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Geos 103 > Topic 8 Rivers and Landscapes > Flashcards

Topic 8 Rivers and Landscapes Flashcards

1
Q

What is Fluvial Erosion?

A

erosion by running water

Kinetic energy of streams works to cut into Earth’s crust and transport roc fragements downslope towards oceans

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2
Q

How are Drainage Basins Defined?

A

Topography determines boundaries of drainage basins.

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3
Q

What are drainage divides?

A

A ridge or highland that separates drainage basins and define their boundaries

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4
Q

What is a stream?

A

a channel in which water flows downhill by the force of gravity

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5
Q

What is a drainage basin (Watershed)?

A

a geographical region drained by a single trunk stream and its tributaries

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6
Q

What is a trunk stream?

A

Single large stream into which smaller tributaries merge

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7
Q

What is a tributary?

A

Stream that joins with others to form larger streams (Trunk streams)

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8
Q

What is the hillslope erosion formula?

A

Erosion= Driving force/Resisting force

Driving force: (specific weight of water)(depth of overland flow)(Slope of the ground surface)

Resisting force: Material strength (cohesion, Particle size)

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9
Q

What are the 3 processes of hillside erosion?

A

Rain splash erosion, Sheet erosion, rill and gully erosion

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10
Q

What is rain splash erosion?

A

Soil erosion caused by direct impact of falling raindrops on slope surfaces

Occurs when there is sparce or no vegetation cover

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11
Q

What is sheet erosion?

A

Erosion as a result of sheet flow

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12
Q

What is sheet flow?

A

overland flow that forms a thin layer of water over a smooth surface

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13
Q

What is Rill Erosion?

A

Erosion process along small channels called rills

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14
Q

What is Gully Erosion?

A

Erosion process similar to rill erosion creating deep v-shaped channels

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15
Q

What is Dendritic drainage?

A

drainage that resembles a tree

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16
Q

What is deranged drainage?

A

Drainage that forms on surfaces that was recently covered by ice sheets.

Erosion by glaciers leave landscape with many lakes and disorganized (deranged) rivers connecting them

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17
Q

What is radial drainage?

A

Drainage formed on the flanks of volcanoes or conical mountains.

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18
Q

What is rectangular drainage?

A

drainage formed where bedrock jointing creates a linear, rectangular pattern with streams flowing in the joints

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19
Q

What is Trellis drainage?

A

drainage that resembles a garden trellis

20
Q

What is centripetal drainage?

A

drainage that occurs in internal drainage basins. (stream flows inward)

21
Q

Explain stream order

A

First-order has no tributaries
second-order has two first-order streams merging
stream order increases only when two streams of same order join

22
Q

What is an intermittent stream?

A

a stream that runs dry during part or most of the year

23
Q

What is an Ephemeral stream?

A

a stream that flows briefly after heavy rainstorms

24
Q

What is a permanent stream?

A

A stream that flows all year

25
Q

What is an exotic Stream?

A

A permanent stream that originates in a humid region and flows through an arid region

26
Q

What is base level?

A

Lowest level to which running water can flow

Temporary base levels can form by creating dams

27
Q

How are streams graded?

A

if sediment transport within the stream equals the rate of sediment input from around the stream

balance between erosion, transport, and deposition of sediments within the stream channel

28
Q

How do you calculate stream Discharge?

A

Q=A x V* = w x D x V* = m^2 x m/s =m^3/s

Q=stream discharge
A=channel cross section
w=channel width
D=average flow depth
V*=average flow velocity

29
Q

When does sediment on a riverbed start to move?

A

When the driving forces exceed the resisting forces

30
Q

What does the competence of a river mean?

A

the maximum particle size that a river can move

31
Q

What does load mean?

A

the amount of sediment transported at a given discharge

32
Q

What are the three stream loads?

A

Dissolved load: soluble minerals that are carried in the water

Suspended load: small particles that remain suspended in flowing water (silt and clay) (muddy appearance)

Bed load: material in stream channel that is too heavy to become suspended in the current (smaller rocks)

33
Q

What are the two channel types?

A

Bedrock (no sediment accumulation)

Alluvial (sediment accumulation)

34
Q

What are the main characteristics of bedrock channels?

A

Steep; high erosion, sediment doesn’t accumulate

35
Q

How do you calculate channel sinuosisty?

A

channel length/valley length

36
Q

name the 5 different types of channels

A

Straight: sinuosity less than 1.3
sinuous channel: sinuosity between 1.3 and 1.5
Meandering: sinuosity greater than 1.5
Braided: unvegetated bars
Anastomosing: vegetated islands

37
Q

Where is the river’s highest velocity in a meander bend?

A

the outside of the river

38
Q

How are oxbow lakes created?

A

A straight river has sediment build up on one side, which erodes the other, This creates cut banks as the sinuosity increases, a cutoff starts to occur, which breaks off the bend and creates an oxbow lake

39
Q

Explain stream sorting

A

Heavy sediment such as gravel and sand settle out first, clay and silt are transported farthest and settle out last

40
Q

Explain longitudinal sorting

A

As you move downstream, bed grain size decreases and becomes more rounded due to abrasion, weathering, and selective transport

41
Q

how does aggradation occur?

A

the buildup of sediment within a stream-bed and along its floodplain.

V-shaped valley can be filled in when the river isn’t able to move the material out fast enough

42
Q

What are the two land forms that form where a river reaches base level?

A

Alluvial fans or deltas form at the mouth of rivers

Alluvial fans: cone shaped, relatively steep alluvial deposits. occurs where stream channel emerges from a steep confined valley

Delta: an accumulation of sediments that forms where a stream reaches base level

43
Q

What happens within the process of subsidence?

A

the lowering of land elevation through the compaction of sediments

44
Q

Explain stream capture

A

the diversion of one stream into another as headword erosion merges the two streams

45
Q

What happens through the process of stream rejuvenation?

A

as the base level of the stream is lowered relative to its drainage basin, the river gains erosional energy. this changes the path of the river

Geos 103 (8 decks)

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