Mar
27
2009

Ever wonder just why the Red River seems to flood so regularly? North Dakota State geology professor Don Schwert says:

"Fargo and Moorhead sit on one of the flattest surfaces on Earth. It's the lakebed of what was a gigantic lake at one time--glacial Lake Agassiz. Lake Agassiz was here from about 12,000 years ago to about 9,000 years ago, and after the lake drained, it left behind sediments that formed this flat surface. These sediments form the basis for wonderful soils, but they form as well this flat surface off of which water is reluctant to drain. And so the Red River is doing the best it can in trying to process water across this flat landscape. But what happens is that, during times of floods, as we're having now, water spills out of the channel and onto the bed of the old glacial lake, and the glacial lake sort of reappears."

"The Red River Valley is unusual compared to other river valleys around the world. Most river valleys are effectively carved by the rivers themselves (if you think about the Colorado River, or the Mississippi River). But the Red River Valley, the river itself couldn't have begun to flow until glacial Lake Agassiz drained about 9,000 years ago. Now the importance of that statement is that we normally measure the ages of rivers around the world in terms of hundreds of thousands of years, millions of years, maybe even tens of millions of years, and here we have a river that began to flow about 9,000 years ago, and began to flow across this flat surface. It hasn't had time and it hasn't had the energy to carve any kind of meaningful valley. The lakebed of Lake Agassiz becomes the effective floodplain in times of flooding, and the river spills out onto the old lakebed, and glacial Lake Agassiz kind of reappears."

"One of the problems with the Red River is that floods can't be confined, in an engineering sense, by means of dams. A dam crosses a river valley, and water builds up behind it, and it can store water. Well, here we have this expansive surface: the feature we call the Red River Valley is actually the lakebed of Lake Agassiz, and in some places it's 60 or 70 miles wide, and there's no way, really, of effectively managing water in terms of reservoir storage in the southern Red River Valley.... There's really no other river in the world like it."

"[The Red River flows north, which is not really unusual.] But it does have a consequence: typically, in the Red River Valley, a spring thaw begins in the southern portion of the valley. So waters are released in the southern portion of the valley and begin slowly to work their way northward at about the same pace, perhaps, as the the thaw is working its way northward along the valley. So as waters are being delivered northward, waters are also being released in portions of the valley. And everything's kind of clumping together and keeps on building up as the river and its waters and the flood are processed northward. So it becomes very problematic, particularly in the northern portion of the valley: massive, shallow, expansive floods. In 1997, in portions just north of the North Dakota border on into Manitoba, one could measure the flood, in terms of width, at 60 to 70 miles wide. An Ohio River flood might be 1,000 yards. Here it's 60 to 70 miles wide, so it's an incredibly expansive flood. It's sort of a rebuilding of the old lake, in that sense."

"Urban development, or urbanization, is a problem worldwide in terms of helping to exacerbate flooding of rivers. If we think about the path of a raindrop before human settlement, that raindrop would take a long time being delivered into the main drainage. But here in Fargo-Moorhead, or cities elsewhere around the world, we can process that raindrop in a matter of minutes or a couple hours in there, and it's immediately delivered into the channel. When we think about parking lots and shopping malls, housing and driveways and streets, highly efficient drainage ditches or drain tiles in agricultural fields--all of that is processing water, all of that is accelerating the delivery of water into the main stem drainages."

(You can listen for yourself at the link above.)

Glacial Lake Agassiz and the Red River Valley: Not all of this huge area was underwater at one time, but Lake Agassiz was bigger than all the Great Lakes put together and held more water than all the lakes in the world today.
Glacial Lake Agassiz and the Red River Valley: Not all of this huge area was underwater at one time, but Lake Agassiz was bigger than all the Great Lakes put together and held more water than all the lakes in the world today.Courtesy Figure 1-2 from A River Runs North, by Gene Krenz and Jay Leitch, Red River Water Resources Council (1993)

Lake Agassiz
Lake AgassizCourtesy North Dakota Geologic Survey

More interesting resources:

Minnesota Public Radio posted this cool time-lapse, shot over 20 minutes, of sandbag operations at the Fargodome on Wednesday, 3/25.

