totally disadvantages federally disadvantaged communities, systemically,” said Zach Friend, a Santa Cruz County Supervisor whose district encompasses Watsonville and the north side of the valley. of the Bird River.

He said what happened to the levee in Pájaro could have been prevented if resources had been provided to the community to rebuild the levee, something they had been requesting since the 1960s.

“The storms that came in and blew out the levee…these are storms with intervals of five to seven years,” he said. “So if our infrastructure can’t even hold up to what really is a relatively regularly occurring storm, climate change, what we’re seeing in the future and what it will do to disadvantaged communities, is kind of beyond the pale.” .

He said the cumulative effect of these storms and the “climate whiplash” between severe drought and severe storms “really tests the possibility of how you build and plan for that level of resilience toward communities that have been sufficiently invested in.” During the last years”. 100 years and they are starting with a net negative rebuild.”

The levee failure on the Pajaro River points to greater dangers that California has yet to address in many areas where communities are vulnerable, said Deirdre Des Jardins, a researcher and independent water advocate.

“Pajaro is just the beginning,” Des Jardins said.

Des Jardins has for years urged state and local officials to invest in flood protection infrastructure in areas that are at risk, and she has He suggested an effective climate adaptation strategy must focus on “measurable and achievable objectives for the protection of vulnerable populations”.

“You look at where to invest the money to protect lives. And we’re not doing that. We don’t have quantifiable targets on protecting lives and protecting these vulnerable communities,” De Jardins said.

In addition to rural communities like Pajaro, he said Stockton and surrounding cities face great flood risks due to its reliance on inadequate levees with known seepage problems.

As the federal government continues to reevaluate how it invests in large infrastructure projects in economically disadvantaged communities, the cost of doing nothing will continue to rise.

“How much flood risk is there in California? A handful. The reason is quite simple,” said Jeffrey Mount, a senior fellow at the Public Policy Institute of California. “The economic consequences of even a modest flood are quite high.”

He said this is especially the case in the LA Basin, where the increasing likelihood of major flooding overlaps with rising surrounding property values.

“There is a long legacy of very poor flood management and land use options along the Los Angeles, San Gabriel and Santa Ana rivers,” Mount said. “That is a high risk equation because eventually a flood will come and the economic costs will be immense.”

Local, state and federal officials have improved flood control infrastructure in the Sacramento area over the past two decades, which has reduced risk in the area, Mount said.

Still, many low-lying communities in the Central Valley face substantial flood risks. And many farms in and around the Delta sit below sea level, requiring levees to keep water out, Mount said.

“Our flood infrastructure is old,” Mount said, “and designed for the hydrology of the past, not the future.

“This will be a big challenge going forward, particularly as we have increased the potential economic costs of flooding by our land use choices.”

In January, when levees failed along the Cosumnes and Mokelumne rivers, causing deadly flooding, Mount said those failures point to greater dangers. “There are two types of levees: those that have failed and those that will fail,” he said.

Mount said he is now especially concerned about the huge amount of snowmelt runoff expected from the central and southern Sierra this spring.

Times staff writer Hayley Smith contributed to this report.