Test 4

Front 1

fluvial

Back 1

(Latin)river

Front 2

Fluvial processes

Back 2

associated with running water dominate 3/4 of the lands area

Front 3

water is the most

Back 3

prevalent shaper of the land surface

Front 4

water generally moves

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slower than wind but moves much more material

Front 5

water moving as

Back 5

sheet flow on the landscape can also remove and transport sediment.

Front 6

most fluvial geomorphologists are interested in

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the ability of water to effect changes on the landscape

Front 7

Erosion, Transportation, and Deposition...

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-(3 phases of a single activity)
-that these are natural processes
-people can alter their rates with changes in land use

Front 8

Erosion

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a process where large rocks and loose materials are dissolved from a part of the earth’s surface.

Front 9

(Erosion)Hydraulic action

Back 9

water easily sweeps away loose materials

Front 10

(Erosion)Abrasion

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material carried in running water is capable of scraping rocks in the bed and bank of a stream.

Front 11

(Erosion)Solution/carbonation

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the dissolving of rocks

Front 12

The greater the sedement load in a stream,

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the more that stream is able to erode.

Front 13

The greater the velocity of the water in a stream—

Back 13

the greater its ability to erode

Front 14

The greater the friction caused by surface roughness in a stream,

Back 14

the greater the amount of turbulance in the water

Front 15

The greater the resistance of rocks,

Back 15

the harder it is to break them down.

Front 16

The steeper the slope,

Back 16

the easier it is for a given amount of water to erode material.

Front 17

The less the amount of land surface cover,

Back 17

the greater the rate of erosion

Front 18

Variation in these factors

Back 18

can occur over short distances leading to substantial differences in the rate of erosion along different parts of the same stream.

Front 19

streams simultaneously erode

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both vertically and horizontally

Front 20

Steeper gradients

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across space lead to more vertical erosion or down cutting

Front 21

relatively gentle gradients

Back 21

cause more horizontal erosion.

Front 22

rivers and streams have

Back 22

steep gradients near their headwaters, moderate gradients along their middle reaches, and gentle gradients further down stream.

Front 23

most streams attempt to

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cut down to base level—a concept intended to describe the depth a stream will ultimately cut down to. Theoretically, base level for many streams is sea level (their ultimate destination), but this is seldom the case in reality.

Front 24

(Many geomorphologists say:) rivers and streams are in dynamic equilibrium with their...

Back 24

environment.(they appear not to change at all)
-until environmental change occurs
-(such as climate change or tectonic uplift)
-the river processes change in reaction to environmental changes

Front 25

Floods are

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-periodic and natural events.

Front 26

Floods occur...

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-the river reaches flood stage
-happens 2 out of 3 years in natural streams.

Front 27

People chose to live in

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-flood plains

Front 28

flood plains--

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-the portion of the stream that usually does not contain water
-but can contain water when the stram nears the flood stage or surpasses it.

Front 29

Floods are important because they have the

Back 29

large amounts of energy needed to cause rapid erosional changes.

Front 30

Floods occur at varying

Back 30

magnitudes and frequency

Front 31

Lower magnitude floods

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have less discharge BUT higher frequency

Front 32

High magnitude floods

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have larger discharge, BUT lower frequency

Front 33

recurrence interval (aka the return period)

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the # of years between floods of equal or greater magnitude.
RI=N+1/Rank

Front 34

Transportation refers to

Back 34

the actual movement of sediment, rocks, or dissolved materials.

Front 35

Once a particle has been eroded, it takes much

Back 35

less energy to continue moving it.

Front 36

a substantial portion of any stream’s

Back 36

load consists of dissolved material.

Front 37

Coarse materials are called

Back 37

bed load because they are too heavy to remain suspended.

Front 38

bed load

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(coarse materials), bounce or slide along the stream load and usually only when there is relatively sediment discharge and velocity.

Front 39

stream’s load is

Back 39

suspended sediment , relatively fine textured material mixed in with the water.

Front 40

Deposition occurs

Back 40

when a stream’s carrying capacity decreases (usually due to reduced volume or velocity). Carrying capacity always changes, and when it declines, some of the stream’s load stops moving.

Front 41

The first materials deposited are the

Back 41

heaviest; then progressively smaller materials are deposited until the stream’s load is reduced to its capacity

Front 42

Very fine textured materials may

Back 42

remain suspended indefinitely.

Front 43

Accumulations of stream laid deposits are called

Back 43

alluvium. Thick deposits are frequently (but not always) found near stream banks and along valley floors and they can be quite fertile

Front 44

Discharge

Back 44

-is the amount of water in a stream passing a particular point in a given amount of time.
-a way of accounting for volume

Front 45

Discharge usually measured

Back 45

either as cfs or cms.

Front 46

the greater the amount of turbulance in the water

Back 46

the greater the water’s ability to erode solid material.

