California’s past megafloods – and the coming ARkStorm

Summary: To boost our fear, activists and journalists report the weather with amnesia about the past. Ten year records become astonishing events; weather catastrophes of 50 or 100 years ago are forgotten. It makes for good clickbait but cripples our ability to prepare for the inevitable. California’s history of floods and droughts gives a fine example — if we listen to the US Geological Survey’s reminder of past megafloods, and their warning of the coming ARkStorm.

” A 43-day storm that began in December 1861 put central and southern California underwater for up to six months, and it could happen again.”
— “California Megaflood: Lessons from a Forgotten Catastrophe” by B. Lynn Ingram (prof of Earth Science, Berkeley) in Scientific America, January 2013.

Sacramento during the 1862 flood
Lithograph of K Street in Sacramento, CA during the 1862 flood. From Wikimedia commons.

One of the key events in California history has disappeared from our minds. For a reminder see this by the US Geological Survey.

“Beginning on Christmas Eve, 1861, and continuing into early 1862, an extreme series of storms lasting 45 days struck California. The storms caused severe flooding, turning the Sacramento Valley into an inland sea, forcing the State Capital to be moved from Sacramento to San Francisco for a time, and requiring Governor Leland Stanford to take a rowboat to his inauguration. William Brewer, author of Up and Down California in 1860-1864, wrote on January 19, 1862, ‘The great central valley of the state is under water — the Sacramento and San Joaquin valleys — a region 250 to 300 miles long and an average of at least twenty miles wide, or probably three to three and a half millions of acres!’

‘In southern California lakes were formed in the Mojave Desert and the Los Angeles Basin. The Santa Ana River tripled its highest-ever estimated discharge, cutting arroyos into the southern California landscape and obliterating the ironically named Agua Mansa (Smooth Water), then the largest community between New Mexico and Los Angeles. The storms wiped out nearly a third of the taxable land in California, leaving the State bankrupt.

“The 1861-62 series of storms were probably the largest and longest California storms on record. However, geological evidence suggests that earlier, prehistoric floods were likely even bigger. There is no scientific evidence to suggest that such extreme storms could not happen again. However, despite the historical and prehistorical evidence for extreme winter storms on the West Coast, the potential for these extreme events has not attracted public concern, as have hurricanes. The storms of 1861-62 happened long before living memory, and the hazards associated with such extreme winter storms have not tested modern infrastructure nor the preparedness of the emergency management community.”

For an account of the flood from that time see this by J. M. Guinn; an excerpt from Exceptional Years: A History of California Floods and Drought (1890).

Flooded area in California: 1861-1862
Flooded area in California: 1861-1862. From The West without Water. Click to expand.

“The great flood of 1861-62 was the Noachain deluge of California floods. During the months of December, 1861, and January, according to a record kept at San Francisco, 35 inches of rain fell, the fall for the season footed up nearly 50 inches {average is 24 inches/year}. As in Noah’s the windows of heaven were opened, and the waters prevailed exceedingly on the face of the earth.

“The valley of the Sacramento vast inland sea; the city of Sacramento was submerged and almost ruined. Relief boats on their errands of mercy, leaving the channels of the rivers, sailed over inundated ranches, past floating houses, wrecks of barns, through vast flotsams, made up of farm products farming implements, and the carcasses of horses, sheep and cattle, drifting out to sea.

“…To the affrighted vaqueros, who had sought safety on the hills, it did seem as if the fountains of the great deep really been broken up, and that the freshet had filled the Pacific to overflowing. The Arroyo Seco, swollen to a mighty river, brought down from the mountains and canons great rafts of drift-wood …{that} furnished fuel to poor people of the city for several years.

“It began raining on December 24, 1861, and continued for thirty days, with but two slight interruptions. The Star published the following local: ‘A Phenomenon – Tuesday last the sun made its appearance. The phenomenon lasted several minutes and was witnessed by a great number of persons.’

“…After the deluge, what? The drought. It began in the fall of 1862, and lasted to the winter of 1864-65. The rainfall for the season of 1862-63 did not exceed four inches, and in the fall of 1863 a few showers fell, but not enough to start the grass. No more fell until March. The cattle were of gaunt, skeleton-like forms, moved slowly of food. Here and there, singly or in small weak to move on, stood motionless with of starvation. It was a pitiful sight. …

“The loss of cattle was fearful. The plains were strewn with their carcasses. In marshy places …the ground was covered with their skeletons, and the traveler for years afterward was often startled by coming suddenly on a veritable Golgotha — a place of skulls — the long horns standing out in defiant attitude, as if protecting the fleshless bones. …The great drought of 1863-64 put an end to cattle raising as the distinctive industry of Southern California.”

