River Processes

Erosion, transportation and deposition

1. Erosion

1) Processes of river erosion (p100)

Hydraulic action

Abrasion

Attrition

Solution

Hydraulic Action

The sheer force of water hitting the bed and banks. Most effective when large volumes of water are moving fast

Abrasion

This is the process by which the bed and banks are worn down by the river’s load. The river throws these particles against the bed and banks, sometimes at high velocity.

Attrition

The load in the river repeatedly hits the river bed and banks, causing material to break off.

Solution

This is the chemical action of river water. The acids in the water slowly dissolve the bed and the banks.

Processes of river erosion

Vertical and Lateral erosion

• Vertical erosion– This is when the river cuts down vertically into the

ground to create a V shaped valley. It is normally in the upper course.

• Lateral erosion– This is when the river erodes out laterally, across

the valley, creating a flat valley bottom. It is normally in the lower course.

Vertical erosion creating a V shape

Lateral erosion creating a wide flat valley

2. Transportation

How is material transported downstream? (p100)

Saltation

Solution

Traction

Suspension

3. Deposition

3) Deposition

• When a river reaches its mouth the energy levels drop. As a result any material that has been carried by the river is deposited in an orderly fashion.

• Normally the bigger, heavier particles are deposited first as the river doesn’t have enough energy to carry them any further while the lighter, smaller particles are dropped last.

3. Deposition

Ganges Delta

Long River Profile (p102)

Upper

Middle course

Video 1 and 2Lower course

Your Turn

• Choose one of the processes (erosion, transportation or deposition) and produce a poem or a recipe about that process!

Example poem:Erosion wears the river banks away,The rocks are so brittle they easily fray. Always flowing and carrying the load, Hydraulic action causes the rocks to almost explode!

Example recipe:Ingredients: ………….Erosion: Take soluble minerals as river flows and dissolve them to make solutionTransportation: Pick up a handful of rocks and throw them so they skip along the river bed