Deck 11: Running Water

Question 1

Briefly explain how a stream might adjust toward an equilibrium state following a heavy rain.

Answer 1

A heavy rain will increase stream volume and velocity.The channel and gradient will be temporarily too small and low,respectively,for the increased volume.Stretches of the stream with a low gradient will experience erosion,and stretches farther downstream may experience deposition as the gradient of the upstream portion is adjusted (increased).

Question 2

Describe the major drainage patterns.

Answer 2

In dendritic drainage,a network of channels resembles tree branching.The pattern develops on gently sloping surfaces underlain by material that erodes roughly equally.Tributaries join larger channels at various angles.In rectangular drainage,tributaries join larger channels at right angles;this pattern is controlled by geologic structures,such as joints.Trellis drainage is a network of nearly parallel streams with tributaries joining them at right angles because the streams follow easily eroded rocks and are separated by resistant rocks.In radial drainage,streams flow outward from a high point like a volcano.Deranged drainage patterns are irregular,with streams flowing into and out of swamps and lakes.

Question 3

What are braided streams,and where do they form?

Answer 3

A braided stream has an intricate network of dividing and rejoining channels separated from one another by sand and gravel bars.Braided streams form when there is an excess of sediment load for the amount of water available and the depth of the stream channel.Braided streams have broad,shallow channels and carry a lot of bed load of mostly sand and gravel.

Question 4

How and where do alluvial fans form?

Question 5

Describe the hydrologic cycle.

Question 6

Briefly explain how a meandering stream can become incised in solid bedrock.

Question 7

Is it possible to change the velocity of a stream but have it maintain the same discharge? Explain.

Question 8

What happens when a stream overflows its banks?

Question 9

What is stream piracy? What happens when one stream pirates another?

Question 10

How often will a flood of a 20-year magnitude occur?

Question 11

What is a 20-year flood?

Question 12

Briefly explain what will happen to a stream's behavior if one drains a lake that is a temporary base level for that stream.

Question 13

What causes a stream to meander?

Question 14

Briefly explain the trade-offs that accompany any flood control project.

Question 15

Describe where flow velocity is highest in a semi-straight channel.Why is this the case?

Question 16

What is the infiltration capacity of a surface? On what factors does the infiltration capacity of a surface depend?

Question 17

What are some of the techniques used to try to control floods?

Question 18

What are the three main types of marine deltas based on? What are they,and how are they different from each other?

Question 19

Describe the evolution of valleys.

Question 20

What is a superposed stream?

Question 21

How do oxbow lakes form?

Question 22

What are some of the reasons why running water is important to humans?

Question 23

The ideal graded stream has a balance among what five factors?

Question 24

In what ways can water be temporarily stored,from a few years to a few thousand years,on the land areas before returning to the oceans?

Question 25

What causes a delta to form?

Question 26

How is the gradient of a stream calculated?

Question 27

What is/are the source(s)of dissolved load in most streams?

Question 28

How is the discharge of a stream calculated?

Question 29

What is the gradient of a stream?

Question 30

In the hydrologic cycle,what happens to the precipitation that falls on the land?

Question 31

What is the difference between the velocity and the discharge of a stream?

Question 32

Why does the velocity of a stream generally increase downstream even though the gradient decreases?

Question 33

What evidence reveals that water may once have been abundant on Mars?

Question 34

Distinguish sheet flow from channel flow.

Question 35

What is meant by the term "divide" as in the continental divide along the Rocky Mountains?

Question 36

What are the three types of beds characteristically exhibited by a prograding delta?

Question 37

Since levees can protect many areas during floods,why are they controversial?

Question 38

Briefly explain what property of water makes hydrologic cycling possible.

Question 39

What powers the hydrologic cycle?

Question 40

In addition to dams and levees,what are two other measures that may be taken to control flooding?

Question 41

The lower limit to which the stream can erode is its ____________________.

Question 42

The gradient of streams tends to be ____________________ in their upper reaches and ____________________ in their lower reaches.

Question 43

A fan-shaped deposit of alluvium that forms adjacent to highlands in arid or semiarid climates is called a(n)____________________.

Question 44

When flow is restricted to long,troughlike depressions,the flow is known as ____________________ flow.

Question 45

The outer bank of a meander in a meandering stream is called the ____________________,where (erosion/deposition)____________________ takes place.The deposit on the opposite side of the channel is called the ____________________,which is where (erosion/deposition)____________________ occurs.

Question 46

When infiltration capacity is exceeded and water begins to move rapidly downslope,a continuous film of water known as ____________________ flow develops.This type of flow can cause ____________________.

