How to get your rivers in the right place

[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'

[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.

[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?

[Neorael]

I wanted to thank you all. Every part of this topic has something to contribute in the learning of how the hydric sistem operates

[Midgardsormr]

The alluvial plain near a lowland river tends to be very fertile because the soil around it is regularly exchanged. While the "Fertile Crescent" eventually wore out and suffered from desertification due to overfarming, the Nile's flood plain, particularly the delta area, remained fruitful through thousands of years of continuous farming. The primary difference was that the Nile floods regularly, which refreshes the nutrients in the soil. The Tigris and Euphrates flood plains have remained fertile, but not to the same extent because their flooding is less reliable. The rest of the land in that area was merely irrigated from the rivers and did not receive the benefit of the floods. As a result, the nutrients were depleted, salt levels rose, and the desert claimed what was once very good farmland.

More obviously, of course, vegetation tends to be thicker around rivers because that's where the water is! In the American Great Plains (where I grew up), the tall grasses will grow everywhere, but you only naturally find trees near the rivers because the rest of the land just doesn't have enough moisture to support them. Trees planted far from the rivers tend to be rather sickly, and they often fall down during windstorms. Typically on someone's car.

[Gumboot]

The alluvial plain near a lowland river tends to be very fertile because the soil around it is regularly exchanged. While the "Fertile Crescent" eventually wore out and suffered from desertification due to overfarming, the Nile's flood plain, particularly the delta area, remained fruitful through thousands of years of continuous farming. The primary difference was that the Nile floods regularly, which refreshes the nutrients in the soil. The Tigris and Euphrates flood plains have remained fertile, but not to the same extent because their flooding is less reliable. The rest of the land in that area was merely irrigated from the rivers and did not receive the benefit of the floods. As a result, the nutrients were depleted, salt levels rose, and the desert claimed what was once very good farmland.

More obviously, of course, vegetation tends to be thicker around rivers because that's where the water is! In the American Great Plains (where I grew up), the tall grasses will grow everywhere, but you only naturally find trees near the rivers because the rest of the land just doesn't have enough moisture to support them. Trees planted far from the rivers tend to be rather sickly, and they often fall down during windstorms. Typically on someone's car.

You're quite right, although trees don't grow where rivers are, as such. Rather both trees and rivers tend to end up in areas of high rainfall. Water in a river isn't much use to a tree, because trees don't grow in rivers. But rivers tend to flow where there's more rainfall. Trees get their water mostly from rainwater falling on the ground where they're standing. The water that isn't absorbed by trees ends up in rivers.

Generally speaking:

Higher rainfall = more trees + more rivers
Lower rainfall = less trees + less rivers

[Hai-Etlik]

You're quite right, although trees don't grow where rivers are, as such. Rather both trees and rivers tend to end up in areas of high rainfall. Water in a river isn't much use to a tree, because trees don't grow in rivers. But rivers tend to flow where there's more rainfall. Trees get their water mostly from rainwater falling on the ground where they're standing. The water that isn't absorbed by trees ends up in rivers.

Generally speaking:

Higher rainfall = more trees + more rivers
Lower rainfall = less trees + less rivers

Actually on the great plains it is the rivers directly allowing the trees to grow, they aggregate the water, and bring in water from rainier areas, which allows the trees to grow in the river valleys despite not having any more rain than the surrounding plains.

[Elothan]

I have collected a bit of the information in this thread and some more in a pdf. I made it for my own use, but if anybody wants it to read off line I`d be happy to share it
It is mostly just copy paste from the forums (with credits and links to the contributors, so nothing really fancy.
But if it is ok, just ask and i will put it up

[Gidde]

Go ahead and post it up, pdf collations are always welcome.