Monday, February 27, 2017

Volcanoes in the Mist (and underground): Travels in Death Valley

The Inyo Mountains, in any other setting in the world, would be considered a major mountain range, preserved as a national park perhaps, and celebrated as scenic wonderland. But just like an accomplished sibling overshadowed by a more famous brother or sister, the Inyos lie across the valley from the most spectacular part of the Sierra Nevada, and south of the higher White Mountains. For better or worse (mostly better), only a few roads penetrate the range, including the main western highway into Death Valley National Park, State Route 190. That was the road we followed on our recent exploration of Death Valley.
As was noted in the previous post, we attempted our trip during the Bombogenesis storm that wreaked havoc across Southern California. This kind of storm can often result in disaster as highways get closed or damaged by landslides, but we were lucky and were able cross the Inyo Mountains and Darwin Plateau without problems. But we did get the opportunity to see some great geology, and even were able to add a new stop to our itinerary (because we missed a different one, but I'm not complaining).

Our first sight as we approached the mountains was the snow covering the desert peaks (first picture above), a hint to the seriousness of the storm we were challenging. The tilted rocks are Paleozoic-aged (300-550 million years) limestone layers. They recall a time when California was very different, completely submerged under a shallow tropical sea. We would be seeing more of these fascinating rocks later on. The road crossed the flat uplands of the Darwin Plateau, and then plunged down a steep incline towards the Panamint Valley.

We actually had fog in this arid environment, since the clouds were crowding against the edge of the steep mountains. As we passed the Father Crowley Vista Point, the clouds briefly parted and we had a view into the deep gorge of Rainbow Canyon. At this point, the slopes and flats are covered with basaltic lava flows ranging in age from 8 to 4 million years old. The immediate question becomes, why volcanoes? Why right here?

In a sense, volcanism is possible almost anywhere on the planet. It's not that there is magma everywhere, but that a hundred miles beneath our feet there is a zone, the asthenosphere, where the rock is almost molten, but not quite (perhaps 5-10% liquid). To melt this rock and create volcanic activity would require raising the temperature (as happens at hot spots like Hawai'i), or releasing pressure (pressure keeps the rocks from melting in the same way that pressure cookers prevent water from boiling). There aren't any hot spots in the immediate vicinity, but the crust across the Basin and Range Province has been stretched and thinned, allowing pockets of basaltic magma to form and rise into the rocks above, often following fault zones to the surface.
Although we couldn't see it through the clouds, there are basaltic lavas across the Panamint Valley that are of the same age and the same exact composition as those at the vista point. In addition, the rocks across the deep valley have no obvious source (the picture below is from last year, a decidedly drier trip). The best explanation for these rocks is that the lavas flowed across an original surface that was later broken up by faulting when the Panamint Valley formed. Since the youngest volcanic rocks are just 4 million years old, the Panamint Valley is younger still. The Panamint Valley is more than a mile deep and 65 miles long! That's a lot of geologic activity in a short period of time.
Looking across the Panamint Valley towards Hunter Mountain. The dark rocks on the left summit area are identical to the rocks at Father Crowley Vista Point.
We made a stop along the road descending into the Panamint Valley to check out some spectacular exposures of the dikes and sills that once fed the eruptions of the basaltic lavas (most years we are in too much of a hurry to get a camping spot at Stovepipe Wells). The magma was following whatever weakness in the surrounding rock that could be exploited by the molten rock. In some cases, vertical fractures allowed the magma to rise, forming dikes. In other cases, the molten rock flowed between limestone layers, forming sills. This extraordinary roadcut (below) showed textbook examples of both kinds of intrusions in the same outcrop. The usually black basalt has been oxidized (rusted) to produce the strange reddish-brown color.
There's a saying that one should never blindly sit on the ground in the desert. There are just too many things with fangs, stingers, or spines. The barrel cacti were looking to grow quickly in these rare wet times!
We headed down the highway. We had reached Death Valley National Park, and we faced whatever Bombogenesis was going to throw at us...

