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EV1005 Environmental Porcessas and Global Change > EV1005 - L7-8 Streams and Floods > Flashcards

EV1005 - L7-8 Streams and Floods Flashcards

1
Q

How many times more water falls on the oceans than it does on the land?

A

4x more water falls in the ocean than on the land

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2
Q

The water cycles consists of inputs (1), migration (2) and outputs (3). What are these?

A

Inputs - precipitation (rain, snow, hail, etc)
Migration - run-off off the land and from rivers, infiltration into ground water
Outputs - transpiration, evaporation and discharge of ground water to ocean or surface

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3
Q

how much water that evaporates over oceans returns to the ocean? (%)

A

90% of the water that evaporates from the ocean returns to the ocean. 10% falls over the land

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4
Q

What are the water reservoirs? (6)

A 
Atmosphere
Oceans
bodies of water on land (lakes, rivers etc)
Glaciers
Snowfields
Groundwater
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5
Q

True or False

Residency times vary greatly in different reservoirs.

A

True

Residency time can vary from days to millions of years

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6
Q

Order these reservoirs in order of shortest to longest residency time

Lakes
Soil moisture
Rivers
Glaciers
Oceans
Seasonal snow cover
Atmosphere
Groundwater - Shallow
Groundwater - Deep
A 
Atmosphere - 9 Days
Soil moisture - 0.2 years
Seasonal snow cover -0.4 years
Rivers - 0.4 years
Glaciers - 40 years
Lakes - 100 years
Groundwater (Shallow) - 200 years
Oceans - 3,200 years
Groundwater (Deep) - 10,000 years
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7
Q

Define Transpiration

A

Process by which water that is absorbed by plants, usually through the roots, is evaporated into the atmosphere from the plant surface, such as leaf pores. One of the ways water travels between reservoirs.

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8
Q

Define condensation

A

Condensation is the process of water vapor returning to its liquid state as temperatures cool. Clouds form when water condenses in the atmosphere. One of the ways water travels between reservoirs.

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9
Q

Define precipitation

A

Rain, snow, sleet, or hail that falls to the ground (or ocean). One of the ways water travels between reservoirs.

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10
Q

Define runoff

A

The draining away of water (or substances carried in it) from the surface of an area of land, a building or structure, etc. One of the ways water travels between reservoirs.

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11
Q

Define infiltration

A

Infiltration is the process by which water on the ground surface enters the soil. One of the ways water travels between reservoirs.

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12
Q

Define Melting

A

The runoff produced by melting snow or ice. One of the ways water travels between reservoirs.

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13
Q

Define groundwater flow

A

The movement of groundwater between infiltration and discharge into streams, lakes or oceans (or man-made pumps). One of the ways water travels between reservoirs.

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14
Q

What areas exhibit the most about of runoff?

A) Polar
B) Temperate areas
C) Tropical areas

A

C)

Tropical areas generally have the highest amount of runoff.

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15
Q

Order these names for the collection of runoff

Rill
Tributary
Sheetwash
Trunk Stream

A

Sheetwash becomes rills which flow into tributaries. tributaries are connected to the main trunk stream; the body of water that flows directly to the ocean.

Sheetwash - Rill - Tributary - Trunk Stream

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16
Q

What is a perennial stream?

A

Streams that run all year long because the water table is always intecepted

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17
Q

What is an ephemeral stream?

A

A stream that dies up for periods during the year. water collected in channel is lost to underground flow and the stream only flows when the ground level intercepts the water table

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18
Q

Define wetted perimeter

A

The perimetre of the ground the water is touching

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19
Q

Define thalweg

A

The deepest part of a water channel

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20
Q

Which has a rougher base? Upstream or downstream channels?

A

Upstream channels are usually rougher and have more turbulence.

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21
Q

Why are clays harder to erode? (2)

A

They have ionic bonds holding them together

they are platy materials and form smooth surfaces with little friction

22
Q

What size particle is the easiest to move?

A) Clay
B) Silt
C) Sand
D) Gravel

A

C) Sand

Sand moves in normal river flow. Clay and silt don’t have a large enough surface area and clays also form ionic bonds that hold them together. Gravels are often too heavy to be transported easily.

