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Bifurcation: The secret giant islands formed when rivers split

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Re: Bifurcation: The secret giant islands formed when rivers split

#31

Post by [deleted] »

madcaptenor wrote: post #23
jameshart wrote: post #8

This is not to take away from the fun of investigating and identifying these ‘bifurcation islands’, but on the question of whether they qualify as ‘islands’: > Like a delta island, it is surrounded entirely by sea and rivers. As an area of land separate from a continent, permanently and entirely surrounded by water, it seems to fit every definition of an island I can find. I agree that by ‘Air Bud’ rules these qualif…

Wikipedia's list of islands ( https://en.wikipedia.org/wiki/List_of_islands_by_area ) starts with a separate table for "continental landmasses", containing Afro-Eurasia, the Americas, Antarctica, and Australia. Australia is ~3.5 times the size of Greenland (the #5 landmass) so between Australia and Greenland seems a nice place to draw the lint. But Greenland is in turn ~2.5 times the size of #6 New Guinea. Maybe if G…

[deleted]

Re: Bifurcation: The secret giant islands formed when rivers split

#33

Post by pyinstallwoes »

jetrink wrote: post #3

The article that follows that one is also very interesting and worth reading. It shows how a coastline that existed 100 million years ago and cut through modern day Alabama is still visible in demographic and election maps. (By a crazy coincidence, I just dug up that article and sent it to someone not even half an hour ago, since we were talking about geology and I remembered reading it. Then I go to HN and see this…

It reflects, it amplifies.

Re: Bifurcation: The secret giant islands formed when rivers split

#34

Post by fuzzfactor »

In Florida a notable non-giant one I remember is because the river is a location which had historically been the legal borderline between different counties.

One county north of the river, the adjacent county existing south of the river.

The island itself, not specifically within either county technically.

Oral history of Rum Island in the Santa Fe river goes back to the time when liquor was prohibited by US law, and regardless of whether local officials knew about it, they could honestly testify that there was no remaining liquor within their jurisdiction.

Re: Bifurcation: The secret giant islands formed when rivers split

#35

Post by Kon-Peki »

bryanlarsen wrote: post #15
elf25 wrote: post #6

Bifurcation occurs at the Great Lakes, where the Mississippi flows into the gulf and the St. Lawrence empties into the Atlantic. This forms the “great loop”, a circumnavigation course known by many power boaters . This makes about half of the United States and island by your definitions.

The Chicago - Great Lakes connection is man made, so doesn't count per the methodology of the OP.

The permanently navigable connection is man made.

It was seasonally connected (and navigable by canoe), requiring a very short portage the rest of the year.

Re: Bifurcation: The secret giant islands formed when rivers split

#36

Post by margalabargala »

Unfortunately, I noticed an error. The Committee’s Punch Bowl Bifurcation Island is much, much smaller than what is reported.

The reason for this, I'm sure you'll be delighted to learn, is about half of that area is in fact another bifurcation island!

See this unnamed lake in northern British Columbia here: 59°03'07.5"N 133°57'08.0"W

This lake has two drainages. The east side drains into Sloko lake and then the Pacific via the Taku river. The west side drains to Atlin Lake, then Tagish Lake, from which flows the Yukon River, traversing all of Alaska to dump out into the far north Pacific just south of Nome.

Thus the one large bifurcation island mentioned, is in fact two much smaller ones.

Re: Bifurcation: The secret giant islands formed when rivers split

#37

Post by chipsa »

hydrogen7800 wrote: post #11

> The Missouri is the largest tributary of the Mississippi River, which flows into the Gulf of Mexico He must mean longest. This chart[0] shows that the Ohio is by far the largest tributary of the Mississippi by volumetric flow, and also shows the Atchafalaya bifurcation. However, the wiki articles for the Missouri[1] and Ohio[2] show average discharges into the Mississippi of 87,520 cu ft/s and 281,000 cu ft/s, resp…

The Missouri basin is largely west of the dry line, and so gets substantially less rainfall.

Re: Bifurcation: The secret giant islands formed when rivers split

#38

Post by EdwardDiego »

robocat wrote: post #29
EdwardDiego wrote: post #19

I live near what used to be several of these - Kaiapoi Island,Coutts Island, McLeans Island, Templar Island, no doubt forgetting some. Created by the Waimakariri River splitting into 3 branches as it neared the ocean. They're no longer islands as the two side-branches of the river caused repeated severe floods in colonial days, so large civil engineering efforts went into restraining the river, ultimately leading to…

For fun include Banks Island? I'm in Akaroa today! The Waimak has drifted over a bunch of the plains - ages ago didn't it go through West Melton to Lake Ellesmere?

Yep, that is the channel blocked off at Templar's Island!

And if you get onto LINZ website, and grab their LIDAR data and visualise it, you can see all the old channels it has carved across the Plains, including ones right through CHC airport into the headwaters of the Avon (this is the route the Waimakariri took when it flooded Christchurch in the late 1800s).

As for Banks Island, well it was an island back in the day, not sure how many thousand years ago that was though.

PS, if you're in ChCh and tech, feel like we might know each other... love how small the net can make the rather large world.

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