Tilikum Light

In the recent Sonic Dish post here, I mentioned that it was a sort of companion piece to Tilikum Light, the nightly lightshow on the Tilikum Crossing bridge. Which is what this post is about. TriMet's Orange Line Art Guide describes it this way:

"Tilikum Light: An Illuminating Conversation between a River and a Bridge", by Douglas Hollis and the late Anna Valentina Murch,takes real time data from the Willamette River and translates it into colorful lighting on the cables and piers of Tilikum Crossing. Below the bridge deck, curved abutment walls are activated by localized sound and the same programmed light as above.

Because TriMet is really a bunch of engineers and not artists at heart, the agency did a rather detailed blog post explaining how it all works, and crediting digital artist Morgan Barnard for this part of the project. To summarize what's going on briefly, there are a number of USGS and NOAA sensors in the river just downstream at the Morrison Bridge, and the current values drive various aspects of the lights' behavior. So here are some links to the raw sensor data, along with what part of the show each of them kinda-sorta controls:

• The river temperature drives the light color. Warmer river, warmer lights, and so forth. The average temperature while I'm writing this is in the low 50s (Fahrenheit obvs), which I assume leads to mostly blues and greens. Which is not as cold as the Sandy usually is, but anything under 60F feels cold and is rapid hypothermia territory for humans, and anything under 70F will feel chilly. Temperature ranges are different for salmon, unsurprisingly: Mid-50s to mid-60s is ideal; high 60s are stressful, and temperatures in the 70s quickly become fatal.
• The lights form a pattern that appears to move across the bridge, and this is controlled by the tides. Again, as measured at the Morrison Bridge. Yes, we do get tides here, believe it or not, even though we're around 100 river miles inland; the graph at that link shows the river level rises and falls by about 3 feet over a tide cycle. It just happens slowly enough that you don't really notice it, or at least I've never noticed it. But now you can just look at the bridge and get a rough idea of what's going on: When the tide is coming in, the lights move toward the center of the bridge. When it's going out, the light pattern moves toward the ends of the bridge. And the higher (or lower) the tide is, the faster the pattern seems to move. So keep an eye out for upcoming "king tide" events if you want to make a good video of the bridge lights.
• The river velocity drives how fast the colors cycle. Like the other measurements, this fluctuates with the tides and right now is hitting a maximum of around 1 foot per second, or 0.68 mph. Meanwhile the Columbia (as measured somewhere near the Interstate Bridge, just upriver of where the Willamette merges in) is moving about three times as fast, with a total water volume over eight times as high. The most interesting bit on the Willamette graph is that at high tide the velocity sometimes drops briefly below zero, slightly into negative territory, so if you happen to be fishing or kayaking when that happens you might notice yourself being carried slightly upriver for a bit.
• The river level controls how "contrasty" the lights are, meaning the lower the river is, the more uniform the colors are. The post doesn't say anything about the bridge having a "flood warning" mode -- maybe having it flash red if the river level is over a critical point or is predicted to. That seems like a bit of an oversight seeing as a lot of people here still remember the 1996 floods. But I suppose if the bridge lights are the only operational source of flood info, there are probably much larger problems going on for the city to deal with.

One interesting detail is that TriMet is contractually obligated to always run the bridge lights as described above, meaning the agency can't switch it to a solid color for the current disease awareness month, or the colors of a national flag to show support after some misfortune has befallen the place, or whatever fancy happens to strike Multnomah County commissioners at the moment. This seems increasingly wise after the county mishandled its response to the Israel vs. Gaza war, first going with blue-and-white lights for solidarity with Israel, and then hurriedly switching to all-white for world peace after a public outcry, a response that satisfied precisely nobody. I imagine the black stripe on the Palestinian flag made for some awkward conversations around the county bridge division as it dawned on them that they couldn't light the bridge in Palestinian colors even if they wanted to.

I am not a lawyer, and I am especially not an art lawyer, and maybe contracts like what TriMet made with the artists are completely routine. But Murch may have had a specific reason to get something in writing about the work going up and staying up. Namely, she had previously designed a lighting scheme for the city's aerial tram tower, with solid colors that (in theory) rotate monthly. I would kind of like to go get some photos of it at night over a few months to give some idea of what it's like, and I've tried to do this a couple of times. But every time I've checked on it, it's always just dark, and come to think of it I'm not sure I've actually seen it in operation for quite some time now. Maybe that's just bad luck on my part, and I just happen to look at times when it's not operating, by pure coincidence. Or maybe it keeps really unusual hours and only comes on after zero-dark-thirty, or it's only lit for half an hour at dusk every other Thursday. Or perhaps someone has to turn it on by hand every night and they don't always remember or can't be bothered. Or it's just out of order a lot, waiting on mildly obsolete spare parts to be shipped from an obscure supplier in some obscure Balkan country. Or who knows, maybe aliens are real, and in their culture the shape of the tram tower, when lit at night in certain colors, is considered unspeakably obscene, and they're all much too embarrassed about it to explain why in any detail, but there's no way they're going to share their advanced technology with us if we keep shoving that... that... thing... in their faces.

Anyway, TriMet does seem to be allowed to turn off the bridge lightshow late in the evening, so I've noticed, and it's been out of order due to Software Reasons at least once, with TriMet blandly calling it a "network issue". Which could be anything, even somebody at TriMet HQ opening a sketchy email attachment. And we won't know because the bridge lights don't have sufficient resolution to display a ransomware message, as funny as that would be.