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.
What is discharge measured in?
Cubic metres per second (cumecs)
What is the equation for discharge?
Discharge = velocity x cross sectional area
What happens to discharge as it goes downstream and why?
It increases as tributaries join in and add their volume of water.
What is the upper course?
The part of the river that starts at the source, usually on high ground.
What is the middle course?
The middle part of the river.
What is the lower course?
The part of the river towards the mouth , usually on low-lying ground.
What is gradient?
The measure if how steeply a river loses height.
What are the key features/landforms of the upper course?
- Waterfalls
- Interlocking spurs
- Gorges
- Rapids
What are the key features/landforms of the middle course?
- meanders
- ox bow lakes
What are the key features/landforms of the lower course?
- Levées
- Flood plains
- Deltas
- Estuaries
What is the long profile like in the upper course?
Starts of at a steep gradient, but starts to slowly decrease.
What is the long profile like in the middle course?
Still fairly steep, but decreasing gradient.
What is the long profile like in the lower course?
Very low gradient, reaches base level at the mouth.
What is the cross profile like in the upper course?
River is fairly narrow and quite shallow. There is low discharge.
What is the cross profile like in the middle course?
River is slightly wider and deeper, with a slightly higher discharge.
What is the cross profile like in the lower course?
River is very wide and deep with a high discharge.
What is the Bradshaw Model?
The Bradshaw model shows how the characteristics of a river change from its upper to lower course (triangles).
What happens to the rivers width from U to L?
Gets Wider
What happens to the depth from U to L?
Gets Deeper
What happens to velocity from U to L?
Increases
What happens to discharge from U to L?
Increases
What happens to the gradient from U to L?
Decreases.
What happens to the sediment size from U to L?
Decreases.
