Houston's Horrific Flooding: Thank Goodness It Can't Happen Here...Eh...Right? Think Again...

What's happening in Houston is beyond belief. And tragically, horrible flooding is happening now in southeast Asia as well, with at least 1,200 people dead. Although the extent of the damage in Houston is not yet known, meteorologists are already calling it unprecedented in American history. I can't begin to imagine experiencing feet of rain in the space of days, and it isn't over yet. My heart goes out to those in the midst of the disaster. It may take weeks for the waters to subside, and years for the region to fully recover.

This isn't Houston. It is our own much more modest flood a few months ago.

(I've abridged and adapted the following from a post in 2011)

Seeing events like this unfold on television or on the computer screen can provide a certain emotional distance from the full magnitude of what has happened. Thoughts develop along the lines of "Could it happen here?" and as we realize it might, we think "Are we prepared for an event like that?" Floods occur essentially everywhere, but the Central Valley (the GREAT Valley) is notable in the magnitude and frequency of its flooding. We had a experienced a few terrifying days in the early part of the year when it seemed that one of our largest dams, Oroville, was in danger of failing, and we have become aware that almost all our dams are aging, and need maintenance or replacement.  It makes one wonder how bad it could possibly get. Pretty bad, as it turns out.

Climate experts have been analyzing the possibilities that California could be hit by a devastating storm sequence that could leave much of the Central Valley as an inland lake. It sounds unlikely, at best a hypothetical model, but it has actually already happened. In 1861-62, a storm series dropped so much precipitation that a 300 mile long lake covered the valley, and forced the state capital to move operations from Sacramento to San Francisco for a time.

I mentioned Yellowstone in a while back, and it got me thinking once again about those things that are worth worrying about, those that are not, and those that are worth preparing for. Yellowstone last had an eruption 70,000 years ago, and the last major "supervolcano" (i.e. rhyolite caldera event) was more than 600,000 years ago. So how much should we worry about Yellowstone? It could happen, but not likely any time soon. But people are freaked out about the possibility if a quick internet search is any measure. They obsess about it, and even see strange conspiracies.

But what about a "superstorm"? People don't seem to worry about flooding so much, yet huge floods are a disturbingly common occurrence. Besides 1862, evidence has been uncovered of similar intense events in 212, 440, 603, 1029, 1418, and 1605 (sediments from storm runoff are preserved in ocean basins offshore of the state). That adds up to around a 0.3% possibility in a given year; not common, but enough that emergency providers are beginning to seriously consider the possible effects. A report from the US Geological Survey talks about the potential for an atmospheric river storm they have termed an ARkStorm (Atmospheric River Storm). The possible effects make California's expected "Big One" earthquake look, well, medium in comparison. From the USGS ARkStorm Report (PDF download here - 46 mb):

The storm is estimated to produce precipitation that in many places exceeds levels only experienced on average once every 500 to 1,000 years. Extensive flooding results. In many cases flooding overwhelms the state’s flood-protection system, which is typically designed to resist 100- to 200-year runoffs. The Central Valley experiences hypothetical flooding 300 miles long and 20 or more miles wide. Serious flooding also occurs in Orange County, Los Angeles County, San Diego, the San Francisco Bay area, and other coastal communities. Windspeeds in some places reach 125 miles per hour, hurricane-force winds. Across wider areas of the state, winds reach 60 miles per hour. Hundreds of landslides damage roads, highways, and homes. Property damage exceeds $300 billion, most from flooding. Demand surge (an increase in labor rates and other repair costs after major natural disasters) could increase property losses by 20 percent. Agricultural losses and other costs to repair lifelines, dewater (drain) flooded islands, and repair damage from landslides, brings the total direct property loss to nearly $400 billion, of which $20 to $30 billion would be recoverable through public and commercial insurance. Power, water, sewer, and other lifelines experience damage that takes weeks or months to restore. Flooding evacuation could involve 1.5 million residents in the inland region and delta counties. Business interruption costs reach $325 billion in addition to the $400 billion property repair costs, meaning that an ARkStorm could cost on the order of $725 billion, which is nearly 3 times the loss deemed to be realistic by the ShakeOut authors for a severe southern California earthquake, an event with roughly the same annual occurrence probability.

If that doesn't sound like events in Houston, you haven't been paying attention. This is serious stuff.
Flooding rarely gets the epic movie treatment. Volcanic eruptions and earthquakes are so sudden and devastating; rising water just doesn't cut it as a drama setting. I haven't seen a lot of Katrina movies yet. But life isn't a movie. If you live in California, think for a moment about getting hit with a superstorm, and the delta and Central Valley ending up like this:It is a real possibility and a sobering thought....

