There are 4 processes of erosion: What are the Processes of Erosion and Transportation in a river channel? 12th September 2006 Rivers shape the land through processes of erosion, transportation and deposition. There are 4 processes of erosion: Hydraulic action Corrasion/abrasion Attrition Corrosion/solution And 4 processes of transportation: Traction Saltation Suspension solution

Long Profile Height above sea level in meters. 0 50 100 150 200 250 0 50 100 150 200 250 Gradient/slope decreasing 30 25 20 15 10 5 0 Distance from sea in Kms. Source. Upland stream. Lowland river. Mouth. Velocity/flow increasing Cumecs/discharge increasing Energy increases

Summary Task Copy the sketch of a river from source to mouth Summarise in 3 paragraphs the characteristics of the river at each stage Upper course Middle course Lower course

Types of Erosion Hydraulic action Corrasion/abrasion Attrition Corrosion/solution

Hydraulic Action

Corrasion/abrasion

Attrition

Solution

Corrosion: When rocks in the river are dissolved by acid. River Erosion There are 4 main erosional processes in a river. These are attrition, hydraulic action, corrosion and corrasion. Attrition: When rocks and material carried by the river grind into each other and wear down. Hydraulic action: When the sheer force of the water wears away the river bank and bed. Corrasion: When small particles of rock carried by the river rubs against the banks of the river. Corrosion: When rocks in the river are dissolved by acid.

Key Words Hydraulic Action Corrasion/abrasion Attrition Corrosion/solution When small particles of rock carried by the river rubs against the banks of the river. When the sheer force of the water wears away the river bank and bed. When rocks in the river are dissolved by acid. When rocks and material carried by the river grind into each other and wear down.

Types of Transportation Traction Saltation Suspension Solution

Traction Heavy rocks and boulders are rolled along the river bed. Happens most in times of flood, when the current is strongest.

Saltation. Small stones and pebbles are ‘bounced’ along the river bed. Saltation can take place when the river flow is less than that needed for ‘Traction’ to take place.

Suspension Very small particles of sand or clay that are ‘suspended’ in the water. These particles will ‘settle’ if kept in a jar of water overnight and the water will look clear.

Solution. Takes place when material is dissolved in the water, it is invisible and does not colour the water. Occurs often in limestone landscapes where the water if very acidic. Some pollutants like weedkiller are also held in solution in the water

Methods of transport Copy this picture into your books and add the title above and labels for each type of transport Shows the rate of flow needed Traction Saltation Suspension Solution

Homework Rivers – “From Source to Mouth”, Questions 1, 2 and 3 Find out what the “wetted perimeter” of a river means Explain how a large increase in precipitation rates will affect Erosion and Transportation