New Worlds: Rivers

(This post is part of my Patreon-supported New Worlds series.)

To launch us into the New Year, I’m going to go back to the physical world for a moment, rather than the social one, and talk about rivers: how they work, how they’re used, and how not to do them.

Let’s start with that last point. And as my illustrative example, I’m going to use something that is both near and dear to my heart and hydrologically nonsensical: the empire of Rokugan from the game Legend of the Five Rings.

Here is Rokugan! (Please forgive the childish scrawls in MS Paint. Image manipulation is not my strong point, unless we’re talking about editing photos.)

a map of Rokugan from Legend of the Five Rings, with rivers and mountain ranges marked

Because it isn’t a high-contrast image, I’ve marked the major waterways in blue. Red shows you where there are mountain ranges; white marks divisions where you might think the waterways connect, but they actually don’t. Yellow shows . . . well, it attempts to show which direction the water is flowing in. But as you can see, that is not always easy to figure out.

This is not how rivers work.

Let me show you a real-world example for comparison:

a map of the Missisippi River basin

This is the Mississippi River drainage basin (simplified). As you can see, it has a generally fan-like shape: rivers go from areas of higher elevation (the Rocky Mountains, the Appalachian Mountains) toward lower elevations, for the simple reason that water flows downhill. As they do so, they join together to make bigger rivers, until ultimately all of them feed in to the Mississippi — which is why we call this a “drainage basin.” It’s a region that all drains to the same point, which is the mouth of the Missisippi River, emptying out into the ocean. (You can also have what’s called an endorheic basin, with no outlet to the sea: it all converges to a lake or swamp and evaporates from there.)

Rivers in Rokugan do not join together. They separate. That lake in the northeast: okay, it flows down from the mountains, but then . . . does it split? Or is that western branch flowing eastward to the sea, joining up with the eastern branch (which apparently flows through a small mountain range?), only then you have to assume that the major river running from northwest to southeast is the one that splits — just like the one due south of the mountains, down near the coast — or the lake in the eastern edge of the mountains, that somehow both flows north through the mountains and south to the sea — and the tiny little river along the coast that inexplicably has enough flow to form both a substantial bay and split off to form the biggest delta in the Empire — and let’s not even talk about what’s happening in that big patch of mountains at the very bottom of the map. It’s the setting’s equivalent of Mordor; we’ll just chalk it up to evil magic and move on.

Now, as some fans of L5R have pointed out, you can say “but magic” and call it a day. However, if you do that, you have to do that. Make it clear to the reader that this is a setting where the normal laws of nature do not apply: rivers diverge instead of converging (and don’t become smaller as a result), water flows uphill in its determination to cross a mountain range, etc.

You also have to realize that if you do that, you’re screwing with the logic that underpins how human societies relate to waterways. Cities were often founded along rivers not only because they provide a ready source of water, but because they provide a natural highway for travel and transporting goods. Putting things on a barge and floating them downstream is often a damn sight easier than hauling them across dry land. Going upstream is harder, but still possible, and possibly even still easier: barring obstacles like rapids, shallows, or waterfalls (which you can sometimes portage around), you’re looking at what is literally the path of least resistance, because that’s the route water likes to take.

But this peters out as you go further into the fringes of the drainage basin, because the rivers there get smaller and smaller. Large barges can’t make it past a certain point; you have to switch to smaller ones, or little craft like rowboats and canoes, with a shallow enough draft to navigate the shallower waters. So the effectiveness of trade along the waterways depends on where you are in them. And, of course, you may find yourself with a geography where it’s actually easier to haul your goods along the land — even if there’s something like mountains in the way — to get at a more useful bit of river, rather than taking the long way around with the local water.

Confluences are great places to stick your city because then you control the traffic on multiple rivers. So are fords — places where the river is shallow enough to be crossed without a bridge — or, when you get fancier, the bridges themselves. Being at the mouth of river is excellent, because then you get access to all the sea trade and everything heading into or out of the river system. But if there’s a big estuary or a delta, you’re frequently better off being far enough upriver to avoid the brackish water or divergent channels (deltas being one of the few places where a river diverging makes sense, because it’s essentially a giant mudflat).

All of this means that paying attention to how your rivers work isn’t just a matter of geography; it’s also a question of cultural worldbuilding. In high school I drew a map for my Nine Lands stories that originally featured a river which flowed straight from one coast to another, and it took me an embarrassingly long time to notice what I’d done. I would have had a hard time saying anything plausible about trade on that river, because I wouldn’t even have been able to tell you which direction it flowed in. Waterways affect warfare, by influence everything from borders to troop movements to what counts as a strategic target.

If you want those things to feel real, it helps for the land they take place on to feel real, too.

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About Marie Brennan

Marie Brennan is the author of The Memoirs of Lady Trent and the Onyx Court series of historical fantasies. The second book of the Wilders series, Chains and Memory, is on sale now from Book View Cafe. More information can be found on her website, Swan Tower.
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13 Responses to New Worlds: Rivers

  1. The Magna Carta in 13th C England provides for the removal of fish weirs from major rivers because the nets and traps strung across the entire river channel interfered with water transportation. They may have couched their arguments in terms of trade, but the barons and king involved all knew they were talking about troops and engines of war. Never mind that people had to find other sources of food than river fish–like poaching rabbits on royal preserves.

    • I’m curious — does it define what constitutes a “major river”?

      • Clause #33: Henceforth all the fish-weirs shall be cleared completely from the Thames and the Medway and throughout all England, except along the sea coast.

        The document leaves room for a lot of reading between the lines. The reissue of the document in 1216 and 1225 clarified some clauses, but this one remains the same.

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  3. Damien says:

    “a river which flowed straight from one coast to another”

    Could you have relabeled it as a canal?

    • Anthony Docimo says:

      the Nile is essentially a straight line, and the Amazon is – if not a line, then at least a wedge. 🙂

      Also, endorheic is…i think the word is “recursive” – it links to this page; sorry.

      • Oops, thanks for catching that! Yes, I’d forgotten to put in the URL.

        The problem with the river was not its straightness; it was the fact that it ran all the way through a continent, apparently managing to have an outflow at both ends. They just don’t do that.

    • Could you have relabeled it as a canal?

      Not really. 🙂

  4. Lauren says:

    As a fantasy lover and freshwater scientist I just want to say I love this post SO MUCH.

  5. Evan Th. says:

    To complicate things, once in a while a river really does split. It’s very rare, though; there’re maybe three navigable river bifurcations in the world.

    • Yeah, the majority of those bifurcations seem to be at least partly artificial. The fact that they occur over and over again in the map of Rokugan strongly implies that the original map artist just didn’t understand, not that they were doing it deliberately. (Especially since nothing I have ever seen in canon calls out the bifurcations as being unusual in any way.)

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