The Other California: Spring Arrives in the Prairie Lands

California has a rather sullied reputation these days; a lingering depression (at least in our Central Valley), high unemployment, urban nightmares, Hollywood, and a legislature that lacks the will to support the education of its children and young adults. And yet, 38 million people choose to live here. They have a lot of reasons, and some think they want to leave, but frankly California is a nice place to live. Especially if you have any interest whatsoever in geology. There is hardly any place in the world that packs so much geographic variety within its borders: coastlines, mountains ranges, deserts, and valleys. My Other California series is an on-again, off-again exploration of the geologically interesting areas that don't normally show up on our tourist postcards. I started this series with an exploration of the prairie lands of California that surround the state's vast Central Valley. Because I live on the fringe of these prairies, I venture out some afternoons to see what's happening. Friday was an exploration of Merced Falls Road in the Sierra Foothills, a short drive that included a surprise vista of Yosemite's Half Dome and Clouds Rest.

Merced Falls Road connects Highway 59 at Merced Falls to Highway 132 near Don Pedro Reservoir. It provides access to a number of ranches and the recreational areas along McClure Lake. It also includes numerous exposures of the metamorphosed sediments and volcanic rocks of a Jurassic island arc system that was slammed (in a geologic sense) into the west coast of the North American continent in late Mesozoic time. The rocks have been upended and deeply eroded, producing a landscape that looks like a neglected cemetery (the outcrops look like tombstones). The rocks include the Mariposa formation and the Gopher Ridge volcanics.

Friday was a fine day for seeing the early blooms of what promises to be a fine wildflower season. More on that in the next post. When we reached the little village of La Grange downstream on the Tuolumne River, we could see the preparations being made for an exceptional spring runoff. The snowpack in Yosemite is somewhere around 150-160% of normal after three years of drought, and the water authorities are emptying out Don Pedro Reservoir to make room for the much needed onslaught of snowmelt that begins soon. Below is the artificially induced mild flood being conducted to avoid an out-of-control flood in a few weeks.

What else did I discover? I found out my hay fever is alive and well...sniff...

A Different Kind of Snow...

There was supposed to be a snowstorm in San Francisco last night, the first in a very long time, and snow levels in our valley were supposed to reach as low as 100 feet or so, so we set out to see if any had fallen in the Sierra Nevada foothills above our home. If there was any, it melted early, but we found a different kind of snow on the almond orchards that cover the low hills: blossoms!

I can't help but think that the blossoms are blooming earlier every year, but it always happens, and my hay fever follows soon thereafter. Still, it is a beautiful sight to see thousands of acres of flowers and deliriously happy bees. California's Central Valley (we call it the Great Valley) is one of the most productive agricultural regions in the world, but it rarely offers much to look at in a scenery sense, or in a geological sense for that matter.

But for a few weeks in the spring, it's a happening place, and is well worth a visit.

High Water in Yosemite III

We continue our journey through Yosemite Valley during the peak runoff last week (part I here, and part II here), when the Merced River exceeded 7,000 cubic feet per second, and reached flood stage. Numerous meadows and trails were underwater, and it was a wonderful thing to see! Above is the view from in front of the chapel at Old Yosemite Village. The slope on the right is the lower part of the Three Brothers, with the Cathedral Rocks in the distance.

And above we have a flooded portion of the meadow at the base of El Capitan. Once again, we are looking at the incredible Cathedral Rocks with the Cathedral Spires on the left.

The gaging station that measures the discharge of the Merced River is just upstream of Pohono Bridge. The problem with bridges is that we tend to put them at the narrow parts of river channels. When the floods come, the bridges can cause a bottleneck effect, having all kinds of implications upstream and downstream. Some of the bridges have been redesigned in recent years to allow the river to flow in a more natural pattern and to stabilize bank erosion.

As noted in the previous posts, floods are not a particular problem for the natural ecosystems of the valley. The ecosystem developed under a seasonal pattern of flooding and drought. The floods can be a minor inconvenience to hikers on the valley floor, as in the picture above where the riverside trail is flooded.

