What We Can Learn from 5 Times Rivers Ran Backward

Usually, you can count on a river to flow in one direction, but some things can make it reverse course. Aside from being weird and surprising, these river reversals can often reflect geological changes and have long-lasting impacts on the surrounding ecosystems.

Hosted by: Hank Green

----------
----------
Huge thanks go to the following Patreon supporters for helping us keep SciShow free for everyone forever:

Alisa Sherbow, Silas Emrys, Chris Peters, Adam Brainard, Dr. Melvin Sanicas, Melida Williams, Jeremy Mysliwiec, charles george, Tom Mosner, Christopher R Boucher, Alex Hackman, Piya Shedden, GrowingViolet, Nazara, Matt Curls, Ash, Eric Jensen, Jason A Saslow, Kevin Bealer, Sam Lutfi, James Knight, Christoph Schwanke, Bryan Cloer, Jeffrey Mckishen

----------
Looking for SciShow elsewhere on the internet?
----------
Sources:
Amazon

Mississippi

Slims

Kaituna

Qiantang

Images:

[miriam]

The river Emajõgi, which translates as 'mother river' here in Estonia flows between the two biggest lakes in the country, so, depending on the weather in different parts of Estonia, it can flow either way.

[jasonwebb]

I have seen the Mississippi river run backwards twice now. It is crazy. The water just starts acting weird and getting deeper and deeper.

[icewink]

How did you not mention tye Tonlé Sap in Cambodia? It changes direction every six months based on the monsoon. During the rainy season it flows from the Mekong River into the Tonlé Sap lake, while during the dry season it flows from the lake back into the Mekong River.

[brandonmarr]

Then there's that time when a drilling company in a lake accidentally dug into an underwater mine. The lake completely drained into the mine, reversing the river for a while, and destroying houses and boats all along the waterfront in the process, due to the powerful current and weakened foundations. Everything that was too close to the water got pulled into the massive whirlpool and sucked into the flooded mines, while the building around the mineshaft exploded from the back pressure.

[beaker_guy]

Fun fact: as someone who has been to New Madrid (and also Cairo, Illinois); the locals tend to pronounce it "New MAD-rid" not "New Muh-DRID". (Also, Cairo is pronounce "Caro" (like the syrup.) :) For the morbidly curious.)
But, as Webster's dictionary once said, "There is no such thing as a CORRECT pronunciation, merely pronunciations that are more (or less) common."

[dereklam]

I enjoyed the technical depth of this episode a lot! The detailed descriptions, excellent maps and sheer variety of the mechanisms for all these river reversals is awesome and thought-provoking. The "complex fluid dynamics" of the Qiantang river would be the cherry on top. Time to dig into the sources!

[jeffreybernath]

A great sequel to this would be, "When Humans Reversed Rivers." Huge engineering projects, like the one that reversed the Chicago River, have also reversed rivers.

[howie]

During the 2011 flood, I watched the local tributaries around Missouri Valley, IA flow backwards from the increased volume of the Missouri River. That was amazing.

[dougbishop]

One river the reverses twice a day is the reversing fall in St John New Brunswick Canada which I visited. It was amazing

[angelindenile]

It's interesting to me that YouTube seems to 'pick' events, history, or a phenomenon that I didn't know about and suddenly hear about it from three different channels because of the algorithm or all the channels I follow release it at the same time.
This time it was about that Mississippi River earthquake back in 1812, I didn't even know that happened until Deep Dive did an in depth video exploring how terrible earthquakes can be in the mid US.

[sophroniel]

I was so hoping you'd include something from New Zealand! Not only did I used to holiday in Kaituna as a kid, but my dad literally got the funding for that project you mentioned!! We have the highest concentration of braided river networks in the world (due to the concentration of greywake I think?) and, as someone who lives on the canterbury plains (aka most recent victim of massive, christchurch-destroying earthquakes...) the whole artisian wells vs rivers vs glacial recedings etc is of great interest. My dad works for the national institute of water and atmospheric research and he lives and breathes this stuff! The Kaikoura eq in 2016 also set an undersea river flowing differently too, I believe, and has had a massive effect on ecology there if memory serves

[TonksMoriarty]

Part of the River Aire flowed backwards when it drained into a coal mine... The site today is now a bird sanctuary just outside Leeds & the River flows in the right direction once again.

[mikedowd]

The Mississippi could have been mentioned twice, since it only flows south now due to isostatic rebound instead of into the Great Lakes like it did before the northern edge of the continent started rising due to the lack of glaciers.

[SnarkNSass]

Being from Central Arkansas and having also lived in NW Tennessee, I've heard about the New Madrid fault my whole life. The stories of when the "Mighty Mississip" ran backwards and the crazy ground explosions are terrifying. Especially when the red alert for the fault to shift again went out 20+ yrs ago.
I have actually felt 3 earthquakes in central Arkansas... Supposed to be because of frakking.🤷🏻‍♀️

[rmdodsonbills]

Just a small pronunciation note: I believe that the people in Southeastern Missoura pronounce the town of New Madrid with the emphasis on the first syllable of Madrid so that it rhymes better with "bad bid" better than it does "undid." And for the record Prague, OK rhymes with "beg" not "dog, " Pierre, SD rhymes with "leer" not "the air" and Lead, SD rhymes with "reed" not "red."

[Gamepro]

While New Madrid was named after the Spanish capital, us Missourians don’t know how to pronounce anything so it’s actually pronounced New MADrid here.

[Larixlaricina]

I lived for a bit in Hangzhou near the Qiantang river, and I often walked along the riverwalk. I missed the tidal bore every time, so it was cool to see it here!

[adellutri]

These five instances are very interesting. But we should not only look at "natural" river reversals, but also a artificial ones. Like the Chicago River, which naturally should flow into the lake, but through engineering flows south to St. Louis.

[anthonyappleyard]

Once3 there was a severe drought in England, and the Thames was so low, that to get enough water for London, the waterworks had to pump out the whole flow of the Thames, and the water from two suburban tributaries called the Mole and the Hogsmill flowed westwards (i.e. backwards) up the Thames to the pumping place.

[pjschmid]

Oh my, New Madrid is not pronounced like the city in Spain it’s pronounced MAD-rid because…the Midwest. We loved to name places after exotic foreign destinations and then butcher the pronunciation it’s just what we do. Cairo Illinois pronounced KAY-roe and Milan Illinois pronounced MY-lin. Just two more examples but you get the gist.