Little Dry Creek: The Grand Tour

I've mentioned that I like following waterways from beginning to end. I've finally gotten around to following the neighborhood stream, Little Dry Creek, from it's head near Yosemite and Arapahoe, to it's mouth near Dartmouth. I almost finished early enough to photograph the river end but, alas, it was quite dark when I got there.

I started at the spring behind the Safeway offices. Everything above that is runoff.

My elevation was 5720 feet according to my topographical map. Air temperature was 74.7° F so I was shedding clothes. The stream water was at 3.5° C. It was coming directly from the Dawson formation so it was cold. I'm flip flopping between Fahrenheit and Centigrade because most weather is reported in Fahrenheit but I like to know how far above freezing things are. Water freezes at 0° C.

I tried to get an idea of the flow rate when I took samples for later analysis. I measured approximately average depth and width and tried to clock a piece of balsa wood floating downstream. But the wood wouldn't move. The flow rate at all three sites was "a trickle". I know that the water was moving because it was flowing over the weirs 

The stream here was two inches deep and 12 inches wide.

The Dawson aquifer isn't very productive and having watched the flow rate recorder by the gauge near Arapahoe (It has been nonfunctioning for a couple of months now) and keeping an eye on the spring, it looks like the flow rate responds to rain fall and snow melt almost entirely. 

A network of runoff channels between Yosemite and Alton Way carry Stormwater into Little Dry Creek for and initial boost. The creek shows a good start at valley building.

This view is just west of Yosemite from the spring at the beginning of the Little Dry Creek Greenway. From here on, rocks and weirs (overflow dams) have been added to the bed and shoulders to manage erosion.

Any large rocks in the area are primarily brought in for landscaping and erosion control, so this is not a good area for studying the indigenous bedrock. The top soil is shallow and the underlying material is clayey, weathered bedrock. The bedrock is colluvium, the pulverized material washed out of the Rockies that filled the Denver Basin in recent geologic times 

My second sampling site was between Little Dry Creek Park and Uinta Street. The banks of the stream are steep and there are several slumps where gravity is pulling chunks of the bank into the creek. Closer inspection show these slumps to be saturated with water. They look like seeps, slow moving springs from the underlying Dawson aquifer.

There was a small slump that was just big enough for a foot and a knee. I knelt on that to take a temperature reading and water sample. The temperature was 6.6° C. Trying to stand, I overbalanced and went in head first.

I came out really quickly 

Little Dry Creek is polluted and smells bad. I hoped that the rest of the ten mile hike would give me a chance to dry and air out. On the train back home, no one looked particularly offended so it must have worked.

The water here was 3 degrees warmer than at the spring. I would be tempted to credit that to kinetic energy of flow but it probably had much more to do with the amount of surface area exposed to the sun. The creek was 50 inches wide there. The depth was 14 inches (just enough to totally submerge me and make me actually swim to get out.) Air temperature was down from the spring....68° F., about 7 degrees colder.

This was where I gave up trying to measure the flow rate by throwing chips of balsa into the water. There was flow. Water was trickling over the weir downstream, but the surface was dead calm. There was an active storm sewer dumping into the creek upstream and the aquifer was adding volume at the seeps.

The creek is geologically young but the material under it is clayey debris and crumbly arkose sandstone so it has no problem cutting into it. The whole length has vertical banks from 2 to over 20 feet high, moderate meanders, and a broad valley.

Here's a topographic view of the first quarter of the course of Little Dry Creek from "Highlands Ranch Quadrangle, Colorado, 7.5 minute series." If you're not familiar with topographic maps, the brown lines are elevation contours. The closer they are, the steeper the incline. The v-shaped contours around the creek point upstream.

One advantage of this hike is that it follows a creek that's flowing downhill. There's not a lot of "up".

The third (and last) sampling site is a pretty little cascade just before Spruce Street. It's not "natural". Those granite and gneiss boulders were artistically placed there by Parks and Recreation workers. They did a nice job. A culvert empties an intermittent tributary into Little Dry Creek below where I sampled. (See the blog "Walnut Hills: The Big Hill")

Little Dry Creek was colder here (3.4° C), almost as cold as at the spring. That's interesting since the air was warmer (68.2° F) than at the second site. And I would have expected those rocks to have been soaking up sunlight and transferring the heat to the water.

