1
Q
What are the steps of the hydrologic cycle?
A
- evaporation
- condensation
- precipitation
- runoff
- infiltration
- percolation
(repeat)
2
Q
Is the water flow of the North Saskatchewan River relatively fast?
A
no
3
Q
stream vs river
A
- stream - body of flowing water confined to a channel, regardless of its size
- river - major branch of a stream system
4
Q
drainage basin
A
region from which stream draws its water supply
5
Q
where are the divides of a drainage basin usually found?
A
usually between countries/provinces
6
Q
stream discharge? units? calculation?
A
- volume of water that passes a given point in a given time through a channel of a certain width and depth; m^3/s
- cross sectional area x velocity of flow
7
Q
laminar flow
A
- straight or gently curved streamlines run PARALLEL to one another (no mixing)
- characteristic of SLOW rivers or along EDGES of FAST rivers
8
Q
turbulent flow
A
- streamlines mix, forming eddies
- characteristic of FAST rivers
9
Q
How do streams do work?
A
transport sediments down hill
10
Q
total sediment load
A
stream’s capacity
11
Q
stream’s competence
A
stream’s ability to carry a material of a given size
12
Q
How is capacity related to discharge?
A
faster the stream flows, the more water is present; the more (and larger) material can be moved
13
Q
How does stream velocity impact sediment sorting?
A
- slow water = fine-grained sediments
- fast water = wide range of grain sizes
14
Q
TRUE or FALSE: sediments are commonly WELL SORTED by size and density
A
TRUE
15
Q
graded stream? are low spots filled in/eroded? high spots?
A
- stream in which various factors combine to yield an average of neither erosion nor sedimentation
- AT EQUILIBRIUM
- low spots filled in
- high spots eroded
16
Q
What is the velocity of a stream largely dependent on?
A
its gradient - steepness of a stream’s channel
17
Q
base level? What happens to gradient as the stream approaches base level?
A
- base level = lowest elevation to which a stream can flow
- gradient DECREASES as it reaches the base level
18
Q
What is one way that the base level of a stream can be changed?
A
human intervention –> BUILD A DAM
19
Q
On what kind of gradients do meandering streams often occur? Are they erosive? if so, what materials do they erode?
A
- occur on gentle gradients
- erode unconsolidated sediments and weak bedrock –> carry FINE sediments
- path may shift significantly with erosion and deposition
20
Q
On what kind of gradients do braided streams often occur? Are they typical of low or high sediment loads?
A
- many diverging and merging channels
- steep gradient
- high sediment load
21
Q
Describe the formation of a braided stream during low discharge period (summer).
A
- high velocity, high sediment streams flow over nearly flat, easily eroded terrain
22
Q
Describe the formation of a braided stream during high discharge period (spring snow melt).
A
- high velocity, high sediment streams does NOT form OXBOW BENDS
- instead, cuts across soft sediments at edges of existing channels, creating braided channels
23
Q
When do braided streams usually form? (high or low discharge period)
A
high discharge period (spring snow melt)
24
Q
Describe the formation of a meandering stream.
A
- current faster at outside banks, which are eroded
- sediment deposited at inside banks, where current is slower –> FORM POINT BARS
25
TRUE or FALSE: building bridges can disrupt stream flow.
TRUE
26
As floodwaters spread out over the floodplain, what happens to the velocity and the capacity of a stream?
decrease velocity and capactiy
27
What are natural levees and how are they formed?
- ridges of coarse material that confine the stream within its banks between floods
- formed by successive floods
28
What is a hydrograph? What does it record? why is it useful? What is on the vertical axis? horizontal axis?
- plot of stream discharge at a point over time
- records fluctuations in discharge or stream height over time
- usefule to monitor stream behaviour REMOTELY
- vertical axis = discharge
- horizontal axis = time
29
TRUE or FALSE: hydrograph does not use a logarithmic scale.
FALSE --> IT IS LOGARITHMIC
30
What are some factors that govern flooding?
