Rivers 1- The Drainage Basin

Question 1

Drainage basin

Answer 1

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

Question 2

Hydrological cycle

Answer 2

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

Question 3

Water balance

Answer 3

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

Question 4

Soil moisture budget

Answer 4

1. Soil moisture surplus
2. Soil moisture use
3. Soil moisture deficiency
4. Soil moisture recharge

Question 5

Uses of water budget graphs

Answer 5

Help people to manage river basins

Plan for irrigation or floods

Question 6

Factors that affect water flow

Answer 6

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

Question 7

River discharge

Answer 7

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

Question 8

Lag time of a hydrograph

Answer 8

The time delay between peak rainfall and peak discharge

Question 9

Causes of a ‘flashy’ flood

Answer 9

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

Question 10

Long profile

Answer 10

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

Question 11

Upper course

Answer 11

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

Question 12

Middle course

Answer 12

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

Question 13

Lower course

Answer 13

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

Question 14

Types of erosion

Answer 14

Hydraulic action
Abrasion
Solution
Attrition

Question 15

Hydraulic action

Answer 15

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

Question 16

Abrasion

Answer 16

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

Question 17

Solution

Answer 17

The removal of chemical ions in the rock (corrosion)

Question 18

Attrition

Answer 18

The wearing away of the load carried by the river

Question 19

Types of transportation

Answer 19

Traction
Saltation
Suspension
Solution

Question 20

Types of load

Answer 20

Endogenic- eroded material form the bed and bank

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

Question 21

Traction

Answer 21

The load rolls and bounces along the riverbed

Question 22

Saltation

Answer 22

Smaller particles or stones bounce along the riverbed

Question 23

Suspension

Answer 23

Finer particles are carried within the flow of the river

Question 24

Solution

Answer 24

Chemical ions carried in solution, dissolved in the river

Question 25

The Hjulström curve

Answer 25

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

Question 26

Capacity

Answer 26

The amount of material that can be transported

Question 27

Competence

Answer 27

The size of the largest particle that can be transported

Question 28

Trends in the Hjulström curve

Answer 28

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

Question 29

Reasons for deposition

Answer 29

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

Question 30

Erosion velocity

Answer 30

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

Question 31

Fall velocity

Answer 31

The rate of fall at which a river drops particles

Question 32

Wetted perimeter

Answer 32

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)

Question 33

Hydraulic radius

Answer 33

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

Question 34

Bradshaw's Model

Answer 34

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

Question 35

Characteristics that increase downstream

Answer 35

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

Question 36

Characteristics that decrease downstream

Answer 36

Load particle size, channel bed roughness and gradient