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Earthsci 2GG3 > Lecture 5 - Flooding and Landslides > Flashcards

Lecture 5 - Flooding and Landslides Flashcards

1
Q

What is a region that is drained by a single stream?

A

A drainage basin/watershed/river basin/catchment

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2
Q

Gradient of a river?

A

The drop in elevation over distance

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3
Q

Where is the gradient of a river highest/lowest?

A

Greatest in headwaters, lowest at the river mouth

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4
Q

Bed load?

A

The particles of sand and gravel that slide along the bottom of a channel in rapidly moving water

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5
Q

Suspended load?

A

Silt and clay particles carried in the water (90% of total load)

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6
Q

Dissolved load?

A

Ions that are carried in solution in water

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7
Q

Discharge?

A

The volume of water flowing through a cross section of a river per unit time (V*A=Q)

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8
Q

What forms where a river deposits sediment?

A

Alluvial fan (on land) or delta (in water)

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9
Q

Braided channel?

A

A large number of intersecting channels

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10
Q

Anastomosing channels?

A

Two or more channels with stable islands/bars where sediment is stored

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11
Q

Meandering channels?

A

Migrate back and forth across a floodplain

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12
Q

Cutbanks?

A

erosion on the outside of curves due to higher velocity

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13
Q

Point bars?

A

deposition on the inside of curves due to slower movement

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14
Q

Avulsion?

A

riber abandons a looping section of the old channel

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15
Q

When does flooding of a stream begin?

A

When the stream achieves bankfull discharge

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16
Q

Flood Discharge?

A

the level of river surface at a point (stage)

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17
Q

Flood stage?

A

indicates that a river has reached a level likely to cause property damage

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18
Q

Recurrence interval?

A

Avg time between floods

19
Q

Where do flashfloods occur?

A

Upper parts of watersheds and in small tributary basins of large rivers

20
Q

What causes a flash flood?

A

Large quantities of rain in a short time

21
Q

Downstream Flood?

A
  • affect larger areas than flashfloods, more destructive

- produced by storms of long duration, or rapid melting of snowpacks

22
Q

Glacial Lake Outburst Floods (GLOF)

A

Sudden-onset outburst floods that result from the failure of a moraine-dam, ice dam

23
Q

Where are many GLOFs found?

A

SHIT TONS IN PERU

24
Q

Dykes?

A

Thick wall constructed to prevent flooding

25
Q

What are some natural service functions of floods?

A
  • fertile land
  • aquatic ecosystems
  • sediment supply
26
Q

Dynamic equilibrium?

A

River can maintain the gradient and cross-sectionalshape that provides the flow velocity it needs to move sediment load
- Forest –> agriculture increases the amount of sediment delivered, it must flow faster (opp is also true)

27
Q

Levee

A

Naturally forming dyke

28
Q

Flood proofing?

A

Construction methods to protect buldings from floods

29
Q

Canada water conservation act, 1953

A

federal govt can hep people financially

30
Q

Canada water act, 1970

A

planning on all water uses

31
Q

Flood damage reduction program, 1975

A

agreement not to build on an area with flood risk, except for flood proofed structures

32
Q

Quick Clay Landslide at Rissa, Norway, 1978

A
  • farmer wanted a basement, was digging out dirt and making a pile
  • shore line slid into the lake
  • complete liquifaction of the quick clay
  • only one person died
  • waves moved across the lake and caused flooding in another town
33
Q

Fall?

A

bounding of rocks

34
Q

Slide?

A

downslope movement of a block of rock

35
Q

Slump?

A

Failure plant curved upward

36
Q

Flow?

A

All particles move semi-independently of each other, often with water

37
Q

Debris flows?

A

Mix of mud/debris/water

38
Q

Creep?

A

Very slow flow of rock/sediment

  • Sackung large mass of rock
  • Topple rock mass pivots about a point
39
Q

Factor of Safety?

A

The ratio of resisting forces to the driving forces

- stable when greater than 1, unstable when less than 1

40
Q

How does the shape of the slip surface affect the landslide?

A

Rotational slides: slumps are curved

Translational slides: planar

41
Q

How does slope steepness effect the landslide?

A

The steeper the slope, the greater the driving force

42
Q

What type of landslides are arid regions prone to?

A

Rock falls, debris flows, soil slips

43
Q

What type of landslides are humid regions prone to?

A

Landslides, creep, slides, slumps

44
Q

How can landslides be prevented?

A
  • Drainage control
  • Grading: material from the upper slope can be moved to the base
  • Slope supports: retaining walls of concrete/brick

Earthsci 2GG3 (12 decks)

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