Friday, February 24, 2017

A Place Where Water Once Was But Was No Longer, But Once Again Was - Travels in Death Valley

I'm finally not "liveblogging the deluge" anymore. I thought back at the beginning of January that I was monitoring a historic flood event that was going to be over with in just a few days. Somehow, new storms kept blowing through, and I was watching and monitoring flood activity around the state. Those "few days" turned into a six-week series of observations. But now that the storm activity has subsided a bit, the observations are going to be in the past tense. I didn't have much in the way of internet access over the holiday weekend, and we went and stared into the abyss of the storm with little to defend us but waterproof jackets and the nylon walls of our tents. We explored Death Valley National Park during one of its most intense storms of the year.
On the whole, we were pretty lucky. We got drenched by rainstorms on the first two nights of the trip, and rain played havoc with our travel plans during the first two days, but most of the principle roads in and around Death Valley remained open, and we were able to get to most of our objectives. The first day was certainly typical of this; we missed a planned fossil hunt because of the driving rain, but we managed stops at the other three localities, and even added two extra stops that weren't in the original plans. Our first stop was at Red Rock Canyon State Park near Mojave for a look at the colorful terrestrial deposits of the Ricardo (or Dove Springs) formation. If the exposures look familiar, you've probably seen them in a number of Hollywood movies. I've written extensively about the geology of Red Rock in the past; check out this post for some details of this fascinating place.

The real thrill of the day was to see water where water once was but was no longer, but once again was. Shall I explain?

During the Pleistocene Ice Ages between 2 million and 12,000 years ago, the climate of the northern hemisphere swung wildly from warm to cold and back to warm again, perhaps as many as twenty times. Ice accumulated across broad swaths of Canada and northern Europe, and several times crept across the border of the United States, ultimately covering around 30% of the lower 48 states. The thick ice cap never reached Oregon or California, but the Cascades and the Sierra Nevada developed an extensive network of alpine glaciers. Some streams of ice, for instance in the Tuolumne River basin, reached a length of 40 miles.
The glaciers of the Sierra Nevada never reached far into the desert basins to the east, but the influence of the cooler and wetter conditions was unmistakable. Meltwater filled the enclosed basins which then spilled over into adjacent basins, forming a series of what are now called pluvial lakes. Mono Lake is a small remnant of the glacial Lake Russell, and Owens Lake still contained water as recently as the 1920s (before Los Angeles diverted the incoming streams). Other lakes included China Lake, Searles Lake, Panamint, and ultimately Lake Manly in Death Valley. Vigorous fast-flowing rivers connected the widely separated lakes. Our second stop concerned one of those rivers, the one that flowed from Owens Lake to China Lake through the Indian Wells Valley.

From several hundred thousand years to as recently as 10,000 years ago, basaltic lava flowed from cinder cones and fissures of the Coso Volcanic Field. Some of these flows blocked the river, and formed a forty-foot high waterfall. The river scoured a channel, and the waterfall eroded in an upstream direction. Boulders trapped in river eddies swirled around, forming amazingly deep potholes. And then the ice receded. The level of Owens Lake dropped below the rim, and the river through what we call Fossil Falls ended.

The river ended thousands of years ago, but on rare occasions there is an echo of the days when a wild river flowed through the gorge. I've seen it only twice, but when the rains have been plentiful in the Owens Valley, a small stream of water flows through Fossil Falls. That's what we got to witness last week, thanks to the Bombogenesis storm (or Lucifer, or whatever they called it). A river the color of a creamy latte made its way through dark basalts.
It was a fine introduction to our exploration of the geology of the Death Valley region, and it wasn't the first time we were going to see water in places where water was not normally found. Death Valley is a place where the water once was, but was no longer, but once again was...
This last picture is kind of cheat. I didn't climb down into the gorge for a close up, so this is from 2005, the only other time I've seen water at Fossil Falls.

Thursday, February 23, 2017

Liveblogging the Deluge: Checking out the Spillway at Don Pedro Reservoir

It's probably not too hard to figure out what happened. I get home from a five day trip only to find that the spillway at Don Pedro Dam has been opened for the first time since the floods of 1997. It's a big event in these parts, an acknowledgement that the reservoir was full and in danger of spilling over in an uncontrollable manner. So I had to go and have a look. Mrs. Geotripper and I had a few hours this afternoon and headed on up the river. We had no idea what to expect, or whether we would be allowed anywhere near the spillway.
We were pleasantly surprised to find that there is some limited access for the public. If you want to have a look, you need to drive Bond's Flat Road to the Blue Oak Campground at Don Pedro (trying to approach from the south side - the Fleming Meadows side -  doesn't work as Bonds Flat Road is closed two miles away from the dam). The campground and day use area is open, and provides a limited view of the spillway and the spray from the water releases.
The spillway opens up into a former meadow that was carved down to bedrock during the floods of 1997. A portion of the flow can just be glimpsed from the viewing area. The spillway is similar to the one that failed at Oroville Dam, but at Don Pedro the slope is more gentle, so uncontrolled erosion of the rock is unlikely (especially since the flow rates are not nearly as high as they were in 1997).
The long concrete structure in the top two photographs is the weir that serves as kind of a last ditch spillway. The crest lies at an elevation of 830 feet, and the water this afternoon had reached 829.5 feet. As a consequence, the outflow through the spillway has been increased to 14,600 cubic feet per second (well above flood level) to start bringing the water level down.
There is a high point in the campground that provides a better look at the spillway from the lake side. On this sparklingly clear day, the view of the valley was also spectacular.
For the first time in twenty years the lake is absolutely full. It is quite a sight!

