Stories tagged Moorhead

It's been a very snowy winter so it should come as no surprise that the flood risks in Minnesota are going to be high as well. There's a 60-percent chance that the Mississippi River will be creeping up close to our backdoor here at the museum in the latest forecast announced today. Start packing the sandbags right now in Moorhead and Fargo. There's a 98-percent chance that the Red River will flood this spring.

Check out the Science Buzz 2010 flood feature now.

CNN posted a cool series of photographs of folks working to hold back the Red River. View the slideshow.

By 10:15 this morning, the Red River reached 40.6 feet, beating the record high water mark of 40.1 feet set 112 years ago. The river's rise shows no signs of slowing, and the National Weather Service predicts that the river will crest at 43 feet on Saturday afternoon. (That's 3 feet higher than the 1997 flood, and 1-3 feet above earlier predictions for this year. Two inches of rain and snow in the last four days prompted the higher forecast.) Emergency officials can no longer rely on historical data to help them make decisions.

Fargo's main dike protects the city at the 43-foot level, and city officials have no plans to try to raise it any further. (There's no time.) In other areas, volunteers are continuing to lay sandbags, hoping to protect cities, homes, and farms in the river's path. But water is breaching some dikes and evacuation orders are being issued for some areas. Forecasters say the river is likely to remain at more than 40 feet for as long as a week, putting pressure on the already taxed sandbag and temporary dike system.

Minnesota Public Radio's Bob Collins is writing from Fargo on the News Cut blog. Check it out.

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."