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Hello there, it's my first time posting, so I'm sorry if I'm going against formatting.

I'm making a continent for a fantasy setting, and have been firstly focusing on geography. This continent should be about as long as the U.S. and twice as tall, with the bottom half positioned about where the U.S. is in the northern hemisphere.

I think I went a little bit crazy on rivers, and I would like some advice on if this map is realistic, or which rivers would be the most powerful so I can thin the map.

Also, I have a vague idea as to the climate due to location and Worlds-History Simulator, but because of all the mountains I will need to add in to make the rivers flow, I don't know how much of the continent will be desert or lush Forrest due to the rain shadow effect.

Any advice and criticism would be greatly appreciated, and I apologize if I'm asking too much.

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    $\begingroup$ Elevation first, water last. If it makes you feel any better, geologists hate on Middle-Earth too. $\endgroup$ – John O Jan 31 at 17:20
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    $\begingroup$ No spillways to the seas from your lakes? Perhaps underground rivers are in order in a fantasy setting.... $\endgroup$ – Tantalus' touch. Jan 31 at 17:21
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    $\begingroup$ Is it me, or most lakes have no outflow? I have not seen it happen outside of deserts. I would imagine with more rain and less evaporation, lakes will fill up until they overflow somewhere. $\endgroup$ – Bald Bear Jan 31 at 17:22
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    $\begingroup$ Thats a lot of [endorehic basins][(en.wikipedia.org/wiki/Endorheic_basin). There's nothing wrong with having lots of rivers, but having lots of lakes which don't drain to the sea is a bit weird. If its so desertlike that the lakes evaporate fast enough that they don't need to drain, how come there's enough water to fill all those rivers? $\endgroup$ – Starfish Prime Jan 31 at 17:36
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    $\begingroup$ @John: Endorheic basins of the world. I would say that one third of Asia makes a rather significant portion of a continent. $\endgroup$ – AlexP Feb 1 at 8:22

11 Answers 11

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Rivers flow from mountains to the sea. They may take a round about way, depending on geography, but they almost always follow this path. Lakes form in valleys where water gets trapped before emptying into another river (or multiple). There are, of course, exceptions to this (like the dead sea), but you should generally follow this rule: a river must maintain an unbroken path from its source (mountain) to its destination (sea).

Probably the most common mistakes when it comes to rivers in fantasy maps have to do with branching and merging. It is very rare for a river to randomly branch into two separate rivers. When this does happen, it rejoins soon after, creating an island. (Note that, as mentioned before, a lake may contain multiple outlets, so it's fine in that case. Edit: it was brought to my attention in the comments that lakes with multiple outlets are also very rare, especially stable ones, so avoid these too) (Also note that rapid branching can occur in river deltas, as it enters the sea.)

On the other hand, rivers merge together all the time. It would also be exceptionally rare for a river to make it all the way from its source to its destination without merging with another along the way. Rivers start in the mountains as small streams. As they flow downward they begin to merge together into small rivers. These rivers then merge into large rivers (with additional small rivers merging into them) before emptying into the sea. Essentially, in the end, you have a bunch of tiny sources in the mountains that ultimately converge into a few large destinations at the sea.

Here is a perfect example of what this looks like in the real world. (The rivers are enlarged to indicate their water flow, not their width. There is, of course, some widening as rivers merge, but most fantasy maps ignore this and just show the paths, so you're good there.)
enter image description here Source: Pacific Institute

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    $\begingroup$ Thank you! I found it on google myself ;) $\endgroup$ – WillRoss1 Jan 31 at 18:33
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    $\begingroup$ Not all rivers run to the sea. A lot of rivers go to lakes, groundwater other rivers and so on. In Brazil there is a hole area that pretty much all rivers end up in the continent. Also big maps with scales like that one don't show most of rivers. But the answer is pretty accurate. $\endgroup$ – GaboSampaio Jan 31 at 19:12
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    $\begingroup$ There are many large endorrheic areas in the world; it is not all unusual for a river to flow into an endorrheic lake or be lost in the desert. Instead of North America, do a map of western and central Asia and see. And sometimes rivers do bifurcate; leaving aside deltas, which are very common, there are also famous bifurcations where the waters of a river part irreversibly; for example, the Casiquiare distributary of the Orinoco. $\endgroup$ – AlexP Feb 1 at 0:20
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    $\begingroup$ @AlexP the answer is still correct: bifurcations are rare. $\endgroup$ – Tim Feb 1 at 11:26
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    $\begingroup$ Lakes form in valleys where water gets trapped before emptying into another river (or multiple). — IIRC correctly lakes with just two outflows rivers are extremely rare(it requires them to have almost exact height, slope, throughput, etc) and this situation is very unstable (it will be reduced to just one outflow in no time). $\endgroup$ – user28434 Feb 1 at 11:30
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You have some severe issues.

