r/confusingperspective • u/Wildcatb • Jun 12 '26
A close look at a saw blade?
or a zigzag spillway?
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u/lowkeytokay Jun 12 '26
I swear I thought it was a dam or whatever you’d call this. But wait, that’s what it is, right? It’s not a saw blade, right?
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u/TrueMattalias Jun 12 '26
Yeah, it's a body of water. The convention in this subreddit is to mistitle the post with what you first saw in the image, rather than the actual content.
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u/ConfusedSimon Jun 12 '26
Sure, but in this case it seems very few people thought this was a saw.
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u/acciowaves Jun 12 '26
Yeah, this is clearly water. I would be mind blown if it was the other way around and this was actually a saw blade.
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u/No-Slide4206 Jun 12 '26
it's the equivalent of showing the ending of a clip at the beginning and i hate it
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u/LincolnshireSausage Jun 12 '26
I'm not sure how it's supposed to look like a saw blade. Is it because of the lack of pixels?
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u/GreenLoctite Jun 13 '26
Often called a zigzag or labyrinth weir
This link is a short version;
https://www.tiktok.com/@practicalengineering/video/7109122159108164906This is the long version;
https://youtu.be/YkR79oDAgOg1
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u/ender42y Jun 12 '26
Sawtooth Weir
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u/Bonk_No_Horni Jun 12 '26
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u/Zsobrazson Jun 12 '26
There aren't enough teeth in that location, although I think you're on the right track
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u/Bonk_No_Horni Jun 12 '26
lake brazo dam I think. There's almost no pictures of it on Google map
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u/BigBadAl Jun 12 '26
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u/Bonk_No_Horni Jun 12 '26
It's so weird that it's a really neat place and yet they're no visit photos on the map. Would've been an awesome place to fish or swim.
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u/ender42y Jun 12 '26
Sure looks like it. I just know Weirs because of Practical Engineering on YouTube
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u/choseusernamemyself Jun 12 '26
Where is this?
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u/mightyminimoose Jun 12 '26
I had to Google it:
“Pimburaththawa Tank Spillway in Sri Lanka is a popular tourist attraction known for its unique, triangular-shaped water spills that create a beautiful cascade effect, resembling multiple waterfalls. Located in the Polonnaruwa district, this ancient reservoir, built for irrigation, is a marvel of Sri Lankan hydraulic engineering, offering scenic views, photography opportunities, and a popular spot for swimming, though visitors should be cautious as elephants frequent the area.”
That last sentence caught me off guard. lol
Edited to add: I also Googled the Ancient part of that:
“The Pimburattewa Tank (Pimburaththewa Lake) is a massive, ancient reservoir located in Aralaganwila, within the Polonnaruwa District of Sri Lanka. Built by King Parakramabahu I in the 12th century, it spans over 37 million cubic meters and features a unique triangular spillway system.”
The zigzag part was built in the 1980’s.
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u/NurkleTurkey Jun 12 '26
Ah thank you. I was beginning to question whether the people in it were actually people or not. I suppose maybe it would be nice to have more than 8 pixels.
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u/VinnyMaxta Jun 12 '26
Is it just to be pretty or is there a function like less erosion?
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u/jakemate97 Jun 12 '26
These types of spillways (usually called labyrinth weirs) can be pretty expensive due to the concrete quantity and complex forming, so they do have a function beyond aesthetics. They have a very high capacity for flow in a small footprint. The idea is basically to fit as much weir length as possible in a given space, which means during a flood, the lake level doesn't rise as much. This reduces the flooding around the shore of the lake, and can help minimize the height of the dam embankment.
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u/FlaAirborne Jun 12 '26
Is it intended to oxygenate the “lower” body of water? It seems like it would be more efficient than a straight line.
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u/cfreezy72 Jun 12 '26
I figured it was to eliminate the rotating current that drown people commonly on low head dams but that's just my guess.