The stream was 112 inches wide here and 16 inches deep. Of course, the stream dimensions can change but there was no reason for big fluctuations Little Dry Creek is historically pretty consistent, so it's reasonable to compare them from site to site. Within about half a mile, the stream has more than doubled. Runoff isn't large so I'll assume that it's being fed by that aquifer.

Past Quebec, Little Dry Creek flows through an HOA, requiring a detour up to Arapahoe and down to where the stream emerges from under Arapahoe to continue it's journey into Holly Reservoir. The approach is over a series of weirs (the area is always flood conscious) that parallel the road.

There used to be a pedestrian tunnel that passed under Arapahoe beside the creek, but they closed it off before I moved to the area over three years ago. People must have still tried to use it, because the county then covered the approach ramp with crushed granite.

Holly Reservoir (by Holly Road) is home to a recreational center with tennis courts, a swimming pool, and water slide. The creek meanders it's way through the basin and under the dam. In the case of a massive(!) storm, there could be a lake here. I can't find any record of there ever having been such an event but better safe that sorry.

Holly Dam

Little Dry Creek at the outflow of Holly Dam

Just below Holly Dam, Little Dry Creek and Willow Creek merge. Usually the resulting Creek takes the name of the larger stream, but not in this case. Willow Creek is usually larger, has traveled further, and occasionally will create a lake behind Englewood Dam but the creek that flows from this confluence is called Little Dry Creek.

That's Willow coming in from the left.

In this stretch, Little Dry Creek widens out and cuts a fairly deep gorge. There's also a steepening incline.

The Highline Canal leaves the mountains in Watertown Canyon and flows under the influence of gravity for 66 miles (in the past as much as 71 miles) to the Rocky Mountains Arsenal in northeastern Denver. Along the way, it crosses several natural streams, including Little Dry Creek. It does so by following lines of elevation contour. Natural streams generally cross contours at right angles. The crossings present engineering problems.

There are several places where the canal crosses over streams on water bridges called "aqueducts". The photos above show the syphon where the canal crosses under Little Dry Creek. I would have taken a picture from the top except the canal usually doesn't flow during the winter months.

The canal flows into the tunnel from the left (south) and exits a little lower from the right (north). It works pretty much like syphoning gasoline (or any other fluid) from a tank. The starting level is above the outflow level, so the syphon doesn't have to be primed, which is good since the canal is dry for most of the year.

Little Dry Creek is temporary home to many water fowl. Ducks are common but I've seen many others including egrets and herons. They don't usually make themselves at home but they visit often.

After a brief run down between a meander in the Highland canal, the creek takes off through backyards in Cherry Village, so I had to start some road work down Orchard and Long to University Boulevard where I picked it up again near Quincy. From there, it's an urban aqueduct, flowing between concrete walls.

It feeds some private lakes...

and water features in a golf course.

but most of it looks like this for the rest of it's course.

This is South Denver and Englewood with many shopping areas and apartments so flood control is pretty tight. As many tributaries that have joined the creek, I would not be surprised to see it clear its banks (I've never seen it but I wouldn't be surprised.) It doesn't get water directly from the mountains so the main thing that leads to flooding, melting snow pack, isn't that much of an issue.

Concrete culverts don't really draw me, but there are some points of interest here 

This was a surprise to me. I have seen many of the early sites of gold finds...Clear Creek, Montana City, Bear Creek confluence with the South Platte. These are all streams from the mountains. They erode mineralized, crystalline rock. This first significant gold find was from Little Dry Creek, a creek that runs it's entire course through the debris that has been washed from the Rocky Mountains. That means that a pocket of gold must have collected somewhere by an ancient stream, waiting until Little Dry Creek found it and washed it down to present day Englewood where it waited for William Green Russell to come along from Georgia to pan it out. Why was he even looking here?

Nearby, the creek runs below ground to travel under the Englewood shopping district.

By the time I got to the other side, it was too dark to finish photographing the last section of Little Dry Creek, but a couple of weeks later I made a supply run to the area and finished the tour.

The tunnel in the background is where Little Dry Creek emerges from underground in Cushing Park. Here at the confluence with a drainage stream from the park, it looks like a rushing mountain stream. It's landscapes....the rocks were placed.... there's no telling where they're from. They're there to prevent erosion of the bank.

A little further down the rocks give way to a concrete channel as the creek passes under the railroads and the CanAm Highway (Santa Fe) on its last approach to the river 

The underpass is decorated by a mural by Boulder muralist and graphic artist Amanda Wolf (2021).

An overlook over the South Platte River gives a good view of the confluence.