Front 47

In streams and rivers steep gradients near

Back 47

their headwaters

Front 48

In streams and rivers moderate gradients along

Back 48

their middle reaches

Front 49

In streams and rivers gentle gradients further

Back 49

down stream

Front 50

The greater the sediment load in a stream

Back 50

the more that stream is able to erode.

Front 51

The greater the velocity of the water in a stream...

Back 51

the greater its ability to erode...

Front 52

The greater the resistance of rocks,

Back 52

the harder it is to break them down.

Front 53

The steeper the slope

Back 53

the easier it is for a given amount of water to erode material.

Front 54

The less the amount of land surface cover

Back 54

the greater the rate of erosion

Front 55

Variation in:
discharge
sediment
velocity
friction
turbulence
resistance of rocks
slope
land surface cover

Back 55

-can occur over short distances
-leading to substantial differences in the rate of erosion
-along different parts of the same stream.

Front 56

Most streams simultaneously erode both

Back 56

vertically and horizontally

Front 57

Steeper gradients across space lead to

Back 57

more vertical erosion or down cutting in any given stream.

Front 58

relatively gentle gradients

Back 58

cause more horizontal erosion.

Front 59

most streams attempt to cut down to

Back 59

base level (a concept intended to describe the depth a stream will ultimately cut down to.)

Front 60

base level for many streams

Back 60

is sea level
-not usually the case

Front 61

rivers and streams are in dynamic

Back 61

equilibrium with their environment.
-they reach an apparent “steady state”(a condition where they appear not to change)
-until environmental change occurs (such as climate change or tectonic uplift and so forth).
-THEN the river processes change in reaction to environmental changes.

Front 62

Floods are

Back 62

periodic and natural events.

Front 63

Floods occur when

Back 63

a river or stream reaches flood stage

Front 64

a river or stream reaches flood stage

Back 64

2 out of every 3 years in natural streams.

Front 65

Floods are important because they

Back 65

have the large amounts of energy needed to cause rapid erosional changes.

Front 66

Floods occur at varying

Back 66

magnitudes and frequency

Front 67

High magnitude

Back 67

floods have larger discharge, BUT lower frequency

Front 68

Lower magnitude

Back 68

floods have less discharge BUT higher frequency

Front 69

The recurrence interval

Back 69

(also called the return period) is the number of years between floods of equal or greater magnitude.

Front 70

Transportation

Back 70

refers to the actual movement of sediment, rocks, or dissolved materials.

Front 71

Once a particle has been eroded,

Back 71

it takes much less energy to continue moving it.

Front 72

a portion of any stream’s load consists of

Back 72

dissolved material.
is suspended sediment ,
relatively fine textured material mixed in with the water.

Front 73

Coarse materials are called

Back 73

bed load

Front 74

bed load

Back 74

-are too heavy to remain suspended.
-They bounce or slide along the stream bottom
-usually only when there is relatively high discharge and velocity.

Front 75

Deposition occurs

Back 75

when a stream’s carrying capacity decreases
-(usually due to reduced volume or velocity).
-Carrying capacity always changes, and when it declines, some of the stream’s load stops moving.

Front 76

The first materials deposited are the

Back 76

heaviest

Front 77

smaller materials

Back 77

are deposited until the stream’s load is reduced to its capacity

Front 78

Very fine textured materials may

Back 78

remain suspended indefinitely.

Front 79

the stream’s carrying capacity is more likely to

Back 79

be exceeded at some places than at others

Front 80

carrying capacity is more likely in:

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-Inside bends of a stream.
-Places where the stream channel widens.
-Along the lower reaches of a stream, especially where a stream empties into a standing body of water
-Behind dams in reservoirs.

Front 81

River systems are separated

Back 81

into watersheds or drainage basins.

Front 82

Small creeks join to form

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larger streams which join to form still larger streams

Front 83

network of creeks, streams and rivers that drain all

Back 83

runoff from watersheds.

Front 84

As tributaries meet a master stream

Back 84

the discharge, width, and depth of the master stream increase

Front 85

drainage divides

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The boundaries of watersheds

Front 86

drainage divides are “topographic...

Back 86

highs” that mark places where water flows down slope in one direction or the other.

Front 87

the most significant drainage divide in North America

Back 87

is the Continental Divide.

Front 88

eroded materials

Back 88

can be washed away in such quantities as to leave badlands.

Front 89

These are large areas of

Back 89

rugged topography created by erosion
-These can also be called erosional hills or mountains because they are formed when large areas are dissected by running water

Front 90

Rivers & their Valleys are Environmental systems that are instabile in

Back 90

climatic, hydrologic, and riparian [river bank] vegetation systems is strongly connected to instability in river channels

Front 91

rivers are

Back 91

dynamic environments.

Front 92

Physical processes make meandering

Back 92

streams the most common form of river channel

Front 93

The “loops” in meandering streams may eventually become

Back 93

so large that they are cutoff from the main channel leaving oxbow lakes (which eventually become filled with sediment.)

