Megastorms could flood portions of California’s Central Coast

November 30, 2012

Editor’s note: The article will appear in the January 2013 issue of Scientific American. They are making it freely available now because of the flooding underway in California.

By Michael D. Dettinger and B. Lynn Ingram

Huge flows of vapor in the atmosphere, dubbed “atmospheric rivers,” have unleashed massive floods every 200 years, and climate change could bring more of them.

The intense rainstorms sweeping in from the Pacific Ocean began to pound Central California on Christmas Eve in 1861 and continued virtually unabated for 43 days. The deluges quickly transformed rivers running down from the Sierra Nevada mountains along the state’s eastern border into raging torrents that swept away entire communities and mining settlements. The rivers and rains poured into the state’s vast Central Valley, turning it into an inland sea 300 miles long and 20 miles wide. Thousands of people died, and one quarter of the state’s estimated 800,000 cattle drowned. Downtown Sacramento was submerged under 10 feet of brown water filled with debris from countless mudslides on the region’s steep slopes. California’s legislature, unable to function, moved to San Francisco until Sacramento dried out—six months later. By then, the state was bankrupt.

A comparable episode today would be incredibly more devastating. The Central Valley is home to more than six million people, 1.4 million of them in Sacramento. The land produces about $20 billion in crops annually, including 70 percent of the world’s almonds—and portions of it have dropped 30 feet in elevation because of extensive groundwater pumping, making those areas even more prone to flooding. Scientists who recently modeled a similarly relentless storm that lasted only 23 days concluded that this smaller visitation would cause $400 billion in property damage and agricultural losses. Thousands of people could die unless preparations and evacuations worked very well indeed.

Was the 1861–62 flood a freak event? It appears not. New studies of sediment deposits in widespread locations indicate that cataclysmic floods of this magnitude have inundated California every two centuries or so for at least the past two millennia. The 1861–62 storms also pummeled the coastline from northern Mexico and southern California up to British Columbia, creating the worst floods in recorded history. Climate scientists now hypothesize that these floods, and others like them in several regions of the world, were caused by atmospheric rivers, a phenomenon you may have never heard of. And they think California, at least, is overdue for another one.

A megaflood every century?

Despite greater scientific understanding, the 1861–62 floods are all but forgotten today. Communities, industries and agricultural operations in California and the West have spent the past century spreading out onto many of the same floodplains that were submerged 150 years ago. Residents everywhere are unaware or unwary of the obvious risks to life and property. Meanwhile, though, anxious climatologists worry about the accumulating evidence that a megastorm could happen again and soon.

The concern grows out of research that is looking 2,000 years back in time to piece together evidence revealing the occurrence and frequency of past floods, like detectives returning to a crime scene of long ago. They are sifting through evidence archived in sediments from lake beds, floodplains, marshes and submarine basins.

Geologists have found more evidence in southern California, where two thirds of the state’s nearly 38 million people live today, along the coast of Santa Barbara. Sediments there settle to the seafloor every spring (forming a light-colored layer of algae known as diatoms) and again in winter (forming a dark-colored silt layer). Because the oxygen concentrations in the deep waters there are inhospitably low for bottom-dwelling organisms that would usually churn and burrow, the annual sediment layers have remained remarkably undisturbed for thousands of years. Sediment cores there reveal six distinct megafloods that appear as thick gray silt layers in A.D. 212, 440, 603, 1029, 1418 and 1605. The three most recent dates correlate well with the approximate 1100, 1400 and 1650 dates indicated by the marsh deposits around San Francisco Bay—confirming that truly widespread floods have occurred every few hundred years. (In October, Ingrid Hendy of the University of Michigan and her colleagues published a paper based on a different dating method; it found a set of Santa Barbara dates that were offset from the six specific dates by 100 to 300 years, but the same basic pattern of megafloods every 200 years or so holds.)

The thickest flood layer in the Santa Barbara Basin was deposited in 1605. The sediment was two inches thick, a few miles offshore. The 440 and 1418 floods each left layers more than an inch thick. These compare with layers of 0.24 and 0.08 inch near the top of the core that were left by large storms in 1958 and 1964, respectively, which were among the biggest of the past century. The three earlier floods must have been far worse than any we have witnessed.

