Along the same lnes : Rivers - left or right?

[markem]

This is an odd question that just popped into my head. Do rivers tend to move more to the right or left? I know they run north to south (in the northern hemisphere) and south to north (in the southern hemisphere). But do rivers have a more leftward movement or more of a rightward movement? I know in Europe there are several rivers that run right to left (so they would have a leftward movement).

An example in the US would be the Mississippi River. It does this leftward arc before running mainly straight towards the Gulf of Mexico. But what about the Colorado River? I know the Hudson River goes mainly to the right.

Anyway - opinions? (And I know they all are trying to get to the coast line or maybe a major lake. I'm talking about the journey TO the coast line or major lake.)

[Azélor]

You mean , do they tend to bend according to the Coriolis effect? http://en.wikipedia.org/wiki/Coriolis_effect

I have no idea, I never actually though about it but that is a very interesting question.

[The_Great_Lestrade]

I haven't seen stats for a whole continent or hemisphere but as a hydrologist, i'd say it depends entirely on the geology and geomorphology of the area around the river and this can vary significantly with country, region and hemisphere. For instance the Yenesi river in Russia flows south to north in the northern hemisphere as do many others. You can't really make rules about which direction rivers flow that easily at either a local or continental scale. In europe rivers are split between ending in the north sea, the Baltic, the Mediterranean, the Atlantic and the Black Sea, so that's seas on the N,E,S and W sides. In the US most rivers will end on east or west coast but at a smaller scale a river could end in the lakes of the north, or the gulf in the south.

[The_Great_Lestrade]

I'd be surprised if the Coriolis effect made a detectable difference. The location of mountain ranges, easily errodable rock, coast lines, and the prevailing wind are far more important.

[Redrobes]

Lots of discussion as part of my tut:
http://www.cartographersguild.com/showthread.php?t=3822

I was not aware that there was a specific tendency for rivers to flow in one direction in hemispheres other than the Coriolis effect which is pretty small compared to the downhill flow.

BTW: Lestrade, if your an actual hydrologist then your comments on that thread would be pretty useful.

[markem]

I had never thought about this until now but I would have thought that at least one government would have done a study on this. If not - maybe it would be something for someone in college to look in to???

[Chick]

The Coriolis Force does have an effect on rivers, but not the direction of flow, that is determined by downhill.

In estuaries, the Coriolis effect tends to swing the incoming tidal flow and the seaward flowing river water to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. This results in a higher concentration of inflowing seawater on one side of the estuary and fresh river water outflow on the other side.

In NS flowing rivers, the rotation of the earth causes rivers to erode more on the west bank than the east.

There is also some belief that river valleys erode more on their right banks than left. This effect is called Baer's Law, but is generally considered too small an effect to observe.

[altfritz]

By "coriolis effect" do you mean that water goes down the drain clockwise in the Northern Hemisphere and the opposite in the Southern? That is a myth. Water follows the path of least resistance from a higher elevation to a lower one. Note also that the Mississippi has changed it's path many times. I think there is a wiki page showing some of them over the last 2000 years or so. And there are a whole bunch of really good (and geeky) videos on Youtube that explain the science about how river bends are formed and how they erode. IIRC some even have Math! :-0 ;-)

[johnvanvliet]

left or right
has no real meaning

if you are facing North then right is EAST
if you are facing east then right is south

it has no meaning


as to if east or west
where on the river?????
many meander and flow BOTH east and west ( and north and south)

they ALL however flow DOWN hill

[altfritz]

I'm reading an "Official History of the Gordon Relief Expedition" (probably not the exact wording of the title) and it describes the journey up the Nile in great detail - day by day, in fact. It is all a series of official military reports and what is annoying is sometimes they use East and West but others they say the right bank or left bank! So, should I assume that as they are heading South the right bank is the West bank? Grrr! Otherwise the logistical problems involved and the detailed descriptions of the river are interesting reading. :-) Especially as this is taking place in the 1800's and so before any major alterations to the river.

I have actually been doing quite a bit of research into river forms in preparation to my Tekumel mapping project. IMO, important rivers to look at include the Indus, the Ganges and the Brahmaputra. All three of these change paths frequently as they flood during the monsoon season and may not always follow the same path when the next dry season returns. I found a complete map set of India, based upon surveys from the 1920s, available online at the University of Texas. These maps actually note that the path of the river is subject to change. They also seem to note those paths which are intermittent. I wish I could find earlier maps - before the rivers are tampered with by dams, etc. I also have found a useful map of the Mississippi from the 1860's which shows the massive extent of the flood plain before the Army Corps of Engineers got to work!