At the points marked "1", you have rivers doing things they don't, namely different drainage systems combining and then separating.

All the lakes marked "2" have no outputs. Either your continent is so dry all the water evaporates, or...well, there is no other option, really. Lakes need rivers flowing out that eventually reach the ocean.

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    $\begingroup$ I'm sorry but I disagree. Rivers can combine and separate, and a river can go underground and reach the ocean that way. I'm writing my own answer with examples. $\endgroup$ – Renan Jan 31 at 18:25
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    $\begingroup$ There can be a fork in the flow of a river, but these are typically minor and short-lived; one fork will eventually "win", providing an easier flow of water (even if it's longer), and the other path will dry up as the "winning" fork erodes a deeper channel. You will never see one river forking across into a second river system with two completely different drains, as one of two things will very quickly happen; River A's upstream system will divert into B's drain as a fork of River B, or the channel connecting them will stagnate and dry as each river continues to prefer its own drain. $\endgroup$ – KeithS Jan 31 at 19:03
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    $\begingroup$ While rivers disappearing underground are a thing, they're rare; in your answer, you mentioned two in the entire world, while this one small continent has seven major lakes with no surface drains to the sea. Eventually, a subterranean river flow will erode out whatever it's flowing through, the surface will collapse in a massive sinkhole, and you have a young canyon with the river winding through the bottom (and a much smaller lake if any at all). $\endgroup$ – KeithS Jan 31 at 19:08
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    $\begingroup$ Areas were lakes have no outputs are called endorheic basins. They are not as impossible you seem to imply. There are some on every continent on earth. The fact that each endorheic basic shown includes a major lake implies OP has a grasp on how they work. Also the biggest lake in the middle which you've labeled 2, clearly has an output. $\endgroup$ – Luke Jan 31 at 22:27
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    $\begingroup$ I would argue that the point marked 1 near the bottom-most, biggest lake isn't necessarily wrong. That river could be flowing OUT of the lake (I don't think I've seen OP specify which directions the rivers flow). That, of course, adds two very sharp bends which is a bit unlikely, but not outright impossible IMO. $\endgroup$ – Tamius Han Feb 1 at 19:55
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This continent should be about as long as the U.S. and twice as tall, with the bottom half positioned about where the U.S. is in the northern hemisphere.

So... about the size of Canada and US combined, give or take.

I think I went a little bit crazy on rivers

As many answers on this site show, we humans generally can't go crazier than nature. This is an oversimplified map of the Amazon basin that I found on the Internet. When I say oversimplified, I am oversimplifying the word oversimplify.

Map of the amazon basin

Source: https://hydrosheds.cr.usgs.gov/

Also, I have a vague idea as to the climate due to location and Worlds-History Simulator, but because of all the mountains I will need to add in to make the rivers flow, I don't know how much of the continent will be desert or lush Forrest due to the rain shadow effect.

I can't see the mountains there, but you've got so many rivers that it will probably be forests everywhere. Unless you have mountains between a rive and a plain (probably by the coasts). Now some people may have thought our question is kinda broad in scope, so I suggest you open a new question to ask just about the climate once you have added mountains to the map and settled on the rivers.

Any advice and criticism would be greatly appreciated, and I apologize if I'm asking too much.

So I just checked, and Canada seems to be as rivery as your world. So the climate might be the same. I think you will have lush forests on the bottom half of the continent. Around the middle and upwards you will have pine forests, going onto a tundra as you move northwards. The northernmost rivers could be frozen for most of the year.


Another answers suggests that:

  • Rivers cannot join and then separate. But they can. Look at the rivers around Montreal:

Montreal

They flow from southwest to northeast. The Otawwa river to the west and St. Lawrence to the south river join southwest of Dorval, then separate into Riviere to the west (between Montreal and Laval) and Prairies to the east, then join again after the island. The rivers keep joining and separating all the way to the ocean.

  • Rivers have to touch the ocean on maps.

Underground rivers are a thing. Some reach the sea going below its surface. Some end up connecting to the ocean via a cave, like Puerto Princesa in the Philippines. Aquifers are also a thing for you to research.