You have to cross the river by the nearby footbridge to see the mouth of the creek 

There's a low overflow dam just upstream.

At the river, I checked the elevation again and found it to be 5256 feet. That's an elevation loss of 464 feet. I'm glad it was mostly downhill.

So that's the Little Dry Creek from beginning to end. I'll be saying more about its contents. And I'll show you some rocks I encountered along the tour.

Have you ever followed a creek from beginning to end? Do your homework first and stay safe.

Young Earth

(Keep in mind that my story is woven together from the majority speculation among geologists. There are certainly counter theories floating around. For a good overview of Big History, check out The Teaching Company's lecture series, Big History, presented by David Christian.)

The formation of Earth, around 4.5 billion years ago, bore some resemblance to the formation of the sun. Gravity pulled a lot of stuff together and crushed it, somewhat like a child would form a hard snowball, but there wasn't enough mass to cause the kind of pressures required to start a fusion reaction.

Still, the early Earth was mostly molten, not because of pressure, but because space debris rained down on it and blasted the surface. In fact, soon after the formation of the planet (in geological terms) a huge asteroid hit it and knocked a considerable glob of molten crust out. That became our moon.

There was an atmosphere but, if it contained oxygen, it reacted with everything else until it was all quickly bound up. In that hellscape, there was no life (although life did form much earlier than scientists though a decade ago.) There was no liquid water. It would have quickly boiled off. There were no oceans or continents. Space would have been completely obscured from the surface by dense clouds of methane, ammonia, nitrogen, sulfur, and water vapor. If there was rain, it would have been acid 

The reason we have nowhere near the bombardment now that early Earth sustained, is that we've pretty much swept our orbit clear of major impact bodies.

It took about a billion years for the Earth to cool off enough and to gather the raw materials (water, oxygen, carbon dioxide...probably a little from volcanic venting and a lot from bombardment by icy space debris), to create life. 

Young Earth was not the same planet we have now. The crust has been thoroughly shuffled and reshuffled. The planet has been "terra-formed". It would be impossible to pinpoint a spot that would become Walnut Hill.

By 3.5 billion years, Earth had a magnetic field. Heavy metals, mostly iron and cobalt, but most elements heavier than silicon, sank to the core. The center most part of the core remained solid because of the pressure exerted on it by the surrounding material, but the outer core was (and is) molten. Currents in the molten core created a natural dynamo that produced a magnetic envelope around the planet. That helped to, among other things, hold onto a dense atmosphere. It was a "greenhouse atmosphere" that kept the planet hot and, as water collected on the surface, it didn't melt. There was no ice.

On Young Earth, if you were standing at latitude 39.7392 north and longitude 104.9859 west (the coordinates of present day Denver), you would probably be standing in lava. If you managed to find solid rock to stand on, it would be basalt. The crystalline, granitic rocks, sedimentary and metamorphic rocks you see all around you today didn't exist on Earth then. The air was from volcanic outgassing. There was very little oxygen and a lot of unbreathable stuff like carbon dioxide, methane, ammonia, sulfur dioxide...oxygen is very reactive and doesn't like to hang around in free state. To maintain an oxygen rich atmosphere, oxygen has to be continuously generated. That's why plants are so important to us. The streams I've talked about having been so large in the past didn't exist on Young Earth...there was no liquid water. The sky was colorful and dark.

The surface of Earth was made up of basalt. It's the kind of rock you find on the ocean floor and underlying the continents today.  It's what happens when molten rock is extruded onto the Earth's surface to cool quickly. Oceanic crust, basalt, is heavier than continental rock, and it has more heavy elements like iron, making it dark. In fact, a very important fact for understanding geology is that continental crust floats on denser basaltic crust.

Young Earth went through a period of differentiation. The laws of physics were well established by then... everything worked the same way that it works today. Heavy sinks down through light, so the heavy elements sank down through the lighter elements. Most of the iron and cobalt ended up in the core. Gold, for instance, so important historically to Denver, is one of the rarest elements in the Earth's crust. Here's a chart of the predominance of all the elements in the crust (from Wikipedia, "Abundance of the Chemical Elements"), . Gold is rarer than most of the "rare earth" elements like niobium, yttrium, and tantalum. It's down in the super-rare, yellow area.

