Landslides and Slope Mitigation in California's Great Valley...Wait...What?

 

I used to talk to my students about the geological hazards that we face as inhabitants of California's Great Valley (or Central Valley, for those who don't appreciate its actual greatness). I would go down the list of things to worry about: earthquakes, droughts, wildfires, volcanic eruptions, flooding, and so on. But then I somewhat jokingly described things we didn't have to worry about such as hurricanes (Florida's problem), tsunamis (a problem for coastal cities), tornadoes (Oklahoma's problem), and mass wasting (also known by the generic term 'landsliding').

Unfortunately, over the years I've become aware that some of those unlikely hazards actually can be a factor in living in the valley. We've had a fair number of tornadoes in recent years, including two that came within a few miles of my house (they weren't anything like the monsters of Tornado Alley in the Midwest, but still a bit scary). A powerful tropical storm hit Southern California last summer that came up just short of being a hurricane, and the heavy downpours were statewide. And then there is mass wasting (slope failures and landslides). I know of at least two fatalities caused by mass wasting in the last few years. One was a homeless person who had dug a tunnel into a river embankment that later collapsed, and another was a person who was driving along a freeway in heavy rains when the freeway embankment collapsed as a mudflow and spread across the lanes causing a fatal accident.

The Great Valley is famously flat so mass wasting doesn't seem to be much of a danger to those who live here, since landslides and other slope failures require, well, a slope to happen. But the valley is not quite so flat as people may think. The valley is 400 miles long, and most of it is close to sea level. Much of it is low-lying river floodplains, but other sections sit at slightly higher elevations because of complex history of climate change and glacial ice ages over the last 1,000,000 years. These bluffs and terraces protect my city and others nearby because even the worst floods are contained within the floodplains and do not spill over onto the terrace surfaces where cities like Modesto and Turlock have been built near the Tuolumne River.

During the ice ages glaciers never reached the valley floor, but meltwater from the Sierra Nevada glaciers swelled the rivers to several times their average flow, and they carried tremendous amounts of muddy sediment that spread widely across the valley floor building up alluvial fans. When the glaciers receded, the rivers flowed less, but carried clear water that was more capable of eroding the soft sediments of the alluvial fans, forming channels and floodplains several tens of feet deep. Once these channels developed, floods never covered the terraces again. It's the bluffs that form the boundaries of these terraces that provide the conditions that can result in slope failure.

The heavy rains of 2022-23 led to widespread flooding across many parts of California including some real problems on the Tuolumne River Parkway Trail when I regularly go birdwatching. I wrote about these in January of 2023 in the aftermath of one of the biggest storms. The most serious problem was the access road to our town's water treatment plant. It's on the river floodplain about 60 feet below the river terrace. Slumping had caused major cracks to form in and near the pavement.

Eventually the rains subsided and the soil dried up. The slide seemed to stabilize, but the threat to the roadway remained and would eventually have to be dealt with. That is what was new this week: the cranes and were in place to start the slope mitigation process.

The main problem is that the access road traverses unstable debris and soil that slumped in the 2023 event. They would need to re-engineer the slope by rebuilding it from scratch. Their strategy was complicated by the fact that all the equipment and materials had to traverse the very road they were trying to repair. Truckloads of heavy boulders were going down the road every few minutes. Meanwhile a huge long-reach excavator was digging away at the slope below the road!

After digging away and smoothing off the slope they covered it with felt matting and then started piling many tons of boulders on the slope. The boulders are intended to buttress the slope and hopefully keep it stable during future weather events.

It's a lot of work being done to keep a single paved road open, but it's a pretty important road since it provides the only access to the water-treatment plant for the city of Waterford. And thus we are dealing with slope mitigation in what is supposedly the flattest place in the country!

You Can See Yosemite Valley from the Tuolumne River! In a Manner of Speaking...

Those of you who know the layout of Yosemite National Park will also know that the title of today's post must come with some kind of caveat because any hiker or cartographer knows that the Tuolumne River in Yosemite National Park flows through a vast gorge the depth of the Grand Canyon (it's even called the Grand Canyon of the Tuolumne River). You just can't see the one valley from the other.

But...the Tuolumne River also flows across the flat plains of the Great Valley of California, and if we count "Yosemite Valley" as being also some of the significant peaks and cliffs that ring Yosemite Valley like Half Dome, El Capitan, and Sentinel Dome, you can in fact see the valley from the Tuolumne River.

This is not one of my occasional posts about the better-known spot for viewing Half Dome from Hall and Keyes Roads near Turlock. I get in enough internet trouble over that one, but it is indeed possible to see the very top of Half Dome and El Capitan from my daily walking trail along the Tuolumne River in Waterford. But the additional caveat is that it has to be a really clear day, and we have precious few of those over the course of year. Sometimes weeks can pass between sightings of any mountains at all. But following our huge storm this week, the air was crystal clear today.

