River landscapes

Question 1

What are the four processes of erosiomn?

Answer 1

Hydraulic action
Abrasion
Attrition
Solution

Question 2

What is hydraulic action?

Answer 2

The force of the river water colliding with rocks breaks rock particles away from the river channel

Question 3

What is abrasion?

Answer 3

Eroded rocks picked up by the river crash into each other and break into smaller fragments

Question 4

What is solution?

Answer 4

River water dissolves some types of rock

Question 5

What are the four methods of transportation?

Answer 5

Traction
Saltation
Suspension
Solution

Question 6

What is traction?

Answer 6

Large particles like boulders are pushed along the river bed by the force of the water

Question 7

What is saltation?

Answer 7

Pebble-sized particles are bounced along the river bed by the force of the water

Question 8

What is suspension?

Answer 8

Small particles like slit and clay are carried along by the water

Question 9

What is solution?

Answer 9

Soluble materials like limestone dissolve in the water and are carried along

Question 10

What is deposition?

Answer 10

It is when a river drops eroded material

Question 11

Why do rivers slow down and deposit material?

Answer 11

• They lose velocity and energy
• The volume of the water falls
• The amount of eroded material increases
• The water is shallower
• The river reaches its mouth

Question 12

How do waterfalls form?

Answer 12

When a river flows over an area of hard rock followed by an area of soft rock, the soft rock is eroded by hydraulic action and abrasion

This creates a step in the river which is eroded even more once more water flows over it

A steep drop is eventually formed

Question 13

How do gorges form?

Answer 13

After a waterfall is made, the hard rock is eventually undercut by erosion. It becomes unsupported and collapses

The collapsed rocks are swirled around at the foot of the waterfall where they rode the softer rock by abrasion. This creates a deep plunge pool

Over time, more undercutting causes more collapses. The waterfall retreats, leaving a steep-sided gorge

Question 14

How do meanders form?

Answer 14

A relatively straight river begins to bend.

The current is faster on the outside of the bend because the river channel is deeper (less friction)

More erosion takes place on the outside of the bend, forming river cliffs

The current is slower on the inside of the bend because the river channel is shallower

More eroded material is deposited on the inside of the bend, forming slip off slopes

It could eventually become an oxbow lake

Question 15

How do ox-bow lakes form?

Answer 15

When a meander becomes larger over time, erosion can cause the outside bends to get closer

This is until there’s only a small bit of land left between the bends. This is called the neck

The river breaks through this land (usually during a flood) and the river flows along the shortest course

Deposition eventually cuts off the meander forming an oxbow lake. An example would be the River Calder

Question 16

What are flood plains?

Answer 16

They are flat areas of land that flood

Question 17

What are levees?

Answer 17

They are natural embankments along the edges of a river channel

Question 18

How are levees formed?

Answer 18

During a flood, eroded material is deposited over the whole flood plain

The heaviest material is deposited closest to the river channel because it gets dropped first when the river slows down

Over time, the deposited material builds up, creating levees along the edges of the channel

Question 19

What are estuaries?

Answer 19

They are tidal areas where the river meets the sea

Question 20

What are some characteristics of a meander?

Answer 20

On the outside of the meander, there would be a river cliff. It is deeper here due to faster flowing water, causing erosion

On the inside of the meander, there would be a slip off slope which would have shallower, slower flowing water

Question 21

Explain how river meanders may change over time?

Answer 21

The river starts off relatively straight.

Due to erosion, deposition and helicoidal flow, the river begins to bend

Over time, the river deepens on the outer end and shallower on the inner bend, causing the meander to bend even more.

Afterwards, an oxbow lake may begin to form

Question 22

What were the natural causes of the flash flooding of Boscastle, Cornwall?

Answer 22

Heavy rainfall caused the river to burst its banks

Ground was already saturated from previous wet weather

The rock type is hard sandstone with limited permeability

Steep valley sides increased surface run-off

Question 23

What were the human causes of the flash flooding of Boscastle, Cornwall?

Answer 23

Deforestation higher up in the river valley meant water was not intercepted

Building on the floodplain meant less infiltration (car parks-tarmac)

Both of these increase surface run off

Question 24

What were some of the primary effects of the Boscastle floods?

Answer 24

No deaths but property damage was high

Telephone, water, electricity and gas supplies were all interrupted

6 properties collapsed entirely due to the force and speed of the floodwaters

Question 25

What were some of the secondary effects of the Boscastle floods?

Answer 25

Many residents suffered stress and anxiety in the year that followed

Many businesses suffered-loss of stock

Question 26

What were some of the immediate responses to the Boscastle floods?

Answer 26

Emergency services are on the scene to helps with the rescue operation

Helicopter winches lifted stranded home-owners off the roofs of their houses and trees

Question 27

What were some of the long term responses to the Boscastle floods?

Answer 27

Large clean up operation

A £4.5 million scheme to improve flood defences