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Geological Hazards > Geological Hazards Final > Flashcards

Geological Hazards Final Flashcards

1
Q

Why do people choose to live near rivers?

A

Fertile soil

Transportation

Food source (fish)

Trade

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2
Q

What are the dangers of rivers?

A

Susceptible to flash flooding

Fast flowing water

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3
Q

What is the ‘hydrologic cycle’ and how can it be altered?

A

The natural cycle that circulates water throughout the environment to maintain an overall balance between water in the air, on the surface and in the ground.

Human activities that can alter the hydrologic cycle include:

Agriculture

Industry

Alteration of the chemical composition of the atmosphere

Construction of dams

Deforestation and afforestation

Removal of groundwater from wells

Water abstraction from rivers

Urbanization

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4
Q

What affects stream flow?

A

Weather

Snow accumulation and melting

Rainfall and snowmelt

Evaporation

Water use by plants

Vegetation

Subsurface water flows

Water withdrawal for irrigation and municipal water needs

Diversion for hydropower generation

Urbanization

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5
Q

What causes streams to either erode or deposite sediment?

A

Adequate stream flow

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6
Q

How do people mitigate against flooding dangers?

A

Levees

Dams

Channel straighening

Inundation maps

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7
Q

Transpiration (hydrologic cycle)

A

Water inside of plants in transferred from the plant to the atmosphere as water vapor.

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8
Q

Condensation (hydrologic cycle)

A

Vapor to liquid

Forms clouds

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9
Q

Precipitation (hydrologic cycle)

A

Rain or snow

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10
Q

Evaporation (hydrologic cycle)

A

Occurs when the physical state of water is changed froma liquid to a gaseous state.

Water comes from lakes or oceans

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11
Q

Run-off (hydrologic cycle)

A

Rivers or streams

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12
Q

Infiltration (hydrologic cycle)

A

The physical process involving movement of water through the boundary area where the atmosphere interfaces with the soil. The surface phenomenon is governed by soil surface conditions. Water transfer is related to the porosity of the soil ad the permeability of the soil profile. Water that is infiltrated and stored in the soil can also become the water that later becomes subsurface runoff.

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13
Q

Percolation (hydrologic cycle)

A

The movement of water through the soil, and its layers, by gravity and capillary forces.

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14
Q

Stream profile: head, mouth, gradient

A
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15
Q

Discharge

A

The volume of water flowing through a channel in one second.

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16
Q

Drainage area

A

Drainage basin is an extent or an area of land where surface water from rain and melting snow or ice converges to a single point, usually the exit of the basin, where the waters join another waterbody such as a river, lake, reservoir, estuary, wetland, sea, or ocean.

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17
Q

Local base level

A

Where a stream’s gradient temporarily approaches or reaches zero before increasing again.

Can be a lake or reservoir or a layer of rock that is highly resistant to the stream’s erosive force.

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18
Q

Ultimate base level

A

All rivers and streams erode toward sea level, which is also known as the “ultimate base level.”

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19
Q

Capacity

A

The total amount of load that the stream can move.

Controlled largely by discharge.

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20
Q

Competence

A

Measures the largest particles that the stream can transport.

Controlled largely by velocity.

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21
Q

Hydrosphere

A

Water

  • Oceans
  • Lakes
  • Rivers
  • Groundwater
  • Ice
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22
Q

What percentage of the hydrosphere is fresh water?

A

2.8%

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23
Q

Drainage systems

A

Defined by topography

Streams and mass wasting influencing topography

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24
Q

Stream processes (x3)

A

Sediment production

Sediment transport

Sediment deposition

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25
Q

Stream Morphology

A

Tributary (head)

Trunk

  • Anastomosing streams
  • Meandering streams
  • Straight streams
  • Braided streams

Distributary (mouth)

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26
Q

Sinuosity

A

Is a ratio expressing the amount of curvature along a stream.

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27
Q

Straight Streams

A

A single straight channel without sediment bars and with low sinuosity.

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28
Q

Braided Streams

A

Relatively straight channels carrying latge amounts of sediment typically found in mountainous areas.

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29
Q

Anastomosing

A

A river with several separate channels which divide and join along the river.

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30
Q

Meandering River

A

Have many bends which change the shape of the river through time by erosion on one bank and deposition on another.

High sinuosity

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31
Q

Meandering river: cut bank and point bar

A
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32
Q

Floodplain

A

An area of land between or beyond a stream which receives water when the river is at flood stage.

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33
Q

Terraces

A

Abandoned floodplains that formed when a river flowed at a higher level than it does today.