- excessive rainfall
- snowmelt off in mountains
- severe storms
- hazardous blockage of stream channel (e.g. trees, avalanches)
31
stage vs crest (flood characteristics)
- stage: elevation of water (flood stage = stream exceeds crest)
- crest: maximum stage is reached
32
upstream flood vs downstream flood vs flash flood
- upstream flood: occurs in small, localized upper part of basin
- downstream flood: occurs in a larger, lower part of basin
- flash flood: type of upstream flood; rapid rise of stream stage (water elevation)
33
describe the peak of an upstream vs downstream flood in a hydrograph.
- upstream flood = sharp peak
- downstream flood = broad peak
34
What is the rate of surface runoff influenced by?
1. ground cover - different rates of infiltration occur with diff soils, rocks, pavement
2. topography - steepness of terrain determines infiltration vs surface runoff
3. presence of vegetation - plants provide physical barrier that decrease water velocity; increase infiltration; absorb water
4. climate - determines level o rainfall and periodicity of storms; frozen soil during spring runoff
35
How can we predict floods?
flood-frequency curve
36
What is on the vertical axis vs horizontal axis of a flood-frequency curve? What is the formula for recurrence interval?
- vertical = discharge
- horizontal = recurrence interval
- R = (N+1)/M
note: R = recurrent interval; N = number of years; M = ranking of annual maxima
37
How do asphalt and concrete affect flood plains?
reduce infiltration
38
How do buildings affect flood plains?
replace water volume; raise stream height
39
How does filling in floodplain land affect flood plains?
reduce volume
40
How do storm drains affect floodplains?
rapid delivery of storm water to streams --> INCREASE IN STREAM HEIGHT
41
how does vegetation loss affect floodplains?
- streams can "silt up"
- silt reduces stream capacity to rapidly carry water away
42
In general, hos does development affect flood stage for a given discharge?
development INCREASES flood stage
43
TRUE or FALSE: building a dam increase flood risk and urban growth decrease flood risk
FALSE:
- dam --> decrease flood risk
- urban growth --> increase flood risk
44
How does climate change affect the hydrological cycle and floods?
warmer climate --> faster hydrological cycle --> more frequent floods
also sea levels rise
45
How does straightening a stream affect flooding?
- speed up flow and reduce local damage --> decrease risk of upstream flood
- increase erosion --> higher flood stages downstream --> increase risk of downstream flood
46
TRUE or FALSE: artificial levees contain high discharge, but cause flooding.
FALSE: high discharge without flooding
47
Which dam caused earthquakes by their added weight on the rocks?
Hoover Dam
48
What is the issue with flood control dams?
- as velocity rapidly decreases at dam site, waters deposit their load --> increase stage --> lead to failure of dam
- sediment free water released by dams --> erosion downstream
49
which company was fined $1 million for polluting incidents that impacted fish in Alberta?
Sherritt
50
which river tailings spill caused downstream communities to not draw water in Alberta?
Athabasca River
51
What was the world's most catastrophic floods caused by?
breaching of ice dams of the retreating continental ice sheets
52
Describe the Channeled Scablands. Which 3 rivers encircle the Scablands? How did it form? Which ice sheet? What is the floor made of?
- erosional features result of giant flood during Great Ice Age
- basalt floor
- Columbia River, Spokane River, Snake River
- formation: CORDILLERAN ICE SHEET formed an ice dam, creating Glacial Lake Missoula --> ice dam breach caused 40 catastrophic floods --> Channeled Scablands
53
Describe thermohaline circulation.
1. warm water from tropics goes to poles
2. water at poles cool from ice and SINK --> deep water formation
3. water goes back to tropics
54
What drives thermohaline circulation?
deep water currents
EAS 205
flashcards
Decks in class (16)
# Cards
-
Intro20
-
Plate Tectonics and Continental Drift38
-
Earthquakes62
-
Induced Earthquakes7
-
Great Oxidation Event36
-
Snowball Earth32
-
Volcanoes 1 and 251
-
Volcanoes 3 and 454
-
Extinctions58
-
Landslides51
-
Flooding54
-
Messinian Event30
-
Flooding the Black Sea9
-
Hurricanes and Coastlines29
-
Asteroids28
-
Impacts17