The additional caveat is that you need binoculars or a good zoom lens to see the domes and cliffs. With the naked eye, the mountains are difficult to distinguish from one another. But on those rare clear days, and with the right equipment, and knowing where to look, you can indeed see some of Yosemite Valley's most famous landmarks. In a way of course it is frustrating. I'd rather be there than here, but chances will start increasing as the pandemic finally begins to subside.

If you are wondering about the cranes in the foreground, our 1964 vintage bridge is being replaced by a safer, wider bridge. The anchoring columns of the present bridge are unstable during floods; all bridges are perfectly safe, the engineers say, right up until they are not.

In any case, if you couldn't make out the various domes and cliffs and peaks in the opening picture, they are labeled below. 

If you live in the Central Valley (we call it the Great Valley) and wonder if you can see any particular Sierra peaks, check out caltopo.com and find the dropdown command for "simulated view". You can adjust the map for a view from anywhere covered by the program. Below is an example of the view I used to label the peaks shown in this post.

When Treasures are Discovered, for Better or Worse: A Tale of Two Tuolumne Rivers

Today on "my" river.

It looks like I'm about to complain bitterly, but it is more nuanced than that.

The river is not mine of course, I just inhabit it almost every day. It belongs to our community. But there has never been a day like this. The parking lot has 85 spaces, and including street parking there were 100 cars parked there today (I've never seen more than 20 or so). With the nearby state parks and recreation areas closed, this was a free spot to gain access to the river, but they had to "earn" it by going down and then back up a 135-step stairway (close to  a 100-foot climb). Then they had to climb down an embankment to get to the rocky river shore, carrying the canopies, bbqs, and ice chests. But it looks like the family groups were spread out. And nobody seemed to be blocking the stairwell by exercising (that was BIG issue yesterday; total lack of physical distancing with 30 junior high kids). So all good.

But I'm really worried about how this is all going to look tomorrow (or Tuesday; I'm not going down there until they're all gone). Ever since the shutdown, the garbage on the trail has increased radically. It's bad enough that some of the trail regulars are carrying trash bags and picker-uppers when they hike.

I'm glad people are discovering the treasure that flows through their community, but I wish they also had a sense of ownership and a desire to take care of it and keep it clean and beautiful. The Tuolumne is a special river.

Photo by Mrs. Geotripper

So what was I doing on this hot, but beautiful day? I'm not going to take chances during a pandemic with so many careless people, so Mrs. Geotripper and I headed upstream to a couple of other spots that are less "discovered". We had a pleasant walk up a dirt road that we had to ourselves along the Tuolumne. It was lonely, beautiful...and quiet.

Photo by Mrs. Geotripper

 There are treasures somewhere near you. Seek them out!

A Tuolumne River Mystery for the Fish Experts

Paging my fish expert friends...what are these fish? I realize the pictures aren't great, since they were across the river from me and I couldn't get much of an angle on them. They were rather big, between 1 to 2 feet long, I'm guessing.

I cannot even pretend to be any kind of an expert on the fish of the Tuolumne River, but I can't help but wonder if these are Chinook Salmon. They were bunched up on the far shoreline, and seemed to be competing for space among the pebbles and rocks in the shallow water. There was a lot of splashing and chasing.

But the thing is, there apparently hasn't been a springtime salmon run in a long time around these parts. But I did find an intriguing statement on a NOAA website: "Recently, ‘spring-running’ Chinook salmon have been observed in the Stanislaus and Tuolumne rivers. Some scientists believe this means a very small population of self-sustaining (i.e., capable of reproducing without hatchery influence) CV spring-run Chinook salmon may exist in the Stanislaus and Tuolumne rivers". So I am curious...I would be so thrilled to know that salmon might be back on the river.

I know I'm expressing my ignorance, so someone please gently correct me and identify these fish if you can! I appreciate the assistance.

A Bit of Drama on the Tuolumne River...

Every visit to the wilds holds the possibility of the unexpected surprise. There is the "usual" sense of discovery when one finds a new bird species, or some otters playing in the water, and then there is the just plain weird. I don't see snakes very often, as there are a fair number of people on the trail and the snakes wisely stay out of sight. In fact, the only snake I'd ever seen before today was dead.

But today was something. I was on a low bluff over the river gravels, and I happened to look down to see what looked like a huge snake (of course every snake looks really big at first). I realized it was a California Kingsnake (corrections welcome), and it was big, maybe three feet, but not huge. I got the camera out and got a few shots before it disappeared into the brush.

But then the weird part: it was being followed by a California Quail. I couldn't tell if it was chasing or harassing the snake or carefully monitoring the snake. I have to think that in some way it had to do with the defense of a nest, but I have no real basis for the speculation. Maybe it was just curious...