Old floodplains that are cut into by the current stream.

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34
Q

Deltas

A

A discrete shoreline protuberance formed at a point where a river enters an ocean or other body of water.

The distributary portion of a river with no set morphology.

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35
Q

3 Types of Deltas

A

Stream dominated (Yukon River, Nile River)

Tide dominated (Amazon River)

Wave dominated (Rhone River)

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36
Q

Natural Levees

A

Deposition of coarse sediment near the river channel when the river is in flood.

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37
Q

3 Types of Sediment Load

A

Bed load

Suspended load

Dissolved load

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38
Q

Sediment Load: Bed Load

A

Large material that moves along the bottom of a stream channel (rolling and saltation).

Material size: sand, gravel, and boulders

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39
Q

Sediment Load: Dissolved Load

A

Dissolved inorganic and organic material present in the water column.

Salts and organic compounds:

  • Halite
  • Silvite
  • Pesticides
  • Fertilizers
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40
Q

Flood

A

When the discharge of a stream becomes so great that it exceeds the capacity of its channel and overflows.

Too much water in the stream channel.

Events are often described as probability floods.

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41
Q

4 Types of Floods

A

Flash floods

Regional floods

Jokulhlaup

Dam-failure floods

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42
Q

Flood Types: Flash Floods

A

Occur with little warning, produce rapid rise in water level and may have very high discharge.

Common in mountainous, desert, and urban areas.

Localized devastation.

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43
Q

Flood Types: Regional Floods

A

Seasonal floods caused by snow melts and spring rain.

Common in relatively flat aras where rivers join.

Regional devastation

44
Q

Flood Types: Jokulhlaup

A

Glacial outwash flood

Occur with little warning when a volcano erupts under a large mass of ice or water breaches an ice dam.

Relatively uncommon

Regional devastation

45
Q

Flood Types: Dam Failure Floods

A

May occur with little warning process occurs by failure of a dam or levee designed to retain water.

Relatively uncommon

Local devastation

46
Q

Mitigation Methods for Flooding

A

Levees

Dams

Channel straightening

Inundation maps

47
Q

Mitigation Methods: Levees

A

High mound of sediment placed parallel to a channel to prevent flooding.

48
Q

Mitigation Methods: Dams

A

Dam types by use:

  • storage,
  • diversion,
  • detention

Dam types by materials:

  • Earthfall
  • Rockfill
  • Steel
  • Wood
  • Concrete
49
Q

Mitigation Methods: Channel Straightening

A

A process were-by meander bends are removed from a channel in order to increase the discharge.

This leads to increased erosion and increased river gradients.

50
Q

4 Drawbacks to Flooding

A

Loss of property

Loss of infrastructure

Loss of life

Toxic waste in water

  • Sewage
  • Chemicals
  • Other waste
51
Q

Benefits of Flooding

A

Fertile soil

Healthy wetland ecosystem

  • Increased biodiversity
  • Increased water quality
52
Q

Significant Floods (3)

A

California Flood (1861-1862)

ARkStorm Model

Big Thompson Flood 1976

53
Q

California Flood of 1891-1862

A

Started December 24th 1861

Raining lasted 45 days

Creation of inland sea

  • Area flooded
    • 480km (300mi)long
    • 32km (20mi) wide

State government moved to San Francisco and stayed for 18 months

Deaths unknown

Property damage unknown

54
Q

Big Thompson Flood, Colorado 1976

A

Peak discharge 3.8 x higher than 100 year flood.

Low probability flood

~12.5 “ of rain in 4 hours

1/3rd of the drainage basin

15 mph

Crest of the flood ~19’

Exceeded previous record by 10’

139 people died

55
Q

Oxbow lakes

A

A U-shaped body of water formed when a wide meander from the main stem of a river is cut off to create a lake.

56
Q

Energy for geohazards

A

Hurricanes, thunderstorms, tornadoes, etc. driven by the SUN’s energy.

