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Thread: River placement

  1. #1
      davoush is offline
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    Default River placement

    Hello,

    I'm trying to work out river placements which would be mostly plausible. So far I'm pretty happy with how they are, but there are a few areas which have no major rivers running through them at all - I'm not sure how much this would effect possible civilisation in that area especially in the Western continent around the equator. Do there seem to be too few / too many rivers? Any suggestions or criticism welcome.

    Also, the rivers are just a guideline for now, I haven't started to think about artistic details so excuse the crudeness of it.

    Thanks!

    River placement-rivers.png
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      Gidde is offline
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    Default River placement

    At first glance you have several rivers running parallel to coastlines which wouldn't happen unless there were hills/mountains in between, which i don't see. i'll take a longer look tonight

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    Guild Master Gracious Donor Midgardsormr's Avatar
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    There are also a couple that appear to be running parallel to the slope of a mountain rather than flowing on downhill. The westernmost that has its headwaters at a latitude around -15, for instance. I would expect it to flow away from the ridgeline first before turning southward, unless it's running in a canyon that isn't obvious from the low resolution of the height data.

    Likewise, there are a couple flowing from the "point" of a mountain range rather than the "pocket," if that makes sense. The spots where the lowlands are closest to the ridges are going to be valleys, which will be likely to collect rain and snow, and thus form rivers.

    Semi-arid areas that don't show much in the way of major rivers are likely to support more pastoralist cultures rather than farming ones. Without a source for irrigation, agriculture is likely to be a supplementary subsistence activity rather than a primary one. That's not going to be a 100% thing, of course. Humans (and presumably other culture-using species) are very good at adapting to their environment and also at adapting the environment to themselves.

    For examples of the kinds of cultures that will grow up in a land with few rivers, consider the steppes of Asia and the Great Plains of America, west of the Mississippi. These aren't deserts, but they are also not characterized by many rivers.
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      waldronate is offline
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    One of the nice things about contours on your maps is that they make running the rivers easier. Rivers will always run perpendicular to contours because water always follows the path of steepest descent.

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      priggs is offline
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    Here is some information:
    Question for the River Police (TM)
    Philip Riggs
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      priggs is offline
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    In these two areas, I'm wondering why the river went the long way instead of the short? I would thing the rivers would have gone to the shortest ocean.
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    Name:  river_2.png
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    Philip Riggs
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      chick is offline
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    Rivers flow downhill, not necessarily the shortest distance. If there is higher land between the river and the seacoast, the river may run a long way roughly parallel to the seacoast before it finds a downhill route to the sea.

    I am a geologist, and I think the rivers you have placed on the map look fine. At a local scale, rivers run downhill. At a large scale as in your map, you should expect the rivers to run generally from the mountains to the sea, through lower and lower elevations.

    In the larger areas without mountains, there will still be rivers. Crossing large flat areas, rivers meander back and forth slowing working toward the coast. You can add rivers in those areas, starting distant from the seacoast and winding through the plains to the sea.

    When you make the smaller scale local areas, just be careful that you don't put a range of hills between lower elevations and the sea that would interrupt the always-downhill flow of rivers.

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      jbgibson is offline
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    Have you taken a look at the most excellent tutorial titled How To Get Your Rivers in the Right Place, in the tutorial forum? It explains water behavior vs. landform behavior very well.

    Neither your river network nor your landforms are outright nonsensical, but the combination is, like the folks above have said, not plausible in some places. One problem is that a certain pattern of rivers implies a certain topography:

    River placement-impliedshapes2.gif

    Even just a set of coastlines implies a lot about what's going on altitude-wise onshore:

    River placement-implied-shapes1.gif

    Your rivers paralleling coasts could be explained away by another intermediate altitude color - say your original darkest two grays are 1000ft and 2000 ft altitude. Rivers where you put them kind of imply some more raised land, say the new second-lightest gray, at maybe 200 ft altitude:

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    I say a mere 200 on purpose - it doesn't take but a few feet of altitude differential to steer a river one way instead of another. so the implication is not necessarily a bunch of massive mountains that you don't intend. Trouble is, when you stick altitude indications on a map the natural guess is that all other things being equal, it's a straight slope from a higher band to the nearest point on a lower band, and in turn straight to the ocean. That would result in a bunch of fairly gentle slopes across the wide areas of your lowest land color.... slopes which your rivers seem to violate (crossing across-slope , or even going uphill).

    In general it's best not to buck your viewer's assumptions & instincts. If you *want* a river that flows along a coast 50 km away for 500 km, then somehow indicate a bit of raised terrain in between. If you want a river to flow through a narrow gap in a mighty range go ahead, just indicate there's water-level land there to allow the passage. That does happen, by the way, all over the real world, so the second mountain arrangement in my first illustration above is perfectly legit.

    Contour lines crossing a river will "point" upstream, whether the lazy lower Mississippi, or some mountain stream in the Rockies. So any "V" shape conversely could be expected to have a river coming from the sharp point to somewhere between the separated parts, in a downhill direction. Another way to say the rule of thumb is that water lives in concave shapes not convex ones. Yet another generality would be you expect rivers to reach the sea at the back of bays, not at the tip of peninsulas. See tyhe dotted line on my extra-200-ft-altitude band version of a snip of your map? THat's where the experienced eye expects to see another river.

    THere.... my normal mode of 'clarifying' thing is with many, many words - I sincerely hope this hasn't been too many :-).

    By the way, I love your overall continent shapes. those two world-girdling near land-bridge arcs of islands are going to be great choke points yet enablers for commerce, invasion, migrations, and who knows what-all !
    Last edited by jbgibson; 10-19-2014 at 01:09 AM.
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      priggs is offline
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    Thanks, jbgibson. You described exactly what I was thinking, and did so thoroughly and eloquently.
    Philip Riggs
    Decorative-Maps.com

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