Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

2115 > Rivers > Flashcards

Rivers Flashcards

1
Q

what is river planform

A

the configuration of the channel in a plan view or aerial

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

what is an alluvial river

A

a river that flows through the sediments or alluvium

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what is a reach

A

a length of river that has uniform appearance in both character and behaviour.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what is a segment

A

an alternating sequence of reaches

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what is a geomorphic unit

A

a discrete channel or floodplain unit

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what is lateral accretion

A

coarse sediment deposited inside a meander bend which gets incorporated into the floodplain.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

what is vertical accretion

A

the vertical rise of a floodplain due to the overbank deposition of suspended load.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what are levees

A

a ridge along the channel with suspended and bedload couplets due to overbank vertical accretion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

what is a backswamp

A

the lowest part of the distal floodplain which has fine grained sediments

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

what is a crevasse splay

A

when the levee breaches depositing bed load.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

what is a cutoff

A

when a meander bend cuts through its neck leaving a paleochannel

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

what is the energy, sediment mix and valley setting of high energy floodplains

A
  • > 300 W/m2
  • non cohesive sands and gravels with some boulders
  • confined and partly confined valleys on high slopes
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

what is the landscape position, formation and reworking processes and river type of high energy floodplains:

A
  • uplands and headwaters
  • vertical and abandoned channel accretion
  • floodplain stripping, channel widening and floodchannels
  • confined valley and partly confined
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

what sculpted features are found with high energy, high slope

A

waterfalls, step pool, cascades, rapids, riffles and runs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

what mid channel depositional units are found

A

boulder mound, longitidunal bar, diagonal bar, transverse bar, islands and gravel/sand sheets

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what bank attached features can be found

A

lateral bars, point bars, ledges, tributary confluence bars and benches

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

what sculpted fine grained erosional features can be found

A

sculpted point bars, sculpted lateral bars, runs and poolsha

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

what are the two mechanisms of accretion that build floodplains

A

lateral and vertical accretion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

what is the energy setting, sediment mix, valley setting and landscape position of medium energy floodplains

A

10-300 W/m2, non cohesive sands and gravels, partly confined and middle to lower reaches

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

what is the formation and reworking processes and river types of medium energy floodplains

A

vertical and or lateral accretion
avulsion, cut offs, channel expansion and floodchannels
braided, meandering and wandering gravel bed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

what is the energy setting, sediment mix, valley setting and landscape position of low energy floodplains

A

<10 W/m2
cohesive sands, silts and clays
wide, alluvial valleys on low slopes
lower valley reaches

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

what is the formation and reworking processes and river types of low energy floodplains

A

vertical accretion
abandoned channel and avulsion
anastomosing, discontinuous watercoarses

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

what are flood channels

A

a channel cut through the floodplain initiated upstream by flows shortcutting the floodplain pocket

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

what are cut offs

A

a shortening of the channel by cutting through the neck of a meander bend

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

what is avulsion

A

occurs when a river is ready to shift channel state. a decrease in channel stability over time may lead to a breach of avulsion threshold.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

what are the 3 process zones in a catchment

A

source, transfer and accumulation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

what does a squashed hydrograph mean

A

long distances between tributaries, not geomorpically significant and dont experience flash floods as often

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

what does a peaked hydrograph mean

A

short distance between tributaries, geomorphically significant and experiences flash floods.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

how to calculate relief ratio

A

maximum relief / basin length

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

why are most rivers show a concave longitudinal profile

A

because they are trying to erode to base level

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

what makes longitudinal profiles irregular

A

geological and long term environmental changes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

what is sediment limited transport

A

when a river doesnt have enough sediment to transport due to higher carrying capacity. these rivers will be erosional and incise (headwaters region)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

what is transport limited transport

A

when a river cant move the sediment. sediment is too large (competence limited). the sediment supply exceeds the capacity of transport (capacity limited)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

what happens along the drainage area of a catchment

A

bedload size decreases, stored alluvium increases and width, depth, flow velocity and discharge increases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

what are the 5 scalar components of a river landscape

A

catchment
landscape unit - valley setting
reaches - gorge river, meandering stream
geomorphic units - benches, cutoffs
hydraulic unit - water characteristics such as turbulent flow

