fandomsecrets | [ SECRET POST #3124 ]

[ SECRET POST #3124 ]

⌈ Secret Post #3124 ⌋

Warning: Some secrets are NOT worksafe and may contain SPOILERS.

01.

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02. [repeat]

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03.

[Sherlock]

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04.

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05.

[Video Girl Ai]

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06.

(Whiplash)

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07.

(Hannibal fan commenting on Neil Gaiman's American Gods series)

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08. http://i.imgur.com/WNtDaEJ.jpg
[Bram Stoker's Dracula, linked for porn / iirc it's rape in the story]

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09. [WARNING for rape]

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10. [WARNING for rape/child abuse]

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11. [WARNING for child abuse]
http://i.imgur.com/f8cCfkZ.png
[For the Love of a Child, linked by OP request]

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12. [WARNING for suicide]

[Welcome To Hell]

Notes:

Secrets Left to Post: 00 pages, 000 secrets from Secret Submission Post #446.
Secrets Not Posted: [ 0 - broken links ], [ 1 - not!secrets ], [ 0 - not!fandom ], [ 0 - too big ], [ 0 - repeat ].
Current Secret Submissions Post: here.
Suggestions, comments, and concerns should go here.

Flat | Top-Level Comments Only

I'm trying to work this out for a story, but I skipped too many math lessons at school and am regretting it now. I do not even know how to start calculating this or what it even means. Can you help please?

Okay, here is what I have to work out:
If a river is 60 miles long and is five hundred meters at headwater, how many feet per mile does it drop? And is it a raging torrent filled with precipitous waterfalls, or a relatively steady stream?

I feel so stupid for even having to ask this, I'm sure there is a simple formula, but I just cannot visualize numbers at all.

I am also terrible at math. And if that is considered easy math, I need to take read a book or something on math.

Well, I'm not solving it, because screw unit conversions, but basically what's going on is you have a river that's 60 miles long, and over the course of that length it descends by 500 meters. Given that information, you can tell how quickly it descends (in principle, it's just 500 meters / 60 miles). And once you have that, you can evaluate how steep or how flat it is - if it's really steep, it's going to be a raging torrent, if it's flat it's going to be a steady stream.

The tricky part is you have to convert units.

.005178

So I'm guessing it's a pretty calm river.

Here I drew you a helpful (and beautiful) diagram:

http://imgur.com/JN0RKg6

that is actually a pretty helpful diagram for the OP

+1!

I posted the number above and it's totally wrong. That was foot/foot. Foot/mile is more like 27.

OK, I thiiiink you might have to convert the 'five hundred meters' bit to feet, and then multiply that by 60 miles, which will give you the 'feet per mile' measurement.

I can't answer the second part though, because it doesn't give you any context for what a 'raging torrent' is. What a frustrating question!

I assume there's some kind of outside information to judge what the normal rates of fall are for different rivers and streams

No, you have to divide the 500 meters by the 60 miles, not multiply. "Per"
is your clue. Like 12 eggs per box could be written as "12 eggs/box."

500 meters is about 1460ft, so it's dropping about 27 feet per mile. I'd say it'll be pretty fast, but that depends in part on the terrain. If it's a consistent slope across those sixty miles, then I'd say that's a fairly fast river, though more rapids than waterfalls, but if it's, say, a sharp drop off at the start and then a more gentle last forty miles or so, then it might have waterfalls at the top and slow down a bit over the plains before hitting the sea/lake.

The volume of water moving through it will also affect the speed somewhat as well. If the last bit is gentle, it could silt up and slow down, especially if it dragged a lot of material with it in the fast phase higher up, but a high volume of water could keep the speed up.

Either way, it's losing a lot of height in a reasonably short distance, so I'd say it's pretty fast, but the arrangement of the terrain will have a big impact on where along it most of that speed is expressed. Er. If that helps any.

It also doesn't say anything about volume of water, how deep and wide makes a big difference too.

Put a lake or a strait in it somewhere and it sounds like a pretty good salmon stream.

This was my thought. It could be a nice constant, if fast, river...or it could be a slow flat river with a sudden 500 metre drop in it somewhere.

