Ch. 15 - River Systems

Question 1

Where is the head/mouth of the Fraser River?

Answer 1

Head: Mt. Robson (high elevation)

Mouth: Delta/Richmond (sea-level)

Question 2

What is a Tributary?

Answer 2

A river or stream flowing into a larger river or lake

Question 3

What is a Distributary?

Answer 3

A branch of a river that does not return to the main stream after leaving it (as in a delta)

Question 4

What happens at the “Base Level” of a river?

Answer 4

The river joins itself to a much bigger body

Question 5

What three processes account for the “work” of a river?

Answer 5

Erosion

Transportation

Deposition

Question 6

What is meant by the term “Ultimate Base Level”?

Answer 6

When a river reaches sea-level, it can’t get any lower.

The final place where water from a river can end up

Question 7

What is a Drainage Basin?

Answer 7

The basic spatial geomorphic unit of a river system; distinguished from a neighbouring basin by ridges and highlands that form divides, marking the limits of the catchment area of the drainage basin

Question 8

What are the three main watersheds for greater Vancouver?

Answer 8

Capilano

Coquitlam

Seymour

Question 9

What is the largest Drainage Basin in Canada?

Answer 9

Hudson Bay

Question 10

What is the largest Drainage Basin in the US?

Answer 10

Mississippi River

Question 11

What do Dendritic river patterns look like?

Answer 11

Looks like a tree, with branches growing in all directions off of a larger branch

Most common pattern in the world

Question 12

What do Trellis River patterns look like?

Answer 12

A drainage pattern characterized by parallel main streams intersected at, or nearly at, right angles by their tributaries

Question 13

What do Radial river patterns look like?

Answer 13

Common form that is found on a volcano/mountain, with rivers moving in all different directions down the slope. Creates a radial pattern

Question 14

What do Parallel river patterns look like?

Answer 14

Caused by steep slopes with some relief. Because of the steep slopes, the streams are swift and straight, with very few tributaries, and all flow in the same direction

Question 15

What do Rectangular river patterns look like?

Answer 15

Rectangular drainage patterns have rivers with right-angle bends. Commonly found on landscapes with fractures. Water flows through the fractures and joints of the land

Question 16

What does an Annular river pattern look like?

Answer 16

A drainage pattern in which streams follow a roughly circular or concentric path along a belt of weak rock, resembling in plan a ringlike pattern

Generally structured by dome shapes

Question 17

What is a Deranged river pattern?

Answer 17

There is no obvious pattern of flow. Often found in areas where the old pattern was completely destroyed

Question 18

How is stream discharge (Q) measured?

Answer 18

Q = Width (m) x Depth (m) x Velocity (m/s)

Question 19

What are the three types of Fluvial Erosion?

Answer 19

Hydraulic Action

Abrasion

Dissolution

Question 20

What is Hydraulic Action?

Answer 20

The erosive work accomplished by the turbulence of water; causes a squeezing and releasing action in joints in bedrock; capable of prying and lifting rocks

Question 21

What is Abrasion?

Answer 21

Mechanical wearing and erosion of bedrock accomplished by the rolling and grinding of particles and rocks carried in a stream, removed by wind in a “sandblasting” action, or imbedded in glacial ice

Question 22

What is Dissolution?

Answer 22

Dissolving minerals through chemical processes

Question 23

What are the four types of Fluvial Transportation?

Answer 23

Traction

Saltation

Suspension

Solution

Question 24

How does Traction work?

Answer 24

A type of sediment transport that drags coarser materials along the bed of a stream

Large, heavy pebbles are rolled along the river bed. This is most common near the source of a river, as here the load is larger

Question 25

How does Saltation work?

Answer 25

Pebbles are bounced along the river bed, most commonly near the source. Particles jump around

The transport of sand grains (usually larger than 0.2 mm) by stream or wind, bouncing the grains along the ground in asymmetrical paths

Question 26

How does Suspension work?

Answer 26

Lighter sediment is suspended (carried) within the water, most commonly near the mouth of the river. Very fine, very tiny, allowing them to be suspended within the stream. Dust in the air is another example

Fine particles held in suspension in a stream. The finest particles are not deposited until the stream velocity nears zero

Question 27

How does Solution work?

Answer 27

The transport of dissolved chemicals. This varies along the river depending on the presence of soluble rocks

Question 28

What is Stream Competence?

Answer 28

A measure of the ability of the river to transport sediment, erode landscapes, etc. All related to the concept of the work

Question 29

What is Stream Capacity?

Answer 29

The amount of sediment that a river is capable of moving

Question 30

What are the characteristics of a Straight Channel?

Answer 30

Things move in a straight line. Most efficient pattern for moving water from one place to another

Question 31

What is a Meandering Channel?

Answer 31

The sinuous, curving pattern common to graded streams, with the energetic outer portion of each curve subjected to the greatest erosive action and the lower-energy inner portion receiving sediment deposits

More common than a Straight Channel. Formed over long periods of time by “disturbances”

Question 32

What is an Oxbow Lake?

Answer 32

A lake that was formerly part of the channel of a meandering stream; isolated when a stream eroded its outer bank, forming a cutoff through the neck of the looping meander

Question 33

What’s a Point Bar?

Answer 33

In a stream, the inner portion of a meander, where sediment fill is redeposited

Question 34

What’s a Cut Bank?

Answer 34

In streams, a steep bank formed along the outer portion of a meandering stream; produced by lateral erosive action of a stream

Question 35

What’s a Meander Scar?

Answer 35

A geological feature formed by the remnants of a meandering water channel. They are characterized by a crescentic cut in a bluff or valley wall, produced by a meandering stream

Formed when an Oxbow Lake dries up

Question 36

What’s an Incised Meander?

Answer 36

A river meander which has been cut abnormally deeply/ is well-developed into the landscape because uplift of the land has led to renewed downward erosion by the river

Water is allowed to “downcut”

Question 37

What’s a Braided Channel?

Answer 37

A stream that becomes a maze of interconnected channels laced with excess sediment. Braiding often occurs with a reduction of discharge that reduces a stream’s transporting ability or with an increase in sediment load

Braided streams form where the sediment load is so heavy that some of the sediments are deposited as shifting islands or bars between the channels

Question 38

What is a Nickpoint?

Answer 38

The point at which the longitudinal profile of a stream is abruptly broken by a change in gradient; for example, a waterfall, rapids, or cascade

Question 39

What are characteristics of a Youth river?

Answer 39

A fast flowing river characterized by a deep, narrow erosion pattern forming a V shaped channel or valley

Carries the most material, runs fastest, has steepest gradient

Question 40

What are characteristics of a Mature river?

Answer 40

The slope becomes gentler and the river becomes much wider as it is joined by many tributaries. The river is also carrying a load now that has been eroded from further upstream.

Water slows down, sediments begin to deposit

Question 41

What are characteristics of an Old Age river?

Answer 41

Widest, Deposits the most sediment, has the flattest gradient, lowest elevation, moves the slowest

Question 42

What is a “Rejuvenation” of a river?

Answer 42

Results from a drop in sea-level or rise in land. Faults occuring on land can form waterfalls/cliffs, rejuvenating the river and making it run faster.

A change in gradient along a river can increase it’s competence