fluvial processes Flashcards

1
Q

fluvial systems

A
  • distributed network operating from very small to very large scale
  • comprise physical and living
  • transport water and sediments from areas of erosion to deposition
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2
Q

hydrological cycle

A

This is how water moves between reservoirs on the Earth. Without the cycle there would be no oceans, rivers, groundwater or life on earth.

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3
Q

surface water

A

flows occur when soils are saturated or when the rain is so heavy it cannot infiltrate the soil.

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4
Q

explain what hillslope-fluvial couple means?

A

water flows from the hills into the stream

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5
Q

overland flow

A

excess water from rainfall or snowmelt runs across the surface and can deliver large amounts of sediment

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6
Q

Drainage basin

A
  • distributed channel network which eventually converge into a single channel
  • drainage basin is an area from which a river or stream and their tributaries carry all the surface runoff
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7
Q

what separates drainage basins?

A

topographic highs, which are referred to as watersheds or divides

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8
Q

shape of a drainage basin affects its response to the catchment. How would dendritic basins compare to long narrow basins in a rainfall?

A

dendritic basins would respond quickly, long and narrow would be a slower response

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9
Q

whats it called where two 1st order streams meet?

A

2nd order stream

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10
Q

if a 3rd order stream meets a 1st order stream, what results?

A

still 3rd order

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11
Q

4th order stream occurs when?

A

two 3rd order streams meet

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12
Q

what is the main thing that influences stream velocity?

A

river gradient. higher = faster velocity. faster velocity = more erosion

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13
Q

ultimate vs local base level

A
  • ultimate base level is the ocean because rivers flow into the ocean so they cant erode any lower than that.
  • Local or temporary base levels may occur e.g. if there is a lake half way down the mountain the river is flowing down.
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14
Q

how does turbulence affect river velocity? where about is the greatest velocity of the river?

A

decreases it.

highest velocity in the middle of the surface.

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15
Q

greatest turbulence occurs where?

A

bed of the channel

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16
Q

3 types of sediment load in a river

A
  1. dissolved load (from chemical weathering)
  2. suspended load (silt and clay)
  3. bed load (larger sand and gravel)
17
Q

when will you get a braided stream? (one of those capillary bed looking things)

A

braided streams are streams which have too much sediment and deposit sand and gravel bards in their channels

18
Q

what is a meandering stream?

A

single sinuous channel with looping curves known as Meanders.

19
Q

Outer bank of a meander is called? inner bank is called?

How does the erosion compare?

A

outer bank is called cut bank and has the highest velocity, so there is erosion.
inner bank is called the point bar and is the site of deposition.

20
Q

over time what happens to meandering streams?

A

the loops become larger and larger as the cut banks shrink and the point bar grows

21
Q

floodplain

A

broad strip of land built up by sedimentation on either side of the stream/channel. Called a floodplain because in a flood they may become covered in water with suspended clay and silt

22
Q

Delta

A

A delta forms when a running body of water enters another body of water and the running body of water slows and deposits its sediment which builds up a local, prograde shore line as a result

23
Q

alluvial fan (whats a colluvial fan?)

A

large fan-shaped pile of sediment that forms when a streams flows through a gully onto a flat plain and its velocity slows and its sediment is deposited.
Its called a colluvial fan if its formed from debris flow.

24
Q

when will a flood occur?

A

when the streams or rivers receive more water than their channel can handle

25
Q

coastal flood

A

caused by wind-generated waves and storm surges

26
Q

urban flood

A

Urbanisation has removed the infiltration capacity of the soil. Backed-up storm sewers are common causes

27
Q

urban hydrograph

A

building, concrete and asphalt have removed the infiltration capacity of the soil.
Surface runoff increases

28
Q

4 flood mitigation measures

A
  1. Dam -capture and slowly release the extra water
  2. levees - artificially deepen the water
  3. floodways - add extra channels to deal with larger volumes
  4. floodwall - wall protects low lying areas of the town
29
Q

All things being equal the channel with the lowest wetted perimeter will have the _______ water velocity

A

greatest