Oxbow Park EarthCache EarthCache
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This EarthCache is located in Fargo's Oxbow Park, placed with the permission of Fargo's Director of Parks.
Reaching the coordinates will be easy most of the year, but as this is an old oxbow lake snow melt and rains can make this a wet location.
To record a Find for this EarthCache send me the answers to the following questions.
1) The Reference Point "Red River" is located midstream of the Red River due east of the EarthCache. How far east has the river channel moved?
2) The U.S. Geological Survey web page RED RIVER OF THE NORTH AT FARGO, ND will take you to a page showing the current stage (river level) of the Red River of the North at Fargo. The current river level added to 861.8 feet (the elevation above sea level of the river bed) will give you the elevation the river reaches. Take an elevation reading at the EarthCache coordinates. How do the two elevations compare?
3) In the park, right next to Oak street, is a row of poles. How would you describe them?
The making of an oxbow lake.
Rivers have three types of channels; straight, braided and meandering. A straight channel is a section in which the stream flows in one direction. A braided channel has multiple channels, the stream splits and rejoins itself, forming small islands, called eyots. A meandering channel is one in which the stream curves and bends, these are called meanders.
In the flat, broad Red River Valley meanders are formed as streams cut through the sediments left in the old lake bed of Glacial Lake Agassiz. Meanders on a floodplain, like the Red River Valley, move from side to side over long periods of time. This is caused by the erosion, or wearing away, of the outside bend in the river and the deposition, or deposit, of sand and other material on the inside bend of the river.
As water moves in a stream it pushes and carries mud, sand and gravel. The faster the water is moving the more material it can carry. When a river has a bend or meander the water on outside of the curve is moving faster, so it is able to pickup and carry more material. This added strength results in the river eroding, or carrying away, some of the river bank on the outside of the curve. This erosion changes the location of the river bank, causing it to ‘bow’ outward. At the same time that the outside bend is being shifted the inside bend is also moving. Water on the inside bend slows down. As the water slows it loses some of its ability to carry eroded material. This material then settles to the bottom of the stream bed and over time the deposited material forms a point bar, a buildup of mud, sand and gravel. So as one bank of the bend is moving away from the center of the stream the other bank is moving toward the center. The movement of the two banks changes the location of the river, causing it to bend into a meander.
Sometimes as meanders change over time the bends get closer and closer to one another, as shown in the diagram below. The bends of a meander can get so close that during a flood the river may cut across the neck of the loop, creating a new channel for the river. Over time material deposited in the old stream bed can result in the old meander being cut off from the rest of the river, creating an oxbow lake.
Here are a few more things to think about as you stand in the former river meander and later oxbow lake.
In many places rivers are used to mark boundaries. Rivers and streams have been and are being used as borders, such as the Minnesota River between Big Stone and Lac qui Parle counties in Minnesota; the Red River between North Dakota and Minnesota, and the Rainy River between the United States and Canada are examples of boundaries marked by rivers. But what happens when the river moves?
In 1959 that very thing happened, the Red River moved. Not little by little, as is the case when a meander forms, but a big jump of more then 900’ to the east.
A disastrous flood in 1943 and another major flood in 1952 resulted in the people of Fargo working with the Army Corps of Engineers to implement new flood protection. Before the project the river had a bend in it that took it west to a point just short of 4th street near Island Park. Rerouting the river and building a dike (the current dike and sledding hill) was less expensive then building a new hospital to replace St. John’s. The rerouting and dike would also protect the Island Park area, thus named due to the fact that during flooding the location became an island in the river.
To help move river water through Fargo/Moorhead more quickly two weir dams were built near 23nd Avenue North. A weir dam is a spillway or alternative water course that comes in to use when river levels reach a set point. The weir dams cut two meanders out of the travel distance for some of the river water during floods. In addition to the two weirs one of the meanders in north Moorhead had a permanent cut-off created, the course of the river was moved to the east to straighten and shorten the river between Fargo and Moorhead. This move, along with the downtown changes to the river, resulted in 22.54 acres of Minnesota land being cut off from the rest of the state. In 1961 the U.S. Congress signed the North Dakota-Minnesota Interstate Compact and the two cut off riverbends became part of North Dakota.
References
Farndon, John (1994). Dictionary of The Earth. New York: Dorling Kindersley Publishing, Inc.
Press, Frank & Siever, Raymone (1993). Understanding Earth. New York: W. H. Freeman and Company.
U.S. Geological Survey web page http://nd.water.usgs.gov/floodtracking/charts/05054000.html
St. John’s Dike and River Change. Clay County Historical Society, Vol XIII No. 5
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