Rivers

Question 1

What is the course of a river?

Answer 1

The downhill flow of the river

Question 2

What are the characteristics of the Upper Course?

Answer 2

Steep, V shaped Valley, Deep channel, Narrow Channel

Question 3

What are the characteristics of the Upper Course?

Answer 3

Medium Gradient, Sloping Sides, Widening deepening channel

Question 4

What are the characteristics of the Lower Course?

Answer 4

Wide channel, flat valley, deep channel

Question 5

What is vertical erosion?

Answer 5

Deepens the valley and channel, scraping angular erosion

Question 6

What is lateral erosion?

Answer 6

Widens the valley and channel, forms meanders

Question 7

What is Hydraulic Action?

Answer 7

The force of the river colliding with rocks to break them

Question 8

What is Abrasion?

Answer 8

Eroded rocks are picked up by the river and scrape against the channel

Question 9

What is attrition?

Answer 9

Rocks crash into eachother, shattering into smaller fragments, the rocks round off

Question 10

What is solution?

Answer 10

When rock is dissolved by river water

Question 11

What is Traction?

Answer 11

When large boulders are forced across the river bed by water

Question 12

What is saltation?

Answer 12

Pebbles are bounced off the river bed

Question 13

What is suspension?

Answer 13

When small particles are suspended in water and carried by it

Question 14

What is solution?

Answer 14

When materials are dissolved in water

Question 15

What factors cause deposition?

Answer 15

• Water losing energy
• The volume of water falls
• There’s more eroded material and the water can’t carry it
• The water gets shallower
• The river reaches its mouth

Question 16

How is a waterfall formed?

Answer 16

• Water flows over hard and soft rock
• Soft rock erodes by abrasion
• Creates a step
• Water flows over the step
• The waterfall undercuts the area under the step
• This causes the step to collapse
• The step falls and is swirled under the waterfall
• This erodes into a plunge pool
• Repeat! Causing Retreat

Question 17

How do meanders form?

Answer 17

Faster currents on the outer bend, erode the outside bend

Small River Cliffs form at the bends

Since current is stronger inside, material is deposited on the outside of the bend

A slip off slope makes the inside bend shallower and the outside deeper

Question 18

How are oxbow lakes formed?

Answer 18

Meanders continue to widen

The neck gets closer and closer until it breaks through

The river takes the shortest course and doesn’t carry sediment into the meander because there’s not enough energy

Deposition occurs and closes off the meander

Question 19

What are levees?

Answer 19

Natural embankments along the edges

Question 20

Why do we get levees?

Answer 20

The river floods and rises over the channel

The heaviest material is deposited at the edges of the channel

Deposited Material creates levels

Question 21

What is a Floodplain?

Answer 21

The valley floor around the sides of a river where flooding occasionally occurs\

Material builds up here due to deposition

Question 22

What are the 4 types of Soft Engineering?

Answer 22

• Warnings
• Zoning
• Tree Planting
• River Restoration

Question 23

What do Warnings do?

Answer 23

Alerts through TV, Radio and Mobile Phones

Question 24

Warnings: Negatives

Answer 24

Doesn’t prevent flooding, may give a false sense of security

Question 25

Warnings: Positive

Answer 25

Allow for planning and preparedness, moving possessions etc.

Question 26

What is flood plain zoning?

Answer 26

Refraining from building on parts of a flood plain

Question 27

Zoning: Positives

Answer 27

Fewer impermeable surfaces are created No Buildings to damage

Question 28

Zoning: Negatives

Answer 28

Not helpful in already developed areas. Limited expansion of urban areas

Question 29

What is tree planting?

Answer 29

Increasing interception and lag time

Question 30

Tree Planting: Benefits

Answer 30

Discharge and flood risk decrease

Question 31

Tree Planting: Negatives

Answer 31

Reduces land that can be used for agriculture

Question 32

What is river restoration?

Answer 32

Making the river more natural, allowing the floodplain to flood naturally

Question 33

Restoration: Positiives

Answer 33

Less Maintainance required Less risk of flooding downstream

Question 34

Restoration: Negatives

Answer 34

Local flood risk increases

Question 35

What are the 4 Hard engineering tactics?

Answer 35

Dams and Reservoirs Channel Straightening Embankments Flood Relief Channels

Question 36

What are Dams?

Answer 36

Artificial lakes form behind a large dam in the upper course

Question 37

What is channel straightening?

Answer 37

Meanders are removed, making channels straighter

Question 38

What are the positives and negatives of channel straightening?

Answer 38

P: Water leaves the area quickly N: Faster moving water may cause erosion downstream.

Question 39

What are Embankments?

Answer 39

Raised walls along river banks

Question 40

What are Embankment Positives and Negatives?

Answer 40

P: The river can hold more water N: Severe flooding may occur if the embankments break

Question 41

What are flood relief channels?

Answer 41

Channels are built to divert water around built up areas to divert water

Question 42

What are flood relief channels positives and negatives?

Answer 42

P: The release of water can be controlled N: Increased discharge occurs where the channels meet the river, causing flooding