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AS Geography (physical) > Rivers and Flood Management- Book 1 Key Terms > Flashcards

Rivers and Flood Management- Book 1 Key Terms Flashcards

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1
Q

Define drainage basin?

A

The catchment area, from which a river system gets its water

‘The area of land drained by a river and its tributaries’

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2
Q

Define the watershed

A

The point which separates drainage basins, generally following a high ridge of land, any rain falling within the watershed will flow into the drainage basin

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3
Q

Define an open system

A

A system consisting of inputs, outputs of energy and stores and transfers of water

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4
Q

Define the hydrological cycle

A

The cycle where water evaporates into the air then falls again as precipitation

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5
Q

Define an input

A

The input of water often via precipitation

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6
Q

Define an output

A

The process of water leaving the drainage basin

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7
Q

Define evapotranspiration

A

The joint process of evaporation and transpiration

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8
Q

Define precipitation

A

All ways in which moisture can leave the atmosphere, most commonly rain but it can also be snow, hail, dew and frost

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9
Q

Define interception

A

When precipitation is prevented from reaching the soil, either by plants or man made structures. It creates a significant store of water in wooded areas but is only a temporary store as collected water evaporates quickly

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10
Q

Define vegetation storage

A

All water contained in plants at any one time

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11
Q

What are surface stores of water

A

They include puddles, ponds and lakes

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12
Q

What is groundwater storage

A

Water stored either in the soil or rocks

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13
Q

What is the water table?

A

The top surface of the zone of saturation- zone of soil and rock were all the pores in the soil and rock are full of water.

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14
Q

What are aquifers?

A

Porous rocks that hold water within them

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15
Q

What is channel storage?

A

The water held within the river or stream channel

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16
Q

Define surface runoff (overland flow)

A

water flowing over the land either over the whole surface or through little channels, it’s common in arid areas where torrential rain falls on hard baked land

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17
Q

Define through fall

A

Water dripping from one part of a plant to another

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18
Q

Define stemflow

A

Water running down a plant stream or tree trunk

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19
Q

Define throughflow

A

Water moving slowly downhill through the soil, its faster through ‘pipes’ such as cracks in the soil, or animal burrows

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20
Q

Define infiltration

A

Water soaking into the soil, influenced by soil type, soil structure, and the level of water already in the soil, in a heavy storm where water can’t infiltrate into the soil fast enough, then it flows over the surface

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21
Q

Define percolation

A

Water seeping down into the water table

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22
Q

Define groundwater flow

A

Slow flowing water below the water table through permeable rock. Water flows slowly through most rocks, but rocks are highly permeable with lots of joints can have ground water flow e.g. Limestone

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23
Q

Define baseflow

A

Groundwater flow that feeds into rivers through river banks and beds

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24
Q

Define interflow

A

Water flowing downhill through permeable rock above the water table

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25
Q

Define channel flow

A

Water flowing in the stream itself (also called discharge)

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26
Q

Define evaporation

A

Water turning into water vapour- from a liquid to gas

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27
Q

Define transpiration

A

Evaporation from plant leaves- plants and trees take up water through their roots and transport it to their leaves wheee it evaporates into the atmosphere

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28
Q

Define river discharge

A

Also called river flow is another output

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29
Q

Define the water balance of a drainage basin

A

The balance between inputs and outputs together with changes in ground storages

30
Q

Define a water surplus

A

The ground stores fill with water so there’s more surface runoff and higher discharge so river levels rise

31
Q

Define ground water deficit

A

Ground water stores are depleted due to outputs being higher than inputs

32
Q

Define ground water recharge

A

Refilling of ground water stores

33
Q

Define river discharge

A

The amount of water in a river passing a given point at a given time, it’s measured in cumecs

34
Q

Define the rising limb of a storm hydrograph

A

The increasing discharge of a river in response to water entering a river channel

35
Q

Define peak discharge

A

The highest discharge a river reaches in a time of flood

36
Q

Define the falling or receding limb of a storm hydrograph

A

When river discharge falls due to there being a less input going into the river

37
Q

Define the baseflow of a river

A

The starting or finishing level of the river before and after a storm

38
Q

Define the lag time for a drainage basin

A

The time delay between peak rainfall amount and the peak discharge

39
Q

Define the river’s regime

A

The pattern of seasonal variation in the flow of a river, usually over a years period

