long and changing cross profile Flashcards
What is the long profile?
A line representing the course of the river from its source (relatively high up) to its mouth where it ends, usually in a lake or the sea, and the changes in height along its course
What is the shape of the long profile of a river?
The steep reduction in height near the source gives way to a more gradual reduction further downstream, giving a typical concave profile
What happens to the potential energy of the river’s water through this long profile?
The river has much potential energy near the source due to the steep drop. Later on, this is replaced by energy from a large volume of water
Why is such a perfect long profile rare?
Because the land is being uplifted, sea level changing and bands of hard and soft rock crossing the path of the river
What is the cross profile?
A line that represents what it would be like to walk from one side of a valley, across the channel and up the other side
What happens to a river’s cross profile as it flows downstream?
It’s valley changes shape. Generally, the cross profile shows the valley becoming wider and flatter, with lower valley sides
How is the channel shaped near the source of a river?
It is shallow and narrow
What direction is erosion happening in near the source?
Vertically
What are the main types of erosion near the source?
Hydraulic action, abrasion, and attrition
What types of transportation are happening near to the source of a river?
Some traction and saltation at high flow
Which material is being deposited in the upper course?
Large material
What size is the load near the source?
Large
How is the channel shaped in the middle course?
It is wider and deeper (than the upper course)
What direction is erosion happening in the middle course?
There is some vertical erosion; but lateral erosion is more important
What erosion is taking place in the middle course?
Hydraulic action is less important
What types of transportation are happening in the middle course?
Suspension is the main type of transportation; saltation and traction are still present
What is happening with deposition in the middle course?
Deposition is more obvious
What size is the load in the middle course?
The load size is reduced (compared to the upper course)
How is the channel shaped in the lower course?
It has the widest and deepest channel
What direction is erosion happening near the mouth of the river?
There is less erosion; only a little lateral
What are the main types of erosion near the mouth?
All erosion is much less important
What type of transportation is happening in the lower course?
Suspension is dominant
Which material is being deposited near the mouth of a river?
There is the deposition of fine material
What size is the load in the lower course?
There is a large amount of load, but its size is now very small
