River Environments - River and Landforms

Question 1

Define stores

Answer 1

features such as lakes and rivers which receive, hold and release water

Question 2

Define groundwater

Answer 2

water contained in the soil or underlying rocks, derived mainly from percolation

Question 3

Define transfers

Answer 3

the movement of water between stores in the hydrological cycle

Question 4

Define evapotranspiration

Answer 4

The loss of moisture from the ground through the direct evaporation of water from the soil as well as transpiration from plants

Question 5

Infiltration and percolation

Answer 5

the transfer of water downwards through soil and rock and into an aquifer/groundwater store

Question 6

Throughflow

Answer 6

takes place between the ground surface and the groundwater store; water moves slowly through the soil until it reaches a water body due to gravity

Question 7

Groundwater flow

Answer 7

happens in rock in aquifers and is the underground transfer of water to rivers, lakes, sea, etc

Question 8

Why is the hydrological cycle a closed system?

Answer 8

because it contains a fixed amount of water, as no water enters or leaves the atmosphere

Question 9

why is a drainage basin an open system

Answer 9

because it has external inputs and outputs, with the amount of water in the basin system varying over time

Question 10

inputs of a drainage basin

Answer 10

energy from the sun
precipitation from moisture picked up outside the basin
water from tributary drainage basins

Question 11

outputs of a drainage basin

Answer 11

the river’s discharge
water in the basin which enters the atmosphere through evaporation/transpiration

Question 12

define discharge

Answer 12

the quantity of water flowing in a river channel in a particular location and time

Question 13

watershed

Answer 13

the boundary between neighbouring drainage basins

Question 14

estuary

Answer 14

the mouth of a river as it enters the sea

Question 15

channel network

Answer 15

the system of surface and underground channels that collect and transport the precipitation falling on the drainage basin

Question 16

factors influencing drainage density of a river basin

Answer 16

size, shape, rock type, soil type, relief, land use, vegetation

Question 17

define river regime

Answer 17

the seasonal variations in the discharge of a river

Question 18

what is a hydrograph

Answer 18

a graph showing the discharge of a river over a given period of time

Question 19

unit for discharge

Answer 19

cumecs (cubic metres per second)

Question 20

define lag time

Answer 20

the delay between peak rainfall and peak discharge

Question 21

storm hydrograph

Answer 21

records the changing discharge of a river after a rainstorm

Question 22

define base flow

Answer 22

the usual discharge of a river

Question 23

define storm flow

Answer 23

the additional discharge of a river as a result of a rainstorm

Question 24

6 factors affecting river regimes and storm hydrographs

Answer 24

• amount and intensity of rain
• temperature affecting the form of precipitation and may affect throughflow and run off
• steep vs gentle slopes
• vegetation and land use (plants intercept and delay rain from reaching the ground whereas bare soil and concrete speed up run off and reduces lag time)
• human intervention (dams and reservoirs can hold back discharge, decreasing the risk of flooding downstream)

Question 25

5 processes which play a part in shaping landforms (3 of them are river processes)

Answer 25

• erosion
• transport
• deposition
• weathering
• mass movement

Question 26

explain physical weathering

Answer 26

this breaks rock down into smaller pieces; it is done by changes in temperature and rainfall freezing and thawing in rock cracks

Question 27

explain chemical weathering

Answer 27

this causes rocks to decay and disintegrate; largely done by slightly acidic rain seeping into porous rocks

Question 28

explain biological weathering

Answer 28

the roots of plants growing into cracks in rocks gradually split the rock apart

Question 29

two forms of mass movement

Answer 29

• slumping
• soil creep

Question 30

explain slumping

Answer 30

this occurs when the bottom of a valley side slope is cut away by the river, making the slope unstable and causing weathered material to slump down towards the river
this is also helped when weathered material on the slope is saturated with rain, which makes it heavier and acts as a lubricant

Question 31

explain soil creep

Answer 31

where weathered material moves slowly down the slope under the influence of gravity, collecting at the base and being eroded by the river