Just a note, in case you want to see the sights for yourself...stay behind the fences and follow the directions of the authorities. I didn't find out for myself ("But sir, I'm a GEOLOGIST!"), but the ranger told me stories of the people that they had caught and cited. They were rather vigilant.

Tuesday, February 21, 2017

Liveblogging the Deluge: Big Changes on the Tuolumne River

I've been away for the last five days, experiencing California's storms from an entirely different perspective, that of being exposed and out in the open country of Death Valley National Park. There will be plenty of information and pictures about our adventures soon enough, but there were plenty of events back home that have been rather significant as well. A great many people have been affected as the waters of the San Joaquin River and its tributaries have risen past flood level.

First and foremost, at Don Pedro Reservoir on the Tuolumne River the emergency spillway has been opened for the first time since the floods of 1997. This became necessary when the lake filled nearly to capacity, and a new storm battered the north state over the weekend. The channel downstream floods at around 9,000-10,000 cubic feet per second, but storm runoff threatened to exceed that level. The dam operators had to make a decision to cause some flooding downstream to avoid even greater flooding if runoff was too high.
Flows were ramped up to around 16,000 cubic per second over the weekend, and have since settled back to 13,500 cfs at the latest reading (below). Rain and snow are still falling in the region, so the concern about flooding remains for the time being. The lake fills at 830 feet, and the current level is 828.82 feet. There isn't much room for error.
Source: USGS (

People are understandably concerned about Don Pedro Reservoir as they compare notes with the events at Oroville Dam in the last few weeks. Both dams have an emergency spillway that flows over unlined and unreinforced rock rather than a concrete channel.

There are some important differences, however.

First, the emergency channel below Don Pedro is much less steep than Oroville's, and is therefore less subject to the headward erosion that threatened to undermine the spillway at Oroville. Second, the spillway was tested previously, during the floods of 1997. The runoff amounts in that event were almost astronomically higher than any flows expected in this year's event. A forty-foot channel was carved through the meadow, and the flowing waters are unlikely to do anything worse this time around.
Still, these are nervous times. I had my first chance to see the higher flows this morning as I headed to work. I stopped at the head of the Tuolumne River Parkway Trail to have a look. The picture below was taken on February 5th when flows were around 10,000 cfs. Note that the entire trail was above water level.
The picture below shows the same scene this morning with flows closer to 14,000 cfs. As you can see, the entire trail is under water now, which means I'll have to find another place for my birdwatching for a few weeks or so.
One senses that authorities are just barely keeping ahead of events, which is not surprising given the nearly nonstop barrage of atmospheric river storms battering California. The situation has not quite spiraled out of control, and the storms are letting up for a few days, which will allow for more floodwaters to flow into San Francisco Bay. I hope we'll have a breather.

Wednesday, February 15, 2017

Liveblogging the Deluge: San Joaquin River National Wildlife Refuge - What a difference a few months made (and Rabbits)

The San Joaquin River at the National Wildlife Refuge in November 2017
Just a few months ago, the San Joaquin River, and its major tributary the Tuolumne River, were in big trouble. The worst drought in California's recorded history had left the rivers at a mere trickle, and many parts of the San Joaquin were dry, despite recent efforts to bring back some sort of minimal flows to stretches of river that had been dry for decades (after dam and irrigation levee construction upstream). The invasive weed River Hyacinth had choked channels, crowding out native vegetation and making life difficult for fish and other organisms.

