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River features

You are expected to be able to describe and explain the formation of various river features. These features can come from the upper, middle and lower course of a river. A popular but poorly explained feature is the meander, so we will feature it here, but you should learn more than one feature!

Formation of a meander

Water never flows in a straight line even in an apparently straight river channel. Water twists and turns around stones and other obstructions resulting in areas of slower and faster water movement. Slower areas are found in deeper parts of the river filled with fine sediments and are called pools. Faster areas are found in shallower parts of the river around larger stones and are called riffles.

Over time meanders form resulting in a winding river shape.

How a river changes shape

The river starts to flow from side to side in a winding course but still in a relatively straight channel. The pools tend to move to opposite sides of the channel over time and this is where a meander will develop.

Water moving faster has more energy to erode. This occurs on the outside of the pool.

Revise the types of erosion the river water can carry out - attrition, corrasion, corrosion and hydraulic action.

Deposition occurs where the current is slowest, and erosion occurs where the current is fastest. Erosion results in a retreating river cliff and deposition creates a sand and shingle beach. The channel migrates in the direction of the retreating river cliff.

Cross-section of a river channel

Water moving slowly tends to deposit material as it has little energy left to erode or transport material. This occurs on the inside of the pool.

Revise the types of transportation the river can do - traction, saltation, suspension and solution.

Meanders increase in size over time as land is lost on the outside of the bends, and new land is created on the inside of the bends.

The changing shape of a meander

Meanders migrate downstream and change shape over time. The neck of land between the loops also gets narrower. At the next flood, the river may cut through this to find a faster course. It then deposits material at the entrance to the old meander, cutting off the flow of water and creating an ox-bow lake.



Class Clips

Video clip about meanders and oxbow lakes.



Changes in a river's course from source to mouth

Try something different - download this Audio Bite (mp3). You can also download the transcript (pdf, 33.7 kB).

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