Flooding - Streams

Question 1

streams can be subdivided according to

Answer 1

1. whether they are water-holding or not
2. linear form of the river
3. cross-profile or “transverse section” of the river
4. length-profile or “longitudinal profile”
5. genesis or evolution of the river

Question 2

three types of streams

Answer 2

perennial, ephemeral, intermittent

Question 3

A stream that has flowing water year-round during a typical year. The water table is located above the streambed for most of the year. Groundwater is the primary source of water for stream flow. Runoff from precipitation is a supplemental source of water for stream flow.

Answer 3

perennial

Question 4

A stream that has flowing water during certain times of the year, when groundwater provides water for stream flow. During dry periods, this stream may not have flowing water. Runoff from precipitation is a supplemental source of water for stream flow.

Answer 4

intermittent

Question 5

A stream that has flowing water only during or for a short duration after precipitation events in a typical year. In many states, this term refers to streambeds that are located above the water table yearround and streams where groundwater is not a source of water for the stream.

Answer 5

ephemeral

Question 6

a smooth concave profile which is steep a the source and gentle at the mouth. It has no obstructions.

Answer 6

graded profile

Question 7

The pattern of drainage which arises from and closely follows the trends of the underlying strata is called

Answer 7

concordant drainage

Question 8

Those streams whose courses are the direct consequence of the initial topography

Answer 8

consequent streams

Question 9

this stream flows in the same direction as that of the initial consequent stream, but which develops in response to a new base level formed due to inversion of relief.

Answer 9

resequent stream

Question 10

are loose rock particles/sediments deposited on a stream

Answer 10

alluvium

Question 11

what are the types of load?

Answer 11

bed load
suspended load
dissolved load

Question 12

one of the key factors in a stream’s ability to erode the landscape is __________

Answer 12

velocity of water

Question 13

what happens when water enters a meander bend?

Answer 13

it is forced to slow down on the inner part of the bend, but speeds up on the outer part

Question 14

are unstable overhang located at the outer bank which is produced by the velocity increase on the outer bank and subsequently enhances the ability of the water to erode into the bank

Answer 14

cutbanks

Question 15

accumulation of sediments on the inner bank due to slowing down of water

Answer 15

point bar

Question 16

manifestations of active stream erosion

Answer 16

cutbanks
point bar

Question 17

explain how stream channel migrates and become wider

Answer 17

when a stream erodes away one bank and deposits sediment along the opposite side.

as flowing water erodes cutbanks, it creates an unstable overhang which then will collapse (mass wasting.

the lateral migration of stream combined with mass wasting produces wider valleys

Question 18

Grains are sorted by their size, density, and shape during erosion, transport, and deposition by traction currents.

Answer 18

hydraulic sorting

Question 19

t or f: downcutting by streams is performed by the stream itself

Answer 19

f (performed by sediments)

Question 20

sediments in streams physically scrapes or wears away rock in a process called

Answer 20

abrasion

Question 21

evidence for stream abrasion in solid rock can be seen in

Answer 21

potholes

Question 22

how does potholes form?

Answer 22

during periods of high discharge when water column develops a swirling motion called an eddy current, causing sediments to rotate and grind holes into the rock

Question 23

a circular current of water

Answer 23

eddy current

Question 24

the velocity of a particular stream is controlled by the _______ called ________; also referred to as ____

Answer 24

steepness of the channel ; stream gradient ; grade

Question 25

is described as the change (loss) of elevation of the stream with distance downstream.

Answer 25

stream gradient

Question 26

the lowest level to which a stream can erode

Answer 26

base level

Question 27

this is often referred to as ultimate base level

Answer 27

sea level

Question 28

why is sea level considered as the ultimate base level?

Answer 28

because the ocean is the end or low point of most rivers

Question 29

what is the lowest area that is below sea level?

Answer 29

Dead Sea

Question 30

these form when a streams ability to cut downward is reduced by a resistance rock body, lake, or inland sea

Answer 30

temporary base level

Question 31

what possibly reduces a streams ability to incise thus forming temporary base levels?

Answer 31

resistance rock body, lake, or inland sea

Question 32

the ability of running water to transport and deposit sediment is dependent on _____________ and _________

Answer 32

water velocity ; type of particles being transported

Question 33

describes the fraction of solid particles that is in a suspended state

Answer 33

suspended load

Question 34

t or f: suspended load moves at the same velocity with the water

Answer 34

t

Question 35

this is what makes stream appear muddy

Answer 35

suspended load

Question 36

consists of sediment particles that roll, bounce, or remain stationary on streambed

Answer 36

bed load

Question 37

highly concentrated bedload layers that are developed beneath and driven by turbulent overlying flows

Answer 37

traction carpet

Question 38

the geologic process whereby a current transports larger, heavier rocks by rolling or sliding them along the bottom

Answer 38

traction

Question 39

a sediment transport process that moves grains across the bottom by bouncing or hopping.

Answer 39

saltation

Question 40

anytime a sediment is in motion, individual particles will undergo _____ causing it to become more ______ and more ______

Answer 40

abrasion; smaller; rounded

Question 41

t or f: smaller and rounded grains can be transported farther than angular grains

Answer 41

t

Question 42

the first particles to be removed from the bed load are the _____, ______, and ______-

Answer 42

smallest, least dense, and most angular

Question 43

the process whereby water separates sediment grains based on their size, shape, and density

Answer 43

hydraulic sorting

Question 44

hydraulic sorting sorts sediments base on:

Answer 44

size, shape, and density

Question 45

the combination of ________ and __________ produces relatively pure deposits of sand and clay

Answer 45

hydraulic sorting and chemical weathering

Question 46

this concentrates high-density particles thereby creating valuable ore deposits

Answer 46

hydraulic sorting

Question 47

what are examples high-density particles does hydraulic sorting concentrates?

