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MEANDERS By Andy Frain
Formation Once the river starts to bend, the water is pulled downhill and picks up momentum causing it to travel in a straight line. Since it is travelling in a straight line when it come to a bend, the water collides with the outer wall. This slowly erodes the outer wall, causing material to be deposited into the water. The material that is in the water is then deposited further down the river on the inner wall where the water is moving slower. This gradual erosion and deposition of material forms more bends and curves. The river begins to meander when there is more water moving on its outside. The extra weight, and faster pace, of this water means that there is more erosion. This occurs when the river is deeper. The shallower part of the river is moving slower around the bend, meaning it deposits more of its waste onto the inside of the bend.
Location Meanders can be found at the middle and lower course of the rivers. They are rarely found in the upper course because the river doesn’t have enough momentum to erode the sides at this point. When the river has more water in it, such as the lower of middle courses, it will have enough momentum to erode the bank, so meanders will form, in particular in areas of soft rock, which is easier to erode.
Glen Canyon, Arizona, USA Here is a good example of a meander, in Glen Canyon. Rather than taking the obvious route through the middle, the had rock has forced the river to travel around it and thus it has eroded the softer rock, causing numerous meanders.
Meanders and Ox-Bow Lakes • Meanders eventually turn into ox-bow lakes, as the diagram below shows As you can see, the deposition of material on the slower, inside, bends, coupled with the gradual erosion in a straight line, leads the meander to be cut off from the river eventually.
