ZIMSEC O Level Geography Notes: River Profile
- Rivers can be studied from two aspects viz:
- The long profile-this is the cross section along the river’s entire length from its source to its mouth.
- The short profile-this is the cross section across a river’s valley from the crest line( on one bank) to the channel to the other crest line. This is known as the river’s valley.
- There is only one cross profile but an innumerable short profiles that can be taken at any point in a river’s length.
- The short profile however tends to widen the further one moves downstream.
- The diagram above shows the three main sections of a river/stream’s long profile and the diagram below shows the corresponding typical short profiles at each stage.
- A river’s long profile can be divided into three sections viz:
- the upper course or headwater reaches, the middle course or middle reaches, the lower course or the lower reaches.
- The base level of a river is the lowest point a river can erode its channel, this is equal to the sea level of the ocean into which the river empties.
- it has a steep gradient, less volume of water, there is eddying and splashing as the water flows turbulently.
- Common features include:V-shaped narrow valleys, potholes, interlocking spurs, water falls and rapids, gorges, strewn boulders.
- The most dominant form of erosion is vertical erosion and headward erosion also takes place.
- Its less steep, has more water volume, a wider channel and more velocity due to reduced channel roughness.
- Common features include: Open V-shaped valleys, truncated spurs, meanders, ox-bow lakes and braids.
- Erosion is mostly in the form of lateral erosion.
- Is flat and has a very wide channel with less energy.
- Common features include: bluffs and other flood plain features such as swamps, braiding, deltas, alluvial fans, deferred junctions and natural levees.
- These features are mostly due to deposition which is more dominant than erosion due to the reduced river energy due to the lower gradient and increased wetted perimeter.
To access more topics go to the Geography Notes page.
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