Also if it's a straight river, more speed, but if it's curving it's going to have fast bits then suddenly slow into possible pools at a corner, then speed up again.

one: you have to do a unit conversion. this is a pain. 500 M * 3.28084 Ft/M = 1640.42 Ft
two: you divide feet by miles. 1640.42 Ft / 60 miles = 27.340333... Ft/mile
so the numbers answer is about 27 and a third.

this sounds kind of steep to me but I'm no expert.

Length of river: 316800 ft
How far down it goes: 1640.42 ft

Slope: Rise/Run: -1640.42/316800 = -0.0051780934

That means that, for every foot the river travels, it drops by 0.0051780934 ft = 0.06213712 inches. It's probably not going that fast.

(Put my work out here so anyone can point out if I fucked up. |D)

Some further questions:
- How wide is the river? You deep? What kind of base does it have? (i.e. a river with a rocky bottom will have more turbulence than one that's sandy), etc.?

Edited (I had some further questions. ) 2015-07-24 23:40 (UTC)

Thank you.

I hadn't thought of those other questions. Its for a fanfic for a pretty small fandom, I don't want to say what because people there would know me instantly, but the original creator supposed an island as the caldera of a long dead super-volcano, 70x70miles, in the mid-atlantic at around the latitude of Copenhagen, with a lake at one end and the lake emptying into a cavern where it then flows out to the sea via another cave at sea level on the opposite side of the island (the lake is said to be ten miles in from the cliffs that form the island's rim. At one point the source material says a bunch of explorers set out along that underground river and they became hailed as great explorers of the island's underground kingdom. The source material doesn't give much on what or how on that adventure though.

I'm guessing it must be a pretty rocky bottom, but it probably isn't too deep or anything, you can't get that much rain on a 70 mile area.

A rocky bottom sounds about right for that kind of river, and depth really depends on how wide the river is. It's hard to give you a lot more information, without knowing things like volume and what-not, but that should hopefully give you an idea? At the very least, is anyone in your fandom going to be nit-picking you to this degree?

Trick question! In every fandom there is always at least one guy who will nitpick everything.

"you say waist deep, but on page 231 it mentions clearly that the character of El Wateriso imagines the stream bout his ankles! Are we to suppose he has feet which are 30 inches thick? Hah, I say, hah!". /Comic Book Guy.

Fair enough. :P

OP, is there any mention in canon how deep the river is?

I don't think so. The cave where it leaves the lake is supposed to be bridged with a single spanned stone bridge so it can't be that wide, although the lake itself is supposed to be very wide from all the streams entering it, it is shallow enough to have boats which are a cross between "an Oxford punt" and a Venetian Gondola poled across it. I don't really know what that makes it. The only real description is that the caverns below are supposed to be big and spacious and the party had a "fine old time of it" and it was "rather loud, in parts", and that they found veins of gold, silver, iron, and diamonds which give the island its wealth.

Re: OP

loracarol - 2015-07-25 01:01 (UTC) - Expand

Re: OP

(Anonymous) - 2015-07-25 01:06 (UTC) - Expand

Re: OP

loracarol - 2015-07-25 01:14 (UTC) - Expand

If you need visualization, the River Deveron in Scotland rises at about 500-600 meters above sea level and is just over 60 miles in length. There are some youtube videos, but I'll refrain from posting any links to them so as not tobe mistaken for the poop-video bandit. Just google "River Deveron", it should give you what you need. Happy writing, OP.

Thank you all. You've all really helped me get my ahead around it. Special thanks to the guys who showed the working too, I can't believe it was such a simple calculation. I know at least roughly how to describe it so it doesn't look comically wrong. A series of rapids, short falls and the occasional deep pool. A very varied river, not just one set of falls after falls, but not a sluggish, meandering stream either. Possibly with salmon in it. Thanks.

Don't feel bad, OP. What you asked was actually a very simplified hydraulics question dealing with open channel flow, and it's not exactly something covered in basic math.

"60 miles long and is five hundred meters"

...one of these things is not like the other, not like the other, not like the other...

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[ SECRET POST #3124 ]

I can't do math, help

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nayrt

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OP

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OP

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