Worldbuilding: Ancient Megastructures

Worldbuilding. It’s this critical, wonderful piece of writing science fiction and fantasy, and something we can spend decades trying to get just right as we’re procrastinating. I mean, everything in the world we’re making has to make sense, right? We design architecture and agriculture. We design languages and those little pieces of flare that make fashion unique and interesting. One of my favorite pieces of worldbuilding is the enormous structures designed by ancient people for purposes unknown. They’re the cryptic setpieces of our epic tales, and I love them.

I’m thinking of books like The Lies of Locke Lamora by Scott Lynch or The City of Stairs by Robert Jackson Bennett or Perdido Street Station by China Mieville. Old structures of ancient civilizations immerse the reader in these strange, unique worlds.

When we start to design these structures for our stories it’s easy to think of how they once made sense. An ancient civilization had reasons for everything they did, right? If we follow that logic, then we can build our megastructures.

Case in point: Control of Nature by John McPhee describes three amazing projects in which human beings for one reason or another decided to butt heads with nature. Success is always temporary, but this book describes some truly amazing projects. Firefighters in Iceland alter the direction of lava flow around a bay. Near LA they capture whole rockslides as people build houses closer and closer to a constantly growing mountain.

And then there’s Atchafalaya, which hits a little closer to my heart because it involves the Mississippi. Let’s talk about this megastructure a little bit and see what we can learn about our own worldbuilding.

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And he’s going to need to delve into his past.

She won’t take no for an answer.

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What the Heck is Atchafalaya

Rivers move. It’s in their nature. They break their banks, meander, form oxbows, and sometimes make drastic shifts in their flow. This is what the Mississippi river was doing around the beginning of the 1900s. It had started to divert into the Atchafalaya river, and the percentage of that diversion was increasing.

The Old River project at Atchafalaya froze the diversion at about 30%. It’s a huge project by the Army Corps of Engineers, and it took several attempts to build something powerful enough to control one of the biggest rivers in the world. It’s also a massive maintenance effort. They need to constantly fight everything from silt buildup to runaway barges. During heavy rain someone must decide how much water goes downstream and how much goes into the Atchafalaya Basin, a 1.4 million acre wetland.

What’s the real-world impact? Let’s put it this way: everything south of this point on the Mississippi River is only on the river because of this project. All that shipping, all the commerce, all that agriculture–it only exists because of the Old River project at Atchafalaya.

What Does This Matter for Worldbuilding?

This is our future ancient megastructure. Imagine this in a hundred years. A thousand. The structure itself isn’t going away, but financial support for it might. In a post-apocalyptic America, what happens to the Mississippi? How long before the river fully diverts? What effect will that have on the surrounding terrain? The wetlands? The farmers?

Imagine traveling up the banks of the Atchafalaya River when you come to the blown-out concrete mega-structure towering over the banks. You look left and right to see the crumbling structure of the Atchafalaya Bridge spanning miles upon miles over easily-traveled brushlands. The river as you’ve always known it has flowed far away from this gigantic structure, so what might it have been once used for? Some say it’s just a dam, but this is clearly something different. Bigger. More complex.

How about a thousand years later? Giant trees have grown up through the concrete monoliths. Pillars that once plunged deep into the earth have been exposed by erosion. A city has grown around the ancient structure, and legends tell of its history as a relic of a once-powerful civilization. Why did this civilization fall? Hubris, probably. I mean, look at what they built.

It Doesn’t Always Make Sense

One of our first instincts as we attempt to worldbuild is the urge to have everything make sense, but that’s a dangerous trap. It leads to a kind of logical calculus that doesn’t always exist in the real world.

Why did we start the Old River project at Atchafalaya?

Flooding? Maybe. The banks of the Atchafalaya were swelling more each year. They would have continued to grow. Towns built along the Mississippi’s new path would have had to move. But moving houses is relatively easy. No special engineering project or infinite upkeep is needed to move a town.

Commerce? Businesses along the current Mississippi River would have been ruined. It would have cost a fortune to move or compensate them. That fortune would have been a fraction of the cost of the Old River project, especially considering the ongoing costs. The river diversion would have devastated New Orleans, but dare I say maybe New Orleans isn’t in the best place? Control of Nature mentions the danger of hurricanes to New Orleans, saying, “The threat of destruction from the south is far greater than the threat from the north.” The levees are doomed to fail if ever hit by a large hurricane. The book was published in 1989, in case anyone wants to compare it to Katrina.

Shipping? Apparently shipping on the Mississippi is a big deal. Lots of money. If the river moved, it would disrupt an enormous shipping industry in ways that I don’t fully understand. Could we recover? Yes, absolutely. What would it cost? I have no idea.

I kinda think the big motivations behind the project were almost entirely political. That Army Corps of Engineers came back from the war and needed to keep busy. They needed a project, and there was political support from the party in power. When the first several attempts ran into problems, the project grew. And grew. And grew. Nobody planned for this to be a megastructure. Not at first, anyway.

Our thousand-years-in-the-future characters may or may not be able to discern any of this. Maybe they have a continuous history, or maybe they have a good understanding of the past. Either way, I think it’s safe to say that a lot of what was done in the design, build, and maintenance of the Old River Control structure won’t make any sense.

So there it is. That’s your permission to put giant megastructures in your fiction without a solid understanding of what they were once used for. Bring on the Dyson spheres and Ringworlds. Load us up with pyramids and towers that once stretched all the way to the sky. Why would the ancients build that? Who knows. You’ve just saved hundreds of hours of planning and engineering and designing.

And now you can get back to actually writing.

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