This post is part of a series on worldbuilding; links for the whole series can be found on this page.
As I said, we're going to talk about topography, but strangely we have to talk about trade first. You can see from the post title I'll come around to talking about rivers eventually.
A few things we have to understand about trade. As regards everything that exists in the world, things fall into two important categories where trade's concerned: (a) things we've got; and (b) things we haven't got. When we haven't got something, that's called a "dearth," a shortfall or a scarcity. There are always so many things we haven't got, it's always safe to say we've always got a dearth of some kind. That's important.
When we have just enough of something, where everyone gets their share and there's no more, then there's nothing to trade. Of course, we can clobber our neighbour, steal his stuff and go trade it ... but let's not be dicks. In fact, let's be clear as we're talking, we're in some obscure village somewhere in the game world, counting what we have and what we don't ... and as it happens, the village has just enough donkeys. So there'll be no donkey trading today.
On the other hand, if we have more of something than we need, that's a "surplus." A surplus can be loaded up and taken somewhere, to exchange it for those things we haven't got.
The process of "exchange" bumps into a few issues. For one, the ideal of exchange supposes that our neighbours have things we don't have, while we have things they don't have. We trade our surplus and they trade theirs, and everybody's happy.
But if we happen to live next to neighbours on all sides who live in the exact same kind of village we do, growing exactly the same crops, with the same number of donkeys — and, to make it worse, the same dearth we have AND the same surplus — well, then, trading pretty much sucks. What's worse is that because we probably DO live near each other, in the same climate, on the soil, where the same things grow, in an area that goes on for dozens of miles, that bumps us into issue number two: trade often requires a lot of travel.
Obviously it's nice if there's a big city a few miles away, as we can haul our surplus to the big city and use it to ease some of our dearth — which explains why so many people live within a few miles of a city, even if they don't count among the city's immediate population. We don't, however. We didn't have the money for land in the big city, so we're out here in the boonies. And, too, our ancestors who lived a thousand years ago didn't have a big city either, because it hadn't been founded yet; all they had was a few farms by this cruddy river, hundreds of miles from an even older big city that was founded way earlier.
What I'm saying is this: hauling stuff long distances has always been a problem for someone. At any rate, all that nice stuff we'd like from the city also had to be carried a long way.
That's why when we pick boonies to live in, we check carefully for a "river." A river is a highway — even when it's not deep enough for a great big ship, a river can still support a flat bottomed boat, one that's light enough it can be dragged over shoals or portaged around waterfalls. This isn't fun, but it's still BETTER than walking our surplus the whole long way.
But ... sorry, no, we're not going to talk about rivers yet. Getting there.
In the same way that it's ideal for folks in the next region over to have things we don't have, and vice versa, it's also ideal when we have access to more than one neighbour. A river helps with that. Using an American example, Louisville can trade with Pittsburgh, Cincinnati, Evansville, St. Louis or Memphis, plus a host of other places up and down the Ohio-Mississippi river. If we take a European example, Strasbourg can trade with Basel, Mainz, Koblenz, Cologne or Rotterdam, up and down the Rhine. This greatly increases the possibility of our finding the exact things we want to allay our dearth, while finding options for where we want to trade our surplus.
A sea is even better than a river, especially a small sea. Big oceans provide vast numbers of customers, but also great distances, terrible storms and advanced equipment and scientific knowledge ... whereas a small sea gives us scores of possible trading partners and distances that can be managed inside a month, home and back again.
The continent of Europe is blessed with many, many small seas. Each of these juts up into the core of the European continent, so that no part of Europe is excessively far from water. Even better, Europe is filled with multiple navigable rivers — the Rhine, the Rhone, the Danube, the Vistula, the Elbe, the Guadalquivir, the Loire — that flow out of the interior in every direction, so there's always some easy highway from the darkest corner of Europe that will get products out to the sea and into the hands of paying customers.