I hiked the Pelican Nature Trail in the San Joaquin River National Wildlife Refuge back in November, and despite a few early storms, dryness was the overwhelming feeling. Volunteers have put in a vast amount of work replanting former riparian woodlands, but it felt like the river overflow areas wouldn't see water any time soon. The river was flowing at a sluggish couple of hundred cubic feet per second.
The San Joaquin River in the same exact location on February 14, 2017
I returned to the Pelican Trail yesterday to a changed world. A series of atmospheric river storms over the last six weeks have dumped record amounts of precipitation across northern and central California. Watermasters at the reservoirs upstream joyfully let their dams fill with the prodigious amounts of water, but then the storms kept coming and they realized that some of the dams were in danger of overflowing. They ramped up flows out of the reservoirs and the rivers downstream swelled. The Tuolumne River, for instance, has been flowing at near flood levels (~9,000 cubic feet per second) for the last five weeks, and this week the flows were increased to over 11,000 cubic feet per second. Don Pedro Dam is only 2-3 feet below full capacity, and has only about 30,000 acre-feet of capacity (out of 2.03 million acre feet of storage space). The Merced River has been experiencing high flows as well, and water is high in the usually dry San Joaquin riverbed. Yesterday the river at Vernalis, just downstream of my trail, reached official flood state at 34,000 cubic feet per second.

It was rather stunning to stand on one bank of the San Joaquin, the neglected trickle of water from the southern Great Valley, and not be able to discern exactly where, off in the distance, the other bank was located. And there is this: the water level is probably going to rise soon. Yet another intense storm is headed towards California, and there is going to be another week of rainfall and snow in the mountains upstream. Don Pedro Lake, for one, is just about full and it is possible they will have to let additional water through the system to keep the lake from overflowing.

More than a month ago, on January 4, I wrote the first of a series of blogs that I soon called Liveblogging the Deluge. I quite honestly thought it was going to consist of four, maybe five posts as the first atmospheric river storm passed through California. But another storm soon followed, and then another. I look back now and see that I've published 24 posts on the storms, and they keep coming. This has been an extraordinary storm event and, for some people, a scary experience. Nature cares little for human beings and our puny attempts to control it can sometimes result in failure and tragedy. Despite the evacuation of 180,000 people because of an unstable situation at Oroville Dam, we've kind of held things together in the north part of the state, but the system is presently strained to the limits. Levees are showing signs of failure in places and reservoirs are getting dangerously full. It is imperative that residents in California keep their eyes open, and when the warnings come and evacuations are ordered that they comply as quickly and orderly as possible. Making a principled stand to defend your house against a rising flood is dangerous and may be deadly.

By the way, the other strange sight on the Pelican Nature Trail was the prevalence of Desert Cottontail Rabbits. There were perhaps hundreds of them along the trail. I assumed they had been flooded out of their habitat on the flats below and had gathered on the high ground of the levee where they were nibbling at the smallest shoots of grass, or reaching for leaves on the lower branches of the shrubs.

They barely seemed to register my presence. I was stepping only two or three feet away from them before they would move into the brush along the trail. They only scattered rapidly once, when a Northern Harrier flew overhead. Human beings are not the only beings who are affected by the floods.

I'm not going to be able to liveblog the coming storm, as I will be out in the middle of it. We're headed out to the Death Valley region where we will be navigating between storms and flash floods. I expect to have some interesting observations once the storm is past and we are home again. And yes, we will be careful out there. It's not often that one gets to observe rain in the driest place in North America. See you in a few days!

Tuesday, February 14, 2017

Liveblogging the Deluge: A Tuolumne River Update, and Scenes on the San Joaquin

The travails at Oroville Dam are appropriately dominating the news this week as nearly two hundred thousand people remain isolated from their homes as the operators work to temporarily shore up the failing spillways at the lake. It should not be forgotten that most rivers in Northern California are running very high, and with yet another storm arriving this week, the threat of flooding elsewhere is still very real.
San Joaquin River near Stevinson
I don't have much information on the San Joaquin River, but I crossed the river yesterday near Stevinson on Highway 165, and it was well out of its banks. There are reports of flooding downstream west of Modesto. Although the river was clearly flooding, it was still well below the levees near the bridge I crossed.
San Joaquin River near Stevinson

