Rivers

Question 1

What is erosion?

Answer 1

Is the wearing away of the land in the natural environment

Question 2

Name the processes of erosion…

Answer 2

Hydraulic action
Solution/corrosion
Attrition
Corrasion/abrasion

Question 3

What is hydraulic action?

Answer 3

This process involves the force of water against the bed and banks

Question 4

What is solution/corrosion?

Answer 4

This is the chemical action of river water. The acids in the water slowly dissolve the bed and banks .

Question 5

What is attrition?

Answer 5

Material (the load) carried by the river bump and crash into eachother and so are broken down, smoothed and rounded into smaller particles.

Question 6

What is corrasion/abrasion?

Answer 6

This is the process in which the bed and banks are worn down by the rivers load, the river throws these particles against the bed and banks, sometimes at high velocity.

Question 7

How is a v shaped valley formed

Answer 7

A v shaped valley=upper course of river
River bed- more prone to vertical erosion
River eroded by abrasion, solution and hydraulic action
Sides become unstable due to weathering and undercutting- rocks slide into river=more erosion

Question 8

What is an interlocking spur?

Answer 8

Result of vertical erosion and fluvial erosion in the upper course, they are projections of land that alternate from either side of a valley formed as the river can’t laterally erode - has to go round hillsides (more resistant geology sticks out)

Question 9

How does a waterfall create a gorge

Answer 9

As a waterfall retreats upstream it leaves a steep sided valley downstream which is called a gorge. Every time the overhanging cap rock breaks off the gorge retreats and grows longer.

Question 10

What is a source of a river

Answer 10

The start (upper course)

Question 11

What is a tributary

Answer 11

A small stream that joins a larger river (upper course)

Question 12

What is a drainage basin

Answer 12

An area of land drained by a river and its tributaries

Question 13

What is a confluence

Answer 13

Where a tributary joins a large river

Question 14

What is a watershed

Answer 14

The edge of a river basin

Question 15

What is a mouth

Answer 15

The end of a river, usually where a river joins the sea

Question 16

Name the 4 process of transportation…

Answer 16

Traction, saltation, suspension and solution

Question 17

What is traction?

Answer 17

This is the transportation of the biggest particles, they are to heavy to lose contact with the bed. Some such as boulders roll along.

Question 18

What saltation?

Answer 18

Moves the small stones and grains of sand by bouncing them along the bed. The lighter load uses a hopping motion.

Question 19

What is suspension?

Answer 19

Carrying very fine materials within the water, so that it floats in the river and is moved as it flows.

Question 20

What is solution?

Answer 20

This is the dissolved load and occurs only with some types of rocks that are soluble in rainwater e.g.- chalk and limestone

Question 21

What is a meander and how is it formed

Answer 21

A curve or bend found in the middle and Lower course of a river.
Lateral erosion= abrasion and hydraulic action sideways
Outside bend= greatest erosion=river cliff- cliff collapse and retreats- enlarge bend (fastest flow)
Inside bend= least erosion= deposition- increase size over time (slowest flow)

Question 22

What is a oxbow lake

Answer 22

A curved horseshoe/ crescent like bend in a river in middle and lower courses.
Lateral erosion- greatest and fastest flow on outside bend and least and slowest flow on inside= deposition
Meander gets wider= loop
Loop gets wider = necks narrow
Neck/ends of loops join= cut off meander from main river

Question 23

What is a levee

Answer 23

An embankment built to prevent the overflow of a river, or naturally a ridge of sediment deposited alongside the river by overflowing water
LOWER COURSE

Question 24

What is a floodplain

Answer 24

An area of low lying ground adjacent to a river, formed mainly of river sediments and subject to flooding.
It’s soil is fertile due to these sediments being deposited

Question 25

What is an estuary?

Answer 25

The tidal part of a river where the channel broadens out as it reaches the sea

Question 26

What is a hydrograph

Answer 26

A graph showing how a rivers discharge changes in response to a precipitation event

Question 27

What is peak rainfall

Answer 27

The time of highest rainfall

Question 28

What is a rising limb

Answer 28

The increase in the amount of rainwater reaching the river. Water is reaching the river rapidly by surface run off

Question 29

What is lag time

Answer 29

The amount of time it takes for a river To flood after a period of heavy precipitation

Question 30

What is a falling limb

Answer 30

The water is still reaching the river but in decreasing amounts, reaches the river by through flow

Question 31

What is peak discharge

Answer 31

The maximum level of the river

Question 32

What is a v shaped valley

Answer 32

A steep v shaped valley found in the upper course of a river with a steep gradient and narrow valley floor.

