🏞️ Physical: Rivers

Question 1

What is the drainage basin of a river?

Answer 1

The area of land drained by a river and its tributaries.

Question 2

What is a confluence of a river?

Answer 2

The point where a tributary joins a larger river.

Question 3

What is the river watershed?

Answer 3

The edge of a river basin.

Question 4

Define erosion.

Answer 4

The wearing away of material.

Question 5

Why do rivers tend to erode vertically in the upper course?

Answer 5

Discharge is smaller and the river cuts down due to gravity and the larger size of sediment.

Question 6

Why do rivers tend to erode laterally in the middle course?

Answer 6

Material carried by the river erode the banks.

Question 7

What is attrition?

Answer 7

When rocks bang together to smoothen and break down.

Question 8

What is hydraulic action?

Answer 8

When the force of the water flows into the cracks in the bank and causes them to break.

Question 9

What is abrasion?

Answer 9

When rocks scrape the bed and banks.

Question 10

What is the erosional process of solution?

Answer 10

When soluble materials as rocks get dissolved into the river.

Question 11

What is the river’s load?

Answer 11

The materials that are carried by the river.

Question 12

What is the river’s discharge?

Answer 12

The amount of water in a river at any given time.

Question 13

What is traction?

Answer 13

When large rocks and boulders are rolled along the river bed by the force of the water at times of high discharge.

Question 14

What is saltation?

Answer 14

When small rocks and sand particles are bounced along the river bed by the flow of water.

Question 15

What is suspension?

Answer 15

When fine clay and sand particles are carried along within the water even at low discharges.

Question 16

What is the transported process of solution?

Answer 16

When some minerals dissolve in water and get carried along by the flow of water.

Question 17

What is a floodplain?

Answer 17

An area of low-lying land next to a river which is prone to flooding.

Question 18

When does deposition normally occur and why?

Answer 18

When the velocity of the river slows as they lose energy and drop the sediment.

Question 19

What are the characteristics of the river channel and valley in the upper course of the River Severn?

Answer 19

Steep V-shaped valley sides, channel is very shallow and valley is small.

Question 20

What are the characteristics of the river channel and valley in the middle course of the River Severn?

Answer 20

Valley is wider + deeper, flattening out by lateral erosion.

Question 21

What are the characteristics of the river channel and valley in the lower course of the River Severn?

Answer 21

Very flat and wide.

Question 22

What are the landforms in the upper course of the River Severn?

Answer 22

Interlocking spurs, waterfalls and gorges.

Question 23

What are the landforms in the middle course of the River Severn?

Answer 23

Meanders + Ox-bow lakes

Question 24

What are the landforms in the lower course of the River Severn?

Answer 24

Flood plains, meanders, levees, estuaries and mud flats

Question 25

What processes and size of materials are in the upper course of the River Severn?

Answer 25

Large rocks. Lots of transportation and vertical erosion.

Question 26

What processes and size of materials are in the middle course of the River Severn?

Answer 26

Lateral and vertical erosion all types of transportation and deposition. Rocks are smaller.

Question 27

What processes and size of materials are in the lower course of the River Severn?

Answer 27

All of the processes, pretty much no vertical erosion. Sediment is tiny and deposition is very high.

Question 28

What are examples of erosional river landforms?

Answer 28

Interlocking spurs, waterfalls and gorges

Question 29

How are interlocking spurs formed?

Answer 29

- The start of the river has lots of energy so it erodes vertically due to gravity and creates a steep V-shaped valley - Over time the valley sides become less steep due to freeze-thaw weathering - The river then winds its way around the hard rock and creates interlocking spurs

Question 30

How are waterfalls formed?

Answer 30

- Water runs over alternating bands of hard and soft rock and erosion will start to break down the rocks - Hydraulic actions wears away the soft rock because it is less resistant than the hard rock - Over time the soft rock starts to undercut the hard rock - The hard rock is left unsupported and its weight collapses into the river - Rocks that have fallen either get transported down the river or scrape away and abrade the base of the river bed, a plunge pool is then created with the waterfall

Question 31

How are gorges formed?

Answer 31

After a waterfall is formed it retreats backwards and leaves behind steep sided vertical walls called a gorge

Question 32

What fluvial processes does a meander use to be formed?

Answer 32

Erosion and deposition

Question 33

How are meanders formed?

Answer 33

- Water swings to the outside of the river where there is less friction - As the river erodes the bank, the river will take the shortest route and take on a straight course - On the inside of the bend, the flow is slower so it deposits sediment

Question 34

How are ox-bow lakes formed?

Answer 34

- The neck of a meander grows narrower and when it breaks through the river flow will take the shortest path, straight - The look becomes sealed off altogether as a result of deposition. This is known as an ox-bow lake

Question 35

What is a levee?

Answer 35

A levee is a raised bank formed on the banks of a river in the lower course.

Question 36

How is a levee formed?

Answer 36

- During a flood water passes over the banks and increased friction occurs resulting in slower flow - The heaviest material is deposited first at the closest point to the river as the water doesn't have enough energy to carry it - The levee gradually gets higher after successive floods

Question 37

How are floodplains formed?

Answer 37

- When a river floods, it deposits the heaviest sediment first and lightest last - This build up of sand, silt and clays leads to the formation of a flat piece of land either side of a river - Every time the river floods, deposition build up the floodplain

Question 38

How can you work out the discharge of a river?

Answer 38

Area x Velocity = Discharge

Question 39

What are some physical factors that affect flood risk?

Answer 39

- Relief - Rainfall - Soil Saturation - Basin Size - Rock Type

Question 40

What are some human factors that affect flood risk?

Answer 40

- Urbanisation - Deforestation - Agriculture

Question 41

What are some examples of hard engineering strategies?

Answer 41

- Dams and Reservoirs - Embankments - Flood Reflief Channels - Channel Straightening

Question 42

What are some examples of soft engineering strategies?

Answer 42

- Flood-plain Zoning - Afforestation - River Restoration - Flood Warnings + Preparation

Question 43

How do dams and reservoirs work?

Answer 43

A dam is a large concrete barrier built across a river to hold back its flow. This causes the valley behind the dam to flood and creates a lake called a reservoir. This controls the amount of river downstream with the controlled gates.

Question 44

What are the benefits of dams and reservoirs?

Answer 44

- Can create energy, HEP - Can attract tourists - Provides recreational opportunities like water sports and fishing - Water is released in a controlled way

Question 45

What are the disadvantages of dams and reservoirs?

Answer 45

- Super expensive - Sediment can get trapped - Can lead to rotting and methane production

Question 46

How are estuaries formed?

Answer 46

- Incoming tides bring in sediment which mixes with the sediment being carried by the river - When the incoming tide of salt water meets the freshwater of the river, the river velocity drops and deposition occurs - The deposited sediment builds up in layers to form mudflats which rise above the water surface, particularly at low tide - Eventually the vegetation starts to grow on the mudflats and form salt marshes