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Geography > Rivers > Flashcards

Rivers Flashcards

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1
Q

Tributaries

A

Smaller rivers that join main river

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2
Q

Confluence

A

Point at which rivers meet

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3
Q

Drainage basin

A

Land drained by a river system

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4
Q

Watershed

A

Boundary of the drainage basin, usually made up of highland

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5
Q

Discharge

A

Amount of water passing a specific point at a given time and is measured in cabin meters per scene (dependent on river’s velocity and volume)

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6
Q

Volume

A

Amount of water in the river

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7
Q

Velocity

A

Speed of the river

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8
Q

River channel

A

The area in which a river flows

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9
Q

Describe the changes in a river valley from source to mouth

A

upper course: main process is vertical erosion, is steep sided, narrow, v shaped, lined with boulders, large wetted perimeter, low velocity, low discharge
middle and lower course: sides are less steep, gradient decreases, shape changes from a V to a U, wider, faster velocity, higher discharge (dominant process in middle course is lateral erosion, this increases rate of erosion by hydraulic action and abrasion and dominant process in lower course is deposition)

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10
Q

V-shaped valley

A

river has the power to erode downwards as it is way above the sea. valley sides are steep due to soil and loose rock being washed downhill following heavy rainfall.

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11
Q

Discharge

A

Depends on river’s velocity and volume in the channel. Velocity depends on friction (wetted perimeter) and volume depends on the amount of water reaching the channel either though tributaries or groundwater flow

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12
Q

Why narrow and shallow channel in upper course?

A

As discharge is low, power of erosion is reduced

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13
Q

Why steep gradient in upper course?

A

Harder geology= more resistant to erosion

Dominant process is vertical erosion with means it cuts into rock which leads to a steeper profile

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14
Q

Why does discharge increase downstream?

A

Velocity increases due to reduced friction as a result of reduced wetted perimeter (smoother channel)

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15
Q

Hydraulic action

A

Pressure of water pushing against bank and bed of the river. Includes air compressing into cracks which means more pressure-> rock breaks

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16
Q

Corrosion (solution)

A

Acids in river dissolve rocks

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17
Q

Abrasion

A

Particles (load) carried by river and thrown against banks with force, they wear the bed and banks down

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18
Q

Attrition

A

Rocks in the upper course roll around and knock each other until smooth pebbles or sand are formed

19
Q

How does mass movement impact river landscapes

A

mass movement causes river banks to be washed into the river. Soil creep creates a rippled effect/ causes soil to slowly slide into the river. Slumping, due to saturation of banks, leads to the rotational movement of river banks. Impacts: loss of land, damage to property, damage to river defences, flooding and river blockage

20
Q

How is a V shaped valley formed

A

Upper course river is small, water mostly contacts the bed and banks -> lots of friction, river flows slowly. Most energy used to overcome friction. Rest of energy used to erode downwards (vertical erosion) -> v shaped valley. As river winds its way down between berries of more resistant rock, interlocking spurs are formed

21
Q

Transportation

A

Traction, saltation, suspension and solution

22
Q

Traction

A

Rolling Stones along the bed

23
Q

Saltation

A

Small particles bounce along bed in a leapfrog motion

24
Q

Suspension

A

Silt and clay sized load are thrown through the water flow

25
Q

Solution

A

Minerals dissolve in water

26
Q

Deposition

A

When a river lacks the energy to carry its load; it begins with the heaviest particles, it happens when there is less water or where the current slows down. Large boulders are deposited at the top and very small particles are deposited at the end -> sorting

27
Q

Waterfalls

A

They occur because the river flows over hard rocks which erodes slowly. Beneath is softer rock which is eroded faster to form a ‘step’. Force of water erodes the bottom of the waterfall to form a plunge pool. Hard rock gets undercut as the soft rock erode so that it eventually collapses.

