One of the most important aspects of any map is its rivers. Rivers are a key piece of any world and the societies that inhabit them. They’ve often been the source of great cities and empires, and are essential for travel and trade.
Unfortunately, it’s really easy to mess rivers up if you’re not careful. While the actual science behind river formations and flows is well beyond the scope of this article, we can still look at some ways to keep your rivers from looking out of place. In this article, we’ll look at a handful of ways you can improve your rivers and make them more realistic to how they behave in the real world. It won’t make you a hydrologist overnight, but it will help you improve your map-making and world-building.
One last note, many of the rules below can be broken; I’ve included a few quick notes, in some instances, of exceptions. Consider these as rules of thumb meant to guide you, once you learn the basics you’ll be better equipped to break them. They also only consider a real-world perspective, if your world has a wizard going around making water flow uphill then that completely changes things.
Rivers Flow Downhill
The first and most basic thing to keep in mind when building rivers is to remember that they always flow downhill. Typically, you’ll have rivers that start somewhere high like in the mountains, and then flow out to the ocean. This seems basic, but so many maps still get this wrong.
Also, when planning your river’s route remember that they follow the path of least resistance. The easiest place for your water to move is the route it will usually take. Rivers will always move from high elevation to low and follow the easiest path for them to do so. As long as your rivers follow this basic rule you’ll have the biggest piece of creating realistic rivers done. This rule is also the hardest to break without magic, so if you only take a single thing from this article make it this.
Rivers Rarely Branch But Do Join
While not impossible, it’s rare to have a river branch out into many smaller rivers. This can happen under special circumstances but is generally avoided if you’re not sure it’s correct. The most common example of this is deltas where the river approaches the ocean, but these are a bit different than a river simply branching.
On the other hand, rivers frequently come together. You’ll often see many smaller streams and creeks meet up to form larger and larger rivers. If you think about it, it makes sense.
Presumably, there is an “easiest” path for a river to take, and that’s what rivers will naturally be inclined to flow towards. Many rivers meeting up into a single, larger river, illustrates this point as that happens to be the route of least resistance, so many rivers naturally flow towards it.
This is also a good way to create larger rivers realistically. If you look at any large river you’ll find that it has many small rivers, or tributaries, that feed it. The Danube in Europe, for example, has over 300 tributaries that feed it, so this is a very common occurrence.
Rivers Don’t End In Lakes
In most cases, your rivers shouldn’t end in lakes. Now, this certainly does happen, but it’s usually an exception due to some natural phenomenon, the Dead Sea is an example. In most cases, rivers flow into lakes which further drain out in another river towards the ocean.
In addition, while a lake can have multiple rivers that feed it they typically only have a single one that drains from it. Lakes with multiple draining rivers do exist, but they are a rare case called bifurcated lakes.
Having rivers stop in lakes is perfectly fine, but in most cases there should be a single outflow that continues the water’s journey towards the ocean.
Rivers Can Disappear… With Reasons
As we’ve seen, most rivers flow towards the ocean and ultimately end there. Others might end up in endorheic basins as described above. But, some rivers seem to just disappear. There’s always a reason behind this, here’s a handful of situations that can lead to a disappearing river.
One reason is that the river travels through a very hot and arid region and simply evaporates and dries up. This is the case where the river doesn’t carry enough water to offset the losses, and eventually disappears. Many of these types of rivers might be seasonal and flip between dry and wet depending on the season. Many rivers in Africa that are seasonal and “disappear” for some time during the dry season.
Other rivers can disappear underground leading to subterranean rivers or feeding into underground aquifers. Areas that conform to karst topography are examples as the makeup of the ground encourages water flow below ground. These areas often have a lot of caves and sinkholes as well.
Lastly, there are also examples of temporary rivers that only exist during periods of heavy rainfall. Many of these exist in mountains and carve out channels that quickly evaporate after the rain passes. These areas can be quite dangerous as it can be difficult to predict when they’ll be an actual river, and go from nearly dry to rapid flow extremely quickly.
Faster Rivers Are Straighter
A good rule of thumb is that the faster a river moves the straighter it ends up being. As a river slows down it begins to meander and wind a bit more.
That generally means the steeper the land the straighter and faster the rivers. On the opposite end, flatter land tends to lead to more winding rivers that move more slowly.
Simple Rules For Rivers
Understanding the basics above is going to help you build better worlds that have more realistic rivers. Water features are one of the first things people will notice about your world, so it’s important to understand a bit about their nature so you can create them realistically.
That said, once you know the above rules you are also better equipped to break them. There are tons of exceptions in nature, but there’s often a reason behind that exception. If you’re interested in learning more, check out the various links throughout the article. There’s a lot of interesting concepts to explore, and learning more about how these water features behave is only going to help you build better worlds.
That’s all for now, let us know if we should take a deeper dive into rivers, or what other topics in worldbuilding we should cover.
