Showing posts with label debris flow. Show all posts
Showing posts with label debris flow. Show all posts

Saturday, October 5, 2019

Travels in Cascadia: Howe Sound and the Challenge of Living in Vertical Places, Part 1

We didn't fly over it, so I've clearly needed to borrow this image from Google Earth.

We have (slowly) been reviewing our geological exploration of British Columbia back in July, and when I last posted we had reached Howe Sound, the southernmost fjord on the west coast of North America. We arrived by ferry at Horseshoe Bay (from Vancouver Island), and then spent two days exploring the museums and parks of the city of Vancouver. But now we were headed into the interior, and needed to follow Highway 99 along the south side of Howe Sound.

Howe Sound is, as noted earlier, the southernmost fjord in western North America. A fjord is a glacially carved bay, and as such has nearly vertical rock walls sloping down to the waters of the bay. This kind of topography entails serious engineering difficulties for anyone who wants to live in, travel through, or mine in the fjord. Prior to the 1960s, the only form of transportation to the inlet of the bay at Squamish was by water. A railroad was completed between Squamish and Vancouver in 1956 (after a delay of something like 40 years), and the first iteration of Highway 99 was carved out of the walls of the sound between 1958 and 1969. When Vancouver was selected as the site of the 2010 Winter Olympics, the highway was widened to four lanes to provide access to Olympic venues in the Whistler area.

The development of transportation corridors led to the development of a few small towns and villages along the route. And that caused problems in this steep countryside. We stopped in the little village of Lions Bay to have a look at a perilous situation.
The dangers of the steep mountain slopes are clear. In 1915 and 1921 a short distance to the east at the Britannia Mine and Britannia Beach, mudflows killed nearly a hundred people. The community at Lions Bay faced the same danger, and in 1981 a debris flow took out highway bridges, leading to several fatal accidents. In 1983, boulders and mud roared down Harvey Creek, destroying a number of buildings and killing two people.
Thus it was that we were looking at a strangely shaped Harvey Creek as it appears today. The channel is lined with boulders, but they are cemented in place. Upstream, a dam is visible, but the dam has holes at the base, and is not capable of holding back water. It's not designed to store water at all, but to stop the forward movement of debris flows coming down Harvey Creek.
In our next post, we'll have a look at the Britannia Mine, the largest (and perhaps steepest) copper mine in western Canada.

For more details about the geology of the Sea to Sky Highway and the engineering challenges, check out: http://quimpergeology.org/wp-content/uploads/2018/03/Sea2Skytour.pdf

Friday, September 13, 2013

Into the Great Unknown: Zero Hour at Lava Falls Rapid

I was going to title this post about our trip into the Great Unknown "Courage, Redemption, and the Triumph of the Human Spirit at Lava Falls: Geotripper Rides the Big Rapid", but I knew my fellow travelers would all yell "Bullschist" in four-part harmony like the townspeople in Blazing Saddles. So we'll settle with what I put up up above for a title.

Still, the oarsmen have a saying: "You don't f*ck around with four rapids in the Grand Canyon, Hance, Horn (or Granite? I don't always listen well), Crystal, and Lava Falls". And they were right. I took a long and harrowing swim in Crystal Rapid several days earlier, and I wasn't anxious to do such a thing again. For several days now, the oarsmen in our group had been talking about Lava Falls, and now having passed the massive volcanic plug of Vulcan's Anvil, we were at the top of the worst rapid on the Colorado River, and one of the toughest rapids in North America. It is rated at Class 10 out of 10 on the river runners scale.

Really, how many rapids rate a 90 page geological analysis? You can see it right here: http://pubs.usgs.gov/pp/1591/report.pdf .

A quote from the ever-staid and formal geological investigators:

Lava Falls, at river mile 179.4 on the Colorado River in Grand Canyon, is one of the most
difficult navigable rapids in the continental United States and is the standard against which all rapids in Grand Canyon National Park are judged for navigability.