For a more detailed account see “California Megaflood: Lessons from a Forgotten Catastrophe” by B. Lynn Ingram (prof of Earth Science, Berkeley) in Scientific America, January 2013 (PDF here).  The risk of such megafloods remains today as shown in the video “Central Valley Flood Risk” by the California Department of Water Resources and the Corps of Engineers, July 2011.

Why is flood risk so high in California? This video explores the history, risk and government efforts to reduce flooding with one of the world’s largest flood risk reduction systems.


ArkStorm logo

It will happen again: the ARkStorm Scenario

The ARkStorm scenario was prepared by the US Geological Survey, who gathered a team of 117 scientists and engineers — with contributions from 42 Federal, California, and local agencies and universities. Here is the opening of the introduction to the ARkStorm Scenario. For more information see the press release and the full report.

“The ARkStorm storm is patterned after the 1861-62 historical events but uses modern modeling methods and data from large storms in 1969 and 1986. The ARkStorm draws heat and moisture from the tropical Pacific, forming a series of Atmospheric Rivers (ARs) that approach the ferocity of hurricanes and then slam into the U.S. West Coast over several weeks. Atmospheric Rivers are relatively narrow regions in the atmosphere that are responsible for most of the horizontal transport of water vapor outside of the tropics.

“Using sophisticated weather models and expert analysis, precipitation, snow lines, wind, and pressure data, the modelers characterize the resulting floods, landslides, and coastal erosion and inundation that translate into infrastructural, environmental, agricultural, social, and economic impacts. Consideration was given to catastrophic disruptions to water supplies resulting from impacts on groundwater pumping, seawater intrusion, water supply degradation, and land subsidence.

“…Megastorms are California’s other Big One. A severe California winter storm could realistically flood thousands of square miles of urban and agricultural land, result in thousands of landslides, disrupt lifelines throughout the state for days or weeks, and cost on the order of $725 billion. This figure is more than three times that estimated for the ShakeOut scenario earthquake, that has roughly the same annual occurrence probability as an ARkStorm-like event.”



“We don’t even plan for the past.”
— Steven Mosher (member of Berkeley Earth; bio here), a comment posted at Climate Etc.

The political gridlock on public policy relating to climate change has prevent the most obvious and easy first step — preparing for the almost inevitable repeat of past extreme weather. Events like superstorm Sandy and Hurricane Katrina were warnings, showing our mad lack of preparation for likely weather events. Unless we change soon, we will pay dearly for our folly.

For More Information

This is a follow-up to Lessons learned from the end of California’s “permanent drought”. For more about the great flood see Wikipedia and a brief but eloquent account in the 21 January 1862 New York Times.

If you liked this post, like us on Facebook and follow us on Twitter. For more information about this vital issue see The keys to understanding climate change, see my posts about forecasts of the future world, and especially these…

  1. Ten years after Katrina: let’s learn from those predictions of more & bigger hurricanes.
  2. An eminent climate scientist explains what caused the record rains in Texas.
  3. Have we prepared for normal climate change and non-extreme weather?
  4. Let’s prepare for past climate instead of bickering about predictions of climate change.
  5. Droughts are coming. Are we ready for the past to repeat?
  6. The bottom line: How we broke the climate change debates. Lessons learned for the future.
  7. Important: Climate scientists can restart the climate change debate – & win.

To learn more about the state of water in the Western United States…

The West Without Water
Available at Amazon.

…see The West without Water: What Past Floods, Droughts, and Other Climatic Clues Tell Us about Tomorrow by Frances Malamud-Roam (senior environmental planner at CALTRANS) and B. Lynn Ingram (prof of Earth Science, Berkeley). From the publisher…

The West without Water documents the tumultuous climate of the American West over twenty millennia, with tales of past droughts and deluges and predictions about the impacts of future climate change on water resources. Looking at the region’s current water crisis from the perspective of its climate history, the authors ask the central question of what is “normal” climate for the West, and whether the relatively benign climate of the past century will continue into the future.

The West without Water merges climate and paleoclimate research from a wide variety of sources as it introduces readers to key discoveries in cracking the secrets of the region’s climatic past. It demonstrates that extended droughts and catastrophic floods have plagued the West with regularity over the past two millennia and recounts the most disastrous flood in the history of California and the West, which occurred in 1861–62. The authors show that, while the West may have temporarily buffered itself from such harsh climatic swings by creating artificial environments and human landscapes, our modern civilization may be ill-prepared for the future climate changes that are predicted to beset the region. They warn that it is time to face the realities of the past and prepare for a future in which fresh water may be less reliable.”