I made it down to the Tuolumne River Parkway Trail this afternoon, and found that the river has reached the highest flows since the recent storm assault began in January. It is swollen with water released from Don Pedro Dam upstream.
The capacity of Don Pedro is 2.03 million acre-feet (water elevation 830 feet), and the latest measurements show the lake at just inches below 828 feet. Inflow has declined in the last day or so to 12,544 cubic feet per second, while outflow has been ramped up a bit past flood level, to 10,700 cubic feet per second, so the lake is still rising, albeit much more slowly than a few days ago. An announcement from Turlock Irrigation District indicates that they have no current plans to open the emergency floodgate.  If they do, it will be for only the second time ever. The first time was in 1997, and that event carved a new channel through a pasture area that reached a depth of 40 feet.
It's important in these days of evacuations in the Oroville Dam area to point out that there are big differences between the spillgates at the two dams. The floodgate at Don Pedro is more heavily reinforced and the former meadow slopes more gently, so undercutting of the gate is unlikely. The overflow channel, although not lined with concrete, passes no major infrastructure other than Bonds Flat Road, which washed out in 1997 (but was later repaired). If the storms fill the reservoir, the floodgates could indeed be opened, and some flooding would occur downstream, but not to the extent of the potential flood that threatens Oroville and other towns in the north valley.
Don Pedro Dam, courtesy of Google Earth

In the meantime, I am watching a powerful river changing things along my exercise trail. Portions of the trail were underwater, and the normally placid river is surging noisily downstream. High flows are expected to last for many weeks as the reservoir is prepared to accept the snowmelt that will begin soon. It has been a long time since things have been anything like this.
I'll repeat what I said in the last post. Flooding is a serious matter, one of the most dangerous of geological hazards. One thing that sets river floods apart is their predictability, in that rivers are closely monitored, and flood levels are almost always known with good accuracy hours and days ahead. This means that if you are told to evacuate, your life is in danger, and you should follow any directions and requests made by the authorities. Unlike the give and take of politics, there is no place for "unbelief" that the river will hurt you or your property. The river doesn't care what you believe. Just get out of the way.

Monday, February 13, 2017

Liveblogging the Deluge: Reflections on the Events at Oroville Dam. What Will it Take to Change Things?

This picture is on the San Joaquin River, not the Feather. It's a metaphor for floods all around.

Let me be absolutely clear: this is a serious situation. Nearly two hundred thousand people have been evacuated as officials try to deal with two crumbling spillways at Oroville Dam as high river flows have filled the reservoir past capacity. The situation has briefly stabilized as the lake has been lowered to a level below the auxiliary ("emergency") spillway so temporary repairs can be started. But again, this is serious. If you live in the evacuation zone, follow the orders and get out.

I have a story that will seem pointless at first, but bear with me. I have a fence in the backyard. It was a nice fence at one time. But the years took their toll. Heavy storms would knock some of the slats loose, but I would nail them back in. Dry rot attacked some of the crossbeams, but chicken wire and bungee cords sort of sufficed to hold things together.

The years went by and it got worse. But there never seemed to be enough money, and there were always excuses to do other things instead. But the storms of January hit, and hit the fence hard. Whole sections just fell to pieces. The fence was totally destroyed and finally we had to act, whether we could afford it or not.

What does this small story from my life have to do with Oroville Dam?
From the Los Angeles Times

First, a recap...

Oroville Dam is the highest dam in the United States, at 770 feet, and the second largest reservoir in California with a capacity of 3.5 million acre-feet. It is a major component of the State Water Project, providing water for millions of people in central and southern California. It was completed in 1968.

California has finally ended the worst drought in the state's history with what may turn out to be the wettest year on record (there are still several months left in the season). A series of atmospheric river storms have dumped incredible amounts of rain and snow across the state, and rivers are swollen. Most of the state's reservoirs are nearly full, and operators are carefully draining what they can to avoid flooding now and in coming weeks as more storms roll through. But the big problems cropped up at Oroville Dam.
The main spillway early in the crisis. The emergency spillway is to the left.
When flows get too high, the lakes have to be drained through spillways which are supposed to be designed to accommodate the largest credible flood events. Oroville has such a spillway, but when flows ramped up earlier this week, a huge section of the concrete collapsed and water started tearing away at the adjacent hillside, threatening some of the major electrical transmission lines. It turns out that even though it was never meant to be used, a second spillway had been constructed. No effort had been made to prepare the slopes below for floodwaters, and the cement lip was never really properly reinforced.

