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Terrain and Stream assesment > Midterm 2. > Flashcards

Midterm 2. Flashcards

1
Q

Why are terrain maps important?

A

Terrain and stream stability are a key focus of the mapping. understand which areas are prone to flooding, mass land movements.

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2
Q

What is a Terrain map?

A

Descriptive data on the physical characteristics of the land surface.

  • topography
  • aspect
  • landforms
  • material properties
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3
Q

1st step in watershed terrain analysis

A

Determine what info is available.
Terrain maps, forest cover maps w/Sensitive areas
-Slope stability, geology maps, air photos

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4
Q

What are some general info aspects of Watershed assessment?

A
  • Landforms and slope
  • surficial materials
  • geological processes
  • BEdrock
  • Hydrological characteristics
  • Vegetation
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5
Q

Where can you find map info?

A

Terrain Info BCMoE
Federal Gov
BC Gov Sales Offices

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6
Q

What are possible problems with maps? Air photos

A

Inappropriate scale (Inability to differentiate small units)

  • Area of delineated polygon not field checked
  • Level of map usefulness- who mapped it.
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7
Q

Describe Basal till

A
  • Rock fragments of various sizes and shapes in a matrix of predominantly silt clay
  • Non-Stratified
  • high compaction. variable minerology/texture
  • depends of source materials moved by ice
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8
Q

Describe Ablation materials?

A 
Later stages of glaciation (melting)
non compact-coarse, sandy textures.
 relatively pervious materials
-fine materials are washed away
-hummocky landform
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9
Q

Fluvial sediments

A 
Active braided channels
flood plain
fluvial fans
non sorted-non bedded
rapid aggradation
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10
Q

Glacial Fluvial deposits

A

Eskers, Kames terraces, outwash points, wide range of particle size,

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11
Q

Deltaic Deposits

A

Gravels and sand deposits

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12
Q

Lacustrine

A

Fine sediments settled from suspension in standing fresh water (lake)
-well sorted and stratified materials along beaches
varves- shows seasonal layers when in sediment horizon

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13
Q

littoral sediments

A

transported and deposited by wave action

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14
Q

varves

A

Seasonal layers when you cut into the lake sediment horizon

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15
Q

Glaciolacustrine materials

A

Deposited in or along the margins of glacial (ice dammed lakes) layers of silt and fine sand. kamloops

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16
Q

Marine Deposits

A

Marine mud mixtures
sediments deposited in salt or brackish water; clay silts and sands to well sorted and stratified modern beach
Large valleys at elevations of up to 250m (Kitimat valley, south coast fraser valley)
-shells

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17
Q

Glacial Marine

A

mud, silt, clay, shells

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18
Q

Colluvium

A

Materials that have reached thier present position as a result of direct gravity-induced movement

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19
Q

What are the 3 groups of colluvium?

A
  1. (rock slide) Talus slopes, colluvial mantles, rockslides, snow avalanche deposits ( loose angular rock fragments , non-cohesive , well drained)
  2. Debris flow and mudflow deposits (interlayer debris flow deposits-fluvial deposists
  3. earthflow and slumps, texture depends on source material (weathered bedrock, till) high clay content.
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20
Q

What materials make up colluvium

A

Range of size in poor-well stratified
boulders to rocks, pebbles to clay/
like a rock avalanche

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21
Q

Eolian deposits

A

Material transported and deposited by wind

  • revegetated sand dune
  • medium fine sand
  • coarse silt that is well sorted
  • non compacted
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22
Q

rock and bedrock

A

Soft volcanic rock weathered to clay

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23
Q

what are the two types of weathering

A

Chemical and physical

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24
Q

Volcanic Sediments

A

Ash, cinder lapilli volcanic bombs, tephra (flying magma turned to solid) basalt lava flow

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25
Q

Organic sediments

A

Organice material resulting from the accumulation of vegetative matter; thick level peat bog
-swampy areas

26
Q

Define surficial materials

A

Non-litified unconsolidated sediments

27
Q

how are surficial materials produced?

A

Weathering, sediment deposition, biological accumulation, volcanic activity and human activity

28
Q

How are surficial materials classified?

A

Mode of origin: eroded and deposited by glacial ice; post glacial erosion by wind water and landslides; or accumulation of biological origin

29
Q

What are Schematic Cross sections?

A

rough depictions of where between two points would we find different surficial materials and how large those sedposits may be

30
Q

Alluvial Fans

A

Occur when confined channel enters a broad valley

-sediment deposition causes the channel to swing back n forth, developing a fan like shape`

31
Q

Types of Alluvial fans?