Can You Find the Nest? A Near-future Killdeer Family on the Tuolumne River

The Killdeer (Charadrius vociferous) is a sneaky little bird that hides in plain sight. That sounds like some kind of negative judgment, but really I admire these little Plovers. I wonder sometimes how the species survives, given their habit of building nests right out in the open on stony ground, within easy reach of all manner of predators. And yet somehow they persist.

We watched a nest last year at the Great Valley Museum's Outdoor Nature Lab. This year, the Killdeer nest I "found" is along the Tuolumne River Parkway Trail, but not so much on the trail as on the grounds of the Waterford water treatment plant. They have gravel roads around the aeration ponds, and that's where the Killdeer put its nest. Luckily a city worker noticed and put up a traffic cone to protect the nest from being run over.

If a threat presents itself, the Killdeer will make a lot of distracting noises and actions. The Killdeer are famous for their broken-wing act by which they draw a predator away from the nest. And as you can see from the picture above, the eggs themselves are well-protected by camouflaged coloration.

I found myself wondering how the eggs avoid being fried by the sun in their rocky nest out in the open, but if you look at mama Killdeer watching her nest, you'll notice she is shading her eggs, not sitting on them.

I missed the hatching last year, but if the stars align I might get to see the babies this year, seeing as how my summer field classes got cancelled, and we are still on a shelter-in-place order. We'll see.

A final note...if you are wondering if I was invading the personal space of the bird in this picture, I was actually on a bluff around a hundred yards away. I love the zoom lens on my camera!

Nature, Red in Tooth and Claw, and the Defense Tonight on the Tuolumne River

Nature is wondrous, serene, and spiritually uplifting. And then all of the sudden the "circle of life" thing happens, and we are reminded that nature is also "red in tooth and claw". I've seen some dead animals along the trail of late, some natural, some murdered by humans. It's a jarring reminder that life is hard and often scary, especially for those who occupy the lower parts of the food chain. But sometimes the little ones do okay. Evolution is a competition. When predators evolve new ways of capturing and killing prey, the species who survive are the ones who have evolved new defenses.

And what a defense this little one has! I was wandering as I often do along the Tuolumne River, taking in the beautiful sunset, and feeling peaceful. But the olfactory peace did not last. The last quarter mile of my walk was accompanied by a distinctly terrible odor, the unmistakable scent of a Striped Skunk (Mephitis mephitis). The odor was somewhat diffuse, so it wasn't entirely awful, but I didn't actually expect to run across the individual responsible for the affront.

I saw movement up on the cliff, and realized that the creature was not one of the many feral cats that live along the trail. The skunk was moving along the rim of the canyon where the creature probably accesses a lot of pet food from the yards beyond. I warned my friends on the bluff about their potential problem, and appreciated the first chance to photograph (however poorly) an interesting (and smelly) new species on my daily trail.

The Week's Next Surprise: River Otters on the Tuolumne

It's not like I haven't seen them before. I see River Otters once every few months on the Tuolumne River adjacent to the trail I follow on most free mornings. But until this week, I've never caught any getting out of the river. They've always been swimming. But this morning a pair of otters were searching and playing along the river just downstream of the trailhead. I sat and watched them swim for awhile and then they climbed up on the branches of the river thickets.

I tried a couple of videos, but only one came out well. It's a little bit shaky because I was at total zoom, around 60x, but they came out pretty clear. It's been a week of little nature surprises, with foxes and rare birds and the like. Otters always give me a reason to smile a bit in the midst of lots of challenges.

The Day I Found I Could See Half Dome and El Capitan From Near My House And Why it Was So Hard To Do So

Can you pick out Half Dome in the picture above? It's not easy...

Anyone who follows my other blog (Geotripper's California Birds) knows that I walk the Tuolumne Parkway Trail just about every time I have a free morning, watching for birds and getting exercise. Unfortunately, given the air quality of the Great Valley where I live, I cannot see the source of the Tuolumne River, even though the mountain crest is only 40 miles or so away. But once in awhile a storm blows through, and I am reminded again that I live next to one of the world's great mountain ranges. That happened this week as our first major storms of the season passed through, dropping more than three inches of rain locally, and several feet of snow on the very dry mountains above. The Tuolumne Parkway Trail climbs to the top of the bluff above the river to pass around the water treatment plant, and provides a nice view of the Sierra Nevada crest. I was impressed enough to snap some pictures. 

Later on, while looking at the pictures, I saw what looked like a familiar ridge-top. I consulted with Cal Topo, and by golly, I was right. I had captured a picture of Half Dome, and El Capitan right in front of it! It's not an obvious view, and you would need binoculars or a telescope to see it (or the zoom on my camera), but it's there. I had never noticed it before from this vantage point because both rocks get swallowed up in the rocky ridges behind (the peaks behind Half Dome are half a mile higher in elevation). The snow from two days earlier helped to highlight the summits of both Half Dome and El Capitan. The view of Half Dome from the valley floor is more obvious from other angles, even though the concept that it can be seen at all has been contentious at times...