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    $\begingroup$ Best answer so far, we normally don't realize how many rivers there are around us. We can normally name like 5 rivers in our countries where there are thousands. $\endgroup$ – GaboSampaio Jan 31 at 19:27
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    $\begingroup$ There's a difference between a river's flow separating around an island and splitting into two separate rivers. In the case of the water flowing around the island of Montreal, all of it rejoins to become part of the St Lawrance river as it flows into ocean. The fault that others are highlighting is where two rivers diverge course. $\endgroup$ – sphennings Jan 31 at 20:25
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    $\begingroup$ Branching does happen, but it is rare. When it does happen, the branches usually rejoin, creating an island. Many rivers do empty into aquifers or dry up before the reach the sea, but these are the exception, not the rule. When it comes to creating a realistic fantasy map, it's best to stick with the most common scenarios. If you do diverge from them, you better know what you're doing. $\endgroup$ – WillRoss1 Jan 31 at 20:26
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    $\begingroup$ Some terms to help people who want to research splitting rivers: "River Bifurcation" is when a river splits. "Distributary" is a charming word for the smaller river that splits off of a major one. It's worth looking up to see what kind of circumstances lead to rivers splitting. $\endgroup$ – Luke Jan 31 at 22:39
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    $\begingroup$ The Wikipedia article on distribuitaries clearly enumerates with multiple examples why they are so rare: they are unstable and the process of stream capture eventually makes all the water flow one way. A number of these rivers are artificially kept that way by humans in order to prevent economically important cities (eg New Orleans) from being left behind by the shifting river. $\endgroup$ – March Ho Feb 1 at 2:29
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You have a lot of very very large endorheic basins, which is odd, possible, but unlikely. Even in the places with a lot of them they still only make up a fraction of the land area. While your continent is dominated by them which requires a very specific and odd set of circumstances, basically all your mountains around the basins need to develop at once, otherwise there will be an outlet. Mountain building in a well fed drainage system just leads to canyons. That kind of mountain building just is not possible with the existing arrangement of mountains (the drainage tells use exactly where the mountains are.)

You are also lacking rivers on several coasts, which is down right unbelievable. Even continents with many endorheic basins, like Asia (see below), are still dominated by normal river systems. the act of mountain building itself will build a coastal drainage system. It is basically impossible to get so much highland coastline on that scale.

Also a large endorheic basin near the coast has to mean a massive desert. It is not that the drainage can't reach the ocean just that the water evaporated before it can generate the force needed to cut a path, BUT that means there also will not be enough water to form lakes either, and your lakes are massive. If you want some ideas these drainage maps may be useful.

enter image description here

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    $\begingroup$ Possibly some to all of the large endorheic lakes are remnant pockets of ocean left over from when two or more precursor continents collided to form the present one, which may well have dried out to below sea level (possibly well below) but nevertheless still hold some water (like the Caspian Sea is now, the Black Sea was until the Bosporus broke through in the early Holocene, and the Mediterranean has been at numerous times in the past and will eventually permanently become as its western outlet is sealed off by the continued northern movement of Africa)? $\endgroup$ – Sean Feb 1 at 5:59
  • $\begingroup$ @Sean the issue is not having endorheic basins, it is the size of them, compared to the continent, A basin that size can't be trapped oceanic crust, you would need multiple converging continental masses to isolate it, there are none available on the OP's map, the Asian sea work because they are relatively small compared to the massive mountain building events that isolated them. there is no room for such an even on the OP's continent. $\endgroup$ – John Feb 1 at 14:32
  • $\begingroup$ The size of the lakes (= surface area) is a simple function of a) average precipitation into the endorheic basin and b) the amount of water evaporation per square kilometer water surface. I.e. the lake area is roughly proportional to the precipitation if the heat is kept constant. As such, you can have any size of lakes, if you adjust the climate accordingly. Arid climate gives tiny salt lakes, a wet climate can basically fill the entire basin. $\endgroup$ – cmaster - reinstate monica Feb 2 at 22:56
  • $\begingroup$ @cmaster-reinstatemonica it is less about the lake itself than the geology to get the lake and continent in that shape. If there is significant precipitation while the uplift is happening it will be canyon-land not a basin. There is a reason all the large endoheiric basin are in arid climates. A river can cut faster than mountains can rise. $\endgroup$ – John Feb 3 at 0:25
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This seems like a great time to check out https://azgaar.github.io/Fantasy-Map-Generator/. If you can turn your base map (coastlines) into a digital image, you can upload it there, start painting in height, and then ask the software to generate not only rivers, but also biomes (and, if you like, towns and all sorts of other stuff).

As others have noted, you have a number of odd instances of lakes with no outlets, rivers flowing away from the sea, and the like. (Is the 'top' edge of your map some sort of ridge, with higher land right near the edge and lower land further in?)

