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My rivers and streams are just about as good as my waterways - that is, not too good. I do know that their paths are impacted by elevation, so I generally determine the elevation of an area before drawing in the shapes of rivers. One issue is that waterways change the shape of the land around them - a perfect example being the Grand Canyon.

  • What are the processes that cause rivers to take the shapes they do?
  • What processes impact the shapes of river deltas and the environments within?

Note:

This is part of a series of questions that tries to break down the process of creating a world from initial creation of the landmass through to erosion, weather patterns, biomes and every other related topics. Please restrict answers to this specific topic rather than branching on into other areas as other subjects will be covered by other questions.

These questions all assume an earth-like spherical world in orbit in the habitable band.


See the other questions in this series here : Creating a realistic world Series

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    $\begingroup$ Thoughts for additional questions: vegetation, soil composition, mines, good settlement locations. Keep up the good work! $\endgroup$ – Frostfyre Jul 28 '15 at 17:52
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    $\begingroup$ I would like to write an answer about this but I probably can't explain it better than this : thebritishgeographer.weebly.com/river-processes.html and thebritishgeographer.weebly.com/river-landforms.html $\endgroup$ – Vincent Jul 28 '15 at 19:04
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    $\begingroup$ You might consider stealing. Take a detailed map of rivers and creeks from some locality, copy it into your map as mountains and major rivers. $\endgroup$ – Oldcat Jul 28 '15 at 21:48
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    $\begingroup$ @Oldcat I do have a conscience. $\endgroup$ – HDE 226868 Jul 28 '15 at 21:50
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    $\begingroup$ The continents never bothered to file copyright on major and minor landform shapes. Go for it with a clear conscience! $\endgroup$ – Oldcat Jul 28 '15 at 21:56
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Headwaters

Your headwaters are formed by three things, although not always exclusively one:

  • Rainwater
  • Snow Melt
  • and/or an Artesian Spring (a good classification system is here)

Each has a unique geographic quality to them, and your story will have to procure the appropriate "source" of your river.

Scale

You already know that small creeks from runoff and rainwater form into larger and larger rivers until you have something like the mighty Columbia river.

Types

There are four basic types of river:

  • Young - think steep, relatively deep, and short; not a lot of historical erosion.
  • Created - caused by a tectonic event; these are around more than you might think. This will give you your grand canyons, although not exclusively.
  • Mature - long, with lots of tributaries and picks up a lot of sediment along the way to dump into the sea, such as the mighty Columbia and Mississippi rivers.
  • Old - a long, flat, wide river with low erosion left, such as the Nile.

Waterfalls & Diversions

The basics of geology, insofar as water processes, are your three types of rock:

  • Igneous (very hard, granite, etc.)
  • Metamorphic (like gneiss and marble)
  • Sedimentary (sandstone; "soft" and easily breakable).

When an igneous rock is formed from lava - note: I'm being very elementary here, I know - it pushes up through other rock types and can form mineral dykes or outcroppings of very hard stone.

This means that a water body can erode the soft stone, leaving the hard stone. This is exactly what happens when a waterfall forms, for example. The softer stone was eroded away, but not the harder granite, so the water has to go over the hard stone and drop away where there once was soft stone long eroded away. Diversions happen this way too.

Another forming factor in flatlands is the soil and sediment, which can cause a river to have the long, sinewy look in very fertile parts of your world. A once-straight river pushes sediment aside, which builds up. The side that has the most becomes a barrier, so the river goes the other direction; subsequently, the faster moving (furthest) side builds up. This creates a S-curve as well as oxbow lakes.

Deltas

At the culmination of a river into a sea, lake or (more likely) ocean, a lot of really fascinating things happen. A mature or old river has long flattened out the end of its geology, and fans out into a delta. Because of the sediments it has brought with it, lush flora typically is present, such as that at the end of the Nile.

This also brings a lot of hungry fauna, including people. Furthering the biodiversity is the mixing of fresh and salt waters in the estuary. This is where I go fishing!

Cultural

I shouldn't have to stress how important rivers are, and at the risk of starting a list:

  • Transportation of Goods
  • Travel
  • Water Supply (on mainland and islands)
  • Energy Generation & Engineering
  • Agriculture (leading to mythology about fertility)
  • Hunting & Fishing,

... and on, and on.

Bonus: Have fun!

It is perfectly plausible to have in your story a navigable underground river, super short river, or a river whose watershed is bigger than Alaska. I should think rivers of different material composition on your world (rivers and lakes of methane?) would have a different impact on life on your Earth 2.o.

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    $\begingroup$ Your answer is certainly bounty-worthy, so enjoy the extra reputation points! $\endgroup$ – HDE 226868 Aug 6 '15 at 21:55

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