I had been thinking about Lava Falls a lot over the last couple of days, and after my dunking in Crystal Rapid, I was pretty sure I would elect to walk around the rapid. Looking at my journal, I see that I even said so twice in the days leading up to our arrival. Still, I told myself that I would take a look and consider it.
Two very strange things happened to me when I climbed up to the scouting ledge at the top of the rapid. First, I didn't panic. It made a difference actually seeing the rapid, in contrast to thinking and pondering on the idea of a monster rapid. Somehow the analytical part of my mind was looking at the rapid and picking out the possible route through the pinball arrangement of holes, rocks and ledges, and it managed to suppress the urge of the other part of my brain to run down the talus slope and await the arrival of the broken boats and injured bodies of my comrades at the base of the rapids. I even managed to see the route we needed to follow through the rapid (confirmed a moment later as I listened in on the discussion taking place between the oarsmen).  Where would you go, looking at the picture above? Take a guess, and then look at the photo below...

The second very strange thing that happened was that I experienced a Hitchcockian case of vertigo every time I looked at the rapid. The whole scene swam in front of me whenever I looked at the waves. I've never had vertigo in my life, and didn't even know what to call it at the time, but I would look away to the cliffs above, and no problem. I'd look at the river again, and it would start wavering and swimming in front of me. As best as I can figure, the reptilian core of my brain was desperately trying to overcome the analytical part of my brain and toss it into the river so I would do the safe thing and walk around the rapid.
Why is Lava Falls such a treacherous rapid?

All the rapids on the Colorado River in the Grand Canyon exist because of debris flows. These floods of giant boulders and mud emerge from the tributary canyons and pile into the river, pushing the flow into a narrow channel on one side or the other. The river has to speed up as it passes through the constriction, and it drops anywhere from a few feet to as many as 30. The severity of the rapid is determined by the length of the rapid, the drop, and the arrangement of large boulders along the way. The level of the Colorado River is also an important consideration. Some rapids are better if the flow is higher. Others are better at low flows.

Lava Falls formed because of debris flows that emerged from nearby Prospect Canyon. During intense cloudbursts, water pours down the cliffs of the Supai Group and overlying Permian formations, and drops over a 1,000 foot cliff of Redwall Limestone. The waterfall hits the slope debris at the base of the cliff, and forms the debris flow via what the researchers call the "firehose effect". The deposits along the river record a great many flooding events over the last 3,000 years. One of the prehistoric events dammed the river to a depth of nearly 100 feet. The rapid formed by that event would have dwarfed the present-day Lava Falls. More recent debris flows altered the rapid in 1939, 1954, 1955, 1963, 1966, and 1995. The 1939 event was the largest historical debris flow in the modern history of the Grand Canyon, larger even than the 1966 event that turned Crystal Rapid into such a monster. The flow was estimated at 35,000 cubic feet per second. That would be considered a high flow on the main Colorado River. The pile of debris constricted the river to only 20% of its normal width for a time (about 50% today). Lava Falls had become a monster rapid.

Lava Falls Rapid has a gigantic ledge at the top that forms a huge standing wave that can trap a small raft for hours. Routes can be possible on both the right side and left, but the left side has large boulders that can trap boats near the base of the rapids. High flows can diminish the danger. Most runs occur on the right, but there is another huge hole and standing wave that must be avoided on the far right side. Boats have to punch through the huge V wave, avoid the huge boulder called the Cheese Grater, and then navigate past two other gigantic waves, the Kahunas. It's the worst rapid, but short. The whole ride lasts less than 20 seconds if done right. Done wrong, and you'll be pitched into the water for a wild ride, or caught on a boulder for hours (see an interesting story about one such trapped boat right here).
Let's see what a good run through Lava Falls looks like. Ron was one of the most unflappable oarsmen I've ever seen, and here he can be seen taking Lisa and my nephew Samuel through Lava Falls. He catches the right side of the ledge above...
They punch through the V wave...
They nearly get swamped by the gigantic Kahuna Waves while simultaneously avoiding the Cheese Grater on the right...
And they make it through, wet but unscathed!
My brother Mark and his wife Carol are guided through by their oarsman Gerrish, and even though their boat was oriented almost 90 degrees, they made it through too. 
Mark took a GoPro cam so you can watch the ride from his point of view right here:

Meanwhile, I was still up on the scout rock watching my brother's family running the rapids. The moment of truth had come and someone behind me asked if I was going to ride the rapid. A disembodied voice quite separate from my conscious mind said "yes". I wasn't sure who spoke, but since everyone was looking at me, I guess it had been me. I don't know what I was thinking... I pulled Pete, on whose boat I was riding, off to the side and said to him "I need an honest answer...is it better if I'm in the boat (extra weight, lots of it), or not?" He said he needed the weight to help punch through the waves, so I was going.

