Fluvial Processes

Question 1

What are the three main processes involved in fluvial processes?

Answer 1

Erosion, Transportation, and Deposition

Question 2

Define a stream.

Answer 2

Any channeled flow of water.

Question 3

What do fluvial processes involve?

Answer 3

Running water, encompassing both overland flow and streamflow.

Question 4

What is overland flow?

Answer 4

Unchanneled downslope movement of water.

Question 5

What is streamflow?

Answer 5

Channeled movement of water along a valley bottom.

Question 6

What is a valley?

Answer 6

Portion of terrain where drainage system is clearly established.

Question 7

What is an interfluve?

Answer 7

Higher land above a valley, separating adjacent valleys.

Question 8

Define drainage basin or watershed.

Answer 8

All area that contributes to overland flow, streamflow, and groundwater.

Question 9

What is a drainage divide?

Answer 9

Line of separation between runoff descending to one drainage basin and another.

Question 10

What describes the arrangement and organization of streams within a watershed?

Answer 10

Stream order.

Question 11

What are first-order streams?

Answer 11

Smallest streams with no tributaries.

Question 12

What is splash erosion?

Answer 12

Movement of particles downhill caused by raindrops colliding with the ground.

Question 13

What are rills?

Answer 13

Tiny channels that form when volume of overland flow increases.

Question 14

What is gully erosion?

Answer 14

Occurs after rills coalesce into fewer and larger channels.

Question 15

What enhances erosion by streamflow?

Answer 15

Channeled surface flow increases volume and speed of water.

Question 16

What is stream load?

Answer 16

Material collected in streams.

Question 17

Fill in the blank: The size of the largest particle that a stream can transport is known as _______.

Answer 17

Competence

Question 18

What is capacity in terms of stream transport?

Answer 18

Maximum load a stream can transport under given conditions.

Question 19

What is alluvium?

Answer 19

Stream-deposited sediments that are typically smooth and round.

Question 20

What happens to transported material when stream flow speed decreases?

Answer 20

It will be set down or deposited.

Question 21

Describe perennial streams.

Answer 21

Permanent streamflow in humid regions.

Question 22

What is a flood event?

Answer 22

An increase in stream discharge that can enhance erosion and deposition.

Question 23

What is discharge in relation to streams?

Answer 23

Volume of flow per unit of time.

Question 24

True or False: Urbanization increases infiltration due to impermeable surfaces.

Answer 24

False

Question 25

What are the three dimensions of streamflow in a channel affected by?

Answer 25

Gradient, friction, and channel width/depth.

Question 26

What are the four categories of stream channel patterns?

Answer 26

Straight channels, sinuous channels, meandering channels, braided channels.

Question 27

What is downcutting in valley deepening?

Answer 27

Lowering of the streambed through hydraulic power and abrasive effect of bedload.

Question 28

What causes knickpoint migration?

Answer 28

Intensified erosion that causes movement of knickpoint upstream.

Question 29

What occurs during valley widening?

Answer 29

Lateral erosion of outside of curves occurs where flow speed is fastest.

Question 30

What is headward erosion?

Answer 30

Erosion that cuts into interfluve at upper end of gully or valley.

Question 31

Define stream capture.

Answer 31

Headward erosion causes one stream to be diverted to the basin of another stream.

Question 32

What is a delta?

Answer 32

Depositional landform at the mouth of a river.

Question 33

What is the process called when one stream extends its valley toward another stream?

Answer 33

Captor stream reduces a drainage divide ## Footnote This process involves cutting the channel and capturing the flow of a beheaded or captured stream.

Question 34

What happens to deposits at the mouth of a river?

Answer 34

Deposits build up, partially blocking the channel and forcing flow along new paths ## Footnote This creates a maze of parallel channels called distributaries.

Question 35

What is aggradation?

Answer 35

The process of deposition in valleys ## Footnote It occurs anytime a stream loses power to transport its load.

Question 36

During high-water periods, where is most sediment shifted?

Answer 36

Downstream ## Footnote This occurs when the flow is fast.

Question 37

What is a floodplain?

Answer 37

A low-lying, nearly flat alluvial valley floor periodically inundated with floodwaters ## Footnote It forms where a meandering stream flows across a wide, level valley.

Question 38

What are bluffs in the context of floodplains?

Answer 38

Higher elevation slopes on the outer edge of a floodplain ## Footnote They are elevated areas that border the flat valley floor.

Question 39

What forms when a meandering channel bypasses itself?

Answer 39

A cutoff meander ## Footnote This may remain filled with water as an oxbow lake.

Question 40

What is an oxbow lake?

Answer 40

A body of water formed from a cutoff meander ## Footnote It may eventually dry up into a meander scar.

Question 41

What is the significance of alluvium in valleys?

Answer 41

It is deposited anywhere on the valley bottom when a stream loses power ## Footnote This process leads to the formation of layered beds of sediment.

Question 42

What occurs during low-water periods in relation to sediment?

Answer 42

Flow is slowed and sediment is more likely to settle on the bottom ## Footnote This can even raise the stream bottom.

Question 43

Fill in the blank: The growth of a stream valley downstream involves sediments sorted during _______.

Answer 43

deposition

Question 44

What creates a maze of parallel channels in river deltas?

Answer 44

Distributaries ## Footnote They form as flow is redirected by deposits at the river mouth.