Unlike, for example, China ... where much of the broad lowland produces the same limited crops, meaning we must travel hundreds of miles to find people growing something else. The coast bulges outwards and is filled with tiny islands that make navigation along the coast dangerous ... while the coast is directly adjacent to the Pacific ocean, with its terrible storms that roll in and drown China's vulnerable shoreline. The large navigable rivers, the Yangtze, the Huang Ho, the Han, the Pearl — all flow in the same direction, providing no easy travel from north to south, only east to west. And they're far apart from each other, unlike the Danube and the Rhine, whose navigable headwaters come close together and encourage trade straight through the middle of Europe. While geographically homogeneous, enabling China to consistently form itself into a large entity with periods of strife, as a matter of trade, China had serious problems. This pushed the giant state to undertake giant solutions, such as the construction of the Grand Canal, more than a thousand years before Europe commenced its own canal building.
It probably doesn't occur to the reader to consider TRADE when laying out rivers, coasts, mountains and so on, but as I've pedantically explained, trade is the reason people leave home. They don't wander into the dangerous and trackless world as a lark, for vacation or out of yearning to know what's out there. The 13th century world isn't Disneyland. People undertake the risk of travel because they must ... they need things they haven't go, sometimes things they must have to survive. A tiny class of people make a living from this trade, but historically that takes time to happen. The Hanseatic League arises more than seven centuries after the fall of Rome; and itself doesn't experience serious competition until another 250 years pass after its formation. Global trade doesn't happen until long after the time frame of a fantasy medieval game world ... which means most likely that your world won't have any serious form of organised trade, anywhere. Most trade in 8th century Europe is painfully local. By the 11th century, journeys of hundreds of miles are rare; Marco Polo makes his journey to China in the 13th century ... when merchants have just begun to make trips of that length.
Arguably, long trips were being made across the Sahara from the Guinea Coast to the Mediterranean as early as the 10th century; Mansa Musa doesn't make his historic journey from Mali to Mecca until the 14th. Guinea suffered from the same problems as China. Most of what they had was homogenous; gold only had value outside of Guinea, which meant a tremendous trip across the largest desert in the world to get things like iron, salt and cloth.
Trade should be on your mind as you lay out the details of your first continent.
Okay. Let's talk about rivers.
Make a sheet on a drafting program or drag out a sheet of paper. Maps can be all sorts of goofy crazy-fun things, but let's keep this fairly simple. Create a body of water that takes up about a quarter of your sheet. It can run off the page in any direction or be completely enclosed inside the sheet, it's up to you, but it shouldn't take up more than one quarter of the actual page. Because this water is going to have a river running into it, and because it's pretty big, it's a salt water body. Later, we can talk about lakes, but just now we're going to imagine a river scrubbing salt-like materials from the land and pouring it into our body of water over a million years, where those chemicals are going to stay.
Now, get out your blue pencil or make a blue line that starts at the body of water and runs in a squiggly line, making the line as long as you can. Make the line do "river-like" turns and bends, meaning you shouldn't make it too squiggly. Imagine the water rolling between banks, turning left when it reaches a group of hills, and left when it meets a mountain range, and then back and forth when it settles onto a flat plain. Don't draw in the hills and mountains, just imagine that they're there.
Good. Now pick a place along the length of the river, anywhere from its "mouth" — where it reaches the sea — to three quarters of it's total length. Make sure the place you pick is at least one quarter below where the river starts. Make a small circle on the spot.
Everything between the circle and the body of water is navigable. Different lengths of the river have different depths, as the river gets larger as it goes along, but all of the river up to your circle allows at least some kind of barge or towboat. The circle you've placed is a TOWN. The head of a river's "waterway" is always the best place for a town, or a city, because this is where the river highway "ends." The Mississippi's headwaters reach Minneapolis, which is why Minneapolis is such a big damn place. Ocean-going vessels can move up the Mississippi as far as Baton Rouge — which is why that place exists. The Dneiper river in Russia is navigable as far as Smolensk. Small craft can navigate the Danube as far as Ulm in south central Germany. The medieval Rhine was navigable to Basel in Switzerland (though there were issues above Strasbourg). Relating to my earlier point, the distance between Ulm and Strasbourg is 167 km, or 104 miles. That's all.
