River Long and Cross Profiles Flashcards
What is a long profile?
A long profile shows the gradient of a river as it journeys from source to mouth.
What is a graded long profile?
When a river tries to achieve a smooth curve in order to reach its base level at the sea.
What is erosion like in the upper course?
Mostly vertical erosion by hydraulic action.
What is erosion like in the middle course?
Less vertical erosion, more lateral erosion. Much attrition and abrasion, some solution.
What is erosion like in the lower course?
Very little erosion, no vertical only lateral.
What is transportation like in the upper course?
Mostly traction. Large boulders moved.
What is transportation like in the middle course?
Mostly suspension, increased traction. Load becomes smaller and less angular.
What is transportation like in the lower course?
Mostly suspension and solution. Very small particles of load, great quantity of load.
What is deposition like in the upper course?
Large boulders are deposited.
What is deposition like the in the middle course?
More deposition, especially on the inside bend of meanders.
What is deposition like the in the lower course?
Deposition is now the main fluvial process. Fine material now deposited.
How does the long profile change in the upper course?
- Set in a landscape of high relief
- Starts at its source
- Single channel is formed which flows down a steep gradient
- Steep descent = more potential energy
- May be waterfalls and rapids
How does the long profile change in the middle course?
- In an area of hilly relief
- Discharge has increased as the channel is deeper and volume of water has increased
- Less vertical erosion but more lateral erosion at meanders
- Gradient of long profile becomes concave as vertical erosion decreases
How does the long profile change in the lower course?
- Erosion only at meanders and is lateral
- Lack of vertical erosion means that gradient is almost flat
What is discharge?
The volume of water passing through a given point on a river.