Time to Prepare

With atmospheric rivers likely to become more frequent and larger and with so many people now living in their paths, society would be wise to prepare. To provide an example that California emergency managers could use to test their current plans and methods, scientists at the U.S. Geological Survey recently developed the scenario mentioned at the start of this article: a megastorm that rivaled the 1861–62 storm in size but lasted 23 days instead of 43 (so no one could claim that the scenario was unrealistic). To further ensure that the scenario, which was eventually dubbed ARkStorm (Atmospheric River 1000 Storm), was as realistic as possible, scientists constructed it by stitching together data from two of the largest storm sequences in California from the past 50 years: January 1969 and February 1986.

When project leaders ran the events of ARkStorm through a variety of weather, runoff, engineering and economic models, the results suggested that sustained flooding could occur over most lowland areas of northern and southern California. Such flooding could lead to the evacuation of 1.5 million people. Damages and disruptions from high water, hundreds of landslides and hurricane-force winds in certain spots could cause $400 billion in property damages and agricultural losses. Long-term business and employment interruptions could bring the eventual total costs to more than $700 billion. Based on disasters elsewhere in recent years, we believe a calamity this extensive could kill thousands of people (the ARkStorm simulation did not predict deaths).

The costs are about three times those estimated by many of the same USGS project members who had worked on another disaster scenario known as ShakeOut: a hypothetical magnitude 7.8 earthquake in southern California. It appears that an atmospheric-river megastorm—California’s “Other Big One”—may pose even greater risks to the Golden State than a large-magnitude earthquake. An ARkStorm event is plausible for California, perhaps even inevitable. And the state’s flood protection systems are not designed to handle it. The only upside is that today, with improved science and technology, the megastorms could likely be forecasted anywhere from a few days to more than a week in advance. Proper planning and continuing efforts to improve forecasts could reduce the damage and loss of life.

Californians, as well as people all along the West Coast, should be aware of the threats posed by atmospheric rivers and should take forecasts of storms and floods very seriously. Planners and city and state leaders should also take note as they decide on investments for the future. He who forgets the past is likely to repeat it.  (read the full article here)

This article will be published in print as “The Coming Megafloods.”

Michael D. Dettinger is a research hydrologist for the U.S. Geological Survey and a research associate at the Climate, Atmospheric Sciences and Physical Oceanography Division at the Scripps Institution of Oceanography in La Jolla, Calif.

Lynn Ingram is a professor of earth and planetary science at the University of California, Berkeley, and co-author of The West without Water (University of California Press, Spring 2013).




Inline Feedbacks
View all comments

Blaa, blaa, blaa, storms have been happening for millions of years and millions have been biblical in scale, the seas rise and fall, the weather changes continually and earthquakes will continue to happen…

Chicken little seems to pop up more and more lately and he/she is given more and more press, simply because it is fashionable and the word gets around more…

and don’t forget there is more tax money that can be divereted to the latest “Better do something about this now or else” scare tatic that the goernment has become so good at throwing around

You’re right that storms have been happening for millions of years. The article isn’t saying anything new about that. What it is saying though is that California, now highly populated (30+ million people) is going to be in rough shape (socially and economically) when (not if) the next super storm hits our coast.

So, your blah blah attitude needs to be adjusted to one of preparing for mass devastation and no services and no government for weeks on end. In other words, 911 isn’t going to come when you call them and your power will be out for weeks or months. Prepare now. Don’t wait. If you don’t prepare, please don’t come crying to me and blame the government for not saving you. Americans need to take some level of personal accountability for when things like this happen.

That’s Right…

No Government you say……where do I sign up and how do I get my hands of George Bushes hurricane machine.

You may think you don’t want a government, but trust me, you want one. Our government may not be efficient, but it’s 1000% better than no government at all. Ask the folks in the Somalia how no government at all works our for them.