Question 33

How does a long profile of a river change down stream

Answer 33

In the upper course there is a steep gradient, the water is shallow and the river has a large bed load, more roughness, turbulence and friction.
Further downstream, the rivers channel is much deeper due to the tributaries bringing additional water. Now less water is in contact with the bed and banks as it’s got a higher volume, the velocity increases, even though the gradient is less steep than in the mountains.

Question 34

Key characteristics of interlocking spurs

Answer 34

Steep gradient
Convex slopes
Project from alternate sides of the valley
Separated by narrow valley floor mostly taken up by the river channel.

Question 35

What’s a gorge and what are some key characteristics

Answer 35

A narrow valley with steep, rocky walls located between hills or mountains, in the upper course.
Located down stream of a waterfall
Turbulent fast flowing white water
Boulders litter the river bed

Question 36

Formation of a waterfall

Answer 36

The water flows over different bands of rock. It flows over the more resistant cap rock and a deep plunge pool is formed at the base of the waterfall. Splash back erodes the less resistant rock behind the waterfall. This creates an overhang which later collapses. This collapse causes the waterfall to retreat upstream.

Question 37

How are levees formed

Answer 37

When a river bursts its banks, friction with the land reduces velocity and causes deposition, sediment is deposited closest to the river. This builds up over time creating a natural flood defence.

Question 38

List some of the physical causes of flooding

Answer 38

Relief -The height and slope of the land- steep slopes increase surface run off
Low lying flat flood plains- there isn’t enough gradient to remove water
Impermeable soil/surfaces
Heavy rainfall
Temperature

Question 39

List some human causes of flooding

Answer 39

Urbanisation- impermeable surfaces
Deforestation- removing trees reduced the amount of water intercepted and increases run off
Climate change- higher temperatures- more rain is evaporating therefore more is being released
Rising population
Farming - soil is no longer there to absorb the excess water, poorly constructed plantation drainage systems

Question 40

List the hard engineering strategies used to decrease flooding

Answer 40

Dams and reservoirs- store and control the amount of water being released at a given point, water stored can be used for hydroelectric power and drinking.
Channel straightening-allows water to travel faster along the course.
Embankments- contains water in banks.
Flood relief channel- A back up channel, works like a by-pass. Closes off the river in times of high discharge and diverts it to the artificial one.

Question 41

List some soft engineering strategies used

Answer 41

Afforestation- planting trees near river- greater interception of rainwater and Lower river discharge.
Managed flooding- allowing river to flood naturally in places to prevent flooding In other areas- near settlements.
River restoration- a variety of ecological, physical, spacial and management measures to restore the natural state and functioning of the river system in support of biodiversity, recreation, flood management and landscape development.

Question 42

disadvantages of hard engineering strategies 
Dams and reservoirs 
Channel straightening
Embankments
Flood relief channel

Answer 42

Dams and reservoirs- expensive, rubbish can build up behind dam effecting certain species such as river dolphins
Channel straightening- flooding may happen downstream of the straightened channel as water is carried there faster, more erosion downstream.
Embankments- looks unnatural, expensive, soil and sediment placed can be washed away.
Flood relief channel- require large amounts of land, expensive

Question 43

Disadvantages of soft engineering strategies used

Answer 43

Afforestation- changed appearance, loss of potential grazing land& replacing open grass areas
Managed flooding- takes up and floods any potential agricultural areas, can’t control it, could flood crops near.
River restoration- expensive, not always effective as a practical strategy, lose agricultural land, could flood crops near rive.

Question 44

River features found in the upper course

Answer 44

Steep narrow V shaped valleys 
Interlocking spurs 
Rapids
Waterfalls 
Gorges

Question 45

River features found in the middle course of the river

Answer 45

Wider shallower valleys, meanders and ox bow lakes

Question 46

River features found in the lower course of river

Answer 46

Wide flat bottomed valleys
Flood plains
Deltas