40
Q

Define the long profile of a river

A

It shows the changes in altitude along its course from the source to the mouth

41
Q

Define hydraulic action

A

The force of air and water on the sides of rivers and in cracks

42
Q

Define evorsion

A

The direct force of the water. Most effectiv in turbulent flow

43
Q

Define cavitation

A

This is a process in which bubbles form in flowing water, these bubbles can implode next to it within cracks in the bank. They the. Evict tiny jets of water that can move up to 130m/sec. This can damage solid rock

44
Q

Define abrasion

A

The wearing away of the bed bank by the load of the river. The effectiveness of this is determined by the type of load and type of bedrock and its rate increase as velocity does

45
Q

Define solution

A

The removal of chemical ions in the rock, especially calcium. Key factors being the rate of erosion, geology of the bedrock, solute concentration of the water, discharge and velocity

46
Q

Define attrition

A

The wearing away of the load of a river, it is commonly done by pebbles and rocks banging into each other and so knocking off any sharp corners as well as hitting the river bed

47
Q

Define endogenic material

A

Material eroded from the bed and banks

48
Q

Define exogenic material

A

Material that has arrived into the river channel by mass movement and weathering of the valley sides

49
Q

Define traction

A

Where heavy load rolls and bounces along the river bed, in times of normal flow this is often sand but in times of flood it can be rocks and boulders

50
Q

Define saltation

A

Where smaller particles or stones bounce along the river bed, as each stone lands it dislodges more, which are then moved along in the flowing water

51
Q

Define suspension

A

Where finer particles are carried within the river without touching the beds and banks- this is the largest contribution to the rivers load

52
Q

Define solution

A

When a river runs through a carbonate rock area, weak acids may act in these rocks and dissolve materials into solution

53
Q

Define river capacity

A

The largest amount of material can be transported

54
Q

Define competence

A

The size of the largest particle that can be transported

55
Q

What is the Hjulström curve?

A

The relationship between the velocity of a river and the size of particles that can be eroded, transported and deposited

56
Q

Define erosion velocity

A

The rate of flow at which the river is able to pick up particles of load

57
Q

Define fall velocity

A

The rate of fall at which a river drops particles of load as they become too heavy to transport

58
Q

Define deposition

A

It occurs when the river has reduced energy and it is no longer competent, nor has the capacity, to transport its entire load. When velocity and discharge decrease

59
Q

Define a riffle

A

A shallow or rocky area of a stream where the water flows brokenly

60
Q

Define flocculation

A

Where clay or silt particles coagulate due to electrical charges and sink more rapidly creating mudflats in river estuaries

61
Q

Define mass movement

A

Movement of surface material caused by gravity. Landslides and rockfalls are examples of very sudden movements of this type, geological agents such as water, wind and ice all work with gravity to cause a leveling of the land

62
Q

Define bedload

A

The material lying on the bed of the channel, this is only transported when river levels are high

63
Q

Define dissolved load

A

This consists of soluble materials carried as chemical ions, so there are no measurable particles

64
Q

Define total sediment load

A

The total load of sediment in the river channel, this tends to increase downstream

65
Q

Define the valley cross profile

A

The view of the valley from one side to another. E.g. In the upper course this is the typical V-shape

66
Q

Define the gravitational potential energy of a river

A

The energy it has due to its height above sea level

67
Q

Define the kinetic energy of a river

A

The moving energy of water

68
Q

Define the dynamic equilibrium of a river’s graded profile

A

Where the slope, width and other channel characteristics have adjusted to the volume of water and load carried by a river under prevailing conditions, here all factors are in balance

69
Q

Define channel roughness

A

The amount of friction a river experiences as it moves downstream

70
Q

Define Cross-sectional area

A

The width of a channel multiplied by the average depth of a river

71
Q

Define velocity

A

Usually measured in metres per second

AS Geography (physical) (19 decks)

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