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  • $\begingroup$ I never knew that tool existed. It is seriously one of the coolest things I've seen in a long time. $\endgroup$ – Roddy of the Frozen Peas Feb 2 at 2:35
  • $\begingroup$ +1 for that map tool, just spend the better part of 5 hours playing around with it. $\endgroup$ – Umbra Feb 3 at 14:51
  • $\begingroup$ Ironically enough, I only know about it because I saw it mentioned somewhere here on WB.SE ☺. $\endgroup$ – Matthew Feb 3 at 16:22
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You say your continent is twice as "tall" as the US, with the bottom half at about the same latitude as the US. So basically your continent is US + Canada. A large percentage of the north of this continent should be inhospitable tundra and taiga.

Being this far north, I would expect to see fjords or other evidence of glaciation, which I don't. Without a heightmap it's hard to tell.

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There are some notable issues with the posted river/ lake system:

  • (1) The small lake in the western system is oddly surrounded by a big river system with no connection to it. This river system is very regular and dense compared to the rest of the continent
  • (2) There are multiple (seven) quite large endorheic basins with no outflow, but huge lakes at their end. These would all be salt lakes, because the water must evaporate instead. Many of the rivers contributing to these systems flow away from the northern coast, which suggests that there is a mountain range blocking that direction. In fact, there is no single major river flowing into the northern ocean (4). The basins are also too large to credibly be drained by underwater rivers (Also, then you'd expect no lakes and at least some rivers reaching the northern ocean, not hundreds of miles of underwater rivers). It is important to note that lakes shrink over time due to sediment added to them - huge freshwater lakes will be geologically young (like the Great Lakes, which stem from the ice age) or quite deep with no major river flowing through (like Lake Baikal or Malawi, bot rift valleys).
  • (3) As other pointed out, major rivers generally do not split. And when they do, they nearly always merge back soon after, forming an island. Or this happens in the river delta, where the parts "merge" in the ocean. Generally, the terrain in such areas will be quite flat.
  • (5) the big lake in the south has no tributaries from the south, which makes me wonder, what the topography of the area would be.
  • Many rivers are rather straight with hardly any tributaries, which is not that common. And if there are tributaries, they seem very regular - same size and shape as the other river, rarely any minor tributary joining downstream. Only system (1) breaks this, but there all tributaries are the same.

annotated map

In general, it is hard to imagine the topography of this continent, that is the mountain ranges and basins. You should start with the elevation map and then draw the rivers, because rivers follow elevation, not the other way around.

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I'd suggest it's actually quite realistic.

If we look at the history of this land mass, we might have seen something like this a short while ago. Triangles indicate "high" land while the multi-peak icons represent actual mountains. The white and grey dinosaur skull represents ice.

enter image description here

Here we see the continent as it was during the most recent glaciation. Ice being quite heavy, it has pressed down on the land, especially in the areas marked light grey, where accumulations were densest. Melting along the edges is occurring and is drained away mostly to the south, where four archaeorivers have cut through the uplifted Southern Highlands and also in the west where a gap between the mountain ranges allows for outflow.

Moving up to the present, post-melt period, we might see this:

enter image description here

We have the Great Central Spine, which I'd imagine represents the collision of two smaller proto-continents and also the Great Southwestern Mountains, which might represent a lesser collision or collision in progress of a plate from off the map somewhere.

The ice now melted, what we have left is a ring of higher land, pushed up, and two central areas of depressed land, pushed down, due to isostatic forces. The grey areas where the ice was most concentrated and thus heavier and more oppressive formed deeper basins within the two great basins, and these are where residual melt water that didn't escape Agassizwise through the western channel now forms a series of endorheic lake & river systems.

I would suspect that in some distant future, as the central lowlands continue to rebound from their former depression, the endorheic lakes will disappear along with the ring of (relatively) high land, most of the rivers will reverse course and the lakes will drain to the surrounding Ocean.

Your scenario reminds me a lot of this land:

enter image description here

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  • $\begingroup$ It's definitely not a common continent, but credit to you for figuring out how the map as it currently stands would work $\endgroup$ – Fred Stark Feb 2 at 23:13
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    $\begingroup$ note Greenland will not have much in the way of endoheiric basins if it melted, the melt will cut its way out, it is already doing it now, you end up with the central US with a huge river/lake system connected ot the ocean, not an isolated basin. also you are correct a lot of the depression in the center will rebound. $\endgroup$ – John Feb 3 at 0:34
  • $\begingroup$ Greenland *already" has drainage paths from the interior. Look at the north end; there's a valley nicknamed the Grand Canyon that cuts through the mountains. $\endgroup$ – Keith Morrison Feb 3 at 17:00
  • $\begingroup$ @KeithMorrison -- I know it has paths from the interior. That's why I said it "reminds me" of. Just to be clear, being reminded of a place is not the same thing as saying that place is exactly like the fictional place. $\endgroup$ – elemtilas Feb 5 at 18:22
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If the land mass is as big as you say, I don't think you went too river crazy.

