5.12. (9/23) Fluvial System; Basic Channel Hydrology Flashcards

river and channel types

1
Q

where is sediment-moving water gathered?

A

in drainage basins

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2
Q

What is a drainage basin?

A
  • catchment
  • where precipitated water gathers
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3
Q

What do rivers do with the water?

A
  • conduits in catchments to move water into ocean
  • pick up and move sediment
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4
Q

What are headwaters?

A
  • sediment factory
  • creep, debris flows, landslides
  • move sediment to transfer zone
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5
Q

What are transfer zones?

A
  • sediment and water carried by river channels
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6
Q

What are depositional zones?

A
  • deltas, beaches, offshore to shallow marine environment
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7
Q

What are the characteristics of the meandering channel pattern?

A
  • carries fine-grained mud
  • sticky banks
  • stable discharge: same amount of water every day
  • low slope
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8
Q

What are the characteristics of the braided channel pattern?

A
  • coarse (sand and gravel) sediments
  • loose/unstable banks (fall apart all the time)
  • varied discharge: a lot of water one day and not a lot the next
  • steep slope
  • frequent shifting of sediment, vegetation cannot establish
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9
Q

What is discharge?

A

volume of water moving per unit time
*cubic meters per second

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10
Q

What kind of channel is a pool and riffle?

A
  • deep pools
  • shallow riffles
  • step slope
  • rocks transverse to flow (bubbling rapids)
  • coarse-grained (sand and gravel)
  • some mud
  • steep slope
  • headwaters and transfer zones
  • Saucon Creek (many in Pennsylvania)
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11
Q

What is a point bar?

A
  • landform that is made in big meandering loops
  • as the river goes around a meandering loop, it deposits sediment whose shape points out into the channel
  • inclined surfaces violate steno’s laws
  • sediment accumulates laterally/horizontally
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12
Q

What is lateral accretion?

A
  • sequential build-up in a lateral way
  • sediment accumulates in a lateral way and builds out into the channel horizontally
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13
Q

What pushes a channel to build its looping meanders?

A

lateral accretion

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14
Q

What is a levee?

A
  • natural mounds of sediment that form at the edges of meandering channel
  • help confine water
  • part of the point bar system
  • occur there because as the water rises in the channel, as soon as it flows out - speed falls, depth falls, sediment gets dumped
  • sediment accumulates vertically
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15
Q

How do things move in the floodplains?

A

Settling

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16
Q

what does S stand for?

A

slope m/m = degrees

17
Q

What does d50 stand for?

A

average grain size (m)

18
Q

Where can we find gravel and sand?

A

channel/bedload

19
Q

Where can we find silt and clay (mud)?

A

floodplain

20
Q

what is bedload?

A

sediments carried in the bed of the channel

21
Q

What are the two ways gravel and sand are moved?

A

rolling: along the bottom
Saltation
*grains must be sticky enough

22
Q

What is saltation?

A

jumping - hitting each other

23
Q

What process takes place in the floodplain?

24
Q

What is settling?

A

mud and silt get dumped because water gets stagnant allowing for the material to fall out of the water

25
What is suspended load?
silt and clay "float" in the water
26
What does U stand for?
velocity of the flow how fast water is flowing (m/s)
27
What does W stand for?
width of a channel (m)
28
What is baseflow?
where the groundwater intersects the channel
29
What does Q stand for?
discharge of a channel (measured in m^3/s)
30
What does h stand for?
depth of the flow/water (m)
31
What does bankfull mean?
when the water gets to the top of the bank
32
What is a flood?
when water goes outside a bank
33
What key parts do we want to measure in a river channel and its floodplain?
W, S, h, d50, Q, U
34
How do rivers organize the sediment?
they carry heavy stuff in the channel and light things in the floodplain
35
What defines how high water is in channel?
the height of the water is keyed into the height of the groundwater
36
What is baseflow?
where the groundwater intersects the channel
37
What is a flood?
above/outside the bank
38
What are riffles?
parts that look like rapids