Where can you find delta? What is a delta? A flat depositional plain formed at the river mouth

Delta

Where can you find delta?

What is a delta?

• A flat depositional plain formed at the river mouth

Types of delta

Arcuate delta

• Triangular in shape

• E.g. river Nile, Egypt, Africa.

Bird’s foot delta

• Look like a bird’s foot

• E.g. river Mississippi, U.S.A, North America.

Estuarine delta

• No particular shape

• E.g. river Amazon, Brazil, South America.

Discussion

• What are the uses of delta to man? Explain your answer. Quote examples.

• What are the favourable conditions for the formation of delta? (Think in terms of the river characteristics and the coastal environment……)

Conditions favouring the formation of delta

• Characteristics of the river

• River carries a large load

• There are few or no lakes along the river

• Characteristics of the coastal environment

• Sheltered bay

• Weak tides and waves

• Removal of sediment is slower than deposition

• Gentle offshore slope

• Shallow sea

• Presence of vegetation

Formation of delta

• When a river bring down a large amount of sediment

• River reaches the sea, it slows down

• Particles group into larger and heavier particles (flocculation process)

• When sediment is deposited faster than it can be removed, delta is formed

Exercises

• Complete the worksheet

• Homework – Nam Chung River, p.55-56