Posted by: Brad Nixon | April 20, 2019

Raise the Drawbridge — Or Swing It

If you build your bridge high enough, you don’t have to worry about letting navigation through.

Golden Gate Brad Nixon 4349 (640x484)

The Golden Gate Bridge in San Francisco has 220 feet of clearance between the water and the bridge at high tide: ample for most ships.

Topography, infrastructure and budget require that any number of bridges are something less than 200 feet above a navigation channel. That means you need a drawbridge.

Portland, Oregon is located at the confluence of the Willamette and Columbia Rivers, both of them important transportation corridors. There are also a large number of bridges for every type of traffic, and they represent a wide variety of drawbridges.

One of them, Steel Bridge, was built in 1912.

Steel bridge Brad Nixon 2166 680

You can probably figure out how this one works. That center section lifts straight up, pulled by the elevator towers on either side.

Steel bridge Brad Nixon 2181 680

That is the most straightforward form of drawbridge. Stop traffic, lift the center section, let marine traffic pass.

Technically, it’s a “vertical truss lift drawbridge.” It was built by the Union Pacific Railroad. The lower level carries rail, bicycle and pedestrian traffic. The upper level carries road traffic as well as a line of Portland’s MAX light rail system. Considered one of the world’s most versatile bridges, although a more contemporary term is “multimodal.”

At the top of the elevator towers, you can see the massive counterweights. They counterbalance the weight of the truss, so the elevator has less work to do. The structure on top is the operation center, with a clear view up- and downriver.

Another common form of drawbridge is more familiar than its name suggests: the bascule bridge. Here’s one, the Siuslaw (sigh-OOSE-lah) River Bridge in Florence, Oregon.

Siuslaw bridge Brad Nixon 680

Built in distinctive Art Deco style by the U.S. Public Works Administration in 1936, the Siuslaw is one of a number of historic engineering feats on Highway 101 along Oregon’s coast, crossing the numerous rivers that flow into the Pacific.

I don’t have a photo of a bascule drawbridge in operation, but you can picture the halves of that center section being raised as ramps. Some bascule bridges have one “leaf.” The Siuslaw Bridge is a “double leaf:” Two opposing ramps raise to allow a tall center space for marine traffic.

This blog post was inspired by a bridge just a few miles upstream on the Siuslaw: The Cushman Swing Span Bridge.

Swing bridge Brad Nixon 4211 680

When I encountered it, I was absolutely unaware of how it worked, or why there was that odd-looking shack on top of it.

Built in 1914 to carry a railroad line, the Cushman is one of a large number of “swing span” bridges, although I was unfamiliar with them before encountering this one.

A closer look at the “swing span” helps explain how it works.

Swing bridge Brad Nixon 4217 680

The center span pivots 90 degrees on its central axis, directly beneath the control house, “swinging” aside to leave the channel clear for ships.

I was particularly struck by the picturesque operator’s control station atop the center of the bridge.

Swing bridge Brad Nixon 4216 680

Bridges are iconic structures, dating back to earliest civilization. Almost all ancient cities were located along rivers or lakes, and bridges were critically important. In earliest times, they were merely logs or stone slabs, flopped over streams. River crossings figure in stories from from the dawn of civilization, and figure in tales of errant knights and wayward travelers.

And so today.

Is there a drawbridge in your town? Do you sometimes have to wait for it to allow traffic through? Please leave a comment.

© Brad Nixon 2019

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Responses

  1. Just love the photo of the operator’s cabin perched on top of that bridge. Coincidentally, the last of my posts on Hull to be published In a few days time features what was once the world’s longest single span suspension bridge!

    Liked by 1 person

  2. They have closed the Suspension Bridge between Covington and Cincinnati due to chunks of sandstone free falling. Both states are crying about money and who should pay. This is why it wasn’t repaired or cleaned or sealed twenty years ago. It isn’t Notre Dame. But it’s close.

    Liked by 1 person

  3. I have never seen a post like this. Did you go on some sort of a tour of Oregon draw bridges? Or just decide to seek them out? Or was this an accidental discovery as you drove to other venues?

