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mozltovcoktail
04-15-2012, 11:51 AM
Hi folks,

I was wondering if there's any way at all to justify a lake going over a cliff and creating a waterfall that spans and entire coastal cliff. Maybe 10-20 miles long or so. The lake would be very shallow throughout. Probably about 2-8 feet deep.

The source for this lake would be a mountain range that has very frequent a large storms, and the entire portion of the landmass that the lake would be on would be at a downward slant towards the cliffs, so all the water would drain into that area, but I'm not sure that would be enough considering how much friggin' water would be flowing over that 20 mile long waterfall.

Another option would be for the lake to be farther inland and have a river that run out of it over the cliffs. When the lake floods, it would burst the boundaries of the river coming out of it and flood over the cliffs, creating that massive waterfall afore mentioned. This seems more realistic, but not as awesome.

I've attached a pic of roughly what I'm thinking. I don't mind if it's highly, highly improbably, but impossible is probably a deal-breaker. I really love this feature of my world, so I want to find a way to make it work.

Thanks!

mozltovcoktail
04-15-2012, 12:34 PM
The lake should also be crystal clear, which I think would be hard due to the flowing of the water.

Maybe I should move the lake somewhere else on the map and just have a big river/waterfall(s) running off those cliffs. I'm not sure. Just interested in y'all's opinions.

bartmoss
04-15-2012, 12:52 PM
I'll call it impossible. Erosion would quickly wear down the edges, if you start out with a ragged edge like this you'll probably end up with a number of canyons until the water flow settles into one that happens to be the deepest. Also, you'll need to have as much water flowing into your lake as flows out of your lake. You can actually work that out mathematically if you really want to. iirc such massive "floods" did happen in earth's past, but they were very temporary and always left a heavily eroded canyon-y terrain behind.

octopod
04-15-2012, 03:48 PM
If the volume of those rivers varies a lot seasonally, it's maybe possible that you could have a main channel during the dry season and then a wider flooding surface going over the cliff in the wet season. I don't think it'd be possible to have it like that all the time, though, and it would just be a wide river, not a lake.

mozltovcoktail
04-17-2012, 09:20 AM
Thanks guys. Not what I wanted to hear, but what I suspected. I'll rework things.

Korash
04-17-2012, 12:23 PM
Actually, before you rework the idea...

Of course my thoughts turn to a fantasy setting, and may not suit your needs.....but here goes....

In the real world, and unless there are major engineering works at play, I have to agree with bartmoss. Erosion would kill this idea. However....in fanasy setting where there be MAGIC, of a geological scale, I can see this as a battle between two elemental gods/kings....The water one opening the flood gates to the plane of water in an effort to destroy this plain, and the earth one doing its best to shore up the land and suppress the water. Call it a war between the two who's beginnings is lost in time......Some where in the middle of this lake is the gateway, and possibly an answer to the riddle...

Just some thoughts that may or may not help you make up your mind

Jaxilon
04-17-2012, 12:38 PM
Trying to think of something like this and the only thought I get is Niagra Falls, specifically Horseshoe Falls. They are about 2,600 feet (790 m) wide. You can read about them Here (http://en.wikipedia.org/wiki/Niagara_Falls) but it says "the Niagara River draining Lake Erie into Lake Ontario, is the collective name for the Horseshoe Falls and the adjacent American Falls along with the comparatively small Bridal Veil Falls, which combined form the highest flow rate of any waterfall in the world."

Obviously that's nowhere near 10-20 miles wide but if it's fantasy and you want to go big well, you just need to make up some reason.

bartmoss
04-17-2012, 01:39 PM
Even a magical world needs to follow player/reader expectations, and that means you will generally want to stick to the laws of nature as we know them. If you add weird physics, you need to deal with the consequences. For example, take Korash's idea. Of course it would work. But you'll need to explain it. Why are they fighting? Earth and water are not tarditionally opposed to oneanother. What happens in places where there's no water to keep the earth in check? Does the Earth push up without opposition, resulting in huge mountains? What about erosion? The huge amounts of water would carry a lot of earth downriver, where it would create a gigantic delta/marsh/whatever. And then there's the question - if water and earth fight here, what about the other elements?

