EV1005 - L7-8 Streams and Floods

Question 1

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

Answer 1

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

Question 2

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

Answer 2

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

Question 3

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

Answer 3

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

Question 4

What are the water reservoirs? (6)

Answer 4

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

Question 5

True or False

Residency times vary greatly in different reservoirs.

Answer 5

True

Residency time can vary from days to millions of years

Question 6

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

Answer 6

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

Question 7

Define Transpiration

Answer 7

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.

Question 8

Define condensation

Answer 8

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.

Question 9

Define precipitation

Answer 9

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

Question 10

Define runoff

Answer 10

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.

Question 11

Define infiltration

Answer 11

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

Question 12

Define Melting

Answer 12

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

Question 13

Define groundwater flow

Answer 13

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.

Question 14

What areas exhibit the most about of runoff?

A) Polar
B) Temperate areas
C) Tropical areas

Answer 14

C)

Tropical areas generally have the highest amount of runoff.

Question 15

Order these names for the collection of runoff

Rill
Tributary
Sheetwash
Trunk Stream

Answer 15

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

Question 16

What is a perennial stream?

Answer 16

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

Question 17

What is an ephemeral stream?

Answer 17

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

Question 18

Define wetted perimeter

Answer 18

The perimetre of the ground the water is touching

Question 19

Define thalweg

Answer 19

The deepest part of a water channel

Question 20

Which has a rougher base? Upstream or downstream channels?

Answer 20

Upstream channels are usually rougher and have more turbulence.

Question 21

Why are clays harder to erode? (2)

Answer 21

They have ionic bonds holding them together

they are platy materials and form smooth surfaces with little friction

Question 22

What size particle is the easiest to move?

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

Answer 22

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.

Question 23

Define Saltation

Answer 23

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

Question 24

How does velocity assist in moving boulders underwater?

Answer 24

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

Question 25

Explain the capacity of a stream

Answer 25

The maximum load of sediment a stream can carry

Question 26

Explain the competence of a stream

Answer 26

The largest particle that a stream can transport

Question 27

True or False Erosion happens when Capacity < Load.

Answer 27

False Erosion happens wen Capacity is greater than load

Question 28

True or False Deposition happens when Capacity < Load

Answer 28

True When the load is greater than the capacity, deposition occurs

Question 29

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

Answer 29

A) Low capacity and low competence

Question 30

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

Answer 30

B) High capacity and low competence

Question 31

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

Answer 31

C) Low capacity and high competence

Question 32

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

Answer 32

D) High capacity and high competence

Question 33

True or False Discharge increases as you go downstream

Answer 33

True Discharge increases as you go down stream

Question 34

True or False Channel smoothness decreases as you go downstream

Answer 34

False Smotheness increases as sediments are diposited

Question 35

True or False The gradient/slope increases as you go downstream

Answer 35

False The gradient decreases and becomes flatter as you go downstream

Question 36

True or False More resistant bedrock along water ways is associated with steep valleys

Answer 36

True

Question 37

What are alluvial fans? | How are they created?

Answer 37

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'

Question 38

What are braided streams? | How are the formed?

Answer 38

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)

Question 39

What is alluvium?

Answer 39

River deposits

Question 40

What is an oxbow lake?

Answer 40

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)

Question 41

What are point bars?

Answer 41

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

Question 42

The Nile delta is is A) Wave dominated B) River dominated C) Tide dominated

Answer 42

A) Wwave dominated

Question 43

The Mississippi River delta is A) Wave dominated B) River dominated C) Tide dominated

Answer 43

B) River dominated

Question 44

The Ganges River delta is A) Wave dominated B) River dominated C) Tide dominated

Answer 44

C) Tide dominated

Question 45

The Barron River delta is A) Wave dominated B) River dominated C) Tide dominated

Answer 45

A) Wave dominated

Question 46

Why do flash floods occur in urban areas?

Answer 46

Because of low infiltration and high runoff levels

Question 47

True or False? Riverine floods happen suddenly and with little notice

Answer 47

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

Question 48

Which flood results in the highest amounts of deposition? A) Flash floods B) Riverine floods

Answer 48

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

Question 49

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

Answer 49

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

Question 50

What is a problem with man made levees?

Answer 50

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