Landforms Of Fluvial Erosion And Deposition

Question 1

How does a delta form?

Answer 1

1. As a river enters the sea or lake its velocity decreases because of the reduction of gradient.
2. This decreases its competence and deposition takes place.
3. If tide is strong deposition does not occur.
4. If a river discharges into a tideless sea the alluvium may build into a delta. Rate of wave erosion lower than rate of river deposition and shallow sea.
5. The build of alluvium forces the river to break up into distributaries.

Question 2

Name the different types of deltas ?

Answer 2

Birds foot - Mississippi delta

Arcuate and cuspate.

Question 3

What are the three main categories of deposits?

Answer 3

Bottom set deposits
Fore set deposits
Top set deposits

Question 4

What type of deposition is transported the further from the mouth of the river?

Answer 4

Bottom set deposits - fine deposits.

Question 5

Flocculation where does it occur and how?

Answer 5

When a river mouth meets the sea
Deposition of fine clay
In Fresh water - clay particles repellent each other but in salt they are charged and they are attracted together into clots or floccules. Larger and settle out of suspension easily.

Question 6

Flood plain how are they formed ?

Answer 6

The river can move laterally now as it has enough energy
Creating a flat floor next to the valley.
As the river floods, it deposition takes place because hydraulic radius dramatically decreases as a result of the small cross sectional area to large wetted perimeter.
Levees can form.
Largest coarsest material deposited first
Finest silt deposited last.
Wetted perimeter increase so hydraulic radius decrease.