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AS Geography (mine) > Hydrological Systems > Flashcards

Hydrological Systems Flashcards

(99 cards)

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0
Q

Define Abrasion (corrasion) (erosion)

A

The rubbing or scouring of the bed and banks by the sedimentary material carried along by the river

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1
Q

Define Hydraulic action (erosion)

A

The movement of sediment by the frictional drag of moving water

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2
Q

Define Attrition (erosion)

A

Reduction in size of sediment particles as they collide with each other, the bed and banks

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3
Q

Define Corrosion (erosion)

A

Rocks dissolve in water and are carried away

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4
Q

Define Traction (transportation)

A

Large rocks and material that are too heavy to be picked up by the current. They can roll or slide along the river bed

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5
Q

Define Solution (transportation)

A

Rivers run through an area of carbonate rocks. Weak acids may act on more soluble rocks and gradually remove material in solution. This dissolves the material

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6
Q

Define Saltation (transportation)

A

Material ranging from pebbles to sand may be temporarily lifted and bounced along the floor in a hopping motion

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7
Q

Define Suspension (transportation)

A

This usually comprises of very small particles from fine clays and muds to sand. The particles are carried along by the water. This usually forms the bulk of sediment transported by rivers. More turbulent rivers can carry more suspended load

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8
Q

Why does deposition occur?

A
  • there’s shallow water
  • river enters a lake/sea
  • doesn’t have the capacity or energy to carry it’s load
  • reduction in gradient
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9
Q

What’s the long profile?

A

Balance between erosion, transportation and deposition changes throughout the course of the river

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10
Q

Why is the long profile concave?

A

Source is in the high mountains and river wants to get to sea level by vertical and lateral erosion

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11
Q

Define River competence

A

The maximum size of load it can carry

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12
Q

Define River capacity

A

The maximum volume of load it can carry

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13
Q

What is the Hjulstrom curve?

A

The relationship between velocity and competence

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14
Q

What influences erosion, transportation and deposition?

A

Energy of a river

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15
Q

3 things which contribute to a rivers energy

A
  1. Mass of water
  2. Height above sea level
  3. Gradient of the river
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16
Q

What influences a rivers energy?

A
  1. Altitude (potential energy)
  2. Steepness/gradient (kinetic energy)
  3. Gravity
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17
Q

What is Velocity?

A

The Speed and direction in which a body of water flows

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18
Q

Factors which influence velocity

A 
Channel roughness
Channel shape (hydraulic radius)
Channel slope (gradient)
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19
Q

What is hydraulic radius?

A

The ratio of the cross-sectional area of the channel and the length of it’s wetted perimeter

=cross-sectional area / wetted perimeter

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20
Q

Factors which effect the shape of a v-shaped valley

A
  1. Climate
  2. Geology
  3. Vegetation
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21
Q

What is a waterfall?

A

A sudden fall of water that occurs where there are rapid changes nk gradient in the rivers course

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22
Q

What’s a pool? (Meanders)

A

A dip in the river bed

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23
Q

What is a riffle? (Meanders)

