The map sure makes it look like it “wants” to be, as did the fact that where the waters split around this newly created island, the branch going across the road appeared faster to my eye.
Or does regular maintenance of the road and park (which we Minnesotans take pride in being especially assiduous about) mean that can never happen as long as our industrial civilization perseveres?
It will probably become an oxbow, unless the inner bits of the bend are canalized or else regularly resupplied with sediment in some way. Road and park maintenance won’t stop it as they don’t affect sediment flow.
Oxbows are usually formed after one particular flood event that cuts a new channel, so it might be the next flood that does it, or the one after that, but eventually, one is going to wash the road away.
Looking quickly at both Google Streetview and the Google terrain model, the section of 22nd Avenue that runs westwards is reasonably elevated above the river terrace and seems to rest on a natural spine of higher ground, which maybe why the river took a scenic detour in the first place.
Mr Dibble is essentially right about this happening sooner or later, but if there is a rocky spur there it will take a fair while. Looking further along the river most of the bends are necking but not yet cut through.
And the bit that remains will still belong to Minnesota, confusingly. The same thing happened to the Carter Lake area of Omaha, Nebraska, in which an oxbow lake and the surrounding area still belong to Iowa despite being on the “wrong” side of the Missouri.
Similar situation Here South of St. Louis. What used to be Kaskaskia Island is now firmly attached to Missouri, but still Illinois. The child residents are bused across the river to Chester Illinois to attend school, though I’m sure most of the residents shop in St. Mary which used to be on the river.
Usually a flood is essentially the last straw, but the formation of oxbow lakes is a long-term process- basically where it pinches in, you get what are called “cut banks”, where the river is basically eroding away in the outer parts of the curves, and where it bulges out, you get what are called point bars, where the flow slows, and sediment is deposited.
On this map, your cut banks would be more or less where the “M” on Minnesota is and where the last “A” on South Dakota is, and the point bars would be along the opposite banks. You also get the same process on the most curved part- over where it says “Red River”, and pushes the river channel westward.
It’s a long-term process- this probably started out as a normal bend in the river, and has progressed to this point. It looks like whoever placed your parks along there did so intentionally- all your parks along the river - MB Johnson, Oak Grove, Riverfront and Gooseberry Mound all seem to be in imminent (in geological terms) risk of being oxbowed off. Upstream, Harrison Island is a good example of an oxbow lake forming.
I just came across a fantastic bit of trivia in Bob Berman’s wonderful book on motion, Zoom.
Rivers naturally bend as they seek the softer rocks and more easily displaced dirt. Any deviation forms a curve that creates faster currents on the outer side, which leads to more erosion and a sharper bend. Curves tend to vary over time, and ox-bows remove them, but there are no perfectly straight rivers.
In fact, if you measure the actual twisty length of a river and compare that to the source to mouth straight line, the ratio is… pi.
And it was Einstein who first noticed this.
The NRCS Soil Web Survey describes the whole oxbow as “Urban Land Aquerts complex, 0 to 2 %” that is made up entirely of silty clay and a depth to restrictive feature as “More than 80 inches”. So I don’t think there is any underlaying material.
Thanks. Looking at the terrain model again, I was over-reacting to topographic shadows.
Super interesting stuff, thanks everyone.
I don’t know if topographic lines are standardized in terms of the change in elevation between each, but I can tell you from living here that it is incredibly flat. People from the coasts think all of the Midwest is flat, but a lot of it at least has little hills. Coming here from other parts of Minnesota that I’ve lived in before, I was like “holy shit, this place is flat as a table!”
I was wondering about that. There are no land borders between MN and ND (not SD, BTW) around here that I know of. I had thought that if this happened, they might just give the land to Fargo. But I guess not! They’d either have to put a new bridge there, or you’d have to go over to the freeway (or north to one of the downtown bridges) to get over and circle around. Hard to imagine the Moorhead Parks and Rec would still maintain it as one of their parks.
Wow!!!
Wow! This impressed me enough to Google-find his elegant 1926 paper on river meanders. It increases my respect for that genius, which was already very high. Einstein’s son specialized in sediment transport.
But I don’t see where the 1926 paper provides a meander ratio. In fact, the Googling suggested that meander ratios are quite variable; could the early 3.14 estimate just be a fluke?
And it was Mark Twain who recognized that by systematically removing the bends; in about 600 years the Mississippi between Cairo IL and New Orleans will be only a mile and 3/4 long
I saw an article by James Grime who asked people to crowdsource information about rivers, which returned widely varying numbers. This may be what you Googled. I also read a critique of it saying that the data he collected was far too limited to reach a definitive number.
Also saw a comment that Einstein came up with the comment but didn’t include a number. It appears that the first person to state that the average was 3.14 was Hans-Henrik Stølum in 1996.
So I guess Berman heard something too good to check. And since I had literally just read it before seeing this thread, I did the same. Sorry. Too good to be true, although just the truth that Einstein did a real paper about this is fascinating in and of itself.
Shit! I also did the same IRL. :smack:
I’ve got a book coming out in a few months on robots and I had to lean heavily on myself to doublecheck every wonderful tidbit I came across. I often found that I couldn’t or that the original was being misinterpreted. I even found that quotes in books had been sloppily transcribed. It was an awful, time-consuming pain.
But I’m still surprised by Berman’s error. He’s a well-known name, author of several good books on astronomy, a long-term columnist for *Discovery *and *Astronomy *magazines. The whole of *Zoom *is a collection of such tidbits illustrating motion in all its forms. I’d still recommend it. Fun reading with a zillion snappy science facts I never knew. I have to hope now that the rest of them are better sourced and this one anecdote just slipped by.
Sinuosity is the term for the amount of meandering and it’s the ratio of meandering distance to straight line distance. Slope plays a huge roll in this as steep mountain streams are often almost straight with a ratio close to one. It’s not until you get slope of less than 4% that you get much meandering at all. They consider a ratio above 1.5 to be highly sinuous.
The Red River (and most rivers in that part of the world) make oxbows like they’re going out of style. It’s not hard to spot several oxbows in the satellite imagery as you go north. So if the area wasn’t developed, I wouldn’t be surprised to see it turn into an oxbow.
That said, the local governments are currently planning a diversion channel around Fargo, similar to the Red River Floodway protecting the larger city of Winnipeg downstream on the same river. This would, I expect, alleviate some of the pressure on that particular oxbow, since major flood events would become more rare.
That’s my hometown!
That area, as well as anything 1/4 to 1/8th of a mile from the river, is all water during every flood year. There’s never been any new river routes or major sediment relocation in my 40 years here that I’ve been aware of. I’m always waiting for the river parks to dry out every season for the four disc golf courses that hug the Red River to become playable. Any remarkable change in topology would have been well-known.
Interesting to see some contrary opinions start to show up.
Yeah, I’m all for that project, but some of my wife’s older relatives who grew up on farms in that area are bitterly against it. I imagine there are a lot more voters on the “pro” side, but I guess we’ll see.
I grew up in Winnipeg, and 1997 was my senior year of high school. The floodway basically saved Winnipeg from Grand Forks’s fate that year. So to me, having a diversion like that is a no-brainer if the expected losses in a flood are bigger than the cost of the project.
Are rural residents’ concerns based on the idea that the diversion would make flooding worse in areas outside of the city? Or is something else going on?