River Police

[FarsightX3]

You know, one thing that stings me is when the "River Police" come down and knock your rivers. I understand that everyone gets confused of the general structure of a river. But what gets me is, when they harp on "rivers don't flow" north. They usually pick on little curves in the river that the designer made that go northward instead of south. I'd like to point out that the Nile River flows northward. If you look at the Ohio River Map, you can clearly see in some areas that the river flows northward. Will the River Police pick on that natural state?

Example: http://roble.pntic.mec.es/rmac0040/i...sippiRiver.gif

[Juggernaut1981]

Well to be fair... rivers flow towards the equator... So us "Other Hemisphere" people are used to north-flowing rivers.

It's about "in general" rather than "all and every". In General, rivers flow to the equator. In General, lakes have single outflows and unify (rather than divide). In General, rivers avoid higher-levels-above-sea-level.

So, yeah they'll tell you the rivers should be heading south, because in general that's where they should go. The Nile probably has fair reasons for being the exception (I'd assume there are mountainous or higher-level-above-sea lands to the south)... but it's not just because "I want one that goes north". Unless you have really quite specific reasons for 'not following the general rule'.

[RobA]

Not sure what either of you are talking about. Rivers flow from high ground to low ground, usually stopping when they hit the sea.

If someone has been criticizing rivers because of their cardinal directionality then we need to have a little discussion. Can't have deputies tromping all over the place willy-nilly.

-Rob A>

[Mark Oliva]

Well to be fair... rivers flow towards the equator... So us "Other Hemisphere" people are used to north-flowing rivers.

It's about "in general" rather than "all and every". In General, rivers flow to the equator. In General, lakes have single outflows and unify (rather than divide). In General, rivers avoid higher-levels-above-sea-level.

Some of this is pure myth. Two of Europe's biggest rivers - the Rhine and Elbe as examples - flow northward, i.e. away from the equator. If rivers avoided higher levels above sea level they wouldn't be able to flow down to the sea (not that all rivers do that). They'd have to flow up to it.

[Juggernaut1981]

Some of this is pure myth. Two of Europe's biggest rivers - the Rhine and Elbe as examples - flow northward, i.e. away from the equator. If rivers avoided higher levels above sea level they wouldn't be able to flow down to the sea (not that all rivers do that). They'd have to flow up to it.

Um, that is kind of my point... Rivers LEAVE the areas that are ABOVE sea level and travel TOWARDS Sea Level. And if you look at the geography of Europe, it's a bit hard to flow south with the Alps where they are, consequently those rivers tend to head north.

So Height Above Sea-Level beats centripetal force tendencies for the water to head towards the equator.


*Physics Side-note and the reason for the equator comment...
Any object covered in liquid that is then rotated will have the water move towards the point of greatest radius from the axis of rotation. Catch is that Landform will trump centripetal motion.

[bartmoss]

*Physics Side-note and the reason for the equator comment...
Any object covered in liquid that is then rotated will have the water move towards the point of greatest radius from the axis of rotation. Catch is that Landform will trump centripetal motion.

That's very theoretical though, in the real world you'll hardly find a planet smooth enough. Indeed, I'd argue that the mere presence of rivers axiomatically means that the sphere can not be smooth enough for such a situation.

And how much does deformity of a planet caused by centrifugal force influence water behavior? I certainly am not good enough at math to figure this one out, but geek enough to want to know the answer!

[Hawksguard]

That's very theoretical though, in the real world you'll hardly find a planet smooth enough. Indeed, I'd argue that the mere presence of rivers axiomatically means that the sphere can not be smooth enough for such a situation.

And how much does deformity of a planet caused by centrifugal force influence water behavior? I certainly am not good enough at math to figure this one out, but geek enough to want to know the answer!

I believe what Juggernaut was describing as it would be applied to planetology is the Coriolos Effect, which basically states water and air will move away from the equator as the planet rotates. In the northern hemisphere, flow is deflected to the right and in the southern hemisphere it will be deflected to the left. Of course, on any planet not entirely covered by water, continents are going to muck around with any type of 'perfect flow' and as a result, you generally have clockwise currents in n.h. and counter-clockwise in the s.h. as part of the heating-cooling cycle of the oceans. Generally. The Coriolis effect however only applies to large objects over large distances, and its effect on a river is going to be all but negligible. Also, the fact that the earth bulges at the equator due to centripetal force isn't going to have any impact on what direction a river flows, it will always follow the path of least resistance from a higher elevation to a lower one.

[Redrobes]

I have to admit if there is a rule that said rivers run towards the equator then I had never heard of it. From what I have seen, if you had a circular island then the rivers would run radially out towards the sea - assuming that the middle of the island is the high ground. I would be somewhat confident that all the rivers on the north African coast would be northerly as would those of Norway and the northern realms of Germany and France.

Need links to quoted posts here...

[mmmmmpig]

heck if you have a conic volcanic structure the drainage pattern is a radial drainage pattern.... but eventually the radial streams will coalesce into one drainage feature. Rivers flow downhill regardless of the direction downhill. The big "no-no" that is consistently viewed with rivers is the branching and eventually reconnecting haphazardly, and that doesn't happen in nature except in river deltas and the braided stream areas in a glacial outwash plain. The second worse violation is rivers flowing past each other into different large bodies of water... there has to be some kind of continental divide and drainage basin setup going on with drainage patterns, since all water flows downhill rivers shouldn't flow past each other without some major elevation change in between them.

Have I forgotten any major river police rules?

[Greason Wolfe]

Have to agree with Redrobes, here. Rivers flow from high to low regardless of the cardinal direction, as evidenced by the Willamette, John Day, Deschutes and Snake rivers all of which have a mostly northern flow while being in the northern hemisphere. Of particular note would be the John Day river, which is the third longest free-flowing river (no dams) in the conterminous U.S.

Just my two and a half cents.

GW