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1
Q

Upper course

A

Gradient: Steep gradient
Velocity: Low velocity
Features: Water falls, gorges and rapids
Channel: Narrow and shallow channel

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2
Q

Middle course

A

Gradient : More gentle gradient
Velocity : Faster velocity
Features : Meanders, Ox bow lakes, floodplains
Channel : Wider and deeper channel

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3
Q

Lower course

A

Gradient : Flat gradient
Velocity : Fastest velocity
Features : Floodplains , deltas, estuaries
Channel : Widest and deepest channel

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4
Q

Long profile

A

The gradient of the river from source to mouth

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5
Q

Cross profile

A

The side to side cross section of a river channel or valley

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6
Q

Lateral erosion

A

Sideways erosion on the outside of a meander bend

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7
Q

Vertical erosion

A

Downward erosion of a river bed

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8
Q

Abrasion

A

Rocks carried by the river wear down the river bed and banks

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9
Q

Attrition

A

Rocks smash together and break into smaller pieces

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10
Q

Hydraulic Action

A

Force of the river causes air to be trapped in cracks and weakens the bank

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11
Q

Solution ( Types of erosion )

A

Alkaline rocks such as limestone are dissolved by slightly acidic water

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12
Q

Saltation

A

Particles bouncing down the river bed

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13
Q

Solution ( Types of transportation )

A

Soluble particles are dissolved into the river

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14
Q

Suspension

A

Fine solid material held in the water while it is moving

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15
Q

Traction

A

Rolling of boulders and pebbles along the river bed

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16
Q

Gorge

A

The narrow steep-sided valley formed as waterfall retreats

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17
Q

Potholes

A

A circular or cylindrical hold in the riverbed

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18
Q

Waterfall

A

Sudden descent of a river over a vertical or step slope in its bed

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19
Q

Rapids

A

Area of shallow, fast-flowing water in a stream.

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20
Q

Meander

A

Pronounced ( Khúc cua ) bend in a river

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21
Q

Ox bow lake

A

Arc shaped lake cut off a meander

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22
Q

Deltas

A

A fast, low lying deposit of sediment, found at a river’s mouth.

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23
Q

Levees

A

Embankments of sediment along a river

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24
Q

Floodplain

A

The flat area forming the valley floor on either side of a river channel

25
Waterfalls formation
- alternating layers of soft and hard rocks - soft rocks erode more quickly than the hard rock - due to hydraulic action - plunge pool form due to the collapse of soft rocks - then no support for the hard rock - the hard rocks started to collapse - repeats overtime - water retreats to form a gorge
26
How are potholes formed?
1. abrasion and hydraulic action creates a hole in the river bed 2. holes get bigger so pebbles/rocks may fall inside 3. abrasion makes the hole deeper 4. hydraulic action creates a swirling motion making the holes deeper and cylindrical
27
Meanders features
- Inside bend = slow current - more friction = more deposition - outside of the bend = quicker current less friction - hydraulic action ( erosion ) take place - river cliffs form due to more energy - overtime meanders move across the land
28
Oxbow lakes formation
- Two outside bends move towards each other - the necks cut through - new routes are formed - deposition cuts off the old bend during a flood event then oxbow lakes are formed
29
Gorge Characteristics ( upper course )
- Very narrow valley - Steep, high valley sides - Downstream of a waterfall
30
Gorge Formation
- Soft rock erodes quicker than hard rock - The hard rock/overhang collapses - The waterfall retreats, creating a steep-sided gorge.
31
Lower course land forms
...
32
how are floodplain forms?
- They are created of migrating meanders which latterly erode this is why the floodplain is very wide - when there are floods they deposit layers of silt to form alluvium - this built up over time which is why floodplains are very flat
33
how are leaves formed?
During low flow conditions deposits occurs water flow over the channel and onto the floodplain during a flood deposition of sediment ( rocks, materials etc...) sediments occurs on the river banks - ( bờ sông) built-up after many floods ( the height of the banks can be raised to 2m tall)
34
how are deltas form?
the river meets sea = Deposition occurs at the mouth sediments are deposited = new land will be formed in the middle of the main channel then the river splits into distributaries and flows around the new land more deposition due to low velocity layers of sediment build the delta out to the sea vegetation can begin to grow, trapping more sediment => raising the delta above sea level.
35
middle course landforms
...
36
Upper course landforms
37
Drainage Basins system and processes
Nah
38
sources
is the start of a river
39
Drainage Basin
the area is drained by a river - (khu vực được thoát nước bởi một con sông)
40
tributary
where smaller streams join a larger river
41
confluence
The point at which two rivers meet
42
watershed
the boundary of the drainage basin
43
mouth
where rivers meet the sea
44
watershed
the boundary of the drainage basin
45
Case Study: The River Ganges, Bangladesh, LEDC- (2007)
...
46
What were the causes of the flood? ( Bangladesh)
...
47
physical Factors (1)
Snow Melt from glaciers of the Himalayas,
48
(2)
Low lying country – 80% lies on floodplains of the Ganges
49
(3)
Bangladesh and Meghna rivers, the average height of land 6m...Monsoon climate with 80% annual rainfall falling
50
Humans factors
Rapidly increasing population (162m), building on floodplains = impermeable surfaces.
51
(3)
Deforestation in Nepal in the upper course of the Ganges,
52
What were the impacts/hazards of the flood?
...
53
social
- 11,000km of roads were damaged, blocking communication routes - 1,100 deaths, 10.5 million were made homeless. - 100,000 people caught water-borne diseases like cholera due to flood water - 44 schools were destroyed, 4,444 closed - 20% of factories closed, losing jobs and income.
54
economics
- Rice crops were devastated twice in 2007, causing $290m of damage farmers did not have time to recover their losses and replant 47% of the population rely on farming for their jobs but were unemployed as 2.2m acres of cropland was flooded
55
What are the opportunities of living in a delta/floodplain / near a river? (Why do people live there?)
- The flat floodplains of the delta are very fertile. Rice and Jute are grown as the two main crops - 47% of the population are employed in agriculture (farming and fishing) - They help meet the demand for water – Particularly for irrigation of crops - The rivers naturally improve water quality by naturally filtering out excess sediment and nutrients
56
Environment
75% of the country under water
57
How was the river managed?
- Increased efforts to reduce deforestation in Nepal and the Himalayas - 2500 stilted shelters, raised above 2m, were built for people, crops and animals. - Flood warning systems installed in villages through speakers
58
part (2)
- Flood action plan – A $100m system of 7,500km huge embankments and levees were built along the river, reinforced by concrete. - 3200 drainage canals cleared to allow floodwater to drain away more efficiently. - 55 flood monitoring stations were installed to give locals 72 hours notice of impending

PCT1 revision (12 decks)

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