Howdy all. Merry *insert whatever floats your boat*. I don't really celebrate, and I'm out on the farm hundreds of miles from the nearest family, so I decided to drink some hot toddies and plan for next year. That's my kind of holiday!
I've read up on keyline design, and I figured I'd do a hypothetical design to see if I properly grasp the concept. I really appreciate any feedback.
The first photo shows the elevation lines in blue, and proposed swales in purple. The longer, central swale is on what I think is the keyline. Though maybe not?
The second photo shows just the keyline pattern in orange and swales in purple, and the last photo is everything overlayed. So, did I do this right?
*edit* I forgot to mention that the black lines are existing "roads" that weren't on the most recent map.
Joseph Lofthouse wrote:I'd be inclined to put the key-line 2 to 3 feet lower in elevation.
Thanks for chiming in. I'd love to hear your reasoning, to further my knowledge! What I take from your suggestion is that the keyline should, in reality, be a little bit below the actual spot where the slope shifts from convex to concave; am I on the right track?
Actually, looking at my photos, I can kind of see why you would say that. If I put the keyline 3 feet further down in elevation, it would allow me one long continuous keyline pattern that would essentially approximate the pattern I drew up, but it would be easier to follow on a tractor and still serve the desired effect. Right?
Location: Cache Valley, zone 4b, Irrigated, 9" rain in badlands.
Joseph Lofthouse wrote:I'm looking at the contour lines. They seem the same distance apart on both sides of where the proposed keyline was drawn, but a few feet lower in elevation, the lines get much further apart.
From a pragmatic standpoint, I like sediment to drop out of the sheet flow just before it reaches the keyline, rather than dumping sediment directly into the keyline.
That makes a lot of sense, and I appreciate your input. I suppose there were some factors that led me to this design that should I should have mentioned, which probably influenced why I placed my keyline where I did. A lot of them are coming from being on the land for a full season just observing, and the lay of the land isn't super well represented by the contour lines. (They were done by me, not a professional. The only available USGS datasets for my area weren't detailed beyond 20 ft elevation changes.)
Where I live we get (in a good year) around 7 inches of rain throughout fall, winter, and early spring, and a maybe a few inches of snow. There have never been any sheet flows I've observed, and I've talked to farmers that have been on the property for 40+ years as well so I'm less concerned about sediment deposit, and more focused on helping what water we get more evenly distributed. (Our primary erosion concern is wind.) I was also was under the impression that the keypoint should be at or near the inflection point of a primary valley? I chose the kepypoint using an elevation profile of the primary valley, I can pull up a screenshot once I'm actually on my computer. This placement was the only one where the keyline pattern maintained the slight downslope grade from the "wettest" part of the property (where all the cheatgrass and lambs quarters go crazy before anything else, and stay greener longer during the summer) towards my ridges that are always bone dry and dusty. I did do a mock up of what you suggested, but when I continued the pattern from both 2&3 feet lower in elevation I ended up with my valley being the lowest point in the line, which I thought was a no-no? Or, I will admit, I could have some sort of mental block keeping me from properly grasping this concept, and I'm being an idiot (feel free to tell me so, if this is the case!)
I guess what I'm wondering is whether you had concerns about the effectiveness of my design, or were simply stating that you would personally do the design differently?
You know it is dark times when the trees riot. I think this tiny ad is their leader: