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Geo Systems Thinking > Module 6 > Flashcards

Module 6 Flashcards

1
Q

Rivers and lakes make up how much of the earth total water supply?

A

<0.01%

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2
Q

True or false. water is distributed evenly throughout the world.

A

False

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3
Q

Floodplains provide which benefits?

A
  • Flow regulation
  • Zones of filtration
  • Habitat for plants and animals
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4
Q

Based on the concept of balance, an increase in water discharge and decrease in sediment discharge lead to ….

A

Erosion

= an increase in the erosive power of the stream or river.

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5
Q

Wolves affect the rivers in Yellowstone National Park by predating on deer who eat the vegetation needed to stabilize banks. true or false.

A

True.
without the wolves, there was an overpopulation of deer which was leading to a degradation of the parks ecosystem due to overgrazing.

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6
Q

True or false. flooding and channel migration are unnatural processes; the only way to manage them is through hard engineering practices.

A

false.

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7
Q

What are some other management practices other than hard engineering?

A

implementing fluvial corridors and eco-engineering decision scaling (EEDS).

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8
Q

What is the current trend in river management that most reflects an ecosystem approach?

A

Leaving more room around rivers for flood water and channel erosion, using an ecosystem approach and adaptive governance.

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9
Q

What are the potential problems with hard-engineering structures such as levees?

A
  • Disconnecting rivers from their floodplain
  • Encouraging floodplain development by providing a false sense of security
  • Increasing flow velocity during floods
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10
Q

Oxbow lakes are created by:

A

Meander dynamics

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11
Q

Floodplains are flooded when the river channel exceeds its bankfull discharge. This happens on average :

A

Between 1.5 and 2 years

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12
Q

true or false? Meandering rivers occur when the sediment is small in size and supply, and slope is gentle. They are considered stable channels.

A

True.

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13
Q

true or false? Clean fresh water is a readily available resource around the world.

A

False.

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14
Q

What human modifications were made on the Mississippi River since the early 20th century:

A
  • Building levees
  • Building dams
  • Straightening the channel by removing meander loops
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15
Q

Stream orders 1 and 2 represent:

A

Small, headwater channels, often with steep slopes and gravel particles on the bed.

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16
Q

What are fluvial systems?

A

systems of rivers, lakes, streams and wetlands through which the fresh water flows on this planet

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17
Q

What is the hydraulic cycle?

A

water flows through the different sheered of the planet (hydrosphere, lists-here, biosphere, and atmosphere).

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18
Q

explain the hydraulic cycle (10)

A
  1. water from the ocean will evaporate.
  2. then condense into clouds.
  3. which can fall as rain over land
  4. where it will flow at different speeds over land and into lakes, streams, or rivers.
  5. which will flow into ocean.
  6. this rain can also be infiltrated into the ground
  7. where It will flow at much slower rate as groundwater
  8. evaporated water can also condense
  9. and fall as snow
    which can accumulate into glaciers in cold climates or high altitudes
  10. and eventually melt and runoff into rivers and lakes like rain
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19
Q

in the hydraulic cycle, water can take on which 3 states?

A
  1. liquid (water found in oceans, rivers and lakes)
  2. solid (ice and snow)
  3. gaseous (water vapour formed by evapotranspiration and sublimation and which falls as precipitation
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20
Q

What are fluvial systems?

A

they have clear boundaries( watersheds) and a hierarchy in rivers and streams.

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21
Q

what happens within a watershed?

A

both water and sediments are transferred from upstream to downstream reaches.

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22
Q

What are the 3 zones that a watershed can be divided into?

A
  1. headwaters (or erosion zone)
  2. transfer zone
  3. depositional zone
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23
Q

what happens in zone 1- headwaters?

A

mountain headwater streams flow swiftly down steep slopes and cup a deep v-shaped valley.
-rapids and waterfalls are common here.

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24
Q

what happens in zone 2- transfer zone?

A

low-elevation streams merge and flow down gentled slopes. the valley broadens and the river begins to meander.

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25
Q

what happens in zone 3- depositional zone?

A

at an even lower elevation a river wanders and meanders slowly across a nearly flat valley.
-then it may divide into many separate channels as it flows across a delta built up of river-borne sediments and into the sea.

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26
Q

what are the 9 systems of a fluvial system?

A
  1. source
  2. tributary
  3. confluence
  4. riparian wetlands
  5. floodplains
  6. meanders
  7. oxbow lake
  8. river
  9. delta
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27
Q

explain system 1 (source) from a fluvial system

A

the source of river water, the hydrologic cycle

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28
Q

explain system 2 (tributary) from a fluvial system

A

break off from main channel (the source)

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29
Q

explain system 3 (confluence) from a fluvial system

A

where tributaries join main channel.

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30
Q

explain system 4 (riparian wetlands) from a fluvial system

A

formed in former meander loop. areas of extreme biodiversity. help filter pollutants such as nutrient and sediment.

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31
Q

explain system 5 (floodplains) from a fluvial system

A

formed by river migration and deposition of fluvial sediment due to recurring flooding of rivers

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32
Q

explain system 6 (meanders) from a fluvial system

A

formed by the erosion of rivers in lowlands

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33
Q

explain system 7 (oxbow lake) from a fluvial system

A

formed when meander loops are cut off because of channel evolution

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34
Q

explain system 8 (river) from a fluvial system

A

carves through the landscape by the erosive power of water

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35
Q

explain system 9 (delta) from a fluvial system

A

where rivers flow into the ocean, forming areas with rich mineral deposit and brackish water.

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36
Q

what are watersheds (drainage basins)

A

areas within which water and sediment flow over land and in channels towards the main branch of the river or ocean.
- therefore the drainage network is comprised of a main river and all its tributaries which join the main channel (confluence)

37
Q

describe strahlers stream order.

A
  • small streams without tributaries are order 1
  • when 2 order 1 streams connect, they form order 2 (bigger stream)
  • when 2 order 2 streams connect, they form order 3 (even bigger stream)
  • and so on until the biggest order, 12 , highest stream order recorded.
38
Q

what are valleys and describe the process in one.

A

usually v-shaped in the upstream parts of watershed (headwater streams) and will become wider and flat downstream with higher stream order rivers.
-this forms a floodplain.

39
Q

the widening of valleys is due to what?

A

the meander dynamics and the process called lateral migration.

40
Q

what are floodplains?

A

areas near rivers which are frequently flooded with fine sediments deposited on valley floor near the channel.

  • through time, the channel reworks the entire valley floor.
  • humans are located on floodplains.
41
Q

describe the process of eroison.

A

each river and stream has a channel which has been carved by the water that flows in the channel.

42
Q

the dimension (width and depth) of the channel and its slope depends on what?

A

on the discharge , on the amount and size of sediments and on the valley slope

43
Q

sediment load is what?

A

the eroded material incorporated into the water.

44
Q

what is overbank flow?

A

flow that exceeds the channel capacity. which cases flooding.

45
Q

what are natural levees?

A

when there Is a flood, the sediment from the water will be deposited in each side of the channel. which makes the floodplain highly fertile.

46
Q

why are fluvial systems important?

A

they are crucial for sustaining life on this planet and benefit humans, animals and plants.

47
Q

what are ecosystem services provided by fluvial systems?

A
  • provisioning services
  • supporting services
  • cultural services
  • regulating services
48
Q

what are examples of provisioning services that rivers provide?

A
  • provide freshwater
  • food like fish, shrimp, mussels, etc
  • banks and floodplains of rivers provide habitat for many animals.
  • rivers can be used as transportation.
49
Q

what are examples of supporting services that rivers provide?

A
  • as humans and animals eat aquatic plants and animals, it allows for nutrient cycling because after ingesting it they will transform the nutrients and then redeposit them when they excrete and eventually die thereby returning the nutrients to the ecosystem.
  • vegetation that grows on banks and floodplains act as water filtration which removes pollution such as agricultural practices and toxic runoff.
  • the flooding of rivers allows for very fertile soil on floodplains.
50
Q

problems with water quality (supporting services)?

A

-water degradation is an issue and non-point source pollution is one of the greatest threats.

51
Q

describe the process of water degradation and non-point source pollution (how this happens).