One more interesting/worrisome thing to consider: the area of Canada once covered by the glaciers and glacial Lake Agassiz is still slowly rebounding after being pressed down by the weight of the ice. According to the New York Times,

"For the north-flowing Red River, that means its downhill slope, already barely perceptible, is getting even less pronounced with each passing year, adding to its complexity, and its propensity to flood."

Your Comments, Thoughts, Questions, Ideas

Anonymous's picture
Anonymous says:

Sorry North Dakota! I feel bad

posted on Fri, 03/27/2009 - 1:41pm
Anonymous's picture
Anonymous says:

I never knew North Dakota flooded a lot....

Well, now I know and feel sorta sorry fr them....

posted on Fri, 03/27/2009 - 4:21pm
shanai's picture
shanai says:

I really hope the folks of Fargo and surrounding areas are able to cope with the flood and come out of it safely!

I do wonder, however, about the future of towns like these that sit very precariously in areas that are likely to continue experiencing catastrophic floods? What kinds of long term plans are being developed to prepare for these events and to mitigate the damage they cause, since the floods themselves cannot be prevented?

posted on Sat, 03/28/2009 - 4:17pm
Liza's picture
Liza says:

Here's a map of the levees and secondary dikes in Fargo.

A more protective system has been planned, but is sitting in political and financial limbo.

Today's "Midmorning" program on Minnesota Public Radio featured some flood management experts talking about this very problem.

posted on Mon, 03/30/2009 - 10:53am
Liza's picture
Liza says:

In East Grand Forks, which was devastated in the flood of 1997, the city has put up an "invisible wall" to protect the downtown area from the Red River. It's an interesting solution that seems to be working there, for now. (If you follow the link, you can see photos of the invisible wall during the flood of 2001.) Fargo also uses this system in a few places, including around the Oak Grove Lutheran School which flooded this weekend. I've been unable to suss out if it was the invisible wall system that failed, but, from the descriptions in the news articles, it doesn't sound like it?

posted on Mon, 03/30/2009 - 11:45am
Anonymous's picture
Anonymous says:

I geuss that North Dakota is going to take this flooding with stride, but I can't imagine what is going to happen when another flood happens. I don't understand what a city is doing in a river valley that is known to flood.

posted on Sun, 03/29/2009 - 10:34am
Liza's picture
Liza says:

While the National Weather Service says that the Red River has crested at Fargo, and it appears that the river has crested at Halstead, too, Grand Forks/East Grand Forks and Oslo aren't expected to see the height of the flooding until the end of the week. In Oslo, they're expecting a record crest of 38.8 feet.

The Fargo area is expecting as much as 14 inches of snow. But the cold weather, nasty as it is, is helping to slow the drainage of meltwater into the Red River. (Snow isn't a big factor in the river crest predictions right now.) Engineers are much more worried about wind making the river choppy and eroding sandbag dikes and floodwalls. (Waves up to 2 feet high will batter away at and possibly wash over even the highest levees.)

Flooding along the Red River will continue to be a big news story through the end of the week.

posted on Mon, 03/30/2009 - 12:18pm
Dominic M. Griego's picture
Dominic M. Griego says:

Wow, I never knew either how much North Dakota floods. Atleast they're doing something to try and stop it, but I still feel bad for them.

posted on Mon, 03/30/2009 - 4:02pm
Anonymous's picture
Anonymous says:

Instead of feeling sorry for people near flood zones lets expect them to respect the environment they live in. They simply should not live there! If they do, then they should prepare for the consequences. Understand the ecology, look at engineering including buildings built away or above flood waters, and look at agricultural practices like drain tiling.

posted on Mon, 03/30/2009 - 5:15pm
Liza's picture
Liza says:

Well, the Red River Valley is a bit of a special case.

First, the "valley" isn't really a valley at all. The Red River is only some 9,000 years old, and it hasn't had time to carve a real channel that could help contain the water. Instead, flooding is kind of like spilling a drink on a tabletop. According to an article in the New York Times,

"...the river flows very slowly across a pancake-flat landscape. Imagine raising an eight-foot-long sheet of plywood just enough to slip a single sheet of paper under the raised end. The resulting minuscule tilt of the board represents the average slope of the Red River’s bed."