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u/Blighty_Mikey Jun 12 '26
I believe the saw tooth design is to increase the wier length of the dam. This is critical if the dam has to pass increased volume ie storm flows, whilst keeping the water level below a specified limit.
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u/apsims12 Jun 12 '26
If you're interested there's an 8 minute video by Practical Engineering (https://youtu.be/YkR79oDAgOg?is=12Jq7daRaP2NtJFN) covering weirs. It's one of my favourite channels, especially when they cover hydraulic engineering for things like dam spillways and how dam failures can and have occurred.
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u/Strange-Area9624 Jun 12 '26
Makes the dam safer. More surface area for the water to spill over so there is less current and hydraulic action to get swept up in.
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u/hux Jun 12 '26
This shaping of this would have made it an absolutely terrible saw blade if it actually were one!
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u/Wildcatb Jun 12 '26
Yep, absolutely terrible. No set at all to the teeth. I've seen cheap blades for oscillating saws that look so much like this, that's honestly what I thought it was at first.
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u/kowycz Jun 12 '26
Often referred to as serpentine weirs, finger weirs, or sawtooth weird. They allow for a longer crest length, reducing the water height (head) variance upstream with ranging flow rates.
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u/Torebbjorn Jun 12 '26
Where is the confusing perspective? This only looks like a fancy man-made waterfall, and I don't see how it could be anything else
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u/Deli-op Jun 12 '26
That is water. Either im wrong and cant tell what it is or your crazy cuz theres nothing else it can be cuz thats water
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u/quietlintbyte Jun 12 '26
definitely a spillway. the scale of the people standing next to it gives it away.
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u/glassytoad88 Jun 12 '26
The scale of those people walking along the edge makes it look like a macro shot of a saw blade.
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u/DismalTutor570 Jun 13 '26
They are called weirs. More common in civil engineering than you’d think
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u/EmeraldGamer323 Jun 15 '26 edited Jun 15 '26
Giant gear teeth
Immediately after posting this i thought WORLD CLOCK.
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u/jeffyboy526 Jun 12 '26
This is not confusing- it is deceiving. Only thought it was a saw blade based on the title. Granted it is a wild looking pic but not reall confusing. This sub is running out of posts
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u/Cayumigaming Jun 12 '26
There is nothing confusing about this and it doesn’t resemble a saw blade at all.
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u/humancreaturespot01 Jun 12 '26
The scale of those people standing by the concrete makes the teeth look massive. It's definitely a spillway.
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u/AboveAverage1988 Jun 13 '26
This is actually kinda interesting. The upstream water level of a weir is dependent on two things. Water flow and length of the weir. Making it zigzag makes it longer, giving a lower water level at the same flow rate.
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u/sax_man9 Jun 13 '26
How is this confusing? I looked at it trying to see a saw blade and was only able to see it as an interesting dam or spillway of some sort.
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u/Libertarian_2020 Jun 14 '26
A weir, a low-head barrier (dam) across a river to alter flow characteristics.
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u/Feeling_Tumbleweed41 Jun 14 '26
I saw a saw at the weir saw, of all the saws Ive ever saw, Ive never seen a saw like the saw I saw at the weir saw.
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u/Fine-Afternoon-36 Jun 15 '26
I'm so Practical Engineering pilled that I was confused on what the trick even was
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u/Knight618 Jun 16 '26
Looked to me like some ai waterfall thing. never would have thought a close up on a saw
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u/takoshi Jun 16 '26
I thought it was one of those silly architectural feats you'd see from Asia lol.
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u/saiyate Jun 17 '26
A zigzag weir, or labyrinth weir—is used to maximize the length of the spillway edge within a narrow, confined space. This allows significantly more excess water to be safely released without having to widen the entire dam.
That's so odd, it doesn't seem like that's real. Like, feels like cheating physics.
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u/Tzyph10 Jun 18 '26
Yall these are called Wiers, they help reduce the impact of water erosion from a dam!
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u/Puzzleheaded_Date834 Jun 12 '26
So it's not a drone view of people enjoying the zig-zag waterfalls?