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

formula for total stream power

A

() = yQs
y =specific weight of water
Q = discharge
s = slope

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

what are imposed boundary conditions

A

they do not adjust over geomorphic time, produce the valley setting for a river (confined or unconfined) and contain the base level of the river

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

what are flux boundary conditions

A

dynamic with sediment and flow regimes. (EDIT)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

a river with single channel, <1.5 sinuosity, reflect imposed boundary conditions and laterally stable

A

straight rivers

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

a laterally unstable, with multiple thalwegs, indicative of high and low flow conditions, sinuosity <1.5 and where flow diverges and rejoins multiple times

A

braided river (tasman river)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
41
Q

absent or discontinuous channels, laterally unstable and prone to channel infilling and incision

A

discontinuous coarse rivers (down south near bega)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
42
Q

usually single channel, high sinuosity and laterally variable. contains mixed or suspended load

A

meandering river (colo river)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
43
Q

up to 3 channels, bedload dominated, water flows around islands or vegetated bars

A

wandering gravel bed rivers (rivers in NZ)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
44
Q

a multi channeled, low sinuous river with laterally stable channels that are prone to avulsion. the channels are separated by floodplains

A

anastomosing rivers (outback aus)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
45
Q

what valley setting has discontinuous floodplains

A

partly confined

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
46
Q

what valley setting has isolated or absent floodplains

A

confined

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
47
Q

what valley setting has continuous floodplains

A

laterally unconfined

48
Q

what are features of confined rivers

A

isolated or absent floodplains
found in headwater regions
sinuous <1.5
bedrock dominated
laterally stable
floodplains are prone to stripping

49
Q

what are features of partly confined rivers

A

discontinuous floodplains
sinuousity <1.5 due to channel length = valley setting
found in moderate slopes

50
Q

what are features of laterally unconfined rivers

A

abut valley <10%
continuous floodplains
found in low slopes
suspended load dominated

51
Q

what is a planform controlled river

A

abuts the valley margin 10-50%, highly variable sinuosity with gravel, sand or fine grained material

52
Q

what is a margin controlled river

A

abuts the valley marging 50-90%. sinuousity is low due to valley length = channel length and is bedrock and bedload dominated

53
Q

gravel braided bars indicate?

A

longitudinal bars

54
Q

sand bed braided bars indicate?

A

transverse bars

55
Q

what kind of bars can you find in a wandering gravel river

A

vegetated bars with fine grained sediments

56
Q

what are wandering gravel bed rivers prone to

A

avulsion

57
Q

what is the continuum of rivers through a system

A

plateau - chain of ponds, discontinuous water courses
steep headwaters - gorge, single channel, isolated floodplains
mid slope - partly confined margin controlled river
mid slope - partly confined planform controlled river
mid slope - high energy braided river
low slope - wandering gravel bed river
low slope - anastomosing
low slope - floodout

58
Q

what is the main floodplain process in steep headwater regions

A

vertical accretion

59
Q

what is the main floodplain process in mid slope regions

A

lateral accretion and braid channel accretion

60
Q

what is the main floodplain process in low slope regions

A

vertical accretion

61
Q

what are partly confined rivers prone to

A

channel expansion and contraction

62
Q

what are braided channels prone to

A

thalweg shift

63
Q

what are anastomosing rivers prone to

A

avulsion

64
Q

what are meandering rivers prone to

A

meander lateral shift

65
Q

what are forced units

A

geomorphic units that are created by resistance or obstacles such as large woody debris, vegetation or bedrock

66
Q

what are compound units

A

a range of flow and reworking events that create multiple set of geomorphic units

