G is for Gabion (and a nice hike in Upper Pajarito Canyon) (Shallow Thoughts)

Akkana's Musings on Open Source Computing and Technology, Science, and Nature.

Sun, 12 Apr 2020

G is for Gabion (and a nice hike in Upper Pajarito Canyon)

[Moa on Upper Pajarito Canyon trail] Last week we hiked Upper Pajarito Canyon, a trail I mostly hadn't seen before (I'd been on parts of the trail once, years ago, on a hike I mostly don't remember except as "try not to slide off the slippery rainy hillside).

It turned out to be a beautiful trail. Early on, there are imposing stone cliffs that reminded us all of the moai on Easter Island. [Burned tree in Pajarito Canyon] The trail wound through a rocky canyon, then up along the hillside where I was able to indulge my hobby of arboronecrophotography, eventually climbing out to a viewpoint.

[Nail Trail sign] Eventually it hits the Nail Trail. The name of the trail comes from nails scattered across it many years ago, causing risk to the tires of the mountain bikers who frequent the trail; but accounts vary for why there were nails in this remote location. Was it from some sort of construction work? Or was it deliberate sabotage by someone who didn't like seeing mountain bikers on the trails? I've heard both stories, and I don't know which one is true.

In any case, at the trailhead, someone has gone to a lot of trouble to create an excellent, decorative sign of, yes, nails.

But up at the top, near where the Upper Pajarito Canyon trail hits the Nail Trail (there's also a connector that goes up Pajarito Mountain), we came across a Strange Thing: a large fenced cage with a smaller cage inside it.

[Inexplicable cage with gabion] We speculated endlessly. A place to put a mountain lion or small bear while you take blood samples and other scientific data? A place to stow your dogs while you're hiking? The world's smallest elk exclosure? (An exclosure is the opposite of an enclosure: an area fenced to keep something out. There are several exclosures in the Jemez to study how vegetation changes when elk can't get in to eat young shoots, but they're generally much larger than this, usually half an acre or so. I'm pretty sure this isn't an exclosure.)

Anyway, we still have no idea what the purpose of the cages are, but I learned a new word from our (six feet away at all times) hiking partner. Apparently fencing enclosing rocks, used here to weight down the cage so it can't blow away (or, perhaps, be upended by an enraged mountain lion?) are called a gabion, from the Italian gabbione meaning "big cage".

I'm sure you've seen lots of gabions. They showed up a lot in water projects back when I lived in California: ballot measures would promise clean water and flood control via "natural" methods, which generally meant "we'll pile a bunch of rocks with wire fencing over them, and hope that eventually, some day, dirt appears to fill in the space between the rocks and then maybe stuff will grow and it'll look better." In practice, these gabion water structures never look better; nothing ever grows between the rocks, and it really doesn't look any better than a concrete structure.

Here, in a cage in the wilderness, a gabion makes more sense. The weight of the rocks was significant and that cage wasn't going anywhere. Even if an enraged mountain lion was involved. And yet the rocks can be removed easily, so if the cage fulfills its purpose and is no longer needed, the rocks can be pulled out and the cage removed.

But mostly, I'm glad to know there's a word for these structures that I've seen so often. I can stop using phrases like "rocks in a wire frame".

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