We got in the boat, and this time the camera and the journal were stowed as tightly and securely as possible. I wasn't going to lose a second camera, and the loss of my journal would have been devastating. I hunkered down in the front of the raft and we pushed off.

A story of redemption and courage would end with a victorious run through the rapid, and a confirmation that it is always better to bravely face your fears. Always get back on the horse after you are thrown. Jump back into the battle after your nose has been bloodied. The story ends with an affirmation of the human spirit, and a slow motion montage of arms thrown in the air in victory. That's how the movie script would end. Here's what actually happened, courtesy of Bruce Burger who was shooting our ride from the scouting rock (his effort to get the movie posted is greatly appreciated!):

Yup, we flipped on the V wave. Personally I don't think anything was wrong with our approach. Our boat was just too short and too lightly loaded, and we simply caught the edge of an unlucky wave. In any case, I was in the water again. It was a shock, but it was far less terrifying this time around. I bobbed up quickly and the boat was right there. I grabbed on, and once again I realized I was in front and headed towards being crushed against the Cheese Grater. I quickly shifted to the side of the boat, but the current shifted left, so we missed the big rock. We rode out the two Kahuna Waves and the river quickly settled down. I was in calm water within a minute or less.

I found out that Pete had a worse time of it, because he got trapped under the boat briefly, and tumbled head over heels in the dark water. That had to be a horrific ten seconds (and seriously, they would have been the longest ten seconds of anyone's life), but by the time I was able to check behind me he was swimming too.

Once again, Barry and Bev came to the rescue, and since I had only been in the water for two minutes or so (and being a hundred miles downstream the water was not quite as cold as before), I was able to help climb onto their boat, and I was even able to be an active participant in catching our overturned raft. We got the boat flipped back, and the only losses were my rowing gloves and my hat (I had a spare). The camera was safe, and a few moments later I snapped a self-portrait of the not quite drowned river rat.
And that was that. We had survived the greatest rapid on the river. It's hard to say if I should have walked. I feel good about facing the challenge and being part of the team, but I also just a bit more nervous every time a medium to large rapid loomed. But for the rest of the trip there were only a few, and I ended up with a neat story to tell.

We headed down the canyon to our camp at Middle Chevron. It was situated beneath an immense cliff of basaltic lava that would be a dominant feature of the canyon for much of the remainder of our journey. We had a delightful meal of chili and cornbread with cheesecake for dessert. I laid down to sleep and watched lightning flicker in the eastern skies. The stars blazed overhead, and soon I was asleep. The trip was now "post-lava-falls". I slept soundly.

Thursday, September 12, 2013

Into the Great Unknown: "Disaster" in National Canyon and the Volcanoes of Grand Canyon


Yeah, I was not feeling all that comfortable. It was day 13 on our journey into the Great Unknown, the Colorado River through the Grand Canyon. Day 13, and Lava Falls Rapid, the worst rated rapid on the river was...13 miles downstream. And I didn't know it yet, but we would arrive there at 13:00 hours. I'm not at all superstitious, but it was nice when the message written in the sands of time on the river shore appeared. Okay, I put it there myself, but I was apprehensive just the same!
We were camped at the mouth of National Canyon, which for many years was one of the larger and more popular campsites on the river. And then in the summer of 2012 it was hit by an apocalyptic flash flood that just about wiped the camp out of existence.
It's hard to imagine the scale of the flood. Estimates put the flow at 15,000 cubic feet per second. To put that into perspective, the flow of the entire Colorado River for most of our journey was around 8,000 to 12,000 cfs. And the flood was witnessed. A Western Rivers Expedition boat was passing by, and captured the flood entering the Colorado. Check out the video below by Joe Clark, one of the river guides:

Our campsite was rocky, but we found places to sleep. The rocky plain was barren of plant life. There is hope that a few artificial floods may ultimately deposit more sand on top of the bouldery deposits, but I wonder if the Bureau of Reclamation will be doing any artificial floods in light of the ongoing drought.
In any case, the experienced members of our crew were curious about how much the canyon above the river had been changed by the flooding. To me, the canyon was a beautiful place, regardless of how it might have once looked. How could I know any difference?
I could see that eroded ledges of Muav Limestone had indeed been buried in debris, and barely a single plant was visible along the course of the creek, despite the presence of a clear babbling stream. The going was tough in a few places. Boulders choked the channel.
The barren nature of the canyon was almost disturbing. It felt like there should be plants growing along the water. It drove home the point that no matter what ever else may happen, the rocks remain. Battered, broken, or polished smooth, they will last as everything else passes. But the rocks were also very beautiful, though, and the narrows spectacular. It occurred to me that this canyon, were it to be anywhere else in the country would be a national park or monument in its own right. Here, it was simply a tributary to the larger river, one of many.
The sun was high, and it was getting hot. We got onto the river and rowed downstream. We had reached a fairly long stretch with no major rapids, and lots of quiet passages through vertical canyon walls of Paleozoic sediments. In places we could see all the way to the canyon rim four or five thousand feet above us. The rim, and the world beyond, seemed remote and very far away.
I did a double take at Mile 176. Thousands of years ago massive landslide had broken away from the Supai cliffs out of sight above, and had come thundering over the Redwall Limestone, coming to rest near the river. It is called the Red Slide.
Over time erosion began to tear away at the debris-covered slopes, but here and there a large boulder protected the underlying soft material. The boulders were left standing on spires called hoodoos. It was yet another strange sight along the river.

I was on the lookout, because for the first time we would be seeing a new rock unit (the last "new" rock unit had been 100 miles upstream). It is not a familiar rock to the vast majority of visitors to the Grand Canyon, and in fact, most people are surprised to find out that such rocks are present in the national park: there are volcanoes and lava flows!
I looked high on the walls, and there was the first one, a fragment of black basalt clinging to the cliff. It was an exciting moment for me, because I've never seen these rocks before. I will deal with the profound effects of the lava flows in one of the next posts.
There were more signs of volcanism along the river where a sill had intruded into the Muav Limestone. It was one of the finer examples I've ever been able to photograph.
Soon we could see the source of some of the lava flows, a cinder cone on the high canyon rim called Vulcan's Throne.
We could also see the long tongue of lava from Vulcan's Throne that had reached the river. John Wesley Powell's description remains one of his most poetic writings:

Just over the fall a cinder cone, or extinct volcano, stands on the very brink of the canyon. What a conflict of water and fire there must have been here! Just imagine a river of molten rock running down into a river of melted snow. What seething and boiling of the waters; what clouds of steam rolled into the heavens!
And then, one of the strangest sights of all. A huge mass of congealed lava stuck right in the middle of the river. It was a plug of lava that filled the vent of one of the cinder cones. Called Vulcan's Anvil, it seemed like a message or a warning to river travelers, which indeed it is.
When we passed the anvil, we know we had less than a mile to one of the biggest challenges on the river: Lava Falls Rapid. The moment of truth had arrived...
The Anvil receded into the distance, and we prepared to scout the wildest rapid on a wild river.

Saturday, August 24, 2013

Into the Great Unknown: We Interrupt This Scenery For a Very Recent Flash Flood and a Biological Disaster

After our fourth day on the Colorado River, we pulled into camp at Little Nankoweap Creek. The camp was in a beautiful location (as nearly all of our camps were), but as I selected a campsite, my attention was captured by an oddity. There was a huge splash of reddish brown mud laid across the sandy campsite like the edge of a lava flow. What was going on?
I realized I was looking at some of the very real results of the monsoon storms of the last five days. While Page was getting pounded and nearby Antelope Canyon getting flooded (events we didn't hear about until much later), numerous tributary canyons to the Colorado River were also being flooded. We were the first to see what happened at Little Nankoweap, as there were no footprints anywhere on the new flood deposits. It was no disaster in the big picture of things, but it was a marvelous small scale example of how the Grand Canyon got grand.