[There are navigational issues along the Danube, at the Iron Gates for instance, but we don't need to worry about happy-fun details like that for now; like I said, let's keep this simple]
Your circle on your river is a very important place. Everything on that part of the map spends all its time figuring out how to get it's stuff to THAT town ... so give the town a name you're going to have in your mouth constantly.
All right. I want you to draw another blue line, make another river, or tributary, that starts somewhere along the length of the first river anywhere between the river's mouth and the town we just invented. We can make it start at the town, or we can make it start at the mouth, or anywhere between. Make this second line as long as you like, but have it flow generally in the same direction as the first line. Sort of the way the Ohio or the Missouri flows toward the Mississippi, or the way the Snake River flows toward the Columbia, or the Guyandotte River flows toward the Ohio, or the Tisza flows toward the Danube, or the Marne toward the Seine ... I could do this all day.
Now, decide if this second river is navigable. It needn't be. Depending on our climate, it could dry out half the year or it might roll through a canyon to debouch into our first river. Obviously, if we made the second stream enter where we placed our first town, it's not navigable at all.
Let's say we started the tributary about halfway along the navigable part. And that we've made the second river navigable for about half as far up river as the first. We can put a little circle at the top of the second river's navigability ... and a circle where the two rivers meet. That's also a great spot for a town. Boats can navigate up from the sea, meet with boats coming down the two rivers, so that no one has to travel the length of the river to get the most out of what's available for trade. This is how St. Louis became so important, and Lyons at the confluence of the Rhone and the Saone. Nizhny Novgorod, at the confluence of the Oka and the Volga, is another great example.
We've drawn two blue lines and three circles and already we've got a solid foundation for where the money's flowing; this gives us insight into political interests as well, as politics always "follows the money." We can talk about that another day.
Where the reader sees a blue line, I see a trough. Rivers always flow down, and as they flow they wear away the land and make it lower. If we look at the space between the two rivers, we should recognize this is higher than both of them. It may be only a little higher; as little as 50 or a hundred feet, just enough that when it rains on the land between the rivers, the water flows this way or that. If we want a plateau, then all the land between the two rivers will be littered with additional tributaries, like Nebraska or Poland. Land like this is called "well watered," because the ground water sits below the plain and residents can easily drop a well and get some.
On the other hand, we can put some hills there, not high ones, just enough to annoy residents trying to get from one river valley to the other, pushing more of their local trade towards the easy rivers. Hills divide peoples, as fewer people live in the hills and communication is reduced. On the other hand, hills provide new items of trade, fulfilling the dearth greatly desired from the people who all grow the same crops and raise the same animals in the lowlands. Hills have minerals, clay, gravel, forests and so on (depending on climate), causing the peoples of both river valleys to push roads up into the hills to get at those things. Then those things are rolled down hill to the river and "trans-shipped," which means unloaded from wagons and loaded onto boats. One big important mine creates a road down to the nearest point on the river ... and lo and behold, we have another town that makes all its business loading and unloading things.
We can put mountains between the two rivers, increasing the isolation between the two cultures and providing the potential for even more interesting trade goods: gems, building stone, metal ores, larger timber, furs and so on.
We can pick a place along either river, where it isn't navigable, and call it a "ford" ... a place where the river becomes shallow enough to cross with a wagon. That makes a good place for a village. We can pick another place on the river where the current slows and the water gets deep, where it's easy to row a boat from one shore to the other; this makes a good crossing point, and thus another good place for a town.
If the river has a "gate," where the water falls and is pressed between two steep banks, that small section of the river isn't navigable. This creates another need for one or two towns; so the goods can be unloaded from ships, rolled downstream by wagon, and put back on another ship. This is the "Iron Gates" (there are two) on the Danube I mentioned earlier. Only one has to be circumvented, creating the important cities of Orsova (above) and Turnu-Severin (below) in Romania.
This seems a good place to pause. Take a moment and put in another tributary. Make a whole new river on your map and give IT a tributary. Now make a rough guess at the land between each watercourse, making them nearly flat, hilly or mountainous, as desired. I'll start with "headwaters" next post.