A

A mound of sediment/ an area of deposited sediment

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24
What are braided rivers?
They have multiple channels and islands of sediment inbetween the channels
25
What causes braiding?
Fluctuation in discharge levels, low river velocity and by the river losing capacity and competence
26
What are levees?
Natural raised embankments made up of sand and mud deposits built up along either side of the flood plain of a river
27
What is a floodplain?
The area that would naturally be affected by flooding if a river rises above it's banks
28
What is a delta?
Low-lying plain or landform that occurs at the mouth of a river near the ocean
29
What is rejuvenation?
An increase in the energy of a river cause by either a fall in it's base level (sea level) or an uplift of the land
30
Define Isostatic change
(Ice melting) | Changes in uplift of land relative to the sea level as a result of crustal movements
31
Define Eustatic change
(Water freezing) | Change in relative height of the land and the sea may also result from a rise/fall in sea level
32
What is a knick point?
A sudden break in the gradient along the long profile of a river. They can be shown by waterfalls
33
What is a river terrace?
A remnant of a former floodplain which has been left at a higher level after rejuvenation
34
What is an incised meander?
Rivers have cut deeply into the landscape (Grand Canyon)
35
What is Flood frequency?
How often a flood occurs
36
What is Flood recurrence?
How often a flood of a certain magnitude occurs
37
How do you calculate flood recurrence?
T=n+1 | M
38
What is flooding?
A river exceeds bankfall level
39
Natural causes of flooding
- vegetation - drainage density - soil depth - slope - rock type
40
Human causes of flooding
- ploughing - impermeable areas of Tarmac - dams - sewers - grazing animals
41
What is hard engineering?
Building artificial structures such as dams, aimed at controlling natural processes
42
What is soft engineering?
Works with the natural processes of the river. A sustainable approach to managing the river without using artificial structures
43
Define Dams and reservoirs
Large concrete constructions whose purpose is to hold back the flood waters and release them gradually
44
Define Straightening channels
The process of removing meanders from rivers
45
Define Levees and embankments
Often made of earth, these constructions increase the height of the river banks
46
Define Diversion spillways/relief channels
Artificial channels that branch off the main channel often used to bypass Urban areas
47
Define Dredging
The process by which river channels are made deeper by digging into the bed
48
Define Permeable surfaces
This includes the use of grass, gravel and porous bricks
49
Define Flood walls
Brick or concrete constructions that are found on river banks or in front of properties and businesses
50
Define Basins and ponds
Man made areas created for storing water. The former are only filled with water during the high discharges and the latter are always full
51
Define Flood forecasting and warning
Close monitoring of weather and river responses allows the environment agency to prepare local residents and businesses
52
Define Floodplain zoning and land use management
Area are categorised according to the level of risk abs human activities are controlled as a result
53
Define Naturalisation of channels
Meanders are reintroduced to straighten channels
54
Define Wetland and river conservation
Encouraging ponds and marshes to be left untouched and encourage the natural state of the river and it's surroundings
55
Define Swales
These are long shallow channels that allow water to infiltrate gradually. They are usually found either side of roads and have vegetation
56
Define Filter strips
These are gently sloping areas of vegetation (usually wild grass). Often found at the side of roads
57
What is a Source?
Start of the river
58
Define Drainage basin
An area of land drained by a river and it's tributaries
59
What is the Mouth?
End of the river and meets sea/lake
60
Define Tributary
A smaller river that joins a main river
61
Define Confluence
Where two or more rivers meet
62
Define Watershed
A ridge of high ground that forms the boundary between two drainage basins
63
Define Precipitation
All forms of moisture which reaches the earths surface
64
Define Evaporation
The transformation of water droplets into water vapour by heating
65
Define Transpiration
The loss of water from a drainage basin into the atmosphere from the leaves of plants
66
Define Channel storage
The water in a river
67
Define Surface storage
Total volume of water held on the earths surface in lakes, ponds and puddles
68
Define Groundwater storage
The storage of water underground in permeable rock strata
69
Define Interception storage
The total volume of water held on the surface of vegetation
70
Define Through fall
The water dripping off the leaves
71
Define Stem flow
Where precipitation flows through stems of plants to the ground
72
Define Secondary interception
The movement of rain water from big plants to smaller plants
73
Define Groundwater flow/base flow
The deeper movement of water through underlying rock strata (horizontal)
74
Define Through flow
The movement of water downslope within the soil layer
75
Define Water table
All water the ground can hold before it starts to flood (saturation)
76
Define Percolation
The gravity flow if water In the soil
77
Define Infiltration
The downward movement of water into the soil from the surface
78
Define Surface runoff (overland flow)
The movement of water over the surface of the land, usually when the ground is saturated or frozen or when precipitation is too intense for infiltration
79
Define Capillary action
The upward movement if water in soil
80
Define Channel flow
The movement of water in the river channel
81
Define Antecedent precipitation
Already existing precipitation that can cause additional saturation
82
Define Zone of saturation
Ground below water table the fractures in soil and rocks are saturated with water
83
Define Infiltration capacity
Maximum rate at which soil in a given condition will absorb water
84
Define Water balance
Balance between inputs and outputs of moisture in the soil
85
Define Lag time
Difference between peak rainfall and peak discharge
86
Define Soil moisture deficit
When most of the water in the soil has been used up
87
Define Soil moisture recharge
When the water in the soil is being replenished
88
Define Soil moisture drawdown
When the stores of water in the soil are being used and their levels are lowering
89
Define Soil moisture excess
This is when the soil stores are full (overflowing)
90
Define Peak discharge
The most discharge which you occur during the storm
91
Define Peak rainfall
The highest record level of rain in that day (mm)
92
Define Falling/recession limb
Discharge is steadily going down
93
Define Base flow
Water that reaches the channel largely through slow through flow and form permeable rock below the water table
94
Define Rising limb
Rapid rise in discharge
95
Define Discharge
The volume of water passing by a given point every second
96
Define Antecedent flow rate
Discharge before the storm event
97
Where and when was the flood in Scotland?
River Tay | Mud January 1993
98
What does the flood in Scotland tell us?
That we cannot trust historic events to predict when floods will occur

AS Geography (mine) (4 decks)

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