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Geography - Rivers > The Long Profile and Channel Characteristics > Flashcards

The Long Profile and Channel Characteristics Flashcards

1
Q

What is base level?

A

The lowest point that the river can erode to

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2
Q

Total erosion and deposition along the full course of a river are balanced, why may there still be an uneven profile?

A

Rates of erosion and deposition change along the course, results in formations like waterfalls

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3
Q

What are the 3 stages of a river?

A

Upper course
Middle course
Lower course

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4
Q

Characteristics of the upper course

A

Gradient is steep
River is high above sea level
Lots of potential energy

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5
Q

Characteristics of the middle course

A

Gradient decreases
Potential energy is converted into kinetic energy
River gains velocity

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6
Q

Characteristics of the lower course

A

River has little potential energy
Lots of kinetic energy
Flows faster - greater velocity

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7
Q

What do channel characteristics affect?

A

Velocity and discharge

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8
Q

Do velocity and discharge, increase or decrease downstream?

A

Increase

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9
Q

Why does discharge increase downstream?

A

Tributaries join the river and there is more surface runoff

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10
Q

Why does velocity increase downstream?

A

It’s influenced by gradient, discharge and channel characteristics

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11
Q

What is kinetic energy used for?

A

To overcome friction and causes erosion

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12
Q

How does the energy a river has effect efficiency?

A

More energy a river has for erosion and transportation, more efficient it is

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13
Q

What does an efficient river have?

A

High velocity
High discharge
Little friction

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14
Q

How is efficiency measured?

A

By hydraulic radius

Larger hydraulic radius, more efficient river

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15
Q

How do you calculate the hydraulic radius?

A

Wetted perimeter

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16
Q

What channels are more efficient?

A

Smooth, narrow and deep channels - have larger hydraulic radius’

Larger hydraulic radius means a smaller proportion of water in contact with wetted perimeter, friction is lower, less energy loss, increased velocity and discharge

17
Q

What channels are less efficient?

A

Shallow and broader ones

18
Q

How does channel roughness effect efficiency?

A

Protruding banks and large, angular boulders increase wetted perimeter which causes more friction.

Reduces efficiency, velocity and discharge

19
Q

Where is channel roughness greatest?

A

Upper course

20
Q

Why does channel roughness increasing mean that turbulent flow increases?

A

Turbulent flow is more effective at picking up particles from the river bed than smooth flow - causes greater erosion.

21
Q

What does a long profile show?

A

The river’s gradient from its source to the sea

How the gradient of the river channel changes from the rivers source to its mouth by showing the height of the river bed

22
Q

What is erosion like in the upper course?

A

Manly vertical, by abrasion and a bit of hydraulic action

Occurs in high energy conditions

Rough channel, cause turbulence, large bed load is dragged along river, intense downward erosion

23
Q

What is transportation like in the upper course?

A

Mainly large particles (boulders) carried by traction or saltation during high energy conditions

24
Q

What is deposition like in the upper course?

A

Little deposition, mainly largest particles deposited in the river bed as energy levels drop

25
Q

What is erosion like in the middle course?

A

Mainly lateral and by abrasion

Sediment size decreases at this state through attrition of the larger particles

26
Q

What is transportation like in the middle course?

A

More material carried by suspension as particle size decreases

Some larger particles moved by saltation

27
Q

What is deposition like in the middle course?

A

Sand and gravel are deposited across the flood plain as the river floods and friction reduces

28
Q

What is erosion like in the lower course?

A

Although discharge and velocity are high, erosion is less as turbulence is lower and sediment size is reduced

Some lateral erosion occurs during formation of meanders

29
Q

What is transportation like in the lower course?

A

Mainly smaller particles (silt and clay) carried by suspension, or substances carried by solution

30
Q

What is deposition like in the lower course?

A

Smaller particles (silt, clay and sand) are deposited on the flood plain when floods and in river mouth as sea absorbs rivers energy

31
Q

What does a cross profile show?

A

Shows what a cross section of the river channel or valley looks like

32
Q

What are the characteristics of the upper course in terms of its cross profile?

A

Valleys are steep v shapes

Vertical erosion creates narrow valley floors and steeply sloped sides

33
Q

What are the characteristics of the middle course in terms of its cross profile?

A

Valleys are wider caused by lateral erosion

Deposition creates a floodplain on valley floor

34
Q

What are the characteristics of the lower course in terms of its cross profile?

A

Valley is wide with gently sloping sides

Much wider floodplain caused by deposition

Geography - Rivers (9