Front 94

The inside bends of meandering streams are usually

Back 94

shallower and slower flowing (hence they are sites of deposition ) while the outside bends are usually deeper and faster flowing (hence the site of more erosion)

Front 95

The inside bends of meandering streams are

Back 95

usually shallower and slower flowing (hence they are sites of deposition ) while the outside bends are usually deeper and faster flowing (hence the site of more erosion)

Front 96

When rivers appear to have ______ channels, they are called

Back 96

many/braided channels; and they are caused by excessive deposition and are extremely unstable environments.

Front 97

River channels do not always have

Back 97

water in them.

Front 98

Arid environments frequently

Back 98

have ephemeral rivers or streams.

Front 99

Rivers constantly changes

Back 99

position and this action over time creates (carves) flood plains and valley floors

Front 100

Flood plains are

Back 100

relatively flat areas adjacent to the channel that occasionally hold water

Front 101

The flood plain is formed

Back 101

by the material deposited on the inside of channel bends and the material [alluvium] deposited when the river overflows
its banks.

Front 102

relatively resistant rocks

Back 102

line one or both sides of a flood plain producing bluffs

Front 103

natural levees are

Back 103

the elevated areas of land on either side of a channel's banks

Front 104

When streams overtop their banks, water leaving the channel is quickly exposed to much more

Back 104

friction than in the stream.

Front 105

This overflow slows the water down and forces

Back 105

the heaviest sediments (like sand and course silt) to be deposited on and near the banks creating a natural levee.

Front 106

Levees can be as high as

Back 106

15 feet above the adjacent flood plain along the lower end of the Mississippi River, but in most other (smaller) streams they are usually are much lower.

Front 107

Back swamps are

Back 107

low lying portions of the flood plain lying between the natural levee and edge of flood plain (bluffs).

Front 108

Yet the concept of flood plains comes primarily from the

Back 108

eastern half of the United States where such features are relatively well defined.

Front 109

In many parts of the western U.S., flood plains

Back 109

are not present. Deeply cut (incised) streams may have no flood plain at all and some braided streams may cover a wide area that might otherwise be called a flood plain

Front 110

there is little or no flood plain in relatively young mountain streams

Back 110

presumably because down cutting is too rapid to allow much if any lateral movement. Outside mountainous regions, down cutting is slow enough that lateral shifting (eroding) makes the valley and flood plain wider than the channel itself.

Front 111

river terrace

Back 111

is an abandoned flood plain located above the present stream (including present flood plain)

Front 112

Changing climate or tectonic uplift may cause

Back 112

-cause down cutting below the existing flood plain, and if enough time passes
-a new flood plain is created below the original one.

Front 113

“If incision and aggradation [deposition] occur repeatedly,

Back 113

it is possible to develop any number of terraces.”

Front 114

Waterfalls and rapids are portions of channels

Back 114

with steep gradients. Erosion is most intense here and these features are eventually worn “back.”

Front 115

Deltas

Back 115

-are deposits of alluvium formed when streams enter standing water (either lakes or oceans)
-The word comes from the Greek letter delta, which is the shape of the classic Nile River Delta in Egypt.

Front 116

As with natural levees,

Back 116

the sudden reduction of capacity causes the river to deposit its sediment.

Front 117

Deltas take on a variety of shapes depending on the

Back 117

coastline, sediment load, water depth, and off shore currents.

Front 118

These seaward extensions of (Deltas) the flood plain can be

Back 118

fertile if drained.

Front 119

Alluvial fans are usually found in relatively

Back 119

dry and mountainous environments.

Front 120

Alluvial fans are much like Deltas

Back 120

in that when the swift moving mountain streams reach the valley, they slow down and deposit much material.

Front 121

because Alluvial fans form in dry environments, they usually

Back 121

do not have water
in them.

Front 122

Plateaus are

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extensive areas of relatively flat land in places of higher elevation.

Front 123

Mesas have

Back 123

steep sides and appear to be somewhat smaller plateaus surrounded by lower lying plains.

Front 124

Buttes are

Back 124

even smaller, flat-topped elevated places with steep sides.

Front 125

Glaciers

Back 125

are masses of freshwater ice, formed on land, and which are in or have been in motion.

Front 126

The chief source of glacial ice

Back 126

is snow Accumulations producing glaciers occur only when snowfall is greater than melting & sublimation in the zone of accumulation.

Front 127

Glaciers currently cover a relatively

Back 127

small portion of the earth’s land area (11%).

Front 128

Alpine glaciers

Back 128

are more like frozen rivers that exist at very high elevations, sometimes near the equator.

Front 129

can reach up to a

Back 129

mile in width and maybe as much as 60 miles long.

Front 130

Alpine glaciers exist

Back 130

on all continents except Austalia

Front 131

Continental glaciers

Back 131

(frequently called ice sheets) currently cover huge land areas in very high latitudes.