Chapter 10

Question 1

26. What is a levee?

Answer 1

A bank or levee is the raised portion of the floodplain next to the channel.

Question 2

27. What are the three ways that water can escape a river channel during a flood?

Answer 2

Water can exit a channel in 3 different ways.

1. Over top of the bank
2. Through the bank
3. Underneath the bank as groundwater.

Question 3

27. a. Water escaping a river channel - over the top of the bank:

Answer 3

Once bankful discharge is reached and exceeded, water spills out of the channel over top of the bank.

(SEE PHOTO)

Question 4

27. b. Water escaping a river channel - through the bank:

Answer 4

Water exits the channel through a breach in the bank.

SEE PHOTO

Question 5

27. c. Water escaping a river channel - over the top of the bank:

Answer 5

Water exits the channel as groundwater because of the weight of the higher water in the channel pushing around.

(SEE PHOTO)

Question 6

28. Avulsion

Answer 6

When water leaves the channel through a breach in the bank, it is an avulsion.

Question 7

28. What type of landform does an Avulsion create?

Answer 7

A Crevasse-splay.

A fan shaped deposit that is thicker and coarser near the breech changing to thinner and finer away from the channel.

Question 8

23. 3 flood control measures in common use.

Answer 8

The way to control a flood is to keep excess water in the channel, or if it won’t stay in the channel, a place for it to go.

1. Artificial Levees
2. Artificial Channels

3.

Question 9

23. 1a. ARTIFICIAL LEVEES

Answer 9

Structures, usually piles of sediment, on top of the river bank that raise the bank to create more room in the channel for water.

Question 10

23. 1b. ARTIFICIAL LEVEES - pros and cons

Answer 10

While these are cheap and effective, they do have drawbacks:

Sediment that would normally leave the channel during a flood remains there. This sediment will start to fill the channel, reducing its depth.

Levees can also make a flood worse because they can act as a barrier to the return of water into the channel.

Question 11

23. 2a. ARTIFICIAL CHANNELS

Answer 11

Artificial channels intended to direct excess water back into the river.

Question 12

23. 2b. ARTIFICIAL CHANNELS - Pros and Cons

Answer 12

They will take excess water and redirect around areas needing protection.

Question 13

23. 3a.

Answer 13

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Question 14

23. 3b.

Answer 14

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Question 15

17. Explain the effects that frozen ground has on flooding.

Answer 15

Permafrost/frozen ground makes the ground impermeable.

Precipitation is therefore quickly channeled into the river adding to a faster increase in Q.

If there is flooding, this excess water will remain on the surface, making the flood worse.