Saturday, June 23, 2018

Wahkeena Creek Bridge

In the previous post about the Horsetail Creek Bridge I mentioned something about my projects having a long tail of things I have to do for the sake of completeness, and this post may be one of those. The Wahkeena Creek Bridge at Wahkeena Falls is a nondescript little concrete bridge that ordinarily nobody would care about, but it's an original 1915 bridge on the historic Columbia River Highway, so by virtue of that it counts as a historic structure. I had frankly never paid it a moment's notice until I started this bridge project. And later when I remembered to take a couple of photos of it, I promptly forgot I had them. BridgeHunter, a site run by people who are wayyy more obsessed with this bridge stuff than I am, bends over backwards to make it sound interesting in their page about it:

The Historical Columbia River Highway crossing at Wahkeena Creek is one of the earliest examples of a concrete slab bridge in Oregon. The bridge consists of a concrete slab deck resting on stone masonry abutment walls.

It also mentions that this was designed by Karl P. Billner, who designed a number of other more significant things along the old highway, like the Benson Bridge at Multnomah Falls, and the Shepperds Dell and Latourell Creek bridges. Billner wrote an article for the February 1915 Engineering and Contracting about a number of his bridges in the Gorge; the Latourell one was obviously his pride and joy and he largely focuses on it, but he has shorter items about some of the others where an interesting problem had to be solved, like fitting the Multnomah Viaducts into a cramped space, or bridging over a creek and multiple log flumes at Bridal Veil. He doesn't mention Wahkeena Creek at all. The description above says concrete slab bridges were a shiny new technology in 1915, and Billner was known for doing innovative stuff with concrete, but he must have known his other bridges were more interesting. Maybe this one just didn't fit in the article word limit and was cut for length.

When doing bridge posts, I usually look in the library's Oregonian newspaper database for interesting historical tidbits, which helps a lot when a subject isn't really inherently compelling. I did that again this time and came up with zilch. It doesn't look like this little bridge has ever been newsworthy over the last century and change. I did find one old photo of it at the Library of Congress, but it doesn't look that old, maybe 1950s or 1960s. And the highway's National Historic Landmark nomination mentions this bridge briefly as a "contributing structure" but doesn't have anything interesting to say about it. Again, I'm sure it wouldn't count as historic if it was somewhere else.

I did find one interesting and semi-related thing while searching the library database, so now we're going to forget about the bridge itself and wander off on a tangent. So here's a May 1987 story about Parasimulium crosskeyi, a species of primitive black fly that only lives in the Columbia Gorge, in a limited range roughly from Wahkeena Creek east to Starvation Creek. The article profiles a PhD student who had made it his study creature and had recently made the first sightings of female P. crosskeyi flies here at Wahkeena Creek. It seems they spend the first part of their lives in the "hyporheic zone", meaning they live in mud beneath and along the sides of a streambed, where stream water mixes with groundwater. The adults wash out of the mud, spend a little time flying around and making new flies, and the circle of life repeats itself etc. etc. One positive bit is that (unlike more highly evolved black flies) they don't have piercing mouth parts, and are thought to feed on plant nectar instead of chomping on people. Which is always a good thing in any insect.

The article ends on a note of concern; the researcher failed to find any flies the day the reporter showed up, and he was concerned as the Forest Service had recently run bulldozers along the stream, right through prime P. crosskeyi habitat, with unknown consequences. Earlier the article had explained that the fly might be eligible for an endangered species listing due to its tiny range. I couldn't leave the story hanging there, not knowing if the feds had wiped out a defenseless little bug, so I searched around to find a more recent (2000) paper about it, indicating it was still around as of almost two decades ago. Most of the papers about it date to the 1980s, though. I'm not a biologist, but I understand this happens a lot with smaller and less charismatic species: Research happens in fits and starts when someone takes an interest and manages to find funding, and tails off when they retire or move on to greener pastures & none of their students wants to take over. Then nobody looks again for years or sometimes decades.

To give some idea of how little is known about these little creatures, here's the 1985 description of the related species Parasimulium stonei, by the same discoverer as P. crosskeyi. The latter was discovered first & the paper explains in great detail how the two are different. Toward the end it mentions someone found a specimen that might be P. crosskeyi near Corvallis, and speculates that it might inhabit the Columbia and Willamette rivers too and it just hasn't been noticed yet, since black fly populations along major rivers were little studied and poorly understood, and probably nobody had ever looked for them outside the Gorge. Although elsewhere in the article it notes that collection sites (other than the oddball Corvallis one) have all been on streams with waterfalls, and wonders if "[t]he presence of a waterfall might reflect some ecological requirement, such as a marker for adult swarming behavior."

You might think there would be a photo of everything on the internet by now, but I couldn't find a picture of P. crosskeyi anywhere; the closest thing I've found are a couple of technical drawings of related species, a wing and part of the head. This isn't a lot to go on if you're looking to identify these beasties on sight; all I can say is that if you're visiting the area & maybe standing next to the creek to check out the ugly bridge, and you're holding a bouquet for some reason, and a tiny black fly tries to nom on it, you just might be helping to preserve an endangered species.

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