Of course you can just handwave all of that away, but that's cheating.

Instead, I'd think about the effect I want to achieve. What purpose does my 20mile-wide waterfall serve? Is it just scenery? Do I need it for a climactic scene in a book? Etc. Then try to come up with something else that works. Limiting oneself isn't always a bad thing, it can result in some great work. (Compare old star wars, which had to work under physical and, at first, budget limitations, to the new star wars, where they had all the technology and all the money they could hope for...)

xoxos
04-17-2012, 02:03 PM
i'm not so big on bounding imagination with 'reality', since it's fantasy anyway. to flesh it in if you want, of course massive scale for a flooded/shallow river more than a lake helps.. there could also be high mineral content in the water.

i have seen in certain undisclosed locations :D waterfalls and rivers form 'walled pools', almost exactly like a series of hot tubs squished together with 2-3' smooth walls built around them.. let's see if i can find a pic.. i expect one could conceive of a similar thing happening to a wide waterfall, forming a retaining lip.

ahh, a painting, even more anonymous..

44099

jbgibson
04-17-2012, 06:58 PM
Ah - Travertine Dams (http://en.wikipedia.org/wiki/Travertine). Cool formations. The problem with a 'normal' waterfall for your purposes is that erosion would tend to turn a broad fall into a few narrow ones. Travertine dams are formed due to *deposition* of a dissolved mineral - typically calcium carbonate. So wherever water is flowing gets built up instead of worn down. Large gaps where there's too much water flowing to get much deposition are naturally the places where debris tends to go, and whatever gets stuck (logs, leaves, whatever) will slow the flow, improve the deposition, and 'heal' the rift. Google for images of them. You'll see a number of Earthly examples that are not twenty miles wide, but do span hundreds and hundreds of yards. If you don't need *continual* flow across the *whole* width of your 20-mile waterfall, this could be the situation you need. Travertine dams have the nice characteristic that they bow outward, instead of the inward-curving collapse characteristics of most waterfall rims.

To get at least occasional periods of spectacular wide-rim flow, just postulate flooding -- enough of a storm upstream, and the volume of flow goes way up, turning a trickle into a band of falling water.

Iguazu Falls (http://en.wikipedia.org/wiki/Iguazu_Falls) spans 1.7 miles, but that's not continuous. Victoria Falls (http://en.wikipedia.org/wiki/Victoria_Falls) is "only" 5600 ft wide, but that's a continuous sheet of water... at least in wet season. In dry season it dwindles to a series of smaller cascades separated by rock outcrops. Niagara has a bigger mean annual flow (85,000 cu ft/ sec) but both Iguazu and Victoria have peaked at over 400,000 cu ft/ sec for short periods. Comparison : average flow of the Amazon and Mississippi are about 7.4 million, and 590 thousand cu ft/ sec. Peak for those is more like 10.6 million and 3 million cu ft/ sec, respectively.

Thus a carefully placed waterfall :-) on even an earthly large river could have a flow rate of a hundred to a few hundred times that of Earth's largest waterfalls. So in theory, you could easily get enough water to "look like Niagara" across a twenty-mile span. All you have to do ( ALL :-) ) is devise a hard enough, level enough lip to not wear away in a year or a century, OR devise a way to get a WHALE of a lot of calcium dissolved. For B, how about if your river gathers its water way upstream in rainy mountains, and then flows across a former seabed - like the salt flats in the US southwest. Rivers like the Nile do that - long stretches are in arid surroundings. Say you once had an inland sea, with evaporation jacking up the mineral content of the water. The area shifts to be more arid, and the sea dries up. There's your salt flats. And what can be more level than a former seabed filled over eons with minerals? Nothing the least bit implausible there. Now, do a little creative faulting, and create you a crack across said salt flat. Not just a slim crack - make it like the Great Rift Valley (http://en.wikipedia.org/wiki/Great_Rift_Valley_%28geographical_concept%29). Heck - imagine that such rifting is what drained the inland sea in the first place -- say, a low-ish part of the former rim-of-watershed is breached - now it's no longer an endorheic basin (http://en.wikipedia.org/wiki/Endorheic_basin). Now gather you a whole bunch of rainfall - make it a climate shift and the arid valley is no longer arid, or make it periodic incursions of rain into an otherwise dry zone - take your pick, based on your storyline needs and your wild whims :-).

