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Oxbow Lakes
Billabongs and Bayous Are Just Part of the River
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• Articles: Physical Geography
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• Rivers & Streams
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by Matt T. Rosenberg
January 6, 2000

Mature rivers flow across wide river valleys and meander or snake across the flat plains. These meandering streams create large loop meanders that develop into oxbow lakes adjacent to the stream.

As a mature river begins to curve, it cuts and erodes into the outside of the curve and deposits sediment on the inside of the cure. This is due to the fact that the stream moves more rapidly on the outside of the curve and more slowly on the inside of the curve. Thus, as the erosion and deposition continues, the curve becomes larger and more circular.

Eventually, the loop of the curve reaches a diameter of approximately five times the width of the stream and the river begins to cut the loop off by eroding the neck of the loop. Eventually, the river breaks through at a cutoff and forms a new streambed.

Sediment is then deposited on the loop side of the stream, cutting off the loop from the stream entirely. This results in a crescent-shaped lake that looks exactly like an abandoned river meander. Such lakes are called oxbow lakes because they look like the bow part of the yoke used with teams of oxen.

Oxbow lakes are also known as billabongs in Australia and bayous in Louisiana.

The Mississippi River is an excellent example of a meandering river that curves and winds as it flows toward the Gulf of Mexico.

Take a look at the topographic map of Eagle Lake on the Mississippi-Louisiana border. It was once part of the Mississippi River so the state boundary passes through the middle of the channel. Eventually, Eagle Bend became Eagle Lake as an oxbow lake but the border remains were it originally was, and Australia Island is now part of Arkansas even though it's on the east side of the Mississippi River.

The length of the Mississippi is actually shorter now than in the early nineteenth century because the U.S. government created their own cutoffs and oxbow lakes in order to improve navigation along the river.

 

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