Water on land

Question 1

4 main processes of erosion?

Answer 1

hydraulic action, abrasion, attrition, solution

Question 2

Hydraulic action?

Answer 2

the force of the water hitting the river bed and eroding it

Question 3

Abrasion?

Answer 3

rocks are thrown at the river side knocking bits off, weakening it and eroding the river bed

Question 4

Attrition?

Answer 4

rocks smash against each other breaking into smaller bits

their edges get more rounded as this happens

Question 5

Solution?

Answer 5

certain rock types will be dissolved by the water

e.g. chalk and limestone

Question 6

whats the difference between vertical and lateral erosion?

Answer 6

Vertical erosion deepens the river valley and channel, making it V-shaped - dominant in upper course
Lateral erosion widens the river valley and channel - dominant in middle and lower course

Question 7

4 main processes of transportation?

Answer 7

traction, saltation, suspension, solution

Question 8

Traction?

Answer 8

large rocks are rolled along the river bed by the force of the water

Question 9

Saltation?

Answer 9

smaller stones bounce along the river bed by the force of the water

Question 10

Suspension?

Answer 10

very fine material suspended in the water and carried along

Question 11

Solution?

Answer 11

dissolved load; certain rock types dissolve in the water and are carried along

Question 12

what are the main factors affecting the discharge of a river?

Answer 12

amount and type of rainfall
temperature and weather conditions
rock type and relief
land use

Question 13

what are the physical factors leading to a river flooding?

Answer 13

prolonged rainfall, heavy rain, snowmelt or relief

Question 14

what are the human factors leading to a river flooding?

Answer 14

deforestation and building construction

Question 15

some hard engineering strategies to help with river flooding?

Answer 15

dams, reservoirs, river straightening, flood walls

Question 16

some soft engineering strategies to help with river flooding?

Answer 16

flood warnings, flood plain zoning, afforestation

Question 17

what is a drainage basin?

Answer 17

An area of land drained by a river and its tributaries

Question 18

when does deposition occur?

Answer 18

deposition occurs when a river slows down (looses velocity)

Question 19

what is the discharge of a river?

Answer 19

the volume of water flowing in a river

measured in cumecs

Question 20

what do hydrographs show?

what do storm hydrographs show?

Answer 20

river discharge (and rainfall) - how the discharge at a certain point changes over time
show the changes in the rivers discharge at the time of a storm

Question 21

what is lag time?

why does it occur?

Answer 21

the delay between peak rainfall and peak discharge

because most rainwater doesn’t land directly in the river channel, theres a delay as rainwater gets to the channel

Question 22

what is the rising limb showing on a hydrograph?

Answer 22

the increase in the river discharge as rainwater flows into a river

Question 23

what are hard engineering strategies?

Answer 23

man made structures built to control the flow of rivers and reduce flooding

Question 24

what are soft engineering strategies?

Answer 24

schemes set up using knowledge of a river and its processes to reduce the effects of flooding (without changing the river itself)

Question 25

characteristic of valley and channel in the upper course of a river?

Answer 25

source, steep gradient, steep sides, V-shaped valley, narrow and shallow channel
waterfalls and gorges

Question 26

characteristic of valley and channel in the middle course of a river?

Answer 26

medium gradient, gentle sloping sides, wider and deeper channel
meanders and oxbow lakes

Question 27

characteristic of valley and channel in the lower course of a river?

Answer 27

gentle gradinet, flat and wide valley floor, very wide and deep channel
meanders and floodplains and levees

Question 28

why do rivers slow down and deposit material?

Answer 28

the volume of water in the river falls
the water is shallower
the amount of eroded material in the water increases
the river reaches the mouth

Question 29

what is the falling limb showing on a hydrograph?

Answer 29

the decrease in the river discharge as the river returns to its normal level

Question 30

What is a watershed

Answer 30

The high point which separates one drainage basin from another

Question 31

Confluence

Answer 31

Where 2 rivers join

Question 32

Tributary

Answer 32

A small stream which joins the main river

Question 33

What is a meander?

Answer 33

A bend in the river

Question 34

What is meant by:
Water deficit?
Water surplus?
Water stress?

Answer 34

Where there isn’t enough water
Where there is more than enough water
Where the demand for water exceeds the available amount

Question 35

how is a meander formed?

Answer 35

when water hits softer rock a curve begins to form; The current is faster on the outside of the bend because the channel is deeper, more lateral erosion takes place on the outside bends forming river cliffs. the current is slower on the inside bends because the river is shallower, material is deposited on the inside of the bend forming slip off slopes.

Question 36

what is a floodplain?

Answer 36

an area of flat land located on either side of a river in the middle and lower course

Question 37

what is a levee?

Answer 37

raised natural river banks

Question 38

how is a V-shpaped valley formed?

interlocking spurs?

Answer 38

as the river moves through the upper course, the river erodes downwards (vertical erosion). as the river cuts down, the steep sides are attacked by weathering. the weakened rock eventually breaks off and the river carries it away. The end result is a steep sided (V-shaped) valley
as the river erodes in the upper course it winds to avoid bits of harder rock, this creates the interlocking spurs (which look a bit like interlocking zips)

Question 39

how is a waterfall formed?

gorge of recession?

Answer 39

1. the river flows downstream and meets a band of harder resistant rock, lying over softer rock.
2. the river erodes the soft rock away more rapidly, leaving a steep drop (waterfall)
3. a plunge pool is created at the base of the waterfall
4. splashback occurs and this leads to the harder rock being undercut
5. the harder rock is left as an overhang which eventually can no longer hold its own weight and so falls
6. the waterfall retreats upstream and a gorge of recession is formed (with very steep sides)

Question 40

how is an oxbow lake formed?

Answer 40

meanders get larger over time, they can eventually turn into an ox-bow lake…

1. erosion causes the outer bends to get closer until theres only a small bit of land between the bends
2. the river breaks through this land, usually during a flood and the rivers flows along the shortest course
3. deposition eventually cuts the meander off forming the ox-bow lake

Question 41

how are floodplains formed?

Answer 41

Formed by both erosion and deposition
During flooding, the river spills onto surrounding land, sediment is picked up and deposited on the banks of the river, building up the floodplain.
The plain is shaped as meanders move across the floodplain making it wider - deposition on the inside bend also building up the floodplain.

Question 42

how are levees formed?

Answer 42

when a river bursts its banks large material is deposited on the banks next to the river and creates these natural embankments. The finer material is able to travel further and is later deposited as alluvium ( fertile soil).