28
Q

Meanders and OxBow lakes

A

In the middle course of river there is more energy and a high volume of water. Gradient here is gentle. As river erodes laterally, to the right side then left, it forms large bends, and the horse shoe like loops called meanders. This formation is due to both deposition and erosion. They gradually migrate downstream. The force of the water erodes and undercuts the river banks on the outside of the bend as there is more friction. Overtime the horseshoe becomes tighter until the ends become very close together. As the river breaks through, e.g during a flood, the river has more energy and the ends join, the loop is cut off from the main channel and this is called an ox bow lake

29
Q

Deltas

A

Deltas occur where a river that carries a large amount of sediment meets a lake or the sea. This meeting causes the river to lose energy and drop sediment it’s carrying. Deltas form where river mouths become choked with sediment, causing the main river channel to split into hundreds of smaller channels or distributaries.

30
Q

Levées

A

When a river floods, the coarsest material is deposited first, on the edges of the river, forming a natural embankment called a levée. Deposition happens due to increase in friction when river comes into contact with the bed meaning that energy is lost

31
Q

Flood plain

A

Area of alluvial deposits found beside the river in its lower course. As meanders move slowly downstream they erode away the valley to create a wide valley floor, they deposit layers of alluvial material on the slip off slope, building up into a large flood plain

32
Q

Flooding and prevention

A

Flooding occurs when a river gets more water than its channel can hold. Can be prevented by building houses on stilts, being prepared, evacuation ready, government awareness, education, building dams or embankments

33
Q

Case study: what are the human and physical causes of river flooding?

A

Physical: impermeable rocks (prevent filtration and encourage surface run off), snow melt, steepness of land
Human: deforestation (stops interception), urbanisation (more impermeable rocks so more surface run off)

34
Q

Case study: the benefits and threats of living near a river

A

The Ganges (Bangladesh):
Benefits: fertile soil for farming, job opportunities, shrimp farming, trading, economic growth, nice landscapes, minerals from soil, tourism, resources
Threats: risk of flooding, Bangladesh is low lying and an LEDC so flooding is terrible, could lose housing, could lose crops, poor communications

35
Q

Human causes of flooding

A
  • Nepal has a land clearance of 1.7% a year leading to more discharge
  • global warming
  • urbanisation
  • deforestation
  • inadequate drainage facilities
  • construction of settlements in flood plains
  • bad design of drainage channels
36
Q

Natural causes of flooding

A
  • snow melt
  • tectonic activity
  • low lying
  • monsoons
  • impermeable rocks
  • geology
  • land type
37
Q

Effects of the 1998 flood

A
  • over 50% of land was flooded
  • over 1000 people killed
  • 7 million homes destroyed
  • shortage of food and water
  • diseases spread like cholera
  • rice farms destroyed
  • half a million cattle lost
  • cost the country nearly $1 billion
  • loss of jobs
  • economic decline
38
Q

Case study: Flood management in Bangladesh

A 
Short term:
-boats to rescue 
-fodder for livestock
-camps and shelters
-repair and rebuild 
-aid from other countries
Long term:
-reduce deforestation 
-build large dams
-build flood shelters
-build embankments
-educate and have flood warning systems
39
Q

Case study: Cause of flood in Tewkesbury

A
  • Vulnerable for flooding due to its location with two big rivers (Severn and Avon)
  • Low pressure system located over Calais slowly moved Northwest bringing warm air. When this air met the cold air to the North, created a storm
  • no flood defences
40
Q

Case study: Effects of flood in Tewkesbury

A
  • people died
  • infrastructure destroyed
  • jobs and businesses effected
  • economy declined
  • insurance claims
  • a lot were made homeless
41
Q

How are the effects of flooding reduced?

A
  • flood proof buildings (stilts)
  • embankments, dams
  • forecasting
  • education from government
42
Q

Hard engineering

A

Method of river flood management which involves major construction work

43
Q

Soft engineering

A

Method of river flood management which attempts to work with natural river processes

44
Q

Main case studies

A
  • Opportunities on rivers (Ganges Delta)
  • Threats to coastlines (Ganges- flooding)
  • Management on coastlines (Bangladesh)

Geography (4 decks)

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