Of course, I'm still just going on about the Little Dry Creek valley a couple of blocks over from my house.
I've mentioned that the mountain streams in the Rockies are very different than the ones I knew as a child back east. Little Dry Creek, on the other hand, looks very familiar, but all streams have their own personalities.
On the last walk down the hill, I took some side trips from the main road that parallels the creek, Arapahoe Road, down to the creek to get an idea of the cross sections. You remember that I took one elevation profile down Uinta Street a couple of blogs ago. I supplemented that with three others starting near the rim of the South Platte River valley and stopping at the western end of Walnut Hills, Quebec Street.
Little Dry Creek Park is near the head of the valley where the creek emerges from a culvert under Yosemite Street. On the other side is just storm drainage channels.
Here the creek cuts a shallow channel surrounded by a wide plain. In about 250 feet, there's only a rise of about 10 feet to the surrounding residences. I figure that the plain was carved by the creek because the rise up to the residences have been reinforced by stone to prevent further erosion in that direction.
The headwaters of Little Dry Creek is just building up energy and volume here. There's enough flow to have cut a shallow notch but it looks like it has meandered in the recent past. I doubt if there has been a lot of flooding. The flow has been erratic as shown by water level readings over the last year.
I was in the area in 2020 and 2021 and the maximum flow of 5 cubic feet per second was not enough to flood the creek's banks.
Much of the variance is due to snow melt and occasional spring rains. This data is from the area west of Walnut Hills where the creek passes under Arapahoe Road.
As the creek builds up energy and volume, it cuts a deeper valley with less meandering.
At Uinta Street, the valley drops into the hilly section behind Walnut Hills Elementary School.
The elevation difference between the top of the hill to the bottom, at Spruce Street, is about 70 feet. The ridge passes through Walnut Hills. It's very visible on Arapahoe.
I would think that it's older than the creek...maybe a bump in the Dawson formation that appears as outcrops northeast and south of Walnut Hills. Regardless, the creek has cut deeply through the ridge. The whole length of the creek has erosion prevention features like small weir dams and boulders that have been moved into the stream bed so the back cutting has been slowed considerably.
I like trying to visualize what different places might have looked like before buildings were there. I wonder if there was a Cascade here.
At the bottom of this grade, Spruce Street crosses the creek.
The creek begins to meander again and there's a wider plain. They're also deeper banks.
In 0.2 mile, the walk down from Arapahoe only descends about 40 feet.
The creek begins cutting some fairly deep banks, some about six feet, close to my last stop, Quebec Street at the western boundary of Walnut Hills. These show some nice soil profiles, so I should be coming back later.
Here the valley is broad and the gradient into it is gradual. Over 0.2 miles, the descent is only about 30 feet. On the other side of Quebec, the valley begins deepening again, as shown in the photograph above shot through a fence. (The Little Dry Creek Trail pulls away from the creek for a ways to follow sidewalks around a residential area.)
I have only been looking at the creek valley in Walnut Hills neighborhood. The valley actually extends further on the other side of Arapahoe Road. The rim peaks about a half mile from the creek at Fiddler's Green. Little Dry Creek has slowed down considerably due to erosion controls installed with the residences of Walnut Hill, but it has evidently been much more active in the past
Now, a few words about the AllTrails app. It's a great tool for measuring distances and elevations but it's not terribly intuitive, so let me give you a few tips. My version is 14.3.1 of AllTrails Pro and I use it on an Android phone version 8.0.0.
Use the Navigate command (the middle button on the toolbar at the bottom of the AllTrails window) to get to the tools. Choose "Start without a route" and choose an activity. Hiking or walking is good. Then just press the start button. When you reach your destination, press and hold Pause and the app will ask you if you are finished. Press Finish. It will ask you how your trip was. On my Android, the app has frozen at this point but, if you close the app and restart it, you will find your data saved in History. Later versions may fix this glitch and it may not happen on other operating systems.
Nevertheless, AllTrails is an excellent app to measure the shape of your landscape. There is a free version. The Pro version isn't expensive and provides more reporting features.
Before begining a study outside, it helps to get a lay of the land. What does your neighborhood look like? What does it contain - rocks, plants, animals, attractions, hazards, streams, hills... outcroppings,
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