Question 1

Which is likely to flow farther down to the flatter, wider part of a valley: a debris flow or a mudflow? Why?

Accepted Answer

The answer of Which is likely to flow farther down...

Question 2

What changes upstream from a site would NOT likely lead to a higher and shorter hydrograph?

Accepted Answer

A) increased urbanization ​ 
B) wildfire 
C) clear-cut logging 
D) overgrazing 
E) reforestation for a Christmas tree farm

Question 3

What caused the catastrophic 1997 flood along the Red River in North Dakota?

Accepted Answer

A) thawing to the south of the frozen north-flowing river that backed up water behind the ice to the north 
B) thawing of a heavy snowpack on the nearly horizontal surface of ice-age Lake Agassiz 
C) heavy rains on a deep snowpack on nearly flat ground 
D) a stalled warm front that was unusually far north for that time of year 
E) a cold front from the north that intersected a warm front in the northern Mississippi valley

Question 4

How would a hydrograph for a drainage basin change if major urban growth were to occur upstream?

Accepted Answer

A) The hydrograph would be higher and narrower. 
B) The hydrograph would be both higher and longer. 
C) The hydrograph would be lower but longer. 
D) The hydrograph changes only with wildfire, logging, or overgrazing, not urban growth. 
E) The hydrograph becomes skewed, rising more slowly but dropping very quickly.

Question 5

In the case study "Desert Debris Flows and Housing on Alluvial Fans-Tucson, Arizona, 2006," why did the hydrograph for Sabino Creek show higher and higher discharge rates between July 27 and July 31?

Accepted Answer

The answer of In the case study "Desert Debris Flows...

Question 6

If a 100-year floodplain was flooded in 2003, when should we expect the next 100-year flood?

Accepted Answer

A) 2013 
B) 2053 
C) 2103 
D) 2104 
E) at any time

Question 7

Where do we find potholes, and how do they form? Why do they pose a hazard to humans?

Accepted Answer

The answer of Where do we find potholes, and how...

Question 8

Active alluvial fans are always marked by meandering streams.

Accepted Answer

A) True 
 B)False

Question 9

Sections of bedrock streams tend to steepen abruptly at locations called _______________.

Accepted Answer

The answer of Sections of bedrock streams tend to steepen...

Question 10

Why are flash floods more common in dry climates than wet climates?

Accepted Answer

A) The rainfall intensity is greater. 
B) Individual storms last longer. 
C) The soil is less permeable. 
D) The river channels are not as deep. 
E) The channel gradients are steeper, so the water flows faster.

Question 11

The _______________ of a stream, also known as its channel slope, is its steepness of descent from its highest elevation to its lowest.

Accepted Answer

The answer of The _______________ of a stream, also known...

Question 12

Grain sizes increase downstream as slope decreases in a stream channel.

Accepted Answer

A) True 
 B)False

Question 13

High-gradient bedrock channels generally have shallow, wide cross-sections.

Accepted Answer

A) True 
 B)False

Question 14

The depth of sediment eroded during floods is called _______________.

Accepted Answer

The answer of The depth of sediment eroded during floods...

Question 15

Why does a stream bottom erode more deeply when its water level rises in a flood?

Accepted Answer

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 not-its 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 16

You are attempting to build a house in a valley bottom, but before you break ground on your new project, you want to make sure that the area is not in danger of experiencing a debris flow. What sort of evidence would you look for to ensure that you would be safe building in that location?

Accepted Answer

The answer of You are attempting to build a house...

Question 17

Debris flows are most common in mountainous areas such as the U.S. southwest.

Accepted Answer

A) True 
 B)False

Question 18

What are oxbow lakes and how do they form?

Accepted Answer

A) Oxbow lakes are a stagnant part of a stream that is shaped like an ox's yoke. 
B) Oxbow lakes are formed when a stream channel erodes deeply, forming a local lake. 
C) Oxbow lakes are cut-off meanders, left behind as a flooding stream takes a shorter path downstream. 
D) Oxbow lakes are the name given to plunge pools below wide waterfalls. 
E) Oxbow lakes are watering holes for oxen and cattle near rivers, excavated by humans.

Question 19

A stream that sweeps from side to side in wide turns is called a(n) _______________ stream.

Accepted Answer

The answer of A stream that sweeps from side to...

Question 20

How does urbanization of the upstream drainage area for a floodplain affect the 100-year flood level?

Accepted Answer

A) It lowers flood height, since the water runs through faster. 
B) It raises flood height. 
C) It decreases duration of the peak flood level. 
D) The downstream extent of the highest flood level will be less. 
E) There is no change; the flood level only depends on the total rainfall upstream.

Exam 13: Streams and Flood Processes

Which is likely to flow farther down to the flatter, wider part of a valley: a debris flow or a mudflow? Why?

What changes upstream from a site would NOT likely lead to a higher and shorter hydrograph?

What caused the catastrophic 1997 flood along the Red River in North Dakota?

How would a hydrograph for a drainage basin change if major urban growth were to occur upstream?

In the case study "Desert Debris Flows and Housing on Alluvial Fans-Tucson, Arizona, 2006," why did the hydrograph for Sabino Creek show higher and higher discharge rates between July 27 and July 31?

If a 100-year floodplain was flooded in 2003, when should we expect the next 100-year flood?

Where do we find potholes, and how do they form? Why do they pose a hazard to humans?

Active alluvial fans are always marked by meandering streams.

Sections of bedrock streams tend to steepen abruptly at locations called _______________.

Why are flash floods more common in dry climates than wet climates?

The _______________ of a stream, also known as its channel slope, is its steepness of descent from its highest elevation to its lowest.

Grain sizes increase downstream as slope decreases in a stream channel.

High-gradient bedrock channels generally have shallow, wide cross-sections.

The depth of sediment eroded during floods is called _______________.

Why does a stream bottom erode more deeply when its water level rises in a flood?

You are attempting to build a house in a valley bottom, but before you break ground on your new project, you want to make sure that the area is not in danger of experiencing a debris flow. What sort of evidence would you look for to ensure that you would be safe building in that location?

Debris flows are most common in mountainous areas such as the U.S. southwest.

What are oxbow lakes and how do they form?

A stream that sweeps from side to side in wide turns is called a(n) _______________ stream.

How does urbanization of the upstream drainage area for a floodplain affect the 100-year flood level?