    Liked by 1 person

    • A fairly long story. Thematically, it starts with driving along the Siuslaw River and seeing the swing bridge. I’d never seen one, but it turns out they’re quite common.
      A few miles downstream, there’s the big Art Deco Siuslaw Bridge that carries Highway 101 across the river.
      You can’t go to Portland and NOT see a drawbridge. The vertical lift bridge photo is from a visit quite a few years ago, and the photo of the Golden Gate Bridge is from years earlier than that.
      They just all fell together. I left out antique covered bridges, of which Oregon has many, which may become a blog post over at My Eclectic Cafe.
      Visiting the Northwest, you learn that if you live in a place dominated by waterways, you live in a world of bridges.
      That’s probably no big news to residents of the Netherlands or other places replete with waterways, but remarkable to a guy from arid southern California.

      Like

  4. Nice pictures of Draw Bridges, I’ve seen a few of them along the Rideau Canal which is a historical water route that connects the St Lawrence and Ottawa Rivers.

    Liked by 1 person

  5. I confess I laughed at this: “if you live in a place dominated by waterways, you live in a world of bridges.” Truer words were never spoken. Let’s see…

    There’s the vertical truss bridge between Galveston Island and the mainland that carries rail traffic, and the island’s water supply. What’s interesting about that one is that it crosses the Intracostal Waterway, running parallel to the Gulf Freeway, which carries auto traffic to and fro. It’s left in the “up” position most of the time, in order to allow barges and sailboats clear passage. When a train comes along, the missing section of rails is lowered, and everything comes to a halt while the train passes.

    It used to be a double leaf bascule, and we spent plenty of time circling on one side of the bridge or the other, waiting for it to open for us.

    The Clear Creek channel, which runs from Clear Lake into Galveston Bay, used to have a single leaf bascule which carried auto traffic, and the same thing went on: hordes of sailboats would collect on one side or the other, waiting to pass through. As recreational boating increased, so did common sense, and a high bridge was built over the channel. In the early days there was a ferry, so the drawbridge was a pretty high-tech improvement.

    An interesting note about that: the new Clear Creek bridge accomodates most sailboats — probably 99.9% — but when the space shuttle replica was brought by barge to NASA’s Johnson Space Center, it had to get under that bridge, and there was a lot of tide calculatin’ going on. I wrote about it, and there are some photos of the bridge and shuttle here.

    I’m running on a bit, but there’s one more bridge…

    Liked by 1 person

    • I thought of you immediately. I know — in the abstract — that you’re replete with waterways there, and you’re all about the water. I’m sorry I know nothing about the waterfront infrastructure of the Houston/Galveston area, but I know it’s complex. Thanks for weighing in.
      I’m ‘way tardy in heading just a few miles east of my house to photograph a mammoth new bridge being built to span the main channel of the port of Long Beach, a similar situation to your Clear Creek scenario. There is, truly, a heap o’ calculating to get ships under the existing bridge, and tolerances at the best of times make the pilots, the Coast Guard and everyone else squirm in their seats.
      The new bridge is a spectacular feat of engineering, going up in the midst of busy road and water traffic. But a heck of a place to try to GET TO to photograph, because of all the security, danger, traffic, property restrictions, etc. I hope to get out a blog post about it, but it’s a big challenge just to get there.
      Thanks!

      Liked by 1 person

  6. That “other bridge” is the last swing bridge in Texas. It’s on the ICW at Sargent. We tied up alongside a shrimper near this very bridge in 1988 or 1989, during some trip down the ditch. It pretty much looks today like it did then; you can see a short video here.</a.

    Liked by 1 person

    • Woof! Clearance for that tug pilot is TIGHT! Just another day for him/her, I suppose, but you don’t do that on your first day at the helm.
      Thanks for that one. Until I started researching my post, I had no idea swing span bridges were so common.

      Liked by 1 person

  7. Amazing selection of bridges, but some of them look a bit unsafe.

    Liked by 1 person

  8. I know this isn’t a bridge (and it’s at the other end of the UK to me!) but I thought you might be interested in this boat lift in Falkirk Scotland (you may have already come across it), it’s quite an impressive structure – https://www.youtube.com/watch?v=qHO9gARac-w

    Liked by 1 person

    • Thank you. Yes, interesting to me, and glad to learn about it.

      Liked by 1 person


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