Fluvial Forms

Question 1

List 5 fluvial bedforms

Answer 1

Ripples
Dunes
Plane bed
Antidunes
Obstacle marks

Question 2

What are fluvial bedforms similar to?

Answer 2

Aeolian bedforms

Question 3

What is the medium for fluvial bedforms?

Answer 3

Water

Question 4

What is the medium for aeolian bedforms?

Answer 4

Air

Question 5

What does larger material require to be moved?

Answer 5

Higher stream power

Question 6

What does the presence of fluvial bedforms depend on?

Answer 6

Grain size

Question 7

What are horizontal bedplanes indicative of?

Answer 7

Lower stage plane beds

Question 8

In which direction do ripples migrate overtime?

Answer 8

Down flow

Question 9

Which side do ripples erode?

Answer 9

Upstream side

Question 10

Which side do ripples deposit?

Answer 10

Downstream side

Question 11

Give a place where ripples can be seen?

Answer 11

The beach

Question 12

What is meant by transient?

Answer 12

Adjust quickly to change

Question 13

Are ripples transient?

Answer 13

Yes

Question 14

What energy conditions are required for ripples to form?

Answer 14

Lower energy conditions

Question 15

What transportation process allows ripples to form?

Answer 15

Suspension

Question 16

What do ripples have a high rate of?

Answer 16

Aggradation

Question 17

Are dunes visible?

Answer 17

Yes, they poke out of the water to a greater extent

Question 18

What do dunes cause?

Answer 18

Surface waves that are out of phase with the water bed.

Question 19

Is the amplitude of dunes higher or lower than that of ripples?

Answer 19

Higher

Question 20

What can the amplitude of dunes reach?

Answer 20

10s of cm to 10s of m

Question 21

What shows migration in dunes?

Answer 21

Cross stratification

Question 22

In which direction do dunes migrate?

Answer 22

Downflow

Question 23

How do dunes migrate?

Answer 23

By accretion of the lee side

Question 24

Why are dunes in dynamic equilibrium?

Answer 24

The stoss side is eroding and the lee side is depositing

Question 25

What are two important features of the upper stage plane bed?

Answer 25

Coarser material than lower stage | Some rocks

Question 26

In what plane bed would you find ripples?

Answer 26

Lower stage plane bed

Question 27

In what plane bed would you find dunes?

Answer 27

Lower stage plane bed

Question 28

What are antidunes?

Answer 28

The opposite of dunes

Question 29

What type of feature are antidunes?

Answer 29

Erosional

Question 30

In which direction do antidunes migrate?

Answer 30

Upflow

Question 31

What waves are antidunes associated with?

Answer 31

Breaking waves

Question 32

What is the water flow like around antidunes?

Answer 32

Shallow but fast

Question 33

In which way do antidune beds dip?

Answer 33

Upflow

Question 34

Why is the stoss side of antidunes preserved?

Answer 34

Due to the dip

Question 35

Which side of the antidune is eroded?

Answer 35

Lee side

Question 36

Which side of the antidune moves upward?

Answer 36

Crest side

Question 37

How long are antidunes preserved for?

Answer 37

They are very rarely preserved

Question 38

What are two features of cluster bedforms?

Answer 38

Rocks dip into the flow | Coarser material

Question 39

List 4 obstacle marks

Answer 39

Ice blocks Secondary bedforms Vegetation Anthropogenic sources

Question 40

What flow can ice blocks create?

Answer 40

Horse shoe flow

Question 41

What can ice blocks cause?

Answer 41

Scouring due to horse show flow

Question 42

What changes overtime in rivers?

Answer 42

Discharge

Question 43

What two things do bars require?

Answer 43

Cohesionless sediment | Bedload

Question 44

Why are bars difficult to define?

Answer 44

They depend upon flow depth and discharge

Question 45

What are bars?

Answer 45

Attachments to channel margins

Question 46

Where can bars be found?

Answer 46

Mid channel

Question 47

What are bar types often associated with?

Answer 47

Channel morphological type

Question 48

What transportation process causes bars?

Answer 48

Suspended load

Question 49

Are bars formed in low or high energy environments?

Answer 49

Low energy

Question 50

What bars can braided rivers have?

Answer 50

1st, 2nd and 3rd order bars

Question 51

In what environments do braided rivers occur?

Answer 51

In a number of enviroments

Question 52

Where are braided rivers usually found?

Answer 52

Where there is a lot of sediment

Question 53

Give two examples of wondering gravel bed rivers

Answer 53

River Coquet, Northumberland | Fraser River, British Columbia

Question 54

What can be done to find the age of island bars?

Answer 54

Tree coring

Question 55

What can affect the location of erosion/ deposition?

Answer 55

Positioning of flow cells

Question 56

What happens as the river channel widens? (3)

Answer 56

Flow reduces Sediment transport reduces Change in the type of material transported

Question 57

What are the main features of Anastomosing rivers?

Answer 57

Parallel channels | Aligned by natural levees with flood basins inbetween

Question 58

Define Anastomsing river

Answer 58

"A type of river channel with multiple interconnected, coexisting channel belts on alluvial flood plains, which most often form under low energy conditions near a local base level" Makaske 2001

Question 59

When do braided rivers occur?

Answer 59

When erodibility of bank particles is more than their transportability

Question 60

When do meandering rivers occur?

Answer 60

When erodibility and transportability of bank particles are equal

Question 61

When do straight rivers occur?

Answer 61

When transportability of bank particles is higher than erodibility

Question 62

What is the spacing like for pools and riffles?

Answer 62

It is regular

Question 63

What property changes in pools and riffles can occur and why?

Answer 63

Major changes in hydraulic properties depending upon flow stage

Question 64

What hypothesis is associated with pools and riffles?

Answer 64

Velocity reversal hypothesis

Question 65

What is the velocity reversal hypothesis?

Answer 65

Velocities in pools increase at a higher rate than in riffles

Question 66

Can rivers be damned by their own levees?

Answer 66

Yes

Question 67

When do river terraces form?

Answer 67

After glaciers melt

Question 68

Why do river terraces form after glaciers melt?

Answer 68

There is less discharge

Question 69

What do river terraces reflect a change in?

Answer 69

River channel change in water and sediment flux

Question 70

Briefly explain the magnitude and frequency concept

Answer 70

Argument over whether frequency of floods is more important than intensity. Medium magnitude floods occurring over intermediate timescales achieve most work in terms of sediment transport.

Question 71

What is avulsion?

Answer 71

Rapid channel change

Question 72

What is river terrace formation an example of?

Answer 72

Complex response