Why Do Rivers Curve?

Compared to the whitewater streams that tumble
down mountainsides, the meandering rivers of the plains may seem tame and lazy. But
mountain streams are corralled by the steep-walled valleys they carve – their courses are literally
set in stone. Out on the open plains, those stony walls give way to soft soil, allowing
rivers much more freedom to shift their banks and set their own ever-changing courses to
the sea: courses that almost never run straight. At least not for long, because all it takes
to turn a straight stretch of river into a bendy one is a little disturbance and a lot
of time  – and in nature, there’s plenty of both.
      Say, for example, that a muskrat  burrows
herself a den in one bank of a stream. Her tunnels make for a cozy home,  but they also
weaken the bank, which eventually begins to crumble and slump into the stream. Water rushes into the newly-formed hollow,
sweeping away loose dirt and making the hollow even hollower, which lets the water rush a
little faster and sweep away a little more dirt from the bank…and so on, and so on
. As more of the stream’s flow is diverted
into the deepening hole on one bank and away from the other side of the channel, the flow
there weakens and slows. And since slow-moving water can’t carry the sand-sized particles
that fast-moving water can, that dirt drops to the bottom and builds up to make the water
there shallower and slower, and then keeps accumulating until the edge of the stream
becomes new land on the inside bank.        
Meanwhile, the fast-moving water near the outside bank sweeps out of the curve with
enough momentum to carry it across the channel and slam it into the other side, where it
starts to carve another curve . And then another, and then another, and then another. The wider
the stream, the longer it takes the slingshotting current to reach the other side, and the greater
the downstream distance to the next curve. In fact, measurements of meandering streams
all over the world reveal a strikingly regular pattern : the length of one S-shaped meander
tends to be about six times the width of the channel . So little tiny meandering streams
tend to look just like miniature versions of their bigger relatives.
     As long as nothing gets in the way of a river’s
meandering , its curves will continue to grow curvier and curvier until they loop around
and bumble into themselves. When that happens, the river follows the straighter path downhill,
leaving behind a crescent-shaped remnant called an oxbow lake. Or a billabong. Or a lago en
herradura. Or a bras mort …     
We have lots of names for these lakes, since they can occur pretty much anywhere liquid
flows – which brings up an interesting question: what do the Martians call them?

38 thoughts on “Why Do Rivers Curve?

  1. La présence d'animaux n'est pas nécessaire puisque l'effet s'amplifie.
    Il suffit d'une imperfection et la dynamique se met en marche, comme un drapeau flotte dans le vent…

  2. 3°28'37.7"S 66°03'37.7"W a town in the amazon Forest that will became a oxbow lake.

  3. I watched this entire video because it was labeled "Video instructions and help with filling out and completing l 152" on:
    What the hell do need this info for when trying to fill out form L-152…

  4. This is my favourite minute earth video! That aha moment that made me understand why rivers meander was just amazing. I hope my content can have the same explanatory power as yours does one day.

  5. Pretty hard to find, as the old lakes usually evaporate and are reused for agroculture. I found few examples tho on maps:

    1) around Philippsburg Nuclear Power Plant and Mannheim city in Germany, on a Rhine River before – https://www.google.com/maps/@49.3602828,8.5061477,44574m/data=!3m1!1e3

    On wikipedia there is entire article about ox-bow lakes on Rhine river – https://en.wikipedia.org/wiki/List_of_old_waterbodies_of_the_Rhine

    2) Rhone just south of Geneva around Cartigny in Swtizerland – https://www.google.com/maps/@46.1785687,6.0280262,4035m/data=!3m1!1e3 , I couldn't find any more in Switzerland, as land is quickly repurposed for other uses due to limited space in Switzerland 😀

    3) Odra river in Poland – https://www.google.com/maps/@52.0331004,15.5448208,6412m/data=!3m1!1e3 and https://www.google.com/maps/@51.9869691,15.7006246,9064m/data=!3m1!1e3

    4) Visula river in Poland – https://www.google.com/maps/@51.7080227,21.474588,9017m/data=!3m1!1e3 and https://www.google.com/maps/@50.0335364,19.4932722,4474m/data=!3m1!1e3

    There is so many more, but a lot of them evaporated, got eroded, and are no longer lakes or rivers, but you can still see them in the terrain and vegetation on them.

  6. "Making the hollow more hollower"
    The snow is snowier than before

  7. The river curves because of the running water flows naturally in a direction according to the gravity along the slope and makes it's own way

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