How to get your rivers in the right place

[Midgardsormr]

Very cool! I'd probably call it out, too, if only to get the story behind its formation. I'm sure nobody would put that on a map without a story to go with it.

[Ascension]

Yeah, that's from a crater. I saw it in one of those science shows that I'm always watching on the Science Channel...I think was called "How the earth was made" and it was in one of the episodes. Might be a different tv series, I can't keep them all straight in my head. Normally you'd think that the crater edges would prevent a ring river but the mound-in-the-middle resulting from the impact was very dense so it eroded very slowly while the edges were closer to normal dirt so they eroded faster. There's a few others like this in Asia and Central America if I remember right.

[RobA]

I was looking for some visual aids for describing some terrain to RPG players, and my search was 'Canadian Shield Region'

And I came across This river system.

I thought you guys might find it interesting. If I saw someone draw that on a map I would think it was very 'unrealistic'.

Its with a bunch of other pics in an article on craters, which you can find HERE.

It's not technically a river, but a lake with a large island

http://en.wikipedia.org/wiki/Manicouagan_crater

You might also like this earth impact crater viewer....http://impact.scaredycatfilms.com/

-Rob A>

[Lewas5372]

Texas is a bad example of lake formation, unless you have a race of sentient beavers in your fantasy world . All lakes in Texas are artificial save one, Caddo Lake, and we dammed that one for good measure, too. As for crazy forking Texas rivers, they never split after joining up and all flow to the gulf or the Rio Grand then to the gulf. Most of the time when something violates a rule its because of either heavy rainfall/flooding, which will sort itself out quickly, or because man stepped in a messed with things (i.e. the Chicago river flowing the wrong direction)

[Redrobes]

Absolutely ! This thread is about natural rivers and the long term state of them (and on a non magical earth like planet too). Post flood and tsunami... well almost anything goes. Then in the medium time span there is this braiding and some extreme cases of meandering then longer still you might have oddities from glaciers periodically freezing and thawing in multi decade cycles but generally, in the long term, the idea that rivers don't fork and exit into the sea in one spot holds true. I guess if considered long enough then any river system is dynamic enough that there is no stable state for it but for the maps we make here that's not really applicable.

[Ryan K]

Texas is a bad example of lake formation, unless you have a race of sentient beavers in your fantasy world.

I read that and I think 'dwarves'

[Insufferable Fool]

http://en.wikipedia.org/wiki/Stream_capture
Stream Capture (also known as Stream Piracy) is pretty sweet.

-Rob

Extremely relevant example: the artificially-postponed capture of the Mississippi River by the Atchafalaya. http://en.wikipedia.org/wiki/Old_Riv...trol_Structure

Would make for a pretty decent story in a fantasy setting too; a terrible disaster as a major port dries up. Or else an excuse for extensive ruins of that major port, decades/centuries after the fact.

[kiriona]

Seems about right. It's worth noting that when rivers do split up high in their courses it's most commonly due to stream capture—which takes a very short amount of time, geologically speaking. Probably the most notable example is the Casiquiare which links the Orinoco and Amazon basins. It was originally a separate river, but has currently migrated far enough to capture the upper Orinoco, which will eventually (ie in a few thousand years or so) drain entirely into the Casiquiare. A bifurcating river is possible, just unlikely. A map with lots of bifurcating rivers needs further explanation (eg the area is full of karstic terrain, the bifurcations are artificial etc)

Otherwise yeah... and I must say it's a relief to see a forum where mapmakers actually keep this in mind instead of just filling their maps with circular rivers and rivers flowing from one sea to another etc

[Mixail]

Well, I joined just for these tutorials

[s0meguy]

edit: I'll just make a thread about this because people probably don't look at these stickied threads much.

Question: Soil around rivers tends to be fertile right? So when making maps of fictional areas I always have a tendency to put a bunch of trees next to the rivers, and some forests sometimes, especially in an area where 2 or more rivers are relatively close to each other and lakes because the river is dumping all the soil nutrients there in the lake, so the soil around it would probably be fertile enough to support a forest. I'm always having a hard time over whether the soil around rivers is fertile, and if it is, what kind of vegetation i should put along side it, and also where to put forests in general. I gathered that they are usually next to mountains, because they trap moist air/rainclouds. Any good rules of thumb?