Boom. Waterfall of whatever width you desire; choose travertine process for keep-the-edge-built-up, or posit a nice layer of basalt as the rim for long-term resistance to erosion. Dial the rainfall up or down for duration of full flow vs trickle. Since you're drawing up the whole landscape, pick a larger or smaller drainage basin to collect rain, and slide it north-south to get the desired wet or dry climate. Want some spectacular differences in normal vs. flood, and all you have to do is place this near a coast that's subject to hurricanes -- several times a year you can have immense flow, and the rest of the time some stable amount.

Such a formation might be short-lived, in geological terms. So what? Cities, highways, and nations are all short-lived in geological terms....

If we're doing rationalization exercises here, don't get me started on the effects of a high concentration of industrious beavers....

maxsdaddy
04-17-2012, 10:08 PM
Lol jbgibson.. industrious beavers.. sounds like a great name for a band! When I first peeped this thread my first thought was infinity pools.

Veldehar
04-18-2012, 10:29 AM
There are plenty of rationalizations for this sort of thing, althought the industrious beavers sound best to me. it would all depend on setting. Going outside of purely nature, a magical or high tech culture could certainly produce such a thing and nature with the aid of magic/magic material. It could easily be an "ancient wonder of the world" where an ancient culture assisted nature to create something spectacular, and it leaves the current residents in awe.

mozltovcoktail
04-18-2012, 11:37 AM
This is some fantastic information here.

The infinity pool idea is exactly the sort of thing I was thinking. A huge, mellow lake that spills over the side of an island's cliffs. However, it seems like no matter what we're talking a bout a river here, not a lake or slow-moving shallow body of water, especially one that's relatively free of sediment. That's fine. It just means I'll have to split the two ideas, so I'll have a very wide river going over a basalt lip or using the travertine process causing a looooong waterfall over the edge of a cliff, and then I'll have a very shallow lake elsewhere on the map. It's not exactly what I had in mind, but I'd rather it make some geological sense. Then again, maybe I'll still find a way to make it work, but right now I'm leaning towards "no".

Korash, I do like your idea, but it's not what's going on in my story.

Any more thoughts on this thread are still appreciated!

Thanks.

Korash
04-18-2012, 12:18 PM
Korash, I do like your idea, but it's not what's going on in my story.


*sniff sniff* You have different thoughts than me! How could you??!!...... ;)

just joking Mozltov :) Like I said in my post it was just the idea that first struck me. Your story, your world , your map, so do it the way you want to. :) I take no offence when my suggestions and advice are not taken....how can I when most of the time I don't even follow my own.....I just like putting ideas out there.

I really like that infinity pool idea too. :D

mozltovcoktail
04-18-2012, 02:00 PM
Maybe I'll just make a smaller infinity pool somewhere...

Joshua
04-18-2012, 07:52 PM
Bringing up Niagara Falls was a good point, but I'll also point this out: a HUGE project was undertaken (quite literally stopping the flow of the falls) in order to bolster the earth along the falls. This was because so much earth was eroding that it was changing the appearance of the falls, and since it had become a huge landmark, NY and Ontario took an, "OH MY GOD, SAVE IT FROM CHANGING!" approach. Now, it still has erosion, but it's considerably slowed to the point where it doesn't really matter much by comparison.

What about having a huge dam that just lets water flow over? It could've been build by some civilization long since gone and it's one of the only remnants of their existence. But what a remnant! It was crafted with such skill and ability that people now don't even know how to make it work. So instead of the floodgates opening to release water, it just spills over the top. Is it magical? Is it purely a technological achievement the likes of which we've never seen? Is it some combination? Who knows! :D That opens the doors to huge (and fun!) possibilities.

mozltovcoktail
04-18-2012, 08:28 PM
Dude! You're in my brain! That just. Might. Work!