Question 32

4 methods of erosion

Answer 32

hydraulic action
abrasion
corrosion/solution
attrition

Question 33

explain hydraulic action

Answer 33

water hits the river bed with enough force that the material is dislodged and carried away

Question 34

explain abrasion

Answer 34

material carried by a river is rubbed against the sides and floor of the channel, widening and deepening the channel

Question 35

explain corrosion

Answer 35

minerals in the rocks of the river channel are dissolved by the water flowing past them

Question 36

explain attrition

Answer 36

particles being carried by the river become rounder and smaller as they collide with each other

Question 37

4 methods of transport

Answer 37

traction
saltation
suspension
solution

Question 38

explain traction

Answer 38

when large rocks or boulders are rolled along the river bed

Question 39

explain saltation

Answer 39

when small boulders are bounced along the river bed

Question 40

explain suspension

Answer 40

where lighter material is carried by the river flow

Question 41

explain solution

Answer 41

where material is transported as it is dissolved in the water

Question 42

what is deposition

Answer 42

the laying down of material transported by the river; it occurs when there is a decrease in energy, speed and discharge
it is most likely to happen at the mouth of a river or where there is a decrease in the gradient of the river channel

Question 43

long profile

Answer 43

the section through a river or glacier course, from its source to its mouth

Question 44

things which increase as you go downstream in the long profile

Answer 44

discharge
occupied channel width
channel depth
average velocity
load quantity

Question 45

things which decrease as you go downstream in the river profile

Answer 45

load particle size
channel bed roughness
slope angle (gradient)

Question 46

describe the upper course of the river

Answer 46

long profile is steep
river flows fast
most of the river’s energy is spent on vertical erosion
hydraulic action and abrasion erode the river bed and make the valley deeper
mass movement down slopes of valley due to its steepness and depth
valley floor is narrow and usually completely occupied by river

Question 47

describe the lower course of a river

Answer 47

river channel and valley become wider, deeper and smoother
river velocity and discharge continue to increase
valley cross-section is wider and flatter
valley floor is occupied by flood plain

Question 48

formation of interlocking spurs

Answer 48

streams in the upper course are not strong enough to erode into interlocking hills, so they have to flow around them instead

Question 49

upper course landforms

Answer 49

interlocking spurs
steep V-shaped valleys
waterfalls
gorges

Question 50

formation of waterfalls

Answer 50

1. they occur where a band of hard rock meets a band of soft rock
2. the softer rock is readily eroded by the force of the water as it fall over the hard cap rock
3. plunge pool is excavated at the bottom of the falls by the falling water
4. softer rock under hard rock is eroded by hydraulic action and abrasion, undercutting the hard rock
5. the hard rock overhangs until it cannot carry its own weight
6. overhang collapses and breaks up in the river below, causing the gorge to retreat
7. gorge is prevented from widening by the hard cap rock

Question 51

lowland landforms

Answer 51

levees
deltas
meanders
flood plains
ox-bow lakes

Question 52

formation of levees

Answer 52

sediment is deposited on the flood plain when the river leaves its channel, as the velocity decreases when the river returns to its channel, causing the most sediment to be deposited on the river banks

Question 53

formation of meanders

Answer 53

the river flows faster on the outside of bends and faster on the inside of them, causing lateral erosion on the outside of the bends and deposition on the inside of them

Question 54

formation of ox-bow lakes

Answer 54

eventually the neck of a meander is eroded so much that the river flows straight again, cutting off the meander from the rest of the river as deposition during flooding seals the ends of the meander. This cut off meander is known as an ox-bow lake

Question 55

deltas

Answer 55

these are vast areas of alluvium at the mouths of rivers, which are deposited sediment carried by the river as it flows into the sea, decreasing its velocity
the load is dropped faster than tides can wash it away, blocking the river flow, so the river splits up into smaller channels known as distributaries, which deposit sediment over a wide area to create new land where there was once sea