A

agriculture uses 70% of worlds fresh water. but since crop type diversity is limited and there has been a stop in flooding (hard engineering practices), floodplains aren’t as fertile as they used to be. so people use fertilizers to make the land more productive but these fertilizers are toxic to the water bodies and so lead to water quality problems.

52
Q

what are examples of cultural services that rivers provide?

A

-because of recurrent flooding of rivers, soil is fertile and civilization settle on floodplains of rivers and often had very important cultural roles.

53
Q

what are examples of cultural services that rivers provide?

A
  • floodplains act like regulators that absorb overbank flow to minimize the discharge and therefore the flood.
  • but because of the other services provided by fluvial systems, humans have settles on these floodplains among them endangered to flooding.
54
Q

why are fluvial systems complex?

A

because of the complexities of fluid and sediment dynamics and the complex interconnections with other systems.
-water cycles through the 4 spheres of the planet (hydrosphere, atmosphere, lithosphere, biosphere) and many factors affect the state of water and processes in fluvial systems.

55
Q

example of how fluvial systems are complex?

A

land use type around rivers can affect the water quality and erosive power (agriculture and use of fertilizers). this can affect the way rivers are managed, which will further complicate the fluvial system.

56
Q

what are the 3 things velocity of a stream or river depend on?

A
  1. the slope
  2. the depth
  3. the resistance
    of the channel.
57
Q

how will velocity increase and how will it decrease?

A

increase: the steeper the slope and the deeper the flow, the faster the water will move.
decrease: if we increase resistance with , ex:vegetation, velocity will decrease.

58
Q

what are the 3 types of movements particles can make in the water?

A
  1. can be dissolved
  2. can be suspended
  3. can move along the bed.
59
Q

what are the 2 ways particles can move along the bed?

A
  1. by saltation - a jumping type motion

2. by traction- a sliding or rolling of particles.

60
Q

what are the 3 different types of channels?

A
  1. straight
  2. meandering
  3. braided
61
Q

what are straight channels?

A

occur when sediment is large in size and supply is scarce and slope is steep.
-occurs most often in headwaters of watershed.

62
Q

what are meandering channels?

A

occur when sediment is small in size and supply and slope is gentle.
-occurs in transfer and depositional zones of watershed.

63
Q

what are braided channels?

A

occur when there is medium and fine sediment, and sediment supply is very abundant and slope can be gentle or steep.

64
Q

what is graded fluvial systems?

A

a stable fluvial system. overtime a slope delicately is adjusted to provide the velocity required for transportation of all the load supplied from above.

65
Q

what is a dynamic equilibrium?

A

through time the river will tend towards equilibrium, which is a stable state but since there’s always movement of water and sediment in this stable state, it is called a dynamic equilibrium.

66
Q

what is lanes balance?

A

helpful to understand equilibrium between sediments and water.
-also helps predict the impact of different interventions in rivers: erosion of sediments (degradation) or deposition of sediments (aggradation).

67
Q

explain regime shifts in rivers.

A

natural phenomena like earthquakes or floods can change the course of a river or modify the systems dynamics. however, rivers always tend towards equilibrium and so will adjust their slopes and lengths to accommodate for these changes.

  • more regime shifts occur due to human intervention like dams, levees, and these modify the system by changing the sediment dynamic and supple.
  • rivers will adjust their dimension to accommodate changes in discharge and sediment load and reach new equilibrium.
  • but systems might have more difficulty reaching equilibrium because of these adjustments like take longer and cause of climate change.
68
Q

how is degradation formed in rivers?

A

if sediment load is reduced, which could be due to human interventions (dams), the stream will have too much energy to fight over and will tend to erode its bed.

69
Q

what is aggradation (sediment deposition) in rivers?

A

if sediment is increased, which could be due to deforestation or increased monoculture cropping in the watershed.

70
Q

what happens when rivers or streams are straightened?

A
  • length of channel is decreased
  • then in an increase in slope
  • which results in channel degradation.
  • river will erode its bed which will increase the sediment load of river.
71
Q

what happens when there’s an increase in the rivers curve?

A
  • decrease in slope and stream power

- result in sediment accumulation which is called aggradation.

72
Q

what is trophic cascade ?

A

sometimes changing one small component in an ecosystem can have far reaching effects.

