UK Evolving physical landscape - 4B - River processes

Question 1

Freeze-thaw weathering -

Answer 1

The action of water physical freezing and expanding in cracks causing them to break apart

Question 2

Chemical weathering

Answer 2

The reaction of acidic rainfall with alkali rocks (limestone) causing the rock to break down

Question 3

Biological weathering

Answer 3

The action of plant roots growing into cracks in rock causing the rock to break down

Question 4

Hydraulic action

Answer 4

Fast flowing water is forced into cracks in the bank breaking it apart

Question 5

Abrasion

Answer 5

Sand and pebbles are dragged along a river bed wearing it away

Question 6

Solution

Answer 6

Alkaline rocks are dissolved by the acidic water

Question 7

Attrition

Answer 7

Rocks and stones knock into each other wearing them away

Question 8

4 types of river transportation

Answer 8

Traction
Saltation
Suspension
solution

Question 9

As a type of river transportation, what is Traction

Answer 9

Large stones are dragged and rolled along the river bed

Question 10

As a type of river transportation, what is Saltation

Answer 10

the picking up and dropping of material continuously creating a bouncing motion (causes abrasion)

Question 11

As a type of river transportation, what is Suspension

Answer 11

Tiny particles are carried in the river current

Question 12

As a type of river transportation, what is solution

Answer 12

Dissolved chemical are carried within the water

Question 13

what are 2 different types of mass movement?

Answer 13

Soil creep

Slumping

Question 14

What is a soil creep?

Answer 14

the slow movement of saturated material down a slope over at 2cm per year

Question 15

What is slumping?

Answer 15

the rotational movement of material down a slope due to weathering and water

Question 16

What is Deposition?

Answer 16

The dropping of material due to a loss of energy.

Question 17

How is a v-shaped valley with interlocking spurs formed?

Answer 17

1. River downhill eroding the landscape vertically -> cuts a deep notch down into the landscape using hydraulic action/Abrasion
2. River erodes downwards = sides of the valley are exposed to freeze-thaw weathering -> loosens the rocks ->steepens valley sides
3. Fallen rocks into river = more abrasion
   River transports rocks downstream -> channel = wider and deeper = V-shaped valley between interlocking spurs

Question 18

Waterfall formation

Answer 18

Rivers flows over bands of softer and harder rocks -> softer rock more quickly eroded

River undercuts harder rock through hydraulic action leaving an overhang = plunge pool below waterfall
Overhanging rock unsupported -> falls into the plunge pool
The waterfall is moved upstream – process continues = gorge is cut back into the hillside

Question 19

Meander formation

Answer 19

Water turns round obstructions = areas of slower and faster water movement

Rivers flows from side to side in winding course but still straight channel = helicoidal flow.

Outside bend = water moves faster -> more energy to erode = river cliff

Inside bend = water moves slowly -> deposits material load = river beach/slip-off slope Continuous erosion/erosion = meander

Meander will migrate downstream -> change shape over time

Question 20

How do Floodplains and Levees form?

Answer 20

River on floodplain with a very low gradient -> mainly depositing (silt and sand)
Silt deposited on the river banks and much less on the floodplain -> frequent flooding continues this build up.
When the river is flowing normally it deposits in the river bed
Usually the built-up levees protect the plain from flooding

Question 21

How do Oxbow lakes form?

Answer 21

Meander formation then:
During flood the river will cut through the neck
River continues on its straighter path and the meander is abandoned ->New deposition seals off the ends and the cut-off

Question 22

storm hydrographs

Answer 22

watch video and questiosn

Question 23

Describe the upper course

Answer 23

The upper course as many tributaries which are narrow and. V-shaped

Each tributary doesn’t carry a lot of water but combined the tributaries all fill up the river channel further down

The sides of the tributaries tend to be like a valley With a large gradient either side so water run into the tributary

Question 24

Describe the middle course

Answer 24

The tributaries merge together to form a channel, which is rounder in shape and deeper, to adjust to the increase in water

The more water that passes by, the larger the energy of the water of the water which leads to more erosion to take place to widen the channel The area around the river channel is​flat and low-lying​,which is the ​floodplain​ if the river needs to flood.

Question 25

Describe the lower course

Answer 25

The lower course Carries the largest volume of water it is in a very wide and very deep channel

There are ridges either side of the river banks called levees

this size of the valley has increased so it is even wider and flatter than the middle course

Question 26

Give 2 examples of hard engineering River defenses

Answer 26

River flood wall
Earth embankment

Question 27

Advantages and disadvantages of River flood wall

Answer 27

Flood walls
Pros:
Can be used to raise the height of the river bank to a level where the river might not burst its banks.

Can be permanent features or incorporated into the design of an area and become invisible.

Can also be temporary structures
Cons:
Can prevent access to the river for leisure or economic purposes.

Question 28

Advantages and disadvantages of Earth embankments

Answer 28

Advantages
Cheap with a one-off cost
Allows for flood water to be contained within the river
.
Disadvantages
Looks unnatural.
Water speeds up and can increase flood risk downstream.