Anybody with half a brain does not plan on the government saving their ass from diddly these days. More taxes,less services. We’ve clearly seen this over and over again and the Sandy devastation is just another example. As far as taking personal accountability for being able to exist,that’s what stocked freezers & pantries,generators,private wells and most importantly guns are for. Your battery powered green car, trader Ho’s bags and I love Obama stickers will be futile in your struggle to survive .

Americans have proven over and over that they apparently don’t have half a brain. Every major weather disaster that hits this country catches people off guard and unprepared and then they blame the government for not providing them steak dinners and a warm place to sleep.

Your stocked pantries and stuff is great. I’m glad to hear that you’re prepared. Good for you. Please keep it up and encourage your neighbors to prepare. Lend them a hand if they need it.

I am a little offended by your battery powered green car comment, but that’s how I’m prepared to survive. Unless you’ve got a decaying dinosaur in the backyard, you are going to need fuel for your generator (I have one too). My electric car can be charged by the sun, therefore fuel will not be a concern for me. My private well can also be powered by the sun. In the event that I need to protect my domain from savages who have run out of gas(haha), my tactical arsenal is all sub-MOA and I’m a well trained trigger operator.

Its really hard to buy in to the whole dinosaur thing when so much of comes from the ocean and thousands of feet below ground ? I would maybe believe plant mater .

Don’t come to my house for kerosene when your electric lights and stove don’t work

You sound well prepared, good for that one :) Your right on the steak dinner comment. I cannot understand those who repeatedly rebuilding in a strike zone for hurricanes or tornadoes or floods. Those poor folks probably say the same thing about us and earthquakes though. Having your home wiped out is one thing, putting your family at risk is another. far as Somalia long as we have our guns we have a chance, those poor folks never did. Absolute power maker for absolute corruption in human culture.

Well, the state doesn’t have to wait for the next big mega storm to be in rough shape, it is already theresocially, moraly and economically today, but not because of the weather.

And, I for one am more than prepared and won’t be crying to anyone. In fact I am involved with my community preparedness and we have a disaster plan in place now. We have known for decades that if and when diablo blows, the tsunami or earthquake comes we will be on our own, there will be no FEMA or County help coming for a very long time if at all…

QUOTING EASYMONEY: “Blaa, blaa, blaa, storms have been happening for millions of years and millions have been biblical in scale, the seas rise and fall, the weather changes continually and earthquakes will continue to happen…”

If you really want to make a valid opinion, you need to factor into your opinion the facts pertaining to the vastly increased population, living in dense populations, mostly near the coast.

Human populations have always been more densely populated near the coast. However, with the number of people on the planet now, “densely populated” has taken on much greater proportions.

It wasn’t until very, very recently in human history that “permanent” records of a written type were kept, and that was usually only in large centers of successful populations.

Until recently, we didn’t have records that can help make educated predictions about what the rising level of the sea can portend for humans. It makes common sense to use these records and make proactive choices because the consequences of not doing so can be, and have in the past been, fatal to humans, and in very large numbers.

Im really curious why the oceans are suddenly rising when for decades man has been dumping billions of gallons of treated sewage into the ocean (Effluent). The water for this treated sewage was derived from ground or surface water supplies not the ocean. It is not temperature consistent or close to the oceans temp, typically much warmer. As populations grew, which they have flows also increased. There’s also numerous lakes and rivers who’s flow eventually find their way to the ocean. Los Angeles alone dumps some 30 million gallons into the ocean daily. That’s over 4,000,000 cubic feet of space displaced by this new water.

I can’t quite tell if you’re being serious or sarcastic.

Serious. Not to dispute G/W, but L.A’s contribution to the ocean is 33516 acre feet of water daily. That’s about 2/3’s of Lopez lakes capacity every day from one discharger. Why no change from this decades and decades later? Seriously…how much ice can melt in one day?

Enough to drown you.

Many thanks to Cal Coast News for publishing this important story. The people in New Jersey and New York never expected to see anything like hurricane Sandy, but it happened.