67
Q

what is the continuum of grain size in high energy high slope to low energy low slope in geomorphic units

A

coarse grained to fine grained

68
Q

what is genetically linked in geomorphic units

A

processes that get reworked and affect another unit such as pools and riffles or scroll bars that build ridge and swales

69
Q

what are the four categories of geomorphic units in order

A

sculpted erosional
mid channel depositional
bank attached depositional
sculpted erosional fine grained

70
Q

what are the sculpted erosional geomorphic units that can be observed in high slope regions

A

waterfalls, step pools, cascades, rapids, runs, rifffles, pools and boulder mounds.

71
Q

what is the form and process of waterfalls

A

stepped bedrock with high turbulent flow.
represents headwater knickpoint retreat and important for dissipating energy

72
Q

what is the form and process of step pools

A

staircase like with bedrock, boulder clasts or woody debris creating areas of turbulent flow and laminar flow.
important in dissipating energy and development influenced by local sediment supply and transport conditions

73
Q

what is the form and process of cascades

A

interlocking bed material, separated by tranquil flow
jet and wake action between larger clasts creates tranquil flow inbetween

74
Q

what is the form and process of rapids

A

ridge like sequence of arranged boulders in irregular transverse ribs.
the boulders are structurally aligned during high energy flood events

75
Q

what is the form and process of runs

A

featureless bed, smooth flow or imposed shallow channel like features that connect pools.
caused due to plane bed creating smooth conveyance of water

76
Q

what is the form and process of forced riffle

A

gravel or boulder accumulation that act as steps due to increased roughness.

77
Q

what is the form and process of forced pool

A

scoured features after a forced riffle caused by LWD
fine grain accumulation during low flow and then scoured during high energy events

78
Q

what is the form and process of plunge pool

A

-pool developed after bedrock step
- corrosion, corrasion and cavitation creates scoured pool

79
Q

what is the form and process of pot hole

A
  • scoured feature in bedrock settings
  • sculpted by corrasion (hydraulic and abrasive action of water)
80
Q

what is the form and process of mid channel riffle

A
  • an organised cluster of bedload that spans the channel and act as sediment storage zones that are tightly packed.
  • deposition imposed by sediment storage during high energy events and low flow events maintain it.
81
Q

what is the form and process of mid channel pool

A
  • tranquil flow at low flow occuring at concave banks in alluvial rivers
  • during high energy events, scouring occurs and sediment stored is stripped.
82
Q

what is the form and process of longitudinal bar

A
  • tear drop shaped bar with coarse grain to fine grain anatomy
  • there is too much sediment for river to transport around the bedload deposit and fine material is trapped in the wake.
83
Q

what is the form and process of transverse bar (linguoid bar)

A
  • abrupt channel expasion, with avalanche face which is ramp shaped. arcuate shaped
  • flow moves through centre of bar, and sediment deposited on lee side. this moves the bar downstream as a rib
84
Q

what is the form and process of diamond bar

A
  • diagonal shaped spanning channel
  • indicates reworking of riffles and oblique flow creates bars
85
Q

what is the form and process of boulder mound

A
  • boulders without matrix
  • forms during high flow events and wake allows smaller clasts to form behind larger boulders
86
Q

what is the form and process of sand sheets

A
  • homogenous sheet of sand draped over entire bed
  • formed when transport capacity is exceeded or competence is decreased. moves downstream as a pulse
87
Q

what is the form and process of forced mid channel bar

A
  • induced by diverging flow around vegetation or LWD.
  • coarse grained to fine grain, and may scour the bed in the secondary flow depending on flow stage
88
Q

what is the form and process of lateral bar

A
  • attached to the bank or bench, found at low sinuous reaches
  • formed by lateral and oblique accretion
89
Q

what is the form and process of scroll bar

A
  • an elongate ridge along the convex bend and develop ridge like shape
  • associated with laterally shifting point bars and formed due to helicoidal flows
90
Q

how does a ridge and swale sequence form

A

lateral shift of point bar that contains scroll bars creates ridge and swale topography as is moves laterally.