A
  • flood fans (low gradient channels)

- debris flow fans (steep with landslide deposits

32
Q

What is FCN?

A

Natural Fan Channel Networks

33
Q

What are 2 measures of FCN?

A 
Channel extent (% of the fan surface covered by active channel)
-Channel network complexity (# of channel nodes, where channels fork/join
34
Q

Gullies

A

Steep, incised headwater channels

-sediment and woody debris onto lower valley slopes or into valley bottom streams

35
Q

GAP intends to..

A

Identify the main factors affecting forest management in and around gullies

36
Q

GAP provides..

A

a framework for managin gully systems before and after harvest

37
Q

what are the 3 parts of GAP?

A
  • Collection of field and air photo/map data
  • Assess hazards and resources at risk
  • Selection of management strategies and goals
38
Q

Why gully assessment?

A

major part of riparian/stream network
high frequency of landslides, operationally difficult
hazardous for forestry work, public, water quality, fisheries

39
Q

gully system hazards:

A

debris slides and flows
Water floods
fan destabilization

40
Q

What does gully hazard level depend on?

A 
climate and gully systems
-size of catchment area
# of triburary channels
- slope angels on head wall and side wall
-type of materials
-channel and fan gradient
-other woody debris and sediments
41
Q

What are the components of GAP?

A

reach by reach assessment

reach by reach management strategies

42
Q

What are the 7 GAP form components?

A
  1. Gully system Id
  2. Downstream Impact Potential
  3. Upslope debris flow potential
  4. Water transport potential
  5. Fan destabilization potential
  6. Debris flow initiation potential
  7. Post-logging conditions
43
Q

What is downstream impact potential

A

Assessing the potential downstream impacts of all reaches in the gully. sidewalls and channell materials/ debris etc.

44
Q

What is Upsole debris flow potential

A

Used of fans, transport zone and headwalls

45
Q

What is water transport potential?

A

Used for fans, transport zones and headwalls

46
Q

What is fan destabilization potential?

A

The potential for the stream channels on a fan to be destabilized, to widen or erode or avulse (breakout)

47
Q

What is debris flow initiation potential?

A

Headwall failure potential
Sidewall failure potential
Gully geometry potential for debris flow hazard
debris flow initiation hazard

48
Q

What are post logging conditions?

A

Evaluates the effect of harvesting on logging debris and sediment in the channel
rehab assessments

49
Q

What are some management goals of GAP?

A

maintain gully wall and channel stability

maintain natural rates of erosion and recruitment and transport of sediment and woody debris

50
Q

What is gully restoration?

A
  • reduce volume of logging debris and sediment in gully. must be done immediately after harvest or the debris and sediment become part of the channel structure
  • stabilize gully walls with vegetation
  • protect sidewalls from stream erosion
  • Road deactivation
51
Q

What are some strategies of road deactivation?

A
  • remove bridges, culverts
  • construct fjords
  • pull back fill slopes, stabilize road cuts
  • re-establihs channel geometry+ hydrology
  • armour channel beds
  • clear woody debris immediately upstream and downstream of crossings
52
Q

Terrain analysis

A

Description of the form and character of the land surface and the materials that underlie it
-past and present geological processes that modify the landscape

53
Q

3 Rapid mass movement processes

A
  1. Debris slides
  2. Avalanches
  3. flows
54
Q

Classification of landslide events is by the following:

A

-Failure mechanism
-depth of failure
-rate of failure
-water content
-material type
(rock, debris , earth, mud)

55
Q

Landslide types:

A

Bedrock failures:

  1. Topple (slump)
  2. fall (material free falls)
  3. saskungen- sagging hillslope, bedrock slide
  4. creep
  5. slump
56
Q

Pavilion earth flow

A

Old and very slow moving
-annual snowmelt recharges the groudn water to keep the slide moving

hummocky nature of the earthflow deposit

57
Q

Debris flow

A 
Material movement down channels as slurries of sediment, water and debris
#1 worldwide-money+lives
58
Q

Piping

A

Subsurface water erosion

-occurs in loose, non-cohesive materials overlying a stronger more cohesive material

59
Q

Ravel

A

Dry process where the slope adjusts to its angle of repose.

60
Q

Snow avalanches

A

Failure of large amount of snow on steep mountain. can often occur in the same paths as other failures

61
Q

Landslide

A

Any mass of earth material (soil or rock) displaced by gravity

62
Q

Criteria to delineate TSM classes

A
  • slope gradient
  • surficial material
  • material texture
  • slope morphology
  • drainage
  • geomorphic processes.

Terrain and Stream assesment (8 decks)

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