57
Q

Atmosphere

A

Made of gas: Nitrogen, Oxygen, Argon, Carbon Dioxide

Gets thinner

Separated into layers:

  • Exosphere (gas escapes to space)
  • Thermosphere (very small amounts of gas, Aurora)
  • Mesosphere (small amounts of gas, slow meteors down)
  • Stratosphere (ozone created, NO convection)
  • Troposphere (all weather happens here)

Layers are defined by: thermal charactaristics, density, composition, and movement

58
Q

Redistribution of heat: conveciton cells

A

Convection of air in the troposphere

Influences where wet and dry areas are

59
Q

Redistribution of heat: jet stream

A

Found near temperature gradients

Flow west to east

Follow the sun

60
Q

Redistribution of heat: Oceans

A

Surface current driven by wind

Deep ocean currents driven by density

61
Q

Ocean Circulation

A

Antarctica is isolated from mid-latitude from mid-latitude heat transfer (Antarctic Circumpolar Current)

Greenland is not insulated from mid-latitude heat transfer (Gulf Stream/ Norwegian)

62
Q

Temperature

A

Heat is provided by the sun

Changes with altitude (3-5 degrees F/1,000’)

Land heats and cools quickly

Water heats and cools slowly

63
Q

Humidity

A

Measure of how much water vapor the air contains

Warm air holds more water than cool air

64
Q

Relative humidity

A

The relationship between how much moisture is in the air versus how much it is capable of holding.

50% relative humidity = air is half full

>100% relative humidity = rain

65
Q

Dew Point

A

Is the temperature to which the air must be cooled to reach saturation

High dew points indicate very moist air

Low dew points indicate very dry air

66
Q

Temperature and humidity

A

Changes laterally

Control air pressure

67
Q

Air pressure

A

Amount of pressure exerted by the atmosphere

68
Q

High air pressure zones: diverging air

A

As the air spreads away, cool air from above must sink to replace it and warms

Warm air can hold more water vapor, which means that clouds will tend to evaporate

Why fair weather is often associated with high pressure

69
Q

Low air pressure zones: converging winds

A

Air forced to rise and then cool

Cold air holds less water vapor so some condenses, forming clouds and precipitation

Why there is often inclement weather near low pressure areas

70
Q

Wind

A

Wind follows pressure gradient

The steeper the gradient the stronger the wind

Acted on by gravity, Coriolis effect, friction, and centrifugal forces

71
Q

Coriolis Effect as it applies to weather

A

Leads to deflection of moving air masses

72
Q

5 Types of Weather Fronts

A

Cold front

Warm front

Stationary front

Occluded front

Trough

73
Q

Cold Front

A

Dense cold air displaces warm moist air

Can form thunderstorms

74
Q

Warm Front

A

Warm moist air displaces dense cold air

75
Q

Stationary Front

A

A front between warm and cold air mases that is moving very slowly or not at all.

76
Q

Occluded Front

A

A composite of two fronts, formed as a cold front overtakes a warm or quasi-stationary front.

77
Q

Trough

A

An elongated area of relatively low atmospheric pressure

78
Q

Where do storms form?

A

At the boundaries between fronts

79
Q

Clouds

A

High-level clouds (12km-5km)

Mid-level clouds (5km-2km)

Low-level clouds (2km-okm)

80
Q

Warm Problems (x5)

A

Sever thunderstorms

Lightning

Torrential downpours

Tornadoes

Hurricanes

81
Q

Cold Problems (x4)

A

Blizzards

Windchill

Frostbite

Hypothermia

82
Q

Tornado key points (x4)

A

Surface geohazards, related to the sun (ultimately)

Largely a US phenomenon (spring and summer)

Sometimes funnel is not visable

These days, much easier to predict and get to safety (Doppler Radar)

83
Q

Where do tornadoes come from?

A

Form at trailing end of thunderstorms within warm, moist air in front of eastward moving cold fronts

Can also form in front of hot, dry air flowing from the west

And where air is sweeping up mountains

84
Q

Tornado factoids

A

In an average year,

  • ~800 tornadoes
  • ~80 deaths
  • ~1500 injuries

Wind speeds over 250 mph

Can travel up to 219 miles (typically shorter ~50miles)

Damage over 1 mile wide

Average forward speed of 30mph

  • Can be stationary
  • Top speed 70mph
85
Q

Fujuta Scale

A

F-0 (light damage)

F-1 (moderate damage)

F-2 (considerable damage)

F-3 (severe damage)

F-4 (devastating damage)

F-5 (incredible damage)

Not merely based on wind speed

Takes kinto accound damage using set of 28 “damage indicators”

Also looks at “degree of damage”

86
Q

3 Other words for hurricanes

A

Typhoons

Cyclones

“Big wind”

87
Q

What are hurricanes?

A

Is a large, warm-core, low-pressure storm system over tropical or subtropical waters with water temperatures of at least 25 degrees C

  • Counterclockwise in N hemisphere, clockwise in S hemisphere

Wind sppeds of > 120kph, can exceed 260kph

88
Q

How do hurricanes form?