Answer 47

gold, platinum, and titanium

Question 48

t or f: hydraulic sorting aids in creating placer deposits

Answer 48

t

Question 49

form when mechanical sorting causes concentration of heavy minerals of economic interest

Answer 49

fluvial placer deposits

Question 50

the first particles to return to bed load are the _____, _____, ______

Answer 50

largest ; most dense; most round

Question 51

hydraulic sorting leads to deposits called ____

Answer 51

bars

Question 52

bars located near the headwaters are often composed of ______ and ___

Answer 52

boulders and coarse gravel

Question 53

bars located in downstream areas are composed of________

Answer 53

sand-sized materials

Question 54

t or f: stream gradient in downstream areas is less steep

Answer 54

t

Question 55

crescent-shaped deposits found on the inside of meander bends

Answer 55

point bars

Question 56

are mound-shaped channel deposits consisting of sorted material ranging from boulders to coarse gravel to fine sand

Answer 56

bars

Question 57

crescent-shaped bars

Answer 57

point bars

Question 58

where does point bar develop?

Answer 58

inside the meander bends

Question 59

are formed when a river enters a lake or ocean and splits into smaller channels and begins to deposit sediment due to a decrease in velocity

Answer 59

delta

Question 60

what is the grading of deposition of sediment in a delta?

Answer 60

reverse (prograding)

Question 61

the weight from the continuous influx of sediment in deltas over time can cause the seafloor to sink and cause ______________

Answer 61

land subsidence

Question 62

a land subsidence allows deltas to become _______ and _________, thereby creating new land area

Answer 62

thicker and grow seaward

Question 63

where and how does a delta form?

Answer 63

deltas form at the mouth of a river where velocity decreases therefore, depositing sediments and creating small channels

Question 64

on what gulf does mississipi river feeds into?

Answer 64

gulf of mexico

Question 65

alluvium:streams ; ________:hillslopes

Answer 65

colluvium

Question 66

are large fan-shaped deposits that form where steep mountain streams empty out onto valley floors at the mouth of rivers

Answer 66

alluvium

Question 67

coalition of alluvial fans

Answer 67

bajada

Question 68

a channel that is choked with sediment is called a ______

Answer 68

braided streams

Question 69

streams also transport considerable amounts of dissolved ions (charged atoms) in what scientists refer to as ________

Answer 69

dissolved load

Question 70

how are alluvial fans formed?

Answer 70

abrupt changes in gradient and velocity causes sediment to deposit, choking the stream overtime, the stream migrates across the entrance to the valley creating a fan-shaped deposit

Question 71

flat portion of the valley and the area that is first inundated during flooding

Answer 71

floodplain

Question 72

erosion on the outside of meander bend produces _______ over time, whereas deposition on the inner banks help build a flat plain on the valley floor called a _____________

Answer 72

wider valleys ; natural floodplain

Question 73

what is floodplain's primary role?

Answer 73

periodically store large volumes of water moving through a drainage basin

Question 74

are pair of ridges that run parallel to the bank which are formed due to the deposition of sediment, commonly sand, at the edge of the bank

Answer 74

natural leeves

Question 75

are areas on the floodplain that are poorly drained and can remain wet long after a flood

Answer 75

back swamps

Question 76

are old floodplain left high and dry as river migrates

Answer 76

stream terraces

Question 77

t or f: back swamps are back portion of natural leeves

Answer 77

t

Question 78

well-defined stream terraces are often developed in response to

Answer 78

changes in base level due to: 1. sea level drop 2. tectonic uplift

Question 79

t or f: stream terraces are most likely inundated during a flood

Answer 79

F (less likely)

Question 80

in a __________ stream clay in in suspension while sand are on bed

Answer 80

low velocity

Question 81

in a __________ stream, both sand and clay are in suspension

Answer 81

high velocity

Question 82

t or f: natural leeves are often found along river channels that have well-defined floodplains

Answer 82

t

Question 83

t or f: flooding causes an abrupt decrease in velocity

Answer 83

t

Question 84

are developed where floodwaters are unable to return to the main channel

Answer 84

backs swamps

Question 85

how are natural leeves formed?

Answer 85

formed during flooding where abrupt decrease in velocity causes a deposition of sand-sized particles along the banks

Question 86

what are deposited on the floodplain during flooding?

Answer 86

finer particles of silt, clay, and organic matter

Question 87

as flow erodes the banks, it favors the development of a ______________ channel

Answer 87

meandering

Question 88

abandoned main channel, diverted because of flooding events

Answer 88

oxbow lake

Question 89

an emptied oxbow lake

Answer 89

meander scar

Question 90

explain how oxbow lakes are formed

Answer 90

A point bar grows into the river, making the meander more pronounced. As the meander expands, two adjacent concave banks grow closer to one another. Eventually, continued erosion and high water events like floods or seasonal high water flows can join two concave banks together. The main river channel has changed its course, leaving the riverbend cut off from the main flow of the river.

Question 91

areas subjected to stream channel migration

Answer 91

meander belt

Question 92

the part of a valley bottom across which a stream shifts its channel from time to time especially in flood.

Answer 92

meander belt

Question 93

areas across which the river is prone to move

Answer 93

channel migration zone

Question 94

belt of meandering

Answer 94

meander "train"