Flash floods and debris flows are the tools that erosion uses to deepen tributary canyons and widen the big canyon as a whole. Rock falls and avalanches choke the bottoms of gulches, and every decade or two a cloudburst sends torrents of water down the creeks, forming a slurry mix of mud and rock capable of transporting gigantic boulders. These masses of boulders get dumped in the Colorado and end up blocking parts of the channel, forming the characteristic pools and rapids. The spring floods that once surged through the big canyon would ferry the boulders downstream or grind them into sand and silt, and in this way, the Grand Canyon took shape.
 I had to take a closer look, knowing that the small mud deposit in camp was simply an overflow from the main channel. At the height of the storm, the mud was flowing over a wide area. The main channel (below) was being scoured, and rocky debris was flowing into the Colorado.
In the aftermath, a small rocky delta had formed, and the course of the river slightly changed. This particular event would soon be erased by the normal flow of the Colorado, as it was composed mostly of easily moved pebbles. I imagined the same event magnified several times, as in a once-in-a-century storm, and could see in my mind gigantic boulders changing the river on a larger scale. One of these events happened in 1966 at Crystal Rapids, turning a former riffle into the most terrifying rapid on the river (aside from Lava Falls).
We explored the channel for some distance, and found the Nankoweap Trail where it crossed the streambed. It wasn't there anymore.
The rocky steps the trail utilized to climb out of the channel had been removed by the flood (the trail is a bit left of center in the picture below).

We headed back to camp for a delicious meal of fish tacos, and hit the sack.
In the morning, I was covered with bugs. Or more properly, bug larvae. There were hundreds of them on my tarp. They were crawling all over the tamarisk tree I had camped under, and wriggling in the sand at my feet. I asked what they were, and our trip botanist pointed out that they were tamarisk beetles, and I immediately understood what was going on.

Tamarisk trees (also called salt cedar) are found all over the American southwest along river courses, but they aren't a native species. They come out of Eurasia, and having no natural enemies in their American environments, they have proliferated to the detriment of practically all competing species. They concentrate salt on their leaves which ends up in the soil, preventing the growth of other plants. They tend to form impenetrable thickets on river floodplains. They don't offer much in the way of food or shelter to most native species, and with deep taproots, they tend to transpirate vast amounts of precious groundwater into the atmosphere (some estimates put the water loss at 2 to 4.5 million acre feet per year across the southwest, enough to meet the needs of 20 million people, or to irrigate 1,000,000 acres). Some desert rivers stopped flowing on the surface after being invaded by the tree.
What's worse is that they are hard to kill. Cut them down and the taproot sprouts vigorously. Apply herbicides and many times they will sprout again anyway. A single plant might produce 500,000 seeds a year, and they can travel down the river, sprouting as they come to rest in wet sand.

I had noticed when we left Lee's Ferry that some of the tamarisks were looking a bit yellow (below), but didn't give much thought to it. It turns out that the Tamarisk Beetle loves tamarisk leaves and nothing else. After years of testing, the (also non-native) beetles were released into the wild, and they began an effective campaign of slowing the growth and spread of the tamarisk in the wild. And unlike some other such experiments, the bugs didn't start eating other native species. It is a reasonable hope that the bugs might one day lead to control (but probably never eradication) of the tree.
The trees actually provide some welcome shade in many of the river camps, but so would willows, cottonwoods, and mesquite trees if they weren't getting crowded out.
On the way back to camp, I spied an orange-breasted bird in the catsclaw acacia. I snapped a picture, and thought it might be a nice way to end a post that might seem a little depressing. But then...
 ...a rather majestic buck wandered through the edge of camp. So I will end with him instead.
In the next post, I get to see one of the incredible iconic sights of a Colorado River trip.