By the way, not wanting to stir the pot (or maybe I do), if you are worried about Yellowstone erupting and you live in California, why aren't you giving more thought to our very own active rhyolite caldera, our "supervolcano"?

Maps and second photo from the USGS ARkStorm Report (PDF - 46 mb)

The Airliner Chronicles: Three Faces of California's Great Valley

According to this interesting article from the New York Times, it's larger than 9 American states. It is the largest patch of Class 1 Soil in the world (i.e., the best for agriculture). More than 230 kinds of crops and produce are grown there, and the output represents 8% of the nation's agricultural output (on 1% of the land). Around 6.8 million people live there, and the average per capita income is lower than most of the rest of the country (it has three of the five poorest cities), and unemployment is far higher. It is California's Great Valley, my home.

From http://en.wikipedia.org/wiki/File:Map_california_central_valley.jpg

The valley is 400 miles long, 30-50 miles wide, and is almost entirely flat (except for the Sutter Buttes, the highest elevations are 400 feet or less). It is drained by several major rivers, including the Feather and Sacramento Rivers to the north, and the San Joaquin, Kings and Kern Rivers to the south. Although most of the rivers leave the valley through the Sacramento Delta into San Francisco Bay, those in the south do not. They once ended in huge lakes like Tulare and Buena Vista, but today the lakes are long gone, having been dried up by agricultural diversions upstream.

I've long heard that only 5% of the valley remains in the natural state that existed prior to agricultural development, and from the air, this is obvious. All the times I've flown over it, I have been struck by the continuous patchwork of plowed fields (it clearly resembles the kinds of blankets my grandmother used to make out of the leftover fabric squares). There are a few tracts of undeveloped grasslands off to the south, but for the most part only the rivers retain much of their original vegetation, but only in a few places.

Today's photos come from three distinctly different parts of the valley's river systems. In the colorful top photo, we can see a portion of the Sacramento Delta, where the San Joaquin and Sacramento Rivers come together in a maze of islands that have been mostly converted to farmlands. The islands are protected (somewhat) from seasonal floods by a series of poorly constructed levees that are subject to destruction from even moderate earthquakes. This has set up what potentially could end up as California's worst possible natural disaster (at least in the monetary sense). The islands have been sinking due to groundwater withdrawal, soil loss, and oxidation of organic material in the soils. Most of them are now below sea level, with only the vulnerable levees keeping them from being flooded. Since the intake pumps for the California Water Project lie in the midst of these islands, broken levees will draw salt water into the delta, where the domestic water supply for most of the southern state is tapped. An earthquake has the capability to disrupt the state water system for several years.

The north end of the Great Valley is drained by the Sacramento River which can be seen in the photo above, taken near Colusa. The landscape has been completely co-opted by agricultural fields, right up to river's edge. It looks like the river has been "conquered" and tamed by the works of humankind, but floods like those of 1997 and especially of 1861-62 could leave just about the entire area in the photo above under 10-20 feet of water (see my take on these ARkstorms here).

The San Joaquin River drainage contains some of last remaining natural grasslands and riparian landscapes in the Great Valley. The structure of the valley is that of a series of shallow basins separated by the alluvial fan systems formed by the Merced and San Joaquin Rivers. The basins have essentially caused the river to back up and develop wide floodplains where the streams meandered widely, changing channels in unpredictable ways. The area in the picture above is just north of the town of Los Banos, an area of abandoned meanders, bogs and swamps protected as the San Luis National Wildlife Refuge and Great Valley Grasslands State Park. The land is not entirely unaffected...decreased flows caused by reservoirs and diversions upstream have caused many of the swampy areas to dry up. Efforts (and negotiations) are ongoing to increase river flows in a hope of rebuilding the disrupted ecosystems, especially those of the salmon which used to be common in these waters.

The Airliner Chronicles is one of my on-again/off-again serial features, which is usually updated whenever I fly somewhere.

Queensland's Flooding: Thank Goodness It Can't Happen Here...Eh...Right? Think Again...

Before you read anything else in this particular blog, go to the BBC news and look at 3 minutes and 46 seconds of stunning pictures of the extraordinary flooding this season in Queensland, Australia. The amount of water on the ground in the normally dry landscape is almost beyond belief. The BBC mentions a vast inland sea the size of France and Germany combined. My heart goes out to those in the midst of the disaster. This was an unusual train of meteorological events that ended a long drought, and culminated in the arrival of Cyclone Yasi, a category 5 hurricane. It will take weeks for the waters to subside, and years for the region to fully recover.

