Photo: This is the view of the headwaters of the Stockton channel at El Dorado and Weber streets during the flood of 1893, taken from the dome of the courthouse. During the winter of 1893-94, Stockton received 13.5 inches of rain between November and March. This image shows the water extending east up Weber Avenue, and north well past Fremont Street. (BANK OF STOCKTON)

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A paradigm-smashing scientific study warns that Stockton is Ground Zero for “the most expensive geophysical disaster in global history to date,” a so-called “megaflood.”

For this news to come out during a drought causes intellectual whiplash, but there it is. Climate change has rendered our flood-risk models, our dams and levees, woefully inadequate.

“It’s scary,” said Dan Wright, a Stockton City Council member who chairs the San Joaquin Area Flood Control Agency.

The sort of Old School floods that submerged pioneer Stockton — 8 feet of water, homes totaled, businesses ruined, bodies floating down Main Street — are no longer a question of if but when.

Correction: Severe rains and floodwaters are inevitable. Catastrophic damage is not, if we prepare. That, however, is an if.

The study, “Climate change is increasing the risk of a California megaflood,” uses the worst Valley flood in modern history, the Great Flood of 1861-62, as a benchmark.

It rained 43 days. At a couple points in the Sierra rainfall hit 98.43 inches, over seven times Stockton’s average annual rainfall. Floodwaters turned the Sacramento-San Joaquin valleys into a 300-mile-long inland sea. Ships making for Stockton left the river and sailed straight over farms.

By one account, “Four thousand people lost their lives, one-third of the state’s property was destroyed, a quarter of California’s cattle population drowned or starved, and one in eight homes were a complete loss by floodwaters.”

Were that to happen today, the cost would near $1 trillion in losses to the Valley and the Los Angeles lowlands: over five times the toll of Hurricane Katrina, the costliest disaster in U.S. history.

A flood of that magnitude was thought to occur only five to seven times a millennium: the so-called 200-year flood. Now it may happen several times a century, the study says.

Vineyards outside of Stockton. The San Joaquin Valley, which grows 1/4 of the nation’s food, could be submerged in a megaflood, a new study says. (PHOTO BY SCOTT LINESBURGH)

And the megaflood could be worse than the Flood of ’62, the study says.

It’s climate change. Rising temperatures increase the duration and intensity of atmospheric rivers (Pineapple Expresses, if you prefer). Storm systems will bring rains sometimes lasting 30 days to Stockton, the Delta, and the Valley; dumping more rain per hour than before; drenching the Sierra in up to 39.37 inches of precipitation — falling, moreover, less as snow, and more as rain; the warm rains melting the snow — all washing straight into the Valley.

Rather than peak flows of 75,000 acre feet, 370,000. Stockton’s stormwater system cannot handle it, Wright said.

Nor the levees. “If we have 15 days of atmospheric river, the levees don’t matter,” he said. “We’ll be underwater.”

Kimberly Warmsley, a second Stockton councilmember sitting on the SJAFCA board, said the impact on Stockton will be the opposite of environmental justice.

South Stockton will be hurt worse, “Our most disadvantaged communities, communities of color … an area historically marginalized.”

Not to mention that the county hospital, veteran’s hospital, numerous schools, the Sheriff’s Office, jail, and other critical public safety offices are in that area.

“I’m triggered because I’m thinking about the flashbacks of Hurricane Katrina,” Warmsley said.

SJAFCA is building the Smith Canal Gate to protect against sea rise, improving levees around flood-prone Mossdale and on the Lower San Joaquin to shield Weston Ranch and Brookside.

The two latter projects aren’t fully funded, though.

An unidentified man stands in waist-high water during the floods of 1955 in the Corona Park district of South Stockton. (BANK OF STOCKTON)

Barry Nelson of Western Water Strategies (not one of the report’s authors), said the best defense is to expand flood plains. Other measures include widening and strengthening levees, and creating recharge ponds where floodwaters seep underground and recharge California’s depleted aquifer. 

“This is not a flood risk where we’re going to build one project and the flood risk is gone,” Nelson said. “We have to build projects for a decade or so. If we don’t get ahead of this risk, if we don’t build, those floods will overwhelm us.”

He’s working for River Partners to buy land for flood plains.

The state is spending millions on flood protection – in the Sacramento region. In a glaring inequity, the state is spending $10 on Sacramento and environs for every $1 here, Nelson said.

That needs to change. The state has a fat budget surplus. Governor and legislature are in budget negotiations. Area leaders must demand funding to fight the coming deluge.

Even though it’s bone dry.

“We’re dealing with a drought disaster,” Nelson said. “A lot of our legislators aren’t thinking of climate change. But a lot of our legislators are going to have to walk and chew gum.”

Michael Fitzgerald’s column runs on Wednesdays. Phone (209) 687-9585. On Twitter and Instagram as Stocktonopolis. Email:

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