It is smarter and cheaper in the long run to be proactive and to plan and prepare as much as possible for natural disasters. It might hurt a bit to spend the extra money now, but the Sandy aftermath clearly demonstrates what happens when you don’t face unpleasant possibilities and prepare for the worst.


Fellow TRUE Christians, this is it, the glorious Second Coming of our Jesus!

I am sure that Cindy is looking for her hip boots, and others should as well, because our Judeo-Christian bible has prophesied this day of the floods relating to the Second Coming of Jesus!

“But as the days of Noah were, so also will the coming of the Son of Man be.” “For as in the days before the flood, they were eating and drinking, marrying and giving in marriage, until the day that Noah entered the ark, and did not know until the flood came and took them all away, so also will the coming of the Son of Man be.” ( Matthew 24: 37-39)

Remember, Jesus is not coming back alone! “ ‘When the Son of Man comes in his glory, AND ALL THE ANGELS WITH HIM, then He will sit on his throne in heavenly glory.” (Matthew 25:31)

Do you know how many angels there will be? You’ve heard of guardian angels, haven’t you? Cindy has. Anyway, since there is about six billion people on our planet, and if each one has a guardian angel, then that’s six billion angels!!! So a conservative estimate would be that at least six billion angels will accompany Jesus when He returns with these forthcoming floods.

To say the least, that’s a sky full of glorious angels, but they may black out the sun for awhile. :(


Matthew is saying the Second Coming will be as the flood… it will happen when nobody is expecting it.

I am not even sure why I am replying to your post- your interpretations are definitely your own gospel- the Gospel of Ted.

Want to know what I really think? you are a troll who seeks to give the Bible a bad name.

Now, go ahead and unleash that tainted, furious Gospel of Ted on me… I know you will. (And you will say I am not a true Christian, because you are the only one who knows the TRUE meaning of every verse)


I don’t know why you’re replying to me as well because your out in left field of Satan’s Ball Park.

Dear, we have satellite weather now, therefore we know when the big ones are coming in. With the Second Coming, we can only know in the sense of not expecting that this may be the one! Get it?

Nonetheless, we must always be prepared and ready. “Therefore you also must be ready, for the Son of Man is coming at an hour you do not expect.” ( Matthew 24:44)

How can I give the bible a bad name when I bring forth scripture WITHIN CONTEXT relative to the stories here at CCN? Surely you jest. tsk, tsk.

Always remember, what our God said ONCE, He most certainly did not mean for His creation to take what He said in many different and contradicting ways, aka, different bibles and divisions of the faith. Therefore, as horrific as it may be at times, the literal reading of the bible is godly, whereas the subjective “interpretations” by some, are Satanic.

Id rather be dead than Ted

My new mantra

Ted they said that this has happened on and off for THOUSANDS of years. Hmm did I miss him coming back all those other times? Only once last I checked. We get it Ted. You are very religious. I’m happy for you.


Those other times were obviously false alarms. Jesus/God was testing us.

James says that testing is a blessing, because when the testing is over and we have “stood the test,” we will “receive the crown of life, which God has promised to those who love him” (James 1:12) Who knows, in those other times that you’ve mentioned, the majority maybe weren’t ready.

The irony is that our version of God is omniscient, therefore, He already knows what’s in our hearts, therefore, no testing should be required by God. Oh well.

Listen, be ready anyway because as Fred Sanford stated, “Elizabeth, this may be the big one!”

Oh TED, these fools are not worth the cyberspace to warn against !

You and I are like Noah bulding the ARK against the howls of the heelots and unbelievers prostrated against us TRUE CHRISTIANS ( Halleluuah ! ).

The phony “Christians” hate us, as they should…the HYPOCRITES.

Brother Slowerfaster,

Can you believe that some of the flock are disparaging me for wanting to warn them of the possibility that these forthcoming floods may be the big one relative to the Second Coming? And, they call themselves Christians?!

Our Christian reasoning says that the bible is true because the bible says that the bible is true. Therefore, the passages in question that I bring forth relative to the Second Coming have to be true, and that we should be ready just in case. Simple enough.

You and I will be ready, praise!

