Chapter 15

Question 1

Hydrosphere

Answer 1

Water at and near the surface of the Earth.

Question 2

Reservoirs (%)

Answer 2

• Ocean (97.5%) for millennia
• Ice (1.8%) for millennia
• Groundwater (0.63%)
• Lakes and Rivers (0.016%) for months
• Atmosphere (0.001%)

Question 3

Streams

Answer 3

Body of flowing water confined to a channel with a concave longitudinal profile

Question 4

Stream gradient

Answer 4

Slope of a stream, ratio of elevation to distance.

Question 5

Discharge

Answer 5

Volumetric measure of water that flows through a stream or river. The product of cross-section and average velocity.

Question 6

Head/headwater

Answer 6

Where the stream starts

Question 7

Drainage basin/watershed

Answer 7

Region from which water is collected. All flowing surface water converges to a single point, normally the ocean.

Question 8

Mouth

Answer 8

Where a stream empties into another water body

Question 9

Bed

Answer 9

Base of a stream

Question 10

Banks

Answer 10

Confines of a stream during normal flow

Question 11

Floodplain

Answer 11

Region covered during a flood where sediment is deposited

Question 12

Sediment loads in a stream (3)

Answer 12

Dissolved (chemical sediment), suspended (mechanical sediment), bed (saltation, rolling, sliding, mechanical sediment)

Question 13

Erosion in Graded streams

Answer 13

As the gradient decreases, the ability to erode decreases and the rate of sedimentation increases. The size of sediment particles decreases downstream.
Rock that is more resistant to erosion can change profile with a local base level (EX: Waterfalls)
Graded streams reach equilibrium with gradient and velocity varying together.

Question 14

Base level

Answer 14

The lowest level to which a stream can erode. (EX: The ocean or a lake (local)). Changes in sea level cause changes in base level and changes to the longitudinal profile of a stream.

Question 15

Capacity

Answer 15

The maximum load of solid particles that a stream can transport

Question 16

Competence

Answer 16

The maximum particle size that a stream can transport, proportional to velocity squared.

Question 17

Sorting of sediment in a stream

Answer 17

Sediment too big to be transported will be dropped in sequence (boulders, gravel, sand, silt, clay)

Question 18

V-shaped stream valley

Answer 18

A river cuts down and the sides undergo weathering.
Erosion transports material to the river through gravity and rainfall. Steepness of slopes depends on strength of rock.

Question 19

Wide stream valley

Answer 19

The stream gradient decreases as a stream reaches base level and there is less down-cutting and more widening of the valley. Side-to-side migration of channel produces an erosional floodplain.

Question 20

Meandering streams

Answer 20

Deviation of a slow stream from a straight line is enhanced through positive feedback. As meanders are cut through oxbows lakes are left behind as the river cuts itself off.

Question 21

Point Bar

Answer 21

Inside edge of a meandering stream. Sediment deposited makes flow faster and causes erosion.

Question 22

Cut bank

Answer 22

Inside edge of a meandering stream. More erosion makes bends.

Question 23

Braided streams

Answer 23

High energy streams with high sediment load that is deposited and partially blocks channels.

Question 24

Anastomosing streams

Answer 24

Low energy stream with multiple channels separated by stable islands that are often vegetated

Question 25

Alluvial fans

Answer 25

Develop where the gradient of a stream changes abruptly from steep to flat.

Question 26

Delta

Answer 26

Where a stream enters a lake or ocean.

Question 27

Floods

Answer 27

Discharge exceeds the volume of the channel.

Question 28

Flood Stage

Answer 28

The stream stage exceeds bank height

Question 29

Stage

Answer 29

The elevation of water above a point in a river

Question 30

Upstream (flash) floods

Answer 30

Rapid increase in stage in a short period of time that
does not last long. Affects a small localized area.

Question 31

Downstream floods

Answer 31

Stage rises slower from prolonged heavy rain/snow over a broad area and flooding lasts longer.

Question 32

North Saskatchewan flood of 1899

Answer 32

38 ft (14.6 m) above low water level

Question 33

North Saskatchewan River flood of 1915

Answer 33

42 ft (15.8 m) above low water level

Question 34

Urbanization

Answer 34

Urbanization makes flood worse because replacing areas of vegetation with concrete reduces infiltration. Restoring natural areas and leaving floodplains as natural storage areas can mitigate the risk

Question 35

Levees

Answer 35

Natural or man made embankments that prevent the overflow of a river.
By making the levees higher, the flood is made worse downstream.

Question 36

Flood Control Dams

Answer 36

Can control and spread out the crest of a flood. Eventually fill with sediment as a river adjusts to the new base level
Can generate electricity or be used for irrigation and recreation

Question 37

Channelization

Answer 37

Digging a river deeper or digging a new channel moves the problem elsewhere

Question 38

Seasonal large river floods

Answer 38

Flood in spring as snow melts, prolonged warm weather and heavy rainfall. Too large to be influenced by thunderstorms or a single cyclonic system. (EX: Fraser river, Red river)

Question 39

Seasonal medium river floods

Answer 39

Flood in late Spring and in Fall as rain begins or early snow melts.

Question 40

Seasonal small stream floods

Answer 40

Flood at any time of the year with snow melt, thunderstorms etc.

Question 41

Factors affecting flood severity (3)

Answer 41

Heavy precipitation, topography (steep slope increases runoff while step slopes increases groundwater flow), vegetation (slows runoff as roots increase permeability and absorb water)