24 thoughts on “California’s past megafloods – and the coming ARkStorm”

  1. Timely post. Having been alerted awhile back by a Hydrologist friend at NOAA working on the North Coast about the “inevitable” (his words) turn around in the water situation in CA, I watched the unfolding responses by DWR CA as evidenced by reports and television news conferences lately re: Oroville. Simply the Leadership and senior Management in these things are MIA. The employees who’s focus is required and generally effective, author reports and such that gather dust.
    All the while we are treated to hand waving and who could have seen this?!
    Is this the essential element of modern day management? No wonder the level of trust is in serious decline.


    1. Breton,

      “I watched the unfolding responses by DWR CA as evidenced by reports and television news conferences lately re: Oroville. Simply the Leadership and senior Management in these things are MIA. …Pitiful.”

      This is the script for every disaster in America. We refused to pay the wages to hire skilled technical managers (e.g., people skilled at engineering and public management). We grossly understaff their departments (e.g., the California Geological Survey is staffed at about 1/4 of requirement). We disregard their recommendations about vital infrastructure funding.

      Our role: when events happen, we whine that the response is not what our awesomeness deserves.

      We are the problem.

    2. Wayne Lusvardi’s discussion of the funds the state of CA has available for infrastructure projects is worth a read: “Why Trump Should Not Fund an Oroville Dam Fix“, 15 February 2017.

      Wayne Lusvardi formerly was formerly employed by The Metropolitan Water District of Southern California (MWD) and conducted a mass valuation of probable property damage loss due to potential dam failure for Lloyd’s of London insurance underwriters and MWD.

    1. kukatoa,

      The electicity generated by the dam is not a major factor for California. Peak load in 2015 was 47,358 megawatts. The Orville Dam is rated to produce 819 megawatts (1.7% of peak demand).

      It is nice to have cheap and clean electricity. But given the need for repairs to the dam — perhaps extensive by the time the spring floods are over — it might be off-line for a while. More serious would be compromise of the Dam’s ability to provide drinking water and control floods. Both seem likely during the next several months.

    2. Editor

      Thanks for the wiki link to the dam- the generation (and pumped storage) capabilities at the dam are rather impressive and complex- “The Hyatt and Thermalito plants produce an average of 2.2 billion kilowatt hours (KWh) of electricity each year, about half of the total power produced by the SWP’s eight hydroelectric facilities.[50][51]”

      I assume the folks at CASIO are working up a few scenarios on how to deal with the loss of such a valuable asset to keep the grid up and running.. It’s beyond my capabilities to figure out if curtailment of RE will likely go up or down with the facilities being off line.

      I was a bit surprised that the Wiki post didn’t include any summary data on the capacity factor of the facility over time. Last year’s annual generation was noted at 1490 GWh

  2. We? Careful, sir. That ad hominem echo I am hearing can be applied to any large organization that experiences a failure of management. You may want to re-write your indictment of who is really at fault. Surely you don’t mean that “you” -allowed or encouraged the claimed under employment at Geo Survey Cal.? Is your Post a whine or an attempt to have others look and examine the quality of governance? How awesome is the act of writing?
    If all one can say is that one can rarely trust that government or its highest officers to manage, lead or produce beyond basic results because they never get enough support or funding…..goodness. End the fitful conversation.
    But for sure a case can be made that we do receive mostly what we deserve. Quite obviously as it is, though.
    Yes we are and have been reluctant, disengaged, childishly trusting without verification for too long. Yes, many would rather not pay for much government.
    But that is only commenting about an aspect of the problems ex post facto. Defining a problem is certainly first and that is not a first definition.

    Insist your fellow Citizens engage or fire them!?

    Yes, that is a problem and it is not necessarily “we”.
    Thanks for the informative post, certainly good.


    1. Breton,

      “That ad hominem echo”

      No, it is not. Ad hominem means directed against a person rather than their views or actions.

      “an be applied to any large organization that experiences a failure of management.”

      No, it can not. Many management errors do not result from gross understaffing & under-paying, failure of their bosses to provide adequate funding or follow technical recommendations — let alone all of those.

      “You may want to re-write your indictment of who is really at fault.”

      No, I don’t. I’ve written scores of posts since 2003 documenting this.

      “Surely you don’t mean that “you” -allowed or encouraged the claimed under employment at Geo Survey Cal.?”

      Democracies operate by collective responsibility. We are all in this together, responsible collectively for the affairs of the Republic which runs in our name.

      “Insist your fellow Citizens engage or fire them!?”

      You’re just making stuff up. I said nothing remotely like that. Pointing our responsibility does not imply “firing them”. Spouses point out responsibilities to each other, parents to children, doctors and attorneys to clients, and priests and ministers to members of their flock.