Joshua
04-20-2012, 05:58 PM
Mwahaha! There's a lot of places to run with something like that, and it'd be a huge amount of intrigue for anyone exploring that world. :)

Lukc
04-21-2012, 04:34 AM
Also, if it's a dam, you could easily have a broad, shallow lake behind it. Then, for greater effect, say they built the wall out of mithril reinforced glass and you also have a conflict, with industrious beaver people petitioning the local elves to dig out the mithril wires.

"Hey, we're only going to remove 25-30% of the mithril TOPS, it's ABSOLUTELY not going to impact the stability of the damn. We've done calculations that back this up! Trust us! What could go wrong? Plus, we'll pay you a 10% tax on all the mithril we dig out of your ancestors' dam! Think of all the trees you could plant with that!"

ManOfSteel
04-22-2012, 03:48 AM
I remember an episode of "Life Without People", which was a cool series about how the man-made environment would decay if people were suddenly to disappear. It was amazing how relatively quickly our technological achievements would crumble given enough time and neglect. Nature slowly but surely reclaims the land. It was surmised that after 10,000 years, nothing made by man would survive. If aliens were to land after 10,000 years of man's absence there would be no trace of us, except...maybe...
the pyramids of Egypt, which would be half buried and eroded by the sands of the desert...
Mount Rushmore...
and Hoover Dam.

rdanhenry
04-22-2012, 04:23 AM
They could still find stone in less monumental form. There are identifiable stone tool workings that are more than two million years old. Mind you, flint is fairly hard stone. Marble statues would erode if left exposed, but could be preserved for quite a long time under the right conditions. For that matter, good concrete can last a very long time. Maybe not 10,000 years, but we really can't be sure, since we haven't actually left concrete out for 10,000 years yet. Estimated time for various plastics to decompose varies widely between types. Some may outlast 10,000 years by quite a bit, although it might become unrecognizable to casual examination much sooner. Glass can last a very long time; glass relics are the modern equivalent of historical stone as a commonly-used but highly-durable material. After 10,000 years, there might be little of man left on the surface, but study in more depth and it will take far longer not to turn up clear signs that somebody was here and making a mess.

Crudus
04-23-2012, 03:13 PM
Along the lines of the dam... I was thinking of something slightly different. Maybe an ancient culture built a very long, curving (but only 8' tall) wall across a shallow valley, where there was only a river before. Then they went and died, and geological changes greatly increased the flow of water to the region, creating your shallow lake. The uniform edge of the wall means that water flows over it uniformly. Maybe it was some kind of paved "highway" that cut across the valley instead of a wall. Have it be made of some resistant material like non-rusting metal or glass. The wall could have been artistic, not practical, or maybe it was some other sort of structure that takes a wall form... like an aqueduct? Maybe it was some kind of dam, but only to create a shallowly flooded area, so that they could cultivate rice? Now unregulated and sealed up, the water just flows over instead. Depending on how old the culture is, there are a variety of materials that could feasibly survive. Especially if "modern" people came to value the falls aesthetically, and repaired the rim occasionally.

ManOfSteel
04-26-2012, 02:12 AM
They could still find stone in less monumental form. There are identifiable stone tool workings that are more than two million years old. Mind you, flint is fairly hard stone. Marble statues would erode if left exposed, but could be preserved for quite a long time under the right conditions. For that matter, good concrete can last a very long time. Maybe not 10,000 years, but we really can't be sure, since we haven't actually left concrete out for 10,000 years yet. Estimated time for various plastics to decompose varies widely between types. Some may outlast 10,000 years by quite a bit, although it might become unrecognizable to casual examination much sooner. Glass can last a very long time; glass relics are the modern equivalent of historical stone as a commonly-used but highly-durable material. After 10,000 years, there might be little of man left on the surface, but study in more depth and it will take far longer not to turn up clear signs that somebody was here and making a mess.

When they said "no trace" of human kind visible after 10,000 years, I'm sure they were referring to visible structures. They themselves said that the neat rows of gold bricks in the Federal reserves and Fort Knox would be there indefinitely since gold doesn't corrode. My comment was meant as support to the idea that a structure like Hoover Dam might indeed be a long lasting mechanism for a very wide waterfall.

munch
05-13-2012, 11:58 PM
Could such a waterfall be build? if so they could be the remains of an ancient dam type thing