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Earth Science > (TEST 2) Earth Science, Lecture pt 4 (ch 8) > Flashcards

(TEST 2) Earth Science, Lecture pt 4 (ch 8) Flashcards

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1
Q

Why are stream runoffs considered an important geologic agent?

A
  • Erodes, transports, and deposits ions and sediments
  • Sculpts landscapes
  • Transfers mass from continents to ocean basins
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2
Q

What is overland flow?

A

Precipitation moving downslope over the land surface

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3
Q

What is stream discharge?

A

Volume of water moving through the channel in a given time

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4
Q

What is groundwater baseflow?

A

Groundwater that discharges to the surface

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5
Q

What are some qualities of a gaining stream?

A
  • Water flows all year
  • At or below the water table
  • Humid or temperate climates
  • Sufficient rainfall
  • Lower evaporation
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6
Q

Gaining streams are also known as _____?

A

Permanent streams

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7
Q

What are some qualities of a losing stream?

A
  • Dry up part of the year
  • Above the water table
  • Dry climates
  • Low rainfall
  • High evaporation
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8
Q

Losing streams are also known as ______?

A

Ephemeral streams

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9
Q

Is velocity uniform in a channel?

A

No

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10
Q

What is a hydrograph?

A

Plot of discharge versus time

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11
Q

What is a watershed?

A

An area of land that drains into a stream

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12
Q

What do drainage divides separate?

A

Drainage basins

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13
Q

What is a stream gradient?

A

Change in elevation per distance flowed

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14
Q

What are some physical characteristics near the headwater of a stream?

A

They tend to be steep and straight

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15
Q

What are some physical characteristics near the mouth of a stream?

A

They tend to be flat and curved

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16
Q

Why is erosion is greatest during a flood?

A

Because energy is higher which causes more erosions and more transportations

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17
Q

How do streams erode?

A

Streams break, abrade, and dissolve material
Scouring – water picks up and moves sediment
Breaking and lifting rocks and sediments
Abrasion – the “sandblasting” of rock by particles in fast-moving water
Dissolution – running water can dissolve soluble minerals

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18
Q

What is river erosion?

A

The energy of flowing water is from mass and gravity

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19
Q

How do streams transport sediments?

A

Through sediment load

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20
Q

What is sediment load?

A

Material moved by running water

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21
Q

What are three types of sediment load?

A
  • Dissolved load: ions from chemical weathering
  • Suspended load: fine particles (silt and clay) in the water
  • Bed load: larger particles roll, slide, and bounce along the bottom
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22
Q

Bed load moves by a process called……?

A

Saltation

23
Q

How does decrease in water velocity affect sediment transport?

A
  • Competence reduced, sediment drops out
  • Boulders, then gravels, then sands fill channel bottoms
  • Sands form inside banks (point bars)
    Silts and clays drape floodplains
24
Q

What do meander streams look like from a top-down view?

A

They have winding, looping curves

25
Q

When do meandering streams form?

A
  • The stream gradient is low
  • The substrate is soft and easily eroded
  • The stream exists within a broad floodplain
26
Q

T/F: Meander streams evolve during times of flood

A

True, because the channel is modified during periods of flood

27
Q

How does fast water impact stream bank?

A

It erodes the outside stream bank (or cut bank)

28
Q

How does slower water impact stream bank?

A

It deposits point bars within the curve

29
Q

How are oxbow lakes formed?

A

They are formed from cutoff meanders

30
Q

What are some properties of the base level in meandering streams?

A
  • Lowest level to which a stream can cut downward
  • Sea level is the ultimate base level
  • Lakes, reservoirs, and resistant rock bodies can create temporary base levels
31
Q

What happens as streams approach their base levels?

A
  • Stream gradient decreases
  • Meanders get wider
  • Stream carves out a wider floodplain
  • Oxbows develop during times of flooding
32
Q

How is a delta formed?

A

A delta is formed when a stream enters standing water

33
Q

What happens when a stream enters standing water?

A
  • Stream divides into a fan of distributaries
  • Velocity slows; sediment drops out
34
Q

In flood, the river may break through a levee, which is a process called …..?

A

Avulsion

35
Q

What type of plain forms when distributaries continue to provide sediment?

A

Delta forms

36
Q

When do abandoned delta lobes degrade over time?

A

When sediment supply is reduced/ eliminated

37
Q

How does a reduction of sediment supply causes degradation in abandoned delta lobes?

A
  • Compaction causes subsidence, which causes the delta surface to sink
  • Submarine slumps and storm waves attack the delta front
38
Q

Floods occur when

A

Flow exceeds channel capacity

39
Q

What different conditions are floods triggered by?

A
  • Torrential rains rapidly dumping large volumes of water
  • Long period of continuous rain; ground is saturated
  • Rapid snowmelt across a large drainage basin
  • Failure of dam or levee
40
Q

What are some different types of floods?

A
  • Flash floods
  • Dam failure
  • Downstream floods
41
Q

What are flash floods?

A

Water that rises with little warning

42
Q

How are flash floods caused?

A
  • By intense rainfall or dam failures
  • By rapidly moving wall of debris-laden water
43
Q

What is a dam failure?

A

Catastrophic amounts of water released from impoundment in a very short period of time

44
Q

What are downstream floods?

A

Where a river in the lower part of a drainage basin leaves its channel, flowing out onto its floodplain

45
Q

What are most downstream floods caused by?

A

Most are caused by regional accumulations of water and not just a single storm

46
Q

What structures aim to prevent overflow to floodplains?

A

Levees and flood walls

47
Q

What do artificial levees do?

A

They transmit flood problems downstream and they’re used to protect cities from flooding

48
Q

Why are many parts of the city located below sea level?

A
  • Draining of the back swamps
  • Subsidence
49
Q

What do artificial levees prevent?

A

Sediments from reaching the floodplains

50
Q

What land-use activities increase the hazards associated with flooding?

A
  • Removal of natural vegetation
  • Destruction of wetlands
  • Construction activity
  • Urbanization
51
Q

Why does the removal of natural vegetation contribute to the hazards of flooding?

A

Because it leaves soils exposed and greater overland flow

52
Q

Why does the destruction of wetlands contribute to the hazards of flooding?

A

Because wetlands are used to capture and store large amounts of water

53
Q

What are some ways to reduce flooding?

A
  • Dams
  • Artificial levees
  • Channelization
  • Retention Basins
  • Erosion Controls
  • Wetlands Restoration
  • Floodplain Management
  • Education

Earth Science (7 decks)

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