  3. My favorite bit from the linked SciAm article:

    “It appears that the Native American populations, who had lived in the region for thousands of years, had deeper insights to the weather and hydrology, and recognized the patterns that result in devastating floods. A piece in the Nevada City Democrat described the Native American response on January 11, 1862:
    ‘We are informed that the Indians living in the vicinity of Marysville left their abodes a week or more ago for the foothills predicting an unprecedented overflow. They told the whites that the water would be higher than it has been for thirty years, and pointed high up on the trees and houses where it would come. The valley Indians have traditions that the water occasionally rises 15 or 20 feet higher than it has been at any time since the country was settled by whites, and as they live in the open air and watch closely all the weather indications, it is not improbable that they may have better means than the whites of anticipating a great storm.'”

    It’s an inspiring example that some cultures, despite the extremely poor quality of their instrumentation and data storage media (phrased in jest, but true), apparently were able to “plan for the past” simply because they contemplated much longer time horizons (not being caught up on the treadmill of eternal progress that renders anything more than a few years old as obsolete and not worth thinking about). How much better could we do with our modern technology if we took the same view?

    1. phageghost,

      As an excuse for our disinterest in the past, pre-modern cultures value the past more because they have the same tools as their ancestors — so experience is directly applicable. Our tools are so much greater we tend to be dismissive of past events — “we’re so great, we can handle them”. With respect to floods, California’s hydrologic landscape is engineered like a pinball machine — making floods much less likely. But the USGS warns that we’ve less affected by most floods but still highly vulnerable to extreme events.

      As a positive note, in the past two decades American has become much more aware of our vulnerability. Big money for earthquake preparedness. More resources for training, organization, and planning of first responders. Etc. But we can do much better. Programs like the USGS ArkStorm project are helping to drive this process.

  4. This is completely subjective based on years of living in California, but it seems to me LA was constructed by an evil-genius. Stole the water from Owens valley, like they say in the movie, but also built an ugly but quite effective system of storm drains the drains all the water out of here during storms. Near my house in Glendale there is a storm drain, and this thing is huge. Multiple floors below ground level, at las, maybe about as wide as half of a city block? I’ve never, even on the worst rainy day see this even get close to having much water in it at all. This was built in the old days, with that massive confidence they had in those days. You see these drains in the movies, and they are substantial.

    In comparison, took a trip to Oregon suburbs of Portland to visit relatives, and my brother-in-law is showing me all the construction happening in areas that were flooded a few years back. My sense, pre-WW2 California was built brilliantly, but the newer construction I’m much less confident of.

    1. Storm drain in Glendale? Are you sure you’re not talking about the L.A. river, that paved-over scene of countless movie car chases? It does serve as a storm drain of sorts but also drains the mountains north of the city. The reason it’s so big is not to accommodate typical rainfall but to accommodate the kinds of massive, every-few-decades floods like the one of 1862 discussed here, where it would overflow its banks and wreak havoc. After the 1938 flood, the army corps of engineers decided to just turn it into a huge concrete culvert and be done with it.

    2. Cathryn,

      That’s an interesting perspective. It’s not my field. My impression (for whatever that’s worth) is that modern construction is in many senses better than in the old days, in some ways worse. Major structures are well-built for earthquakes and fire, but smaller structures aren’t designed to last. The infrastructure is (when properly done, without crooked developers) excellent, as a result of modern modeling tools.

      My house was built in 1950. Substantial crawlspace, putting it off the ground (we’re in a flood zone). The structural beams are solid redwood, and massive. Modern houses are often on concrete pads, built of wood products (glue + sawdust). If the interior was gutted down to studs, then new wiring and plumbing was installed, it would be easily good for another 70 years. I doubt that’s true of most modern homes.

  5. Rainfalls are not governed by the ‘ordinary’ statistics of data-crunching tyros – with means, standard deviations, Bell curves, etc. These are technically ‘rare events’ that are subject to Poisson statistics – sometimes called ‘log-normal distribution’ statistics. If you look at the long term average (i.e. 24 inches per year), then there is a significant change of ‘total drought’ (0 inches in a year) and an equally likely chance of double the long term average (i.e. 48 inches in a year).

    1. tadchem,

      “Rainfalls are not governed by the ‘ordinary’ statistics of data-crunching tyros –”

      Which is why the Arkstorm team did not attempt to assess the probability of an ArkStorm event. Its scenario is a repeat of the recent past (climatologically speaking), hence a scenario within the normal risk-management boundaries. To model the 1861-62 event, they used as building blocks events for which we have good meteorological records:

      “In particular, the ARkStorm is a hybrid of a storm that struck southern California from January 19-27, 1969, followed without delay or interruption by a repetition of the storms that struck northern California from February 8-20, 1986.”

      Also, are you calling the ArkStorm team “tyros”? That is, the 117 scientists and engineers on the project, with contributions from 42 Federal, California, and local agencies and universities.

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