Not Australia, this is flood stage on our own San Joaquin in 2006

Seeing events like this unfold on television or on the computer screen can provide a certain emotional distance from the full magnitude of what has happened. Thoughts develop along the lines of "Could it happen here?" and as we realize it might, we think "Are we prepared for an event like that?" Floods occur essentially everywhere, but as I am based in California, my ears perk up whenever I hear about unfolding events along the Pacific coast. We had a pretty wild time of it in the last two months with serious floods in a number of areas, especially in southern California. It makes one wonder how bad it could possibly get. Pretty bad, as it turns out.

Those pesky climate experts have been analyzing the possibilities that California could be hit by a devastating storm sequence that could leave much of the Central Valley as an inland lake. It sounds unlikely, at best a hypothetical model, but it has actually already happened. In 1861-62, a storm series dropped so much precipitation that a 300 mile long lake covered the valley, and forced the state capital to move operations from Sacramento to San Francisco for a time.

I mentioned Yellowstone in a recent post, and it got me thinking once again about those things that are worth worrying about, those that are not, and those that are worth preparing for. Yellowstone last had an eruption 70,000 years ago, and the last major "supervolcano" (i.e. rhyolite caldera event) was more than 600,000 years ago. So how much should we worry about Yellowstone? It could happen, but not likely any time soon. But people are freaked out about the possibility if a quick internet search is any measure. They obsess about it, and even see strange conspiracies.

But what about a "superstorm"? People don't seem to worry about flooding so much, yet huge floods are a disturbingly common occurrence. Besides 1862, evidence has been uncovered of similar intense events in 212, 440, 603, 1029, 1418, and 1605 (sediments from storm runoff are preserved in ocean basins offshore of the state). That adds up to around a 0.3% possibility in a given year; not common, but enough that emergency providers are beginning to seriously consider the possible effects. There was a bit of a stir in the geoblogosphere a few weeks ago about a report from the US Geological Survey about the potential for an atmospheric river storm they have termed an ARkStorm (Atmospheric River Storm). The possible effects make California's expected "Big One" earthquake look, well, medium in comparison. From the USGS ARkStorm Report (PDF download here - 46 mb):

The storm is estimated to produce precipitation that in many places exceeds levels only experienced on average once every 500 to 1,000 years. Extensive flooding results. In many cases flooding overwhelms the state’s flood-protection system, which is typically designed to resist 100- to 200-year runoffs. The Central Valley experiences hypothetical flooding 300 miles long and 20 or more miles wide. Serious flooding also occurs in Orange County, Los Angeles County, San Diego, the San Francisco Bay area, and other coastal communities. Windspeeds in some places reach 125 miles per hour, hurricane-force winds. Across wider areas of the state, winds reach 60 miles per hour. Hundreds of landslides damage roads, highways, and homes. Property damage exceeds $300 billion, most from flooding. Demand surge (an increase in labor rates and other repair costs after major natural disasters) could increase property losses by 20 percent. Agricultural losses and other costs to repair lifelines, dewater (drain) flooded islands, and repair damage from landslides, brings the total direct property loss to nearly $400 billion, of which $20 to $30 billion would be recoverable through public and commercial insurance. Power, water, sewer, and other lifelines experience damage that takes weeks or months to restore. Flooding evacuation could involve 1.5 million residents in the inland region and delta counties. Business interruption costs reach $325 billion in addition to the $400 billion property repair costs, meaning that an ARkStorm could cost on the order of $725 billion, which is nearly 3 times the loss deemed to be realistic by the ShakeOut authors for a severe southern California earthquake, an event with roughly the same annual occurrence probability.

Flooding rarely gets the epic movie treatment. Volcanic eruptions and earthquakes are so sudden and devastating; rising water just doesn't cut it as a drama setting. I haven't seen a lot of Katrina movies yet. But life isn't a movie. If you live in California, think for a moment about getting hit with a superstorm, and the delta and Central Valley ending up like this:It is a real possibility and a sobering thought....

By the way, not wanting to stir the pot (or maybe I do), if you are worried about Yellowstone erupting and you live in California, why aren't you giving more thought to our very own active rhyolite caldera, our "supervolcano"?

Maps and second photo from the USGS ARkStorm Report (PDF - 46 mb)