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AS Geography > Rivers 1- The Drainage Basin > Flashcards

Rivers 1- The Drainage Basin Flashcards

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1
Q

Drainage basin

A

Catchment area of land drained by a river and its distributaries, bordered by a ridge of high land called the watershed

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2
Q

Hydrological cycle

A

Inputs: precipitation
Transfers: surface flow, channel flow, stemflow, interception, infiltration, throughflow, percolation, groundwater flow
Outputs: evaporation, transpiration, runoff

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3
Q

Water balance

A

The balance between inputs and outputs, together with the changes in storage
P = Q + E + DS

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4
Q

Soil moisture budget

A
  1. Soil moisture surplus
  2. Soil moisture use
  3. Soil moisture deficiency
  4. Soil moisture recharge
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5
Q

Uses of water budget graphs

A

Help people to manage river basins

Plan for irrigation or floods

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6
Q

Factors that affect water flow

A

Vegetation & land use, rainfall, gradient, climate, soil type, bedrock, conditions, size & shape of basin

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7
Q

River discharge

A

The amount of water in a river passing a given point at a given time
Area x velocity (cumecs)

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8
Q

Lag time of a hydrograph

A

The time delay between peak rainfall and peak discharge

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9
Q

Causes of a ‘flashy’ flood

A

High intensity/antecedent rainfall, impermeable rock, lack of vegetation, urbanisation (drainage), high density tributaries, steep slopes, circular basin, frozen/baked ground

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10
Q

Long profile

A

Shows the changes in altitude along its course from source to mouth
Theoretically smoothly concave in shape

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11
Q

Upper course

A

Vertical erosion, steep gradient, V-shaped valley, relatively narrow channel

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12
Q

Middle course

A

More gentle gradient, lateral erosion, U-shaped valley, relatively wide channel

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13
Q

Lower course

A

Very gentle gradient, deposition, gentle slopes (if any), very wide channel

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14
Q

Types of erosion

A

Hydraulic action
Abrasion
Solution
Attrition

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15
Q

Hydraulic action

A

Evorsion: the direct force of the water
Cavitation: the process of bubbles imploding in cracks, evicting tiny jets of water (130m/sec)

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16
Q

Abrasion

A

The wearing away of the bank and bed by the load (corrasion)

17
Q

Solution

A

The removal of chemical ions in the rock (corrosion)

18
Q

Attrition

A

The wearing away of the load carried by the river

19
Q

Types of transportation

A

Traction
Saltation
Suspension
Solution

20
Q

Types of load

A

Endogenic- eroded material form the bed and bank

Exogenic- material from the valley sides that has arrived by weathering and mass movement

21
Q

Traction

A

The load rolls and bounces along the riverbed

22
Q

Saltation

A

Smaller particles or stones bounce along the riverbed

23
Q

Suspension

A

Finer particles are carried within the flow of the river

24
Q

Solution

A

Chemical ions carried in solution, dissolved in the river

25
Q

The Hjulström curve

A

Shows the relationship between the velocity of a river and the size of particles that can be eroded, transported or deposited (logarithmic)

26
Q

Capacity

A

The amount of material that can be transported

27
Q

Competence

A

The size of the largest particle that can be transported

28
Q

Trends in the Hjulström curve

A

As velocity increases, the river’s ability to erode and transport particles increases
Exceptions: fine clay and silt particles are cohesive and offer less resistance, so require a greater velocity to be entrained

29
Q

Reasons for deposition

A

A sudden reduction in gradient, decrease in discharge, entering a lake or sea, increase in load, shallow water, entering a floodplain

30
Q

Erosion velocity

A

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

31
Q

Fall velocity

A

The rate of fall at which a river drops particles

32
Q

Wetted perimeter

A

Total length of the river bed and banks in cross section that are in contact with the water in the channel (linked to channel roughness)

33
Q

Hydraulic radius

A

The ratio of the channel’s cross sectional area compared to its wetted perimeter

34
Q

Bradshaw’s Model

A

A geographical model that describes how a river’s characteristics vary between the upper course and lower course of a river

35
Q

Characteristics that increase downstream

A

Discharge, occupied channel width, channel depth and average load quantity

36
Q

Characteristics that decrease downstream

A

Load particle size, channel bed roughness and gradient

AS Geography (12 decks)

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