73
Q

example of a trophic cascade?

A

removal of wolves in Yellowstone national park and how it affected the river.

74
Q

what happened when wolves were removed from Yellowstone national park?

A
  • deer population increased

- resulted in little vegetation

75
Q

the reintroduction of wolves contributing how to the park?

A
  • lowered number of deer
  • changed their behaviour
  • lowered number of coyotes which lead to an increase in Prey which increased number of scavengers who fed on Caracases of wolves. (biotic effect)
  • regenerated vegetation, stabilized the banks rivers which reduced erosion and diminished meandering in the rivers thereby changing course of rivers (abiotic effect)
76
Q

what effects did straightening small tributaries rivers have on the Mississippi River?

A
  • contributed to water quality degradation as very little filtration can occur.
  • alters dynamics of the system downstream
  • meander loops were cut off to render the river more navigable resulting in an increase of the velocity of river.
  • also included the removal of secondary channels for river simplification.
77
Q

why were bank stabilization techniques used?

A

to stop meanders from forming in straightened areas and lateral migration of existing meanders in other areas.

78
Q

what effects did bank stabilization have on the system?

A
  • with less material eroded from bank, sediment load decreases
  • this is combined with steeper slopes due to meander removal and the presence of dams which trap sediment.
  • it alters the dynamics of river which have consequences downstream.
79
Q

why were dams and levees constructed?

A

to regulate flow and facilitate navigation
-to protect structures on banks.

-reduces risk of flooding.

80
Q

how to dams alter river hydrology and morphology?

A

hydrology: is altered because of flow regulation. it can impact fish populations by affecting their spawning habitats.

morphology: is altered because dam blocks sediment from passing through dam, creating an accumulation upstream and deficiency downstream from dam.
- it increases erosive power of river in order to compensate for lack of sediment.

81
Q

how can dams and levees make it a more complex system? (intervention complexities)

A
  • lead to lateral and longitudinal disconnects between the river and the floodplains.
  • has dramatic effect on soil fertility which leads to many farms in Mississippi watershed to rely more heavily on fertilizers
  • in absence of wide riparian zones along floodplains, these fertilizers are then unable to be filtered out.
  • this leads to excessive concentration of nutrients like nitrogen and phosphorus In river which can cause eutrophication where it flows into ocean.
82
Q

what is an approach to make fluvial systems more resilient to effects caused by climate change which increase floods?

A

adaptive river management approaches that work with nature such as freedom space for rivers”.

83
Q

how does “freedom space for rivers” work?

A

(fluvial corridors) rivers are given space on floodplains for natural processes of bank erosion and flooding to occur, while ensuring ecosystem services and social well-being.

84
Q

economic viability of fluvial corridors?

A

it would not be economically viable to mode residents off floodplains because it would also be expensive. however, preventing more people to live on floodplains would limit the effects of floods on human settlement and would then reduce the need for hard engineering.

85
Q

which sustainable mgt approach is best needed for countries like Bangladesh and the Philippines and why?

A
  • room for river approach only in areas that are in extreme risk.
  • because those types of countries are at risk and so it would save millions of lives and billions of dollars and can shift the paradigm(way of thinking) from traditional engineering to more sustainable approaches.
86
Q

which adaptive mgt approach (Alternative mgt) is best needed for countries like Bangladesh and the Philippines

A

eco-engineering decision scaling (EEDS)

87
Q

what is eco-engineering decision scaling (EEDS) ?

A

combines engineering practices and ecosystem based decision making to create a more sustainable alternative to hard-engineering practices.

88
Q

what are the steps to determine EEDS? (4)

A
  • Determining the interests and priorities of the local populations and stakeholders, and the potential management options.
  • Developing a systems model for decision making based on management options.
  • Completing a vulnerability analysis.
  • Evaluating the different outcomes, and determining which option best combines the ecological and engineering needs of the system.
89
Q

what is an alternative mgt to countries that cross rivers (upstream and downstream effects). explain why

A
  • adaptive water mgt (cooperation)
  • because populations actions that live in upstream river have major consequences on pops from downstream river and ecosystem health.
  • is crucial for maintaining health of fluvial system.

Geo Systems Thinking (10 decks)

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