Deck 15: Running Water

Question 1

Streamflow is generally laminar.

Answer 1

False

Question 2

Runoff occurs when the rate of rainfall is greater than the infiltration capacity of the soil on which it is falling.

Answer 2

True

Question 3

The gradient of a stream does not change over the length of the stream.

Answer 3

False

Question 4

Erosion occurs through hydraulic action and abrasion.

Question 5

The total load of a sediment a stream can carry consists of suspended load and bed load.

Question 6

A large stream will tend to have a great competency but little capacity.

Question 7

Competence of a stream is defined by the largest particle that a stream can carry.

Question 8

Alluvial fans are formed where running water flows into another body of water.

Question 9

A 10 year-flood occurs every ten years.

Question 10

A 10-year flood could occur in two consecutive years or it could occur once in a 20 year period.

Question 11

Artificial levees may actually increase the possibility of flooding downstream.

Question 12

A dendritic drainage pattern develops when more sediment is supplied to a stream than can be transported by it.

Question 13

Streams and stream valleys are the result of erosion of the stream along its length to base level.

Question 14

Along a graded stream, no sediment is eroded, transported, or deposited.

Question 15

A v-shaped cross section and an irregular profile characterize a well-developed or "old"valley.

Question 16

Flooding in Johnstown, PA, in 1889 was disastrous and deadly because

A) the town was built on a floodplain
B) the flood wave traveled at velocities as high as 60 km/hr
C) 20-25 cm of rain fell over a 24 hour period
D) an upstream dam failed
E) all of the above

Question 17

The primary purpose of the Tennessee Valley Authority is to

A) oversee river development
B) control flooding
C) generate electricity
D) provide recreation

Question 18

The type of flow, laminar or turbulent, is controlled by

A) flow discharge
B) water temperature
C) flow velocity
D) water viscosity
E) mud content

Question 19

Sheet flow is most likely to occur in areas with

A) dense vegetation
B) low infiltration capacity
C) climates with high rainfall
D) large depressions
E) laminar flow

Question 20

Assuming constant discharge, stream velocity increases as

A) roughness increases
B) depth decreases
C) roughness decreases
D) slope decreases
E) width increases

Question 21

In a downstream direction, which of the following trends occurs?

A) roughness increases
B) velocity decreases
C) slope increases
D) discharge decreases
E) depth increases

Question 22

Velocity increases downstream because

A) roughness decreases
B) discharge increases
C) width and depth increases
D) B and C
E) all of the above

Question 23

Erosion of the streambed occurs by

A) hydraulic action
B) abrasion
C) dissolution
D) all of the above

Question 24

A small, slow-flowing stream would generally have

A) low competence and low capacity
B) low competence and high capacity
C) high competence and low capacity
D) high competence and high capacity

Question 25

Streamflow and sediment deposition on the floodplain is

A) a common event
B) relatively uncommon
C) occurs only on large river systems
D) something that should be prevented if possible

Question 26

Which of the following drainage patterns would be expected to develop in flat-lying sedimentary rocks?

A) trellis
B) dendritic
C) rectangular
D) radial
E) meandering

Question 27

A graded stream represents a balance between which of the following variables?

A) gradient and channel characteristics
B) flow velocity
C) sediment load
D) A and B
E) all of the above

Question 28

If vegetation decreases in a watershed such that sediment supply to the stream is increased, which of the following changes might you expect?

A) slope will increase
B) velocity will increase
C) the stream pattern might become more meandering
D) discharge will decrease
E) roughness will decrease

Question 29

Graded streams tend to be characterized by

A) a smooth, concave longitudinal profile
B) insignificant erosion along its bed
C) insignificant deposition along its bed
D) B and C
E) all of the above

Question 30

Stream terraces will develop if

A) sediment supply to the stream increases
B) base level is lowered
C) the capacity of the stream decreases
D) discharge decreases
E) a dam is built downstream

Question 31

Which of the following describes a well-developed or "old"stream valley?

