Lecture 8 Hyporheic

Question 1

What is the hyporheic layer

Answer 1

Area below a river bed

Question 2

What characteristic of bedforms makes the hyporheic zone possible

Answer 2

Porus bedload

Question 3

What pressure regime causes water movement to the hyporheic zone

Answer 3

High bed pressures, often when flow constricts

Question 4

Why is residence time important between grains in the HZ

Answer 4

Reactions with carbon dioxide and microbial activity governed by movement and replacement of water

Question 5

What is the name for how flow gets into the river bed

Answer 5

Advective exchange

Question 6

How does water get into the bed via advective exchange

Answer 6

flow pathways and channels

Question 7

Which side of a ripple formation does a flow pathway enter the bed

Answer 7

stoss side

Question 8

In meander channels, how can water move in the hyporheic zone

Answer 8

From one channel to another, same in braided rivers

Question 9

What are OFG

Answer 9

Open framework gravels, high porosity

Question 10

What does mixing of different grain sizes lead to

Answer 10

Less porosity as small grains fill in gaps

Question 11

What is the role of darcy’s law

Answer 11

Way of describing subsurface water movement

Question 12

When do we see a drop in permeability with sand fraction percentage

Answer 12

Over 18%

Question 13

What is wrong about conventional velocity profiles with the addition of hyporheic flow

Answer 13

Inconsistency of bed flow understanding, gap

Question 14

What flow is seen from the bed to the main flow channel

Answer 14

Return flow

Question 15

What do interconnected pores lead to

Answer 15

Creation of flow networks and channels

Question 16

What force is adjective exchange said to solve

Answer 16

Lift force

Question 17

What areas of study does the hyporheic zone link to

Answer 17

Ecology and biogeochemisty

Question 18

What species lay there eggs within gravel beds

Answer 18

Salmon, trout species

Question 19

What cycle is the hypirheic zone important in

Answer 19

Carbon cycle

Question 20

What is the name for the amount of time water spends in pores

Answer 20

Residence time

Question 21

What is Greg’s view on the size of hyporheic sizes

Answer 21

Just several grains in diameter below bed

Question 22

How quickly can chemical composition change over the bed boundary

Answer 22

Very significant contrast, quick

Question 23

How does oxygen differ in the HZ

Answer 23

Much less

Question 24

Where does flow come out of the bed

Answer 24

Low pressure zones

Question 25

How has HZ movement been visualized

Answer 25

Tracer tests

Question 26

As well as bed forms, where can adjective exchange be found

Answer 26

Pool riffle

Question 27

Why may water move in the HZ across a meander

Answer 27

Pressure and height difference

Question 28

What is hydraulic conductivity

Answer 28

Ease at which water can move through a substrate

Question 29

What does dh stand for in darcys law

Answer 29

Change in head

Question 30

What is strange about Hyporheic flow

Answer 30

Occur across scales with incredible similarities

Question 31

What does grain size, particle sorting and packing in the river bed change

Answer 31

Heterogeneity of hydraulic conductivity

Question 32

In the natural world, How is ease of movement determined

Answer 32

The mosaic of different bed types

Question 33

How does sediment transport rates effect hydraulic conductivity

Answer 33

Sediment sorting, slow transport leads to avalanching and movement together leading to more mixed substrate

Question 34

What sand fractions are OFGs

Answer 34

Less than 18%

Question 35

What is the assumpted new layer between hyporheic and normal freeflow

Answer 35

Transition layer

Question 36

What is the name of the point where flow speed changes to go to the bed

Answer 36

Inflection point

Question 37

How think is the transition layer

Answer 37

2 grains

Question 38

What is the porosity of gravel bed rivers

Answer 38

Over 40%

Question 39

What does larger porosity give us

Answer 39

Larger amount of space which water can move through

Question 40

What can the lift force lead to

Answer 40

Sediment transport

Question 41

What is the dominant mechanism for HZ exchange

Answer 41

Advenctive exchange (pressure)

Question 42

Where are large shear stress events that move down towards the bed

Answer 42

Sweep events

Question 43

What happens when sweep pushes water into the bed

Answer 43

Forces water outof porespaces into the flow, ejection

Question 44

What does permeanke beds do to horseshoe ejection structure

Answer 44

Gets rid of legs, changes boil structure

Question 45

How can pollutants be effected by HF flow

Answer 45

Fine scale pollutants can be filtered out of the flow, pollutants in the bed

Question 46

Where do we get scour

Answer 46

In the trough

Question 47

What does dune erosion mean with pollutants at HZ

Answer 47

Larger flood events will take pollutants far down, if flow reduces scour will not be as deep and pollutants will stay there

Question 48

What does the Ren and Packman paper show

Answer 48

Chemical (pH) water composition can effect repulsion due to electrostatic nature of substrates, can allow more or less HZ flow, mostly with clay

Question 49

What is the Reaction significance factor

Answer 49

Determines what is more factors within the bed, what is more important, dune forms and bed forms, vs larger scales such as meander bend movement

Question 50

What is the RSF reaction

Answer 50

(Transit / reaction)×(reach / turnover) | Time × length

Question 51

In headwaters reaches, what rsf is more important

Answer 51

Small bed forms and dunes

Question 52

What was found with efficiency with HZ flow

Answer 52

More efficient round meanders and on larger scale than with smaller scale1

Question 53

How does the classic flow model change with added porosity

Answer 53

Recirc becomes squished into the bank, with zone coming back up

Question 54

What substrate is still comparable with impermeable beds

Answer 54

Sand beds

Question 55

What is RIM

Answer 55

Refractive index matched, allows objects to become see through

Question 56

What can be said about pores within substrates

Answer 56

Flow is turbulent

Question 57

How far were fine materials in hyporheic flow paths stores compared to solutes (Harvey et al)

Answer 57

two-thirds as deep as solutes

Question 58

Are fines or solutes more easily mobilized by bedform migration (Harvey et al)

Answer 58

Fines

Question 59

What did floods do to solute storage

Answer 59

drove them deeper below the bed, beneath 8cm

Question 60

What three timescales are important in hyporheic reactions

Answer 60

flood duration, relaxation time of bedforms and hyporheic residence times.