(Abundance of the Chemical Elements in Earth's Crust by Gordon B. Hazel, Sara Boore, and Susan Mayfield, from USGS. https://pubs.usgs.gov/fs/2002/fs087-02)

Gold is so rare for two reasons. First, the most common elements are those that make up stars (it's called "stellar nucleogenesis.") Stars produce elements by fusion, starting with hydrogen and deuterium and sticking atoms together to form the lighter elements like carbon, silicon and iron. It stops at iron. Once fusion starts, it can continue as long as the reaction doesn't require the input of energy from the outside. As the atoms created get larger and larger, less energy is created by the reaction. After iron, energy must be fed into the system to continue fusion.

At the end of a large star's life (our sun is much too small), it explodes. The energies produced are spectacular and a supernova is created. That's where gold is produced. The space junk that our solar system was created from was contaminated by the remains of some supernova.

Another factor against the production of gold is that fusion starts by sticking together atoms with even numbers of neutrons and protons in their nuclei, deuterium and helium, so larger atoms with even numbers of particles are favored. The only stable isotope of gold has 79 particles in it's nucleus.

The other reason gold is so rare in the crust is that most of it sank to the core with iron and cobalt. What's in the crust mostly came with later space junk, dust, meteors, and asteroids, and a little made it's way from deep inside the Earth by convection currents and random diffusion.

About a billion years after Earth formed, life appeared...

Olde Town Arvada to Gold Strike Station

Confluence of Clear Creek and Rolston Creek

The very place of the first gold strike in Colorado.

Rolston Creek, Rolston Point (the earlier name of Arvada), Rolston Ridge, Rolston Road, Rolston Crossing, Rolston Station...who is this Rolston guy?

In 1850, Lewis Rolston, a prospector from Georgia stopped by this very place and panned a quarter ounce of gold out of the creek that now bears his name. They left the next morning on their way to California. In 1858, Rolston returned with another group and set up a placer mine at the same site...the first gold strike in Colorado.

Rolston was born in 1804 in South Carolina but later moved to Auraria, Georgia (after which Auraria, Colorado was named and from where many of the settlers of Auraria, Colorado came). He is also sometimes credited with starting the gold rush in Georgia after he collected a shiny rock in what would later be Lumpkin County, Georgia.

He returned east in his later life, served in the Confederate army and probably died in Georgia around 1870.

When the gold played out in Rolston Creek, many of the miners settled down to farm the area.

My trek started, as usual, in Centennial and I boarded the G Line train at Union Station in downtown Denver.

I detrained at Arvada Olde Town and relaxed for a few minutes with a milk shake. The statue at the station, Frank Swanson's Track Bone, refers to the railroad as the backbone of the community. It's carved out of Colorado rose red granite.

I joined Rolston Creek on the Rolston Creek Trail right in downtown Arvada.

Rolston Creek arises a little to the west in Golden Gate Canyon in northeastern Gilpin County. Rolston Creek Trail begins just north of North Table Mountain near Golden, Colorado and runs about 14 miles to the confluence of Rolston Creek with Clear Creek, where it joins the Clear Creek trail. Since these trails parallel the G Line to Pecos Junction, I'll be making use of them for a while. After that, Clear Creek and the G Line separate. The creek joins the South Platte River in Thornton. I would not want to hike back to Union Station from there 

Clear Creek has enough energy to eat away at it's banks, so there's plenty of meandering. Oxbows aren't common around here. The land isn't quite flat enough for streams to go anywhere they want. But there are a few. One nice example is in the Carson Nature Center in Littleton. There were a couple of places on this hike where it looked like Rolston Creek might make oxbow lakes if left alone. With all the urbanization and industrial parks, there's little chance of that happening.

Oxbow lakes form when a meander is choked with sediment so that it's cut off from the rest of the stream. Check out maps of streams out on the plains and you'll find many examples 

Have I mentioned that Denver likes murals? These murals in Arvada are exhibits from the 2021 Arvada Babe Walls Mural Festival. 

I left the Rolston Creek Trail at the Gold Strike Park, which commemorates the first Colorado gold strike. Along with the interpretive plaque, there are a few pieces of placier equipment on display. I'll get back to this park on my next hike.

Getting from the park to Arvada Gold Strike Station required a little navigation around urban streets but it wasn't too complicated or far and it afforded some nice views of the commuter train...

and the mountains.

The station itself is pretty typical of these G Line stations.

How do the streams in your area differ in appearance than these in the Denver Metro area? What might account for their differences?

Gold prospecting was a trend in the U.S. in the 1800s. Was there a gold rush in your area? You might be surprised. Gold is fairly rare but is widely distributed. Do your homework and you might even be able to find some in your area.