That said, I think you are missing something. A river flows from source to river delta usually. What do your rivers empty into? Since we can't see your mountains yet, we have no way to know what direction the rivers flow.

I notice there is a stretch through the middle of the land mass. That would be a perfect place for a large river to run out to the ocean to the East (or West). Your smaller rivers would be good tributaries. Think along the lines of the Mississippi river in the US.

Looking at the wiki for the Mississippi you will see a map of the Mississippi Basin. This will show you just how big the area is, with all the tributaries. This could be a really good model for you to develop your river map.

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How "real" do you want your world to look? In answer to your question, I can see your world being very real for the liquid present in it. How you will use this map is important as to how much detail you put into it. Your lakes that absorb rivers will have interesting properties, including being fairly concentrated in minerals and other waste that gets floated down-river to them. The oceans tend to be larger bodies of water and absorb these without affecting their overall concentrations.

As for your statement for too many rivers, I've attached one country from my world-building project. The world program generates 1,114,000 rivers for my Avalon world. If you google search how many rivers are in the US, you will find we have about 250K rivers in just the US alone, so a world with over 1 million rivers is fairly accurate. Your US/Canada size map has less than 100.

One country of Avalon

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    $\begingroup$ Number of rivers is somewhat a function of what you consider a "river". For map-making purposes, depending on your scale, you might only care about ones that have economic importance / are large enough for barges (larger scale) or are difficult to ford (medium scale). Otherwise, realistically, you can't walk more than a few miles in a straight line without encountering a waterway. It's almost impossible for any sort of large scale map to have "too many" rivers; for sanity's sake, you stop drawing the smaller ones before you get to the point of having so many it is "unrealistic". $\endgroup$ – Matthew Jan 31 at 21:34
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    $\begingroup$ The answer to that is 1 million rivers reduces down to around 30,000 that have economic purpose. When creating the graphics, I am looking for details that will lend to creation of larger economic areas like river basins that translate into crop lands, or higher altitudes that reflect other possible pursuits like mining or dwarven habitat. $\endgroup$ – user72081 Feb 1 at 1:17
  • $\begingroup$ Interestingly, I note that your examples would seem to make elevation more relevant. It seems you are starting with rivers and trying to work backwards to elevation. Going the other way around might make more sense? (If nothing else, it's fairly straight-forward to derive drainage from elevation; less so to try to work that problem backwards...) Note also that if you're really going to take the problem seriously, you also want to guess rainfall, which involves factors like rain shadow and ocean proximity. $\endgroup$ – Matthew Feb 3 at 16:27
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Your rivers are quite straight which indicates steeper terrain. Meandrous rivers indicates, on the other hand, much flatter terrain.

Water tend to flow in the direction of the steepest descend. When it face an obstacle, in the steep terrain the flow has enough energy to make its path through the obstacle or moving it away. On the other hand, on a plateau, the stream has little energy and it finds a different way to flow.

Splitting the flow in multiple separate branches may occur only when the topography is like rooftop-like and the flow reaches it. Which happens extremely rarely and lasts for a short time, because one of the branches usually gets some preferrence. On plateau this stream splitting occurs more frequently but even there it happens on small scale.

In Europe, where the industrial history is measured in millenia, rivers were the major trade lines for large commodities. Thus water structures are quite old there. One of exaples of splitting the stream in a hilly terrain is here. It allowed logs to be sent either to Vienna (located on Danube river flowing to the Black Sea) or ti Prague (locaed on Moldau river, flowing to North Sea through Elbe river). This was working thanks to an artificial channel system (main line plus supporting streams) that was able to track the stream to the terrain edge.

Another example is a pond system around Třeboň, CZ, where artificial canals connecting rivers Lužnice and Nežárka support water for the ponds. The most significant canals there are called Nová řeka (New river) and Zlatá stoka (Golden channel). This system is localized in the quite small Třeboň plateau, where the low elevation changes allow such structures to be built.

So, you can keep the stream splitting points or the channels but make them artificial. The systems I mentioned above are from 16th century (Třeboň) and 18th century (the channel).

Sorry for the links in german and czech, english wiki does not cover those topics.

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