A

Begin over warm seawater (at least 25 degrees C), typically b/t 5-20 degrees latitude

Air rises due to localized heating, causes condensation, and formation of towering convective “chimneys”

Warm, moist air spreads out at top “chimney”

Rising warm air expands, cools, and releases latent heat

Rise of air in eye wall pulls more moist air into center of the storm from low elevations

Coriolis forces initiate rotation in rising air with the highest winds and lowest pressures focusing toward the core of the storm

89
Q

Hurricane rotation

A

The eye of the storm is generally 20-50km in diameter

  • Wind drops from high speeds to low speeds at wind “wall”

Whole storm may be 160 to >800km in diameter

Follows prevailing winds, traveling at ~25kph

90
Q

Features of hurricanes

A

Defined as a hurricane when sustained wind speeds reach 74mph (119kph)

Always move toward the west and spin about the eye

Need high humidity, light wind, and warm sea surface temperatures

91
Q

Hurricane season

A

The Atlantic: begins June 1st and ends November 25th

The Eastern Pacific: begins May 15th and also ends November 30th

92
Q

Where do hurricanes come from?

A

Often begin in warm waters off the west coast of Africa, then move westward across Atlantic with trade winds

Warm, pick up wind speed and energy, and often develop into hurricanes before they reach Americas

Generally track west, northwest, and then north, either off the southeast US or sometimes onto continent

93
Q

Storm classifications (4)

A

Tropical depression

Tropical storm

Hurricane

Major hurricane

94
Q

Tropical depression (storm classification)

A

A tropical cyclone with maximim sustained winds of 38mph (33 knots) or less.

95
Q

Tropical storm (storm classification)

A

A tropical cyclone with maximum sustained winds 39-73mph (34-63 knotts)

96
Q

Hurricane (storm classification)

A

A tropical cyclone with maximum sustained winds of 74mph (64 knotts) or higher

97
Q

Major hurricane (storm classification)

A

A tropical cyclone with maximum sustained winds of 111mph (96 knotts) or higher, corresponding to a Category 3, 4, or 5 on the Saffir-Simpson Hurricane Wind Scale

98
Q

Hurricane factoids

A

80-90 tropical storms each year

45 hurricanes each year

6 named hurricanes per year in Atlantic Ocean and gulf of Mexico

More than 44 million people live in coastal areas in the US susceptible to these storms

  • Gulf Coast and southern Atlantic coasts
  • ~15% of total population
99
Q

1900 Galveston Hurricane

A

September 8th

Category 4 hurricane

Barometric pressure fell to 28.55 in of Hg

Winds estimated at 140mph

Storm surge of 15.7’

Deadliest in US history (estimated minimum death toll of 6,000, likely 8,000-12,000

100
Q

2005 Hurricane Katrina

A

Category 3

Barometric pressure of 902 mb

125 mph sustained wind

Though not the strongest, one of the costliest and deadliest (over $100 billion in damages, 1,836 dead)

Category 3 storm hit New Orleans dead on

Most of the damage due to levee failure following storm surge (more than 50 failures) –> 80% city flooded

Showed failures in US protection

101
Q

Tornado watch

A

Tornadoes are possible in your area. Remain alert for approaching storms.

102
Q

Tornado warning

A

A tornado has been sighted or indicated by weather radar. If a tornado warning is issued for your area and the sky becomes threatening, move to your pre-designated place of safety.

103
Q

What is the Enhansed Fujita Scale used to measure tornadoes? How is the scale created?

A

Rate the strength of the tornadoes in the US and Canada based on the damage they cause.

Implemented in place of the Fujita scale

It was revised to reflect better examinations of tornado damage surveys, so as to align wind speeds more closely with associated storm damage. Better standardizing and elucidating what was previously subjective and ambiguous, it also adds more types of structures and vegetation, expands degrees of damage, and better accounts for variables such as differences in construction quality.

104
Q

3 common myths about tornadoes

A

It is thought by some people that taking shelter under highway overpasses or in the southwest corner of the building provides extra protection from a tornado, but both of these probably increase the danger of injury or death. Some still believe that opening windows ahead of a tornado will reduce the damage from the storm, but this is not true. Some people also believe that escaping in a vehicle is the safest method of avoiding a tornado, but this could increase the danger in some situations.

105
Q

What is the highest wind speed ever recorded in a tornado?

A

318 mph

106
Q

What is the relationship between thunderstorms and tornadoes?

A

Thunderstorms produce tornadoes

107
Q

How long do tornadoes last?

A

Several seconds to more than an hour.

Geological Hazards (3 decks)

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