Hard choices had to be made. The lake was filling fast, and the longer the main spillway was flowing, more and more concrete was being ripped away. The decision was made to let the lake drain over the auxiliary spillway and only yesterday morning the water started seeping over the edge. By the end of the day, the water was one or two feet deep across the entire structure, and if what I heard is accurate, the flow was around 10,000-15,000 cubic feet per second. For perspective, that's the current near-flood level flow of the Tuolumne River in my own backyard down the valley (below).
Tuolumne River flowing at 9,000 cubic feet per second

It was only a day before a big problem cropped up. A large hole had eroded from the spillway that threatened to cause its collapse. This was the event that precipitated the evacuation event, with warnings that the collapse could happen within an hour. I can't imagine what it must have been like to be living there and hearing such a warning.

What was about to happen? It wasn't a collapse of the entire dam. That's not really in the cards here. Had the spillway collapsed, the water would have starting flowing over the bedrock and loose soil beneath the concrete lip. The breach would have concentrated the flow in one spot, and even though the bedrock is solid metavolcanic rock, the smallest fissures and joints would have been exploited by the rushing water. The result would be a cut of several tens of feet, and that would have drained a significant portion of the reservoir (the top 30 feet out of the 770 feet). That would have been enough water to inundate a wide swath of the floodplain and adjacent areas downstream, and that is what prompted the evacuation order.

The operators of the dam ramped up the flow on the original spillway to around 100,000 cubic feet per second, and that was finally enough to start lowering the level of the lake. By 8 PM this evening the water dropped below the level of the auxiliary spillway, and repairs started immediately (six helicopters are dropping huge bags of boulders into the hole). The immediate crisis passed, but they are still depending on flow down a crippled spillway for the foreseeable future with a stated hope to drop the lake fifty feet beneath the emergency spillway. And we have more storms on the horizon.

What should we take from this perilous situation? My first thoughts as this event unfolded is that this dam and a great many others across the country are decades old. Concrete gets old and crumbles, steel reinforcement beams rust away deep within the concrete, and equipment suffers intense wear and tear. Congress and state legislatures are almost always generous with initial construction funds, but when the time comes for maintenance and renovation, suddenly the deficit becomes important and funds can't be found.

We have chosen to allow our population to grow beyond the capacity of our landscape to support us, and many times over we have chosen to place giant urban centers in places that make no sense (yes, I'm looking at you Las Vegas and Phoenix). We thus depend on gigantic projects bent on controlling nature to provide our water for irrigation and domestic use. We depend on them, and their failure would be catastrophic, both in lives lost, and in damaged infrastructure. And yet we refuse to provide enough funding for their upkeep.

I don't know what caused the failure of the original spillway at Oroville Dam, although I have some suspicions. I think I know the dynamics of what happened with the emergency auxiliary spillway. Whatever the reasons were, they were predictable to those knowledgeable in engineering design. They were in fact predicted in 2005 by environmental groups testifying during the relicensing of the dam according to a note by the California Water Research:

A single operational use or multiple operational uses (with failure to repair any preceding or cumulative damage) of the ungated spillway could result in a loss of crest control of Oroville Dam. A loss of crest control could not only cause additional damage to project lands and facilities but also cause damages and threaten lives in the protected floodplain downstream. An unarmored spillway is not in conformance with current FERC engineering regulations. (emphasis added.)

And that's where we are tonight. A dam in danger of spillway failure, as many as 180,000 people displaced suddenly from their homes, and a government unwilling to take care of infrastructure because it is just too expensive and inconvenient. This is a story that is going to be repeated over and over in coming years. The failure of the levees and the deaths of 1,800 people in New Orleans during Hurricane Katrina was a harbinger. I frankly don't think the events of this evening are going to be enough to convince legislatures to do the responsible thing. What will the tipping point be? The death of hundreds? The death of thousands?

Our country went collectively nuts after terrorists killed 3,000 people in the Twin Towers on 9/11 and we spent more than a trillion dollars on a useless war on terror. Fixing and investing in our failing dams and bridges makes so much more sense, and the benefits go far beyond just safety. It also means putting hundreds of thousands, maybe millions of people to work, and that will strengthen the economy immeasurably.

It's just like the way I put some people to work this week fixing my broken fence. They benefitted and so did I. And my yard is a much nicer place now.

UPDATE (2/13/17): A picture of the damage that was expected to impact the auxiliary spillway, from Peter Gleick on Twitter (@PeterGleick). I certainly looks like the jointed metamorphic rock I expected. This is similar to what happened at Don Pedro in 1997 when a 40 foot channel was carved in a few days.
Circled are people for scale.