A) valleys are v-shaped and narrow with an irregular profile
B) streams meander with a narrow floodplain and relatively smooth profile
C) a broad, flat floodplain with a meandering stream, oxbow lakes, and a graded profile
D) none of the above

Question 32

The total area that provides runoff to a stream is called its ___________ ___________.

Question 33

The gradient of streams tends to be (steeper, gentler)___________ in their upper reaches, and (steeper, gentler) ___________in their lower reaches.

Question 34

The___________ ___________ is the maximum rate at which the soil or other surface materials can absorb water.

Question 35

That there is no mixing between parallel layers in the water is characteristic of___________ flow.

Question 36

A ___________stream cuts directly through a ridge or series of ridges instead of going around them.

Question 37

You are in charge of designing an artificial stream channel to move a certain amount of water which is carrying sediment. At one point along the channel, more water will be added from a side stream.(a) Will the capacity of the main channel be affected? Explain.(b) Can you design the channel so that the competence will not be affected? Explain.

Question 38

Glen Canyon Dam, completed in 1963 near the Utah- Arizona border, controls the water in the Colorado River which flows through the Grand Canyon. Since 1963 several changes have occurred in, along, and near the river as a result of the damming.(a) What are 2 changes that you would predict upstream from the dam?(b) What are 2 changes that you would predict downstream from the dam?

Question 39

Using the concept of a graded stream, describe how a stream whose profile has been faulted will respond to the faulting. Assume it is a normal fault with the downthrown block on the downstream half of the profile.

Question 40

What is the most costly and destructive type of natural disaster?

Question 41

What was the most important lesson learned from the Flood of '93 in the Midwestern United States?

Question 42

How does flood control actually exacerbate problems in many flood-prone areas?

Question 43

Why doesn't Venus have surface water?

Question 44

Very briefly, what is the hydrologic cycle?

Question 45

Approximately what percentage of atmospheric water comes directly from the ocean?

Question 46

Approximately what percentage of the hydrologic cycle precipitation falls on land as rain and snow?

Question 47

What is meant by the term runoff?

Question 48

What characterizes turbulent flow?

Question 49

What is the primary factor that determines whether water moves by turbulent vs. laminar flow?

Question 50

In semi-straight channeled streams, where does the highest velocity of flow occurs? Explain why this is the case.

Question 51

In meandering streams, where does the water velocity tend to be greatest?

Question 52

Briefly explain why a stream with a semi-circular channel has a higher average velocity than a stream with a rectangular or v-shaped channel, all other factors being equal.

Question 53

Approximately what percentage of a stream's kinetic energy may be available to erode and transport sediment?

Question 54

By what two processes can a stream erode material from its banks and bed?

Question 55

What are the two categories of the solid load of a stream?

Question 56

How are the particles of the bed load moved along the bed of a stream?

Question 57

What is the competence of a stream, and on what does it depend?

Question 58

Briefly explain how a streams' capacity differs from its competency.

Question 59

When do streams do most of their erosion, transportation of sediment, and deposition?

Question 60

What is the origin of oxbow lakes?

Question 61

What are natural levees?

Question 62

What are the three types of marine deltas that are recognized, based on the relative importance of the processes involved in their formation?

Question 63

A bird's-foot delta, such as that of the Mississippi River, is typically formed as which of the three types of marine deltas?

Question 64

In what climatic regions do alluvial fans form best?

Question 65

What is the probability of occurrence of a ten-year flood in any given year?

Question 66

Why are predictions of the magnitudes of 50-year or 100-year floods unreliable for most of North America?

Question 67

What is a drainage basin?

Question 68

What is the base level of a stream?

Question 69

What is ultimate base level for a stream?

Question 70

Briefly explain why a dam can create a temporary base level, and what effects this base level can have on the stream system both above and below the dam.

Question 71

How does an incised meander form?

Question 72

What is stream piracy?

Question 73

Briefly explain what happens to the two stream systems when one stream pirates another.

Question 74

What is a stream terrace?