Question 47

If a superposed stream erodes downward into resistant rock and cuts narrow canyons,the resulting feature is called a(n)____________________.

Question 48

A change in base level leading to formation of stream terraces can come about by ____________________ of the land over which the stream flows,or a(n)____________________ of sea level.

Question 49

A stream that cuts directly through ridges that lie in their paths are called ____________________.

Question 50

Water that returns to the oceans as surface flow from streams is ____________________.

Question 51

The process by which water vapor reenters the atmosphere by evaporation from plants is called ____________________.

Question 52

The types of marine deltas that are recognized,based on the relative importance of the processes involved in their formation,are ____________________-dominated,____________________-dominated,and ____________________-dominated.

Question 53

Ridges of alluvium left along a stream's margins by repeated deposition during floods are called ____________________.

Question 54

Water enters the atmosphere by ____________________ from the ocean surface.Most of this water condenses and returns to the ocean as ____________________.

Question 55

The renewal of erosion that results in creation of stream terraces is generally attributed to a change in ____________________ level,or a change in climate resulting in greater ____________________,and thus,discharge.

Question 56

The total surface region that provides runoff to a stream system is known as a(n)____________________.

Question 57

In meandering streams,the water velocity tends to be greatest in the ____________________ portion of the meander.

Question 58

Former meanders that have been cut off from the stream are called ____________________.

Question 59

An uplifted erosional remnant of a floodplain that formed when a stream was flowing at a higher level is called a(n)____________________.

Question 60

Lateral erosion creates conditions along a stream valley that promote movement of material by another geologic process known as ____________________.

Question 61

The percentage of atmospheric water that comes directly from the ocean is:

A)95%.
B)85%.
C)65%.
D)35%.
E)15%.

Question 62

A dry surface has a higher infiltration capacity than a moist surface.

Question 63

A rill is the precursor to a brook,creek,stream,or river.

Question 64

A stream's velocity varies only along its length.

Question 65

A canyon that is much deeper than it is wide with vertical or near vertical sides is called a(n)

A)mountain canyon.
B)grand canyon.
C)slot canyon.
D)deep canyon.
E)stream canyon.

Question 66

The solid particles of a stream include:

A)bed load.
B)suspended load.
C)solution load.
D)bed load and suspended load.
E)suspended load and solution load.

Question 67

Dissolved load is the:

A)invisible load of a stream.
B)abrasive load of a stream.
C)suspended load of a stream.
D)invisible and abrasive load of a stream.
E)abrasive and suspended load of a stream.

Question 68

A delta that has islands reworked by waves on the seaward side,such as the Nile delta,is typically formed as in a(n)____-dominated delta.

A)avian
B)stream
C)wave
D)tide
E)sediment

Question 69

Surface runoff is confined to troughlike depressions of various sizes in channel flow.

Question 70

Streams of rivers possess two kinds of energy.Potential energy is the energy of:

A)water molecules.
B)position.
C)gravity.
D)motion.
E)channeling.

Question 71

A stream erodes material from its banks and bed by:

A)suspension.
B)hydraulic action.
C)abrasion.
D)suspension and hydraulic action.
E)hydraulic action and abrasion.

Question 72

Deep,meandering canyons cut into bedrock are called:

A)hard rock meanders.
B)oxbows.
C)incised meanders.
D)eroded meanders.
E)floodplains.

Question 73

Streams of rivers possess two kinds of energy.Kinetic energy is the energy of:

A)water molecules.
B)position.
C)gravity.
D)motion.
E)channeling.

Question 74

Particles move along a streambed by:

A)rolling.
B)sliding.
C)saltation.
D)rolling and sliding.
E)rolling,sliding and saltation.

Question 75

A delta with long fingerlike sand bodies,each deposited in a distributary channel that progrades far seaward,such as the Mississippi River,is typically formed as in a(n)____-dominated delta.

A)avian
B)stream
C)wave
D)tide
E)sediment

Question 76

The percentage of the Earth's surface that is covered by water is about:

A)10%.
B)30%.
C)50%.
D)70%.
E)100%.

Question 77

The percentage of the Earth's water that is fresh water that is not frozen is:

A)5%.
B)3%.
C)1%.
D)0.65%.
E)0.01%.

Question 78

The ultimate base level for a stream is:

A)sea level.
B)the nearest lake.
C)the nearest stream.
D)the nearest spring.
E)the nearest valley.

Question 79

The percentage of Earth's water that is in the oceans is:

A)100%.
B)97%.
C)93%.
D)55%.
E)50%.

Question 80

The Mississippi River is an example of channel flow.