Deck 12: Running Water Streams and Rivers

Question 1

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

Answer 1

Velocity generally increases downstream because channels are generally smoother downstream and because stream volume tends to increase as more tributaries enter downstream.

Question 2

If the formation of an oxbow lake results in an increase in stream velocity,explain what causes a stream to meander.

Answer 2

A stream meanders when the volume and velocity of a stream is too great for its gradient.An increase in the distance traveled,by virtue of a meandering path,balances volume and velocity with a low gradient.

Question 3

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

Answer 3

The obvious benefits of controlling flooding are offset by loss of sediment deposition area,loss of wetland habitat,loss of the natural evolution of a drainage basin (natural changes in the stream channel such as meandering),increased soil erosion,and decreased natural ability to moderate effects of floods.

Question 4

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

Question 5

Describe the hydrologic cycle.

Question 6

Briefly explain what property of water makes hydrologic cycling possible.

Question 7

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

Question 8

What was the importance of the Nile River to ancient Egypt?

Question 9

What is the gradient of a stream?

Question 10

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

Question 11

Distinguish sheet flow from channel flow.

Question 12

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

Question 13

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

Question 14

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

Question 15

Briefly explain why braided streams are common in regions adjacent to glaciers.

Question 16

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

Question 17

What powers the hydrologic cycle?

Question 18

What is a 20-year flood?

Question 19

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

Question 20

What has been the effect of the Aswan Dam on farming in Egypt?

Question 21

What causes a delta to form?

Question 22

Name three of the processes involved in the evolution of valleys.

Question 23

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

Question 24

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

Question 25

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

Question 26

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

Question 27

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

Question 28

The two types of flow are ____________________ flow and ____________________ flow.

Question 29

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

Question 30

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

Question 31

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

Question 32

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

Question 33

Briefly explain how a stream can apparently have a bed that extends onto the continental shelf or to the shelf-slope break.

Question 34

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 35

Briefly explain the sequence of events that leads to the formation of a stream terrace.

Question 36

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

Question 37

____________________ flow is characteristic of almost all streams.

Question 38

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

Question 39

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 40

Under what conditions will a braided stream develop?

Question 41

Flow in which there is no mixing between parallel layers in the water is known as what?

A) turbulent flow
B) outflow
C) intermittent flow
D) laminar flow
E) stream flow

Question 42

The percentage of the Earth's water that is fresh water and is not frozen is ____.

A) 5 percent
B) 3 percent
C) 1 percent
D) 0.65 percent
E) 0.01 percent

Question 43

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 44

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 45

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

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

Question 46

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

A) 100 percent
B) 97 percent
C) 93 percent
D) 55 percent
E) 50 percent

Question 47

To predict floods,scientists

A) monitor a stream's water levels.
B) evaluate a stream's past behavior.
C) assume the same behavior as last year.
D) monitor water levels and evaluate past behavior for a stream.

Question 48

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

Question 49

The renewal of erosion which 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 50

The Mississippi Delta is a good example of a

A) tide-dominated delta.
B) distributary channel.
C) stream-dominated delta.
D) mixed delta.

Question 51

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

Question 52

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

Question 53

Streams do most of their erosion,transportation of sediment,and deposition of sediment during ____.

A) day-to-day flow movement
B) icy winters
C) flooding
D) rainstorms
E) wind storms

Question 54

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

Question 55

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

Question 56

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 57

The primary factor that determines whether water moves by turbulent or laminar flow is ____.

A) discharge
B) gradient
C) velocity
D) area
E) none of these

Question 58

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 a(n)____-dominated delta.

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

Question 59

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

Question 60

What do 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 61

In each state in the U.S.,hydroelectric power accounts for 6.4% of the electricity generated.

Question 62

When a stream's equilibrium profile shows a delicate balance among gradient,discharge,flow velocity,channel shape and sediment load the stream is

A) superposed.
B) incised.
C) graded.
D) divided.

Question 63

Mass wasting can be an important source of sediment carried in a stream.

Question 64

The Mississippi River is an example of channel flow.

Question 65

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

Question 66

Most of a stream's kinetic energy is involved in eroding and transporting sediment.

Question 67

Alluvial fans form best in humid climates.

Question 68

Headward erosion cuts through a drainage divide and diverts part of the drainage to another stream.This process is called

A) stream erosion.
B) stream piracy.
C) downcutting.
D) stream terracing.

Question 69

In all types of power plants

A) potential energy converts to kinetic energy to generate electricity.
B) a spinning turbine connected to a generator containing a coil of wire produces electricity.
C) fossil fuels are burned to generate electricity.
D) water is heated to generate steam, which turns turbines and generates electricity.

Question 70

By percentage volume,most of the hydrologic cycle is limited to ocean-atmosphere transference.

Question 71

A stream's velocity varies only along its length.

Question 72

Meandering streams have semi-circular cross-sections along most of their length.

Question 73

The average channel velocity increases downstream where the gradient is lower.

Question 74

Streams with broad,shallow channels and narrow,deep channels have a higher flow velocity than do those with semi-circular channels.

Question 75

Flow at all but the slowest velocities is turbulent.

Question 76

What is the ultimate base level for a stream?

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