Why does a stream bottom erode more deeply when its water level rises in a flood?
a. Since its water velocity remains the same, the increased volume of water can carry more sediment.
b. Its water level rises, so water velocity increases and it can carry more sediment.
c. It does notits stream bottom builds up to match the rise in water level.
d. Its gradient becomes steeper, so it can erode deeper.
e. To accommodate the additional water, its velocity slows, and it digs in deeper.
Question 2A river slope or gradient adjusts to what three factors that it has no control over?
a. stream width, depth, and amount of water
b. water turbulence, channel roughness, and grain size of sediment
c. water velocity, water temperature, and stream depth
d. water velocity, grain size of sediment, and amount of sediment
e. channel shape, channel cross section, and channel roughness
Question 3High-gradient bedrock channels generally have shallow, wide cross-sections.
a. True
b. False
Question 4An ice dam is more likely to occur in fall, when temperatures begin to drop.
a. True
b. False
Question 5A glacial outburst flood typically originates from a lake.
a. True
b. False
Question 6Debris flows are most common in mountainous areas such as the U.S. southwest.
a. True
b. False
Question 7Lahars carry volcanic material, making them different from mudflows of clay.
a. True
b. False
Question 8A debris flow can contain less than 40 percent sediment.
a. True
b. False
Question 9Active alluvial fans are always marked by meandering streams.
a. True
b. False
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