See? THIS is why Ted Slanders’ opinions are useful to this message board: he can ALWAYS give us the “paranoid Christian” take on events.

Damn good thing we have KSBY’s accurate predictions to warn us of the coming mega storms…….ha,ha,ha.

Every storm is a mega storm with Dave! But then again we haven’t had a good down poor since he started ?

Maybe a mega storm would give us some much need ground water?

Nice idea but no. Lets even forget the damage for a minute. If it comes to fast and all runs off, not much perks into ground water. A rain here and there is better to let it soak in, dry a bit , then start again.

I was thinking with all the brush in the river it should get stuck under the niblik bridge and make a nice dam? I still rember trees 3 foot around rolling down the river in 69 last time it really ran good! and after the la’s paltis fire in the 80s.

Boy you are so right about the dam. I’ve been in Paso since ’80 and have never seen as much growth in the river as now. We have almost three to four times what there use to be. One good flow down the river, start dislodging trees etc. it could get interesting.

Yes after some thinking its the 13th wares it would get stuck.

Good point. Also, snow is a handy “bank” for precipitation that comes down in bucket-fulls in the Sierras during the winter, and then GRADUALLY melts in the spring.

The trick is the “gradually” parts.

There have been occasions in the last few decades when the “gradually” part didn’t happen, or the rain didn’t come until the air temperature was too warm to store as snow.

This information was published nearly 2 years ago. This is the first that I have seen it in the news. Kudos to CalCoastNews.

I remember the 69 storm vividly. Mt. Baldy got 50 inches in 7 days. I was on the cleanup crew. I don’t remember seeing Al Gore anywhere in the area. Oh that’s right, he was overseeing his family’s mining interests in Tenn.

When Al Gore was age 20, he was graduating from Harvard. When he was 21, he was in Vietnam.

and lets not forget getting a C- in science in college. YEA let’s listen to this BOOB!!

can’t we all get a bong? I mean get alone uh along .

Did your knowledge base stop growing when you were in college? Did you even go to college?

” Cleaning up Mt. Baldy ” That’s a good one.

I bet you were smoking a fatty. Wouldn’t have recognized your own belly-button !

Wow, what were people doing 150 years ago that would cause that?

Here is the funny part. They have document this happening in the past. When this does happen again the first thing everyone will blame irregardless is GLOBAL WARMING!!

If you actually listen to the climatologists, they are saying that Global Warming is like turning up a burner slightly underneath a pot of hot water. If the water isn’t boiling yet, it might push it over the edge to a slow boil. If it is, the boiling will become more intense. So, yeah, Global Warming won’t cause a Megastorm by itself but it could turn a big storm into a bigger one (along with creating more small storms.) The bigger danger is that sea levels will rise enough so that ports and low-lying coastal areas will be damaged more severely by storms and flooding.

While I know that no one can predict the exact effects of Global Warming (particularly to specific areas), the general consensus is pretty strong that we’ll have some serious adapting to do. How fast will it progress? What will all the effects be? No one knows for sure. Will it change weather patterns so that some areas get colder and/or dryer while most get warmer and wetter? Probably, but again, no one knows.

Is it caused by people? Not entirely but people (specifically generation of greenhouse gases and heat by people) are making it happen much faster which means reduced ability of societies to adapt in time.

Can it be stopped without returning to a pre-industrial civilization? That’s the big question. Personally, I think that even if it is possible, way too few people will sacrifice enough to make it happen. People on the whole tend to try to rationalize away unpleasant realities. Ignoring them until they are smacked in the face and then misplacing the blame and trying to get unworkable solutions before coming to terms with the fact that there sometimes aren’t any “win-win” solutions. By that time, even the best options are bad ones.

I am old enough so that I probably won’t have to deal with the worst of the consequences but I have already started planning for bad times. (Survivalists may be sometimes misguided on the nature of societal disasters, but their solutions are often valid no matter what the cause is.) I feel sorry for the youth that will have to face worse ones.

Many scientists say the earth is cooling now… thus the term is now Climate Change, not Global warming…

(The Ozone hole is growing- no, it’s closing. The earth is warming, no it’s cooling.)

