Lower Course Processes and Features

Question 1

What are levees?

Answer 1

The result of deposition left by repeated flooding of the river. They are elongated ridges of sediment deposit alongside the river.

Question 2

How are levees formed?

Answer 2

During a flood, thickest and coarsest sediments are deposited at channel edges. Thin and fine sediments are deposited over the outer parts of floodplain. This builds up after many floods.

Question 3

What are the characteristics of levees?

Answer 3

• Fairly flat top naturally covered by grass
• Gravel stones and alluvium
• Steep sided but steeper on the channel side than on the land side
• Coarsest sediment closest to river channel
• Raised river banks

Question 4

What are flood plains?

Answer 4

Large areas of flat land on either side of a river prone to flooding. They are the result of deposition left by repeated flooding of the river. The sediment is deposited across a wide area of the valley floor.

Question 5

What are estuaries?

Answer 5

Wide part of the river where it nears the sea. Most rivers flow into a tidal estuary when they reach the sea.

Question 6

What are the characteristic of estuaries?

Answer 6

• High tidal range
• Wide
• Mudflats
• Salt marshes

Question 7

How is an estuary formed?

Answer 7

1) A large river, such as the river Severn, entered the sea at a narrow mouth
2) After the ice age, melting ice caused a rise in sea levels. This caused low-lying valley sides either side of the river to become flooded.
3) The original channel of the river is now on the estuary floor where it provides a deep channel for shipping.

Question 8

What is salinity?

Answer 8

The concentration of dissolved salts (how salty it is)