Trees that grow too close to the river will have their roots inundated. If the flood lasts for any period of time, the trees will suffocate and die. Usually the high water backs off within a few days. Today, a week after my trip, the river is flowing at 3,160 cubic feet per second, half of what it was a week ago, but still about 50% above normal for the middle of June.

Update: Martha at Martha's Musings was in Yosemite at the same time. See some nice pictures here.

A Few Snapshots for a Sunday: High Water in Yosemite II

I talked in yesterday's post about the familiar places in Yosemite, places like Yosemite Falls. There is a reason they are famous, and seemingly the focus of almost every tourist picture: they are truly spectacular, especially at times like last week when the runoff is at a peak. I have hundreds of pictures of Yosemite Falls, and as of Tuesday, I have two dozen more!

The Merced River was at flood stage, running at almost 7,000 cubic feet per second, and a number of meadows were filled with overflow from the river. You can see how the walkway is flooded in the picture above. Floods like this are not at all a bad thing, at least not from a natural point of view (displaced tourists may disagree). The flooding brings in new sediment, and floods out tree roots, preventing young saplings from encroaching on the meadows.

Yosemite Falls is unique in the way that it plunges over a vertical cliff, dropping 1,430 feet in an unbroken fall. The water collects into a series of rarely seen cascades for 700 feet before finally tumbling over 320-foot Lower Yosemite Fall for a total drop of 2,425 feet. By various measures, the fall is the highest in North America, and somewhere between the 5th to the 20th highest in the world (Angel Fall in Venezuela in the highest in the world at 3,458 feet).

I was always intrigued by the cleft to the left of the falls. It looks like a river channel, but carries no water to speak of, even during high runoff periods. The trail to the top of the waterfall employs the break in the cliff to reach the valley rim. I thought about it, but never had the insight I needed to complete the story. N. King Huber filled in the story in his wonderful book, published posthumously, Geological Ramblings in Yosemite. I've told the story in a previous post, but in a nutshell, the river used to follow the left channel until it was diverted by a glacial moraine during one of the last ice ages, causing it to spill over the cliff instead.

And what a plunge it makes! I've spent many happy hours of contemplation, just watching a single pulse of water break over the cliff, and follow just that pulse for the quarter mile drop.

From the valley floor, the water seems to spring from the cliff without an obvious source, but a look at the falls from Glacier Point on the south rim of the valley shows that there is clearly a drainage area above. The road to Tuolumne Meadows traverses the headwaters of Yosemite Creek, and there is a small campground on the creek several miles upstream from the falls.

Yosemite Falls is a familiar sight, but it never once has looked the same to me. Every visit has been different, and last week it was spectacular!

What Those Irresistible Numbers Looked Like in the Real World...

I really wonder what the consulting geologist told them about the history of the Merced River here? That's a pretty big resort complex on the western border of Yosemite National Park. They have lots of river view rooms, but still, that berm doesn't seem like the most secure defense against the major floods that are sure to come. But then, I'm not a consulting geologist...

I took a trip up Highway 140 along the Merced River to take in the highest runoff of the season (the irresistible numbers that caused me to hit the road). The flow spent two days at record levels for early June, at about 7,000 cubic feet per second (normal is about 2,000 cfs). I comment on the placement of the resort because during the flood of 1997 (admittedly a 200-300 year flood), river discharge at this location was more on the order of 24,000-25,000 cfs, and the highway was inundated in places, and literally removed in others.

It was a wonderful day for exploring...the grass was turning brown, but many slopes were still covered with blooming wildflowers (lots of pink and blue, the poppies are gone now), and the roar of the river was invigorating. As we approached the boundary of Yosemite National Park (below), the first of the ephemeral spring waterfalls started appearing.

We kept getting distracted by the sights and didn't arrive in Yosemite Valley until the early afternoon, but we kept busy through the sundown and twilight. Many pictures are coming; below is a preview of what we saw of the Merced River in Yosemite Valley...the reflection of the sunset on a flooded meadow at the Swinging Bridge picnic area. The water was all the way up to the base of the bridge, and a ranger on patrol mentioned that about midnight, the flood surge actually covered the top of the bridge.

Needless to say, it was closed, but there is always someone ready to jump over the barriers..