And these are the people we cannot question, we must just do what they say. That is, until they change their minds and move onto the next crisis.

The earth is cooling? Did you just make that up? Ha ha. Very funny.

May I suggest you find a program they did on History Channel called “Little Ice Age.” The last one that happened four hundred years ago, the first thing that happened is that it started to warm first for a period of years. Then it cooled rapidly. The Vikings at the time had conquered and where living in coastal areas of Greenland, because of how much land there was and the temperate climate. Hmm kind of like now. Then over the next fifty years or less (doing this from memory so not exact) it got so cold all the crops they had been growning, no longer would and they about starved to death.

I know I must have made this up. I called the History Channel, told them to invest all this money in non true things, to stir people up.

Oh and one more. You make fun of Commen Sense for saying cooling. Al Gore said back in the sevenities that the earth was cooling and now almost forty years later says the opposite?? Ya probably the messiah you are listening to I bet. Now that is FUNNY!!!

QUOTING COMMONSENSEMAMA: “Many scientists say the earth is cooling now… thus the term is now Climate Change, not Global warming… ”

The climate is CHANGING. In some areas, that means it is more warm than it has ever been before, and in some areas it means it is cooler.

The problem is that human civilization population is organized and located (especially large, dense population centers) to fit old climate realities that are now changing. Our production of resources (such as agriculture) is also located and organized to fit old climate realities that are now changing.

Our planet’s major areas of dense population are near bodies of water. Land areas near bodies of water usually have floodplains, with very small elevation changes. Seasonal floods occur on these floodplains both from seasonal inundations of water from the hills and mountains away from the floodplains, and from seasonal ocean storms.

Dams hold back the water from the mountains and release it in usable, survivable amounts. In the floodplains, where most people live, culverts and other devices channel the water away from human habitat to drain into oceans, rivers and lakes.

The (relatively) quick rise of the ocean by even a very small amount disrupts these important changes humans have made to the lands that allow us to live where we do.

To adapt to even a small increase in the ocean level would take vast financial resources, which we simply don’t have and won’t have. When we should be preparing for what is coming, we are further devastating our earth and its climate by useless wars that make just a few very, very rich and decimate the rest of the population.

A fiction book that paints a good picture of what happens to a human population when there is a “rapid” (in historical terms) change in the level of the sea is “Well of Shiuan” by C.J. Cherryh ( The author was a teacher for most of her life, and the science is sound. The book was written in 1978, and the storyline amazingly predicts what is starting to happen to us now.

May I direct you to this?–chart-prove-it.html

I try and resist the urge to drink the kool-aid.

Climatologists to me are about the same group as Meterologists and how accurate are they? I for one like to defer to GEOLOGISTS. I have been watching and reading many a good story over the last five years. They aren’t going by an infintesmal small time like 150 years of record keeping. They are digging back TENS OF THOUSANDS of years and looking at climate through Geology. I will stick with that.

When I saw the link was to the Daily Mail, I almost ignored it. There is a reason that many people call it “The Daily Fail”. Sloppy fact checking, passing along rumor and opinion as fact and sensationalism are this publication’s stock in trade. They offer stimulating “news” (like CCN) but without the consistent commitment to accuracy (like some CCN posters).

Still, I did check it out. On the surface, their story sounds plausible. But among the commentators, the more knowledgeable take issue with their interpretation of the base data upon which the article is based.

One can find “experts” who disagree with the majority of other experts who believe the global warming theories. Some of them are even honest and not influenced by funding from traditional greenhouse gas-generating corporations. Since I am not sufficiently expert in the field to evaluate conflicting claims, I will continue to accept the views of the vast majority vs. the dissident minority on issues where science is the primary element involved.

Yea the vast majority once thought the earth was flat.

Many people still behave as if it is.

I agree that geologist can tell us a lot about how the earth has changed over time.

However, geologists are not the experts on how human populations will react to such changes. They also cannot tell us how the earth will react to such dense human populations and the demands and changes they make to the earth.