23
Q

Define Saltation

A

Intermittent ‘jumping” of grains that are lifted by turbulence into a flow of water

24
Q

How does velocity assist in moving boulders underwater?

A

Velocity of water passing over a boulder is greater than that passing under the boulder (because the boulder is sitting on the bottom of the stream and further away from the thalweg) therefore boulders roll downstream

25
Q

Explain the capacity of a stream

A

The maximum load of sediment a stream can carry

26
Q

Explain the competence of a stream

A

The largest particle that a stream can transport

27
Q

True or False

Erosion happens when Capacity < Load.

A

False

Erosion happens wen Capacity is greater than load

28
Q

True or False

Deposition happens when Capacity < Load

A

True

When the load is greater than the capacity, deposition occurs

29
Q

Marshlands have

A) Low capacity and low competence
B) High capacity and low competence
C) Low capacity and high competence
D) High capacity and high competence

A

A) Low capacity and low competence

30
Q

Trunk streams have

A) Low capacity and low competence
B) High capacity and low competence
C) Low capacity and high competence
D) High capacity and high competence

A

B) High capacity and low competence

31
Q

Highland streams have

A) Low capacity and low competence
B) High capacity and low competence
C) Low capacity and high competence
D) High capacity and high competence

A

C) Low capacity and high competence

32
Q

Flooded rivers have

A) Low capacity and low competence
B) High capacity and low competence
C) Low capacity and high competence
D) High capacity and high competence

A

D) High capacity and high competence

33
Q

True or False

Discharge increases as you go downstream

A

True

Discharge increases as you go down stream

34
Q

True or False

Channel smoothness decreases as you go downstream

A

False

Smotheness increases as sediments are diposited

35
Q

True or False

The gradient/slope increases as you go downstream

A

False

The gradient decreases and becomes flatter as you go downstream

36
Q

True or False

More resistant bedrock along water ways is associated with steep valleys

A

True

37
Q

What are alluvial fans?

How are they created?

A

Where water leaves a mountain valley and enters a relatively flat plain. the decrease in velocity lowers the streams capacity and competence. deposition causes sediments to settle creating large ‘fans’

38
Q

What are braided streams?

How are the formed?

A

Consist of interlacing channels of water formed after rapid fluctuations in velocity. When velocity drops large amounts of sediment are deposited. Water still flowing through the area erodes small streams through the sediment. (often caused by glacial outwash)

39
Q

What is alluvium?

A

River deposits

40
Q

What is an oxbow lake?

A

When the meanders of a stream are exaggerated to the extent that it doubles back on itself and cuts through. Sediment is deposited along the edges and a lake is created separate to the stream. (eg Australian Billabongs)

41
Q

What are point bars?

A

Where the stream deposits sediments/alluvium. Occur only on the inside bends of meandering streams

42
Q

The Nile delta is is

A) Wave dominated
B) River dominated
C) Tide dominated

A

A) Wwave dominated

43
Q

The Mississippi River delta is

A) Wave dominated
B) River dominated
C) Tide dominated

A

B) River dominated

44
Q

The Ganges River delta is

A) Wave dominated
B) River dominated
C) Tide dominated

A

C) Tide dominated

45
Q

The Barron River delta is

A) Wave dominated
B) River dominated
C) Tide dominated

A

A) Wave dominated

46
Q

Why do flash floods occur in urban areas?

A

Because of low infiltration and high runoff levels

47
Q

True or False?

Riverine floods happen suddenly and with little notice

A

False

They come with many hours, days or weeks notice and last for extended periods of time.

48
Q

Which flood results in the highest amounts of deposition?

A) Flash floods
B) Riverine floods

A

B) Riverine floods

These floods spill over onto the floodplains and therefore velocity and capacity drop

49
Q

Why are flood plains popular places for housing or farming land? (2)

A

1) In flood, sediments and nutrients are deposited on flood plains making the soil fertile for crops
2) the land is flat and good for farming machinery and easy to build houses on

50
Q

What is a problem with man made levees?

A

They may only offer protection for a limited region and cause greater flooding in other areas

EV1005 Environmental Porcessas and Global Change (8 decks)

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