91
Q

what is the form and process of point bar

A
  • found in convex bends of meandering systems. fine grained as it progressives downstream.
  • laterally shifting from deposition on convex bank and erosion on concave bank.
92
Q

what is the form and process of tributary confluence bar

A
  • formed immediately at mouth of confluence with poorly sorted gravels
  • generation of secondary flows at high flow events promotes sedimentation
93
Q

what is the form and process of ridges

A
  • found on top of bars in elongate shape. may be formed downstream of vegetation
  • reflects channel adjustment during high flow events
94
Q

what is the form and process of chute channel

A
  • cuts through a bank attached bar
  • scours during over bar flow and reworks if constant
95
Q

what is the form and process of bench

A
  • sediment storage, stepped unit with obliquely accreted mud deposits in suspended systems and sand deposits in bedload systems.
  • formed by oblique and vertical accretion during small to medium flooding events in widened channels. during rising floods, bedload is deposited and during waning stages, suspended load deposits, creating flood couplets
96
Q

what are benches important for

A

channel contraction in over widened channels

97
Q

what is a flood couplet

A

layer of bedload sand or gravel overdraped by suspended load (mud or silt)

98
Q

what is the form and process of ledge

A
  • flat topped, elongate unit and has same materials as floodplain
  • erosional due to channel widening and unpaired ledges reflect lateral shift.
99
Q

what is the form and process of sculpted lateral bar

A
  • forms along low sinuous fine grained reaches
  • formation due to straight reaches beginning to develop sinuous path.
100
Q

what is the form and process of sculpted point bar

A
  • inclined toward channel at low angle
  • sculpted from sediment of adjacent bank and may form from oblique accretion of suspended sediments
101
Q

how are levees formed

A

overbank accretion with vertical accreted coarse grained sediments

102
Q

what way is the helicoidal flow downstream on a right hand bend

A

anti clockwise

103
Q

what happens in the shear zone

A

sediment transport from thalweg to convex bank through helicoidal flow

104
Q

what is distal fining

A

along the floodplain the grain size fines as it moves from proximal to distal floodplain

105
Q

what is upward fining flood couplets

A

scouring during beginning stages of flood, with deposition of coarse grained suspended load during waning stages followed by fine grained suspended load

106
Q

what does counterpoint accretion create

A

concave bank benches making 20% of floodplain in actively moving meandering rivers

107
Q

what is lateral migration

A

related to lateral shift of rivers, as bends get tighter, potential for thalweg to erode is greater.

108
Q

what is engineering time

A

event driven changes due to extreme events such as 1 in 100 year flood events

109
Q

what is geomorphic time

A

process-form over timeframes of individual events to lagged responses over tens, hundreds or thousands of years

110
Q

what is geological time

A

over time frames of millions of years, with tectonic setting exerting primary control on topography and imposed boundary conditions

111
Q

how do confined rivers evolve

A

over time, incision and valley expansion allows room for floodplains to develop and to become partly confined. this alters the imposed boundary conditions.

112
Q

how are partly confined rivers evolved

A

from low sinuousity to meandering streams

113
Q

how do laterally unconfined rivers evolve

A

changes to flux controls, such as reduced energy resulting in braided river into wandering gravel bed or increased sediment in passive meandering into an active one

114
Q

what are direct factors on river evolution

A

riparian vegetation removal, dams, channelisation and gravel extraction

115
Q

what are indirect factors on river evolution

A

catchment deforestation and urbanisation causing increased sediment yields, increased incision, stream power and discharge

116
Q

what is a sediment slug

A

a pulse of sediment through a river causing channel widening as it fills pools and aggrades the bed. homogenises floodplains

117
Q
A

2115 (10 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions