Features in Different Courses

Profiles

The long profile of a river shows the height and gradient of a river from the source to the mouth.

It shows how the steepness of the river changes.

Long profiles are also used to show the three courses of a river; upper, middle and lower.

Features in Different Courses, figure 1

The cross profile shows the cross section of a river. It shows the width and depth of the river and river valley. Again, it shows the Upper, Middle and Lower course of the river.

Upper Course

Features in Different Courses, figure 1

  • Steep Gradient
  • Narrow Channel
  • Lots of energy
  • Lots of erosion (vertical)
  • Fast (steep)
  • Large load
  • Steep valley sides (V shape)

Because the gradient is steep and the river erodes vertically it creates a steep valley in a V shape.

As the river erodes it takes the easiest route through soft rock and winds to avoid the harder rock. This forms an interlocking spur.

Gorges: As the waterfall retreats backwards (as the process is repeated) it leaves behind a steep sided river channel called a gorge.

Features in Different Courses, figure 2

Middle Course

Features in Different Courses, figure 1

  • Less steep gradient
  • Wider River Channel
  • Less energy (but quite a lot still)
  • Quite a lot of erosion (lateral)
  • Fast flow
  • Smaller load
  • Wider Valley

In the Middle Course of a river the most common features are meanders and oxbow lakes.

Meander – A large bend in a river caused by lateral erosion (through hydraulic action and abrasion). The water on the outside of the bend travels fastest (thalweg) and erodes away to form a river cliff (mainly HA and Abrasion). The water on the inside of the bend travels slowest and deposits material to form a river beach.

Features in Different Courses, figure 2

Oxbow Lake – A Horseshoe ShapeLake

Features in Different Courses, figure 3

  1. The outside of the meanders have the quickest water (thalweg) and are eroded by hydraulic action and abrasion.
  2. The outside of the meanders move closer together narrowing the ‘neck’ in between.
  3. Eventually (usually during a flood) the river cuts straight across the neck following the quickest route
  4. After this the river slows down by the old bend and deposits material cutting off a oxbow lake

Lower Course

Features in Different Courses, figure 1

  • Flat gradient
  • Very wide river channel
  • Little energy
  • Little erosion (lateral)
  • Slower
  • Very small load
  • Very wide valley

In the Lower Course of a river the most common features are floodplains and levees.

Floodplain – A flat area surrounding the river for water to spill on to.

The river erodes laterally (sideways) not vertically.

The river valley is widened creating a large flat area.

When the river overflows (floods) material is deposited as the water loses energy.

Over time the sediment builds up in layers creating a floodplain.

Features in Different Courses, figure 2

Levee – Raised banks along the river.

What is a levee, explain its formation.
Your answer should include: Raised / Banks / Floodpain / Embankments
What processes happen most at each course?
Your answer should include: Upper / Middle / Lower / Erosion / Transport / Deposition
Describe how a river changes as you journey down the long profile.
Your answer should include: Source / Mouth / Deeper / Wider / Shallow / Processes