Can you see it in the picture above? It's a challenge. Give it a shot and then consult the CalTopo wireframe below to see the identity of the peaks in the picture...

Zooming in and centering the two rocks makes them just a small bit more obvious, but it is still hard to see, given that we are only seeing the topmost parts of both Half Dome and El Capitan

Zooming in even more, the summit of Half Dome is even more obvious.

I've annotated the photo to help out a little...

They are from much closer and from a different angle, but the webcams in Yosemite Valley provide an idea on the snow pattern on Half Dome on the day I saw it from the Central Valley.

If you have a small bit of a wild place somewhere near where you live, visit as often as you can. You never know when a new discovery or surprise will be waiting. This week alone, I saw a beautiful Gray Fox in the wild corner of my campus, and a wildly out of place bird a few feet from where I took the pictures of Half Dome.

It's a River Again! Winter on the Tuolumne

All the pictures in this post are from the Tuolumne River Parkway Trail in Waterford.

All in all, it's been a good year (so far). One can judge the quality of a year on the basis of many things, and in this instance I'm talking about water. So much of the time, my part of California is at an extreme in one direction or another. Last year it was a drought up until some late storms in March that salvaged the water year. The year previous was one of floods and threatened floods, unlike anything seen in twenty years, but at least it filled the state's reservoirs after an astounding five-year drought. This year finds us in the sweet spot, kind of in-between, but a bit above average.

The rainy season started a bit slowly, just enough to make one worry a little bit about drought. No storms in September. A single small storm in October. But then in late November the pace picked up with just over 3 inches in my rain gauge, and December added more than 2 inches. The same with January, nearly 3 inches, and now February has already produced 2.5 inches with more storms coming this week. Of course my backyard is not the measure of water conditions in the state. The news reports are full of stories on the incredible snowpack that has built up in the Sierra Nevada in the last few weeks, with single storms producing six feet of snow or more.

The critical Sierra Nevada snowpack sits at between 109% and 135% of normal (measuring from north to south), with a statewide average of 123%. If no more snow fell, our season would end at 84% of normal. It's a comfortable place to be.

But no water planner is ever comfortable. With so much snow in the mountains, the reservoir water masters always have to worry about the possibility of a big atmospheric river storm, the kind that combines the extreme low pressure of an Arctic storm with a stream of extremely humid air out of the tropics. Like the one that could happen this week. In a worst case scenario, such a storm could cause rain at high elevations, melting much of the snowpack and raising the specter of flooding downstream.

And that is why the Tuolumne River came alive this week. For many months, the river has remained at an unnaturally low flow of about 200 cubic feet per second, a minimal amount. There are large reservoirs upstream, especially Hetch Hetchy and Don Pedro, and the operative mode is to save as much water as possible. During the recent storms, inflow to Don Pedro reached as high as 8,000 cubic feet per second, but outflow remained at 200 cfs.

Last week the river was dramatically higher, flowing at 2,000 cubic feet per second. The water masters are clearing out some storage space in Don Pedro in case of a flood emergency. It looks like they intend to go as high as 3,500 cfs in the next few days. Certainly not a flood (it would have to reach 9,000 cubic feet per second for that), but enough to clear the channel of invasive water hyacinth, and enough to make one feel the river is closer to a natural seasonal condition.

It's a nice time of year to walk the Tuolumne.

Fall Finally Arrives, California Style

I would never try to compare our fall season with the hardwood forests of New England and the Appalachians, or even with the aspen groves of Colorado or Utah. But there are a few benefits to experiencing fall here in California.

For one thing, our fall lasts for a couple of months, and our trees are at the height of their color at a time when the trees back east are barren of leaves, and winter-style snows are lashing the landscape. It was 68 degrees out yesterday (though we had a day of light frost last week).

I walked the Tuolumne Parkway Trail this morning after a week on the road, and the changes were pretty obvious. The willows and wild grapes were changing.

There are also some mature cottonwood trees that have been various shades of yellow for weeks now.

But we also have some brilliant colors in the city as well. I had errands in town and took a few shots of the Modesto neighborhoods where Modesto Ash was planted many years ago.

There are other ornamental trees on our west campus that are relatively young, and they turned almost fluorescent over the holiday weekend.

So yes, I would never presume to say our fall show of color can compare to the wild displays back east, but I certainly enjoy having a few weeks to appreciate the changes that are happening here right now.

There is a lot of horror going on right now in so many places. I'll be back to trying to right the wrongs soon, but for a few moments today I took a few breaths of blessedly clean air (the Camp Fire is out, thank heavens) and enjoyed the technicolor show.