Water on the Land - Characteristics of the Upper, Middle, and lower courses

A river is split up into three sections: the Upper course, the Middle course, and the Lower course.

Upper Course:
-Characteristics

• Steep, V-shaped valleys
• Narrow/shallow channel

-Features

• V-shaped valleys
• Interlocking Spurs
• Waterfalls
• Gorges
• Downward erosion

Middle Course:

-Characteristics

• Open, gentle sloping valley with flood plain
• Wider/deeper channel
• More suspended sediment

-Features

• Meanders
• River Cliffs
• Slip off slopes
• Lateral and Downwards erosion

Lower Course:

-Characteristics

• Open, gentle sloping valley with flood plain
• Flat and wide flood plain
• Wide and open valley
• Very wide and very deep channel

-Features

• Ox-Bow lakes
• Flood plains
• Levées
• Lateral erosion

Water on the Land - Processes of Transportation/Deposition

Transportation

Rivers will pick up and move rocks, silt and other material as they move downstream. There are four main ways in which this is done:

Solution: Minerals that are dissolved into the river are carried along.

Suspension: Fine material is swept along in the water.

Saltation: Small pebbles and stones are bounced along the riverbed.

Traction: Larger stones are rolled along the river bed.



Rivers use energy to move material, and a rivers energy level changes between source and mouth.

When energy levels are very high, large rocks and boulders can be transported. Energy levels are usually higher near a river's source, where it's course is steep and valley narrow. Energy levels also rise in times of flood.

When energy levels are low, only small particles can be transported. Energy levels are lowest when velocity drops as a river enters a lake or the sea.

Deposition

When a river loses energy, it will drop, or deposit the material that it is carrying.

Deposition can occur when a river enters an area of shallow water or when the volume of water decreases, for example, after a flood or during a drought.

Deposition commonly occurs at the end of a river's journey, when it enters a lake or the ocean.

Deposition at the end of a river can form river deltas.

Water on the Land - Processes of erosion

Erosion involves the wearing away of rock and soil found along the river bed and banks. Erosion also involves the breaking down of the rock particles being carried downstream by the river.

There are four main forms of river erosion:

Hydraulic Action: The force of the river pressing against the banks can cause air to get trapped in cracks and crevices. This pressure weakens the banks and gradually wears it aware.

Abrasion: Rocks carried by the the river wear down the river banks and bed.

Attrition: Rocks carried by the river smash into each other and break into smaller and smoother rocks.

Solution: Soluble particles like chalk or salt will dissolve into the river.

Topic 1: Water on the Land - Features of a river basin

A river basin or drainage basin is an area of land where surface water converges to a single point, usually the exit of the basin, where the waters join another water body such as the ocean, a lake or a reservoir. Sometimes, drainage basins drain into other drainage basins, with smaller basins combining into larger ones.

This diagram shows some of the key features of river basins -

Watershed: The watershed is the edge of the drainage basin, and usually the top of a hill, any water that falls inside the watershed will flow down into the basin and any that falls on the other side will enter a different drainage basin.

Source: The source of the river is the point furthest from the river's estuary or confluence with another river.

Tributary: A tributary is a stream or river that flows into another parent river, rather than directly into the sea.

Main river channel: This is the main part of the river, which flows to the sea, and to which other tributaries connect.

Confluence: A confluence is where two bodies of water meet one another, either in a tributary meeting a river, or two rivers joining to form another river of a new name.

River mouth: This is where the river enters the sea or a lake.