Lecture 10

Question 1

What’s the main thing that discriminates a braided and a meander river

Answer 1

Multiple mid channel bars in a braided channel

Question 2

What sides does a singular central unit bar deflect water to

Answer 2

Both sides, erosion on both banks

Question 3

What happens to a single unit bar when flow goes either side of it

Answer 3

Can turn into a compound bar

Question 4

Why are cross bar channels Important in braided systems

Answer 4

Can become the dominant channels due to widening and scouring of the channel

Question 5

Barr migration is faster in meander or braided rivers

Answer 5

Braided

Question 6

Can bars migrate even in flow with no flood events

Answer 6

Yes

Question 7

How did the bar move on the jamuna river

Answer 7

Bar appeard, and doubled insize over the space of 2 years

Question 8

What is one way that bars can grow

Answer 8

Accumulates other unitbars

Question 9

Where do bars form

Answer 9

At a confluence site between multiple channels, creates scour

Question 10

What does the scour zone create downstream

Answer 10

A supply of sediment

Question 11

Is the flow on either sides of the bar normally even

Answer 11

No, one side normally sees more flow, creating a lopsided bar

Question 12

How will flow be concentrated around a bar

Answer 12

In one channel

Question 13

What does eneven channel flow cause around the bar

Answer 13

Elongation of one bar side

Question 14

In parker et al how many bars could be tracked over 4 years

Answer 14

1

Question 15

Do bars tracks from one year to the next, parker et al

Answer 15

No not in all cases, dynamic system

Question 16

What is channel cut

Answer 16

Creation of new channels

Question 17

Whag is channel fill

Answer 17

Abandonment of channels

Question 18

When bars are moving how will that effect flow

Answer 18

Moving bars deflect flow differently

Question 19

What can cause channel cut and fill

Answer 19

Bar shape, can stall and stop flows

Question 20

When 2 under water bars merge together what do you get

Answer 20

A larger compound bar that sticks out of the water

Question 21

What can happen with large compound bars with uni bar growth

Answer 21

Smaller unit bars can pile on the the compound bar side, adding sediment and size to the compound bar

Question 22

Where can abandoned channels form

Answer 22

In the middle of bars, caused by abandoned cross bar channels

Question 23

Where may cross bar channels also form

Answer 23

In the topographic low point between bar and compound bar

Question 24

In the south Saskatchewan what bar formed in low flow

Answer 24

Large attached bar, simplified the channel down

Question 25

What happens to braided systems during high flows

Answer 25

Channel cutting and new channels formed, many unit bars

Question 26

In normal flow conditions what does the topography of braided rivers look like

Answer 26

Bell shaped curve, even

Question 27

In a flood event what shape does the topographical chart represent

Answer 27

Uneven, sporadic

Question 28

In rivers with strong banks, what does the system look like

Answer 28

Narrow with less unit bars due to less sediment entering the system and less width to move

Question 29

Bars with weak vegetation growth are stable or unstable

Answer 29

Unstable

Question 30

So with strong banks but weak vegetation growth what does the system look like

Answer 30

Dynamic and quick, unit bars always moving, compound bars do not survive for long

Question 31

What are the key characteristics of a weak bank with low vegetation growth

Answer 31

Wide and unstable channel, many channels, with heavily divided flow

Question 32

In a heavily venerated channel what is common

Answer 32

Fairly stable bars with the main channel acting like a meander system

Question 33

What is laterally accretion

Answer 33

Bars can grow on the side of larger channels

Question 34

What radar is used to see unit bar structure below the bed

Answer 34

Ground penetrating radar

Question 35

How can we see bar movement in ground penetrating radar

Answer 35

Slip face movement

Question 36

How can we see larger scale unit bar migration

Answer 36

Whole strands of sediment diagonally twisted together

Question 37

How can high angle reflections show us bar migration

Answer 37

Can show movement and channel fill due to slip face accretion

Question 38

How can gpr who channel truncation

Answer 38

Up down meander like shapes show channels that have cut through at different orientations

Question 39

Do we get fining up in meander and braided channels

Answer 39

Yes

Question 40

Do we only find lateral accretion surfaces in meander rivers

Answer 40

No, also on the side of braid bars

Question 41

How do braided channels show lateral accretion

Answer 41

Braided channels are sinuous therefore they grow by sediment aggrading laterally

Question 42

Is the process in meander fill and channel filling similar

Answer 42

Yes, toonen et al

Question 43

What is the difference between braid bars and islands (Brice 1964)

Answer 43

Islands are not submerged at bankfull stage

Question 44

Why do bars look different at different flow stages

Answer 44

different river depths produce different erosional characteristics

Question 45

What is the difference between an anastomosing and braided channel

Answer 45

anastomosing channels are a lot longer, and are split of from the main river belt.

Question 46

What is channel diversion associated with

Answer 46

high stage scouring of thalwegs

Question 47

How does a channel become filled in

Answer 47

channel filled with sediment from the upstream end, downstream end blocked by moving channel bars

Question 48

How will despositional unit scale vary

Answer 48

with the scale of the alluvial feature

Question 49

What feature can be seen in a sandstone conglomerate body

Answer 49

complete channel belt

Question 50

What feature can be seen in sets of inclined strata (storeys)

Answer 50

Individual channel bars and channel fills

Question 51

What is depositional imprication

Answer 51

when deposits are aligned or orientated the same way

Question 52

What is a paleocurrent

Answer 52

A geological indicator of flow direction

Question 53

What does paleocurrent depend on

Answer 53

orientation of bedforms and sedimentary structure, what part of the channel bar fill is preserved

Question 54

How do rivers self organise their planform pattern

Answer 54

feedback from bars, channels, floodplain and vegetation

Question 55

What determins bar pattern

Answer 55

width-depth ratio

Question 56

what 3 bar types can form in a point bar (Kleinhaus)

Answer 56

chute, tail and scroll

Question 57

what 4 stages did kleinhaus create for braided rivers

Answer 57

highly braided, braided and meandering, meandering with scroll bars, laterally immobile no bars

Question 58

what does vegetation affect (kleinhaus)

Answer 58

channel mobility

Question 59

What can cause high sinuosity with vegetation in braided rivers

Answer 59

vegetation can stop the erosion of the point bar leading to outer bank erosion

Question 60

according to carson, what 3 groups can river channels be separated in

Answer 60

bed load. mixed load and suspended load