So when flooding happens, the water spills out over the landscape in an unpredictable way. There isn't an obvious "floodplain" for people to stay away from, unless you mean that we shouldn't allow farms or other development along a corridor some 70-140 miles wide along the whole northern section of the Red River. (Remember, too, that the Red River Valley is the site of very fertile farmland, so saying that we won't use it all is sort of a non-starter.)

Communities in the area are using all sorts of engineering solutions to protect cities from floods. You can hear about some of those in this MPR Midmorning broadcast from earlier in the week.

Another interesting point: forecasters and modelers are looking at land use practices in the area to see if some of them might have actually helped minimize the urban flooding. According to the same New York Times article,

"Other wrinkles of the river’s drainage basin, though, are just now being explored, like the odd legacy of homesteading. The land grant system of the 1800’s divided much of the nation into square-mile sections of 640 acres — a pattern still prevalent on the Great Plains, where many roads follow with geometric, if not downright boring, exactitude the old ruler-straight division lines.

Now comes the Red River question: How much water does each square hold? Nobody knows the exact amount, said Aaron W. Buesing, a hydraulic engineer with the United States Army Corps of Engineers in St. Paul, but the next round of computer models aims to provide an answer.

Mr. Buesing said he thought that grid storage might explain why some flood surge predictions were off. The river’s quick rise, accompanied by a cold snap, may have trapped enough water in the grids to keep the worst predictions from materializing, he said."

posted on Tue, 03/31/2009 - 11:46am
shanai's picture
shanai says:

We can't just say that people shouldn't live there because it floods. If we use that logic, there are lots of places that people "shouldn't be" living - including, probably, the areas that you and I live. In almost every case we have to manage some aspect of the natural environment in order to build cities and the societies they make possible. It isn't one or the other, but rather, a process of learning about the dynamics of things like floods in order to (hopefully) design more environmentally attuned processes, practices and communities.

I think the comment about tiling is a good example of this. I think that eventually we will learn that our current agricultural practices exacerbate problems like this AND are creating new problems elsewhere, but this won't happen simply by telling people to move their whole communities somewhere that doesn't have these risks.

posted on Tue, 03/31/2009 - 11:29pm
Liza's picture
Liza says:

The Pioneer Press posted this video today, in which natural resources scientist Henry Van Offelen, from the Minnesota Center for Environmental Advocacy, talks about farm drainage as being a major contributor to flooding.

posted on Mon, 04/06/2009 - 2:39pm
????????????'s picture
???????????? says:

If I were in a flood I would be scared of drowning. I wonder how some kids felt about all this water so close to their houses. Would they feel the same way as me?

posted on Thu, 04/02/2009 - 5:41pm
happy person(at least right now)'s picture
happy person(at least right now) says:

If I lived their I would want to move. Did any people there move because of all the flooding? Where would they move?

posted on Thu, 04/02/2009 - 5:46pm
Anonymous's picture
Anonymous says:

Have the effects of upstream dikes been explored? How much of the new "100 year" floods is due to making the flooding a problem for those further down stream? Are we simply transplanting the problem by eliminating the natural flood plains?

posted on Sun, 04/05/2009 - 11:46am
Anonymous's picture
Anonymous says:

you expekt us to read that.

posted on Sun, 04/05/2009 - 6:32pm
Char Char's picture
Char Char says:

That is horrible and we need to do something!!!

posted on Fri, 04/10/2009 - 5:26pm
Anonymous's picture
Anonymous says:

Himy nme is Katie. I'm wondering about the crest of the Mississippi River. How high will it be this year?

posted on Fri, 03/19/2010 - 1:35pm
Liza's picture
Liza says:

Hi, Katie.

This year, the Mississippi River here at downtown St. Paul is predicted to crest at 19.8 feet on Wednesday, 3/24.

You can see stream gauge data from the downtown St. Paul station anytime.

According to the US Army Corps of Engineers, the river's at 13.44' right now (3pm, 3/19) and forecasted to rise to 15.10' tomorrow.

Follow science_buzz on Twitter to easily keep track of the 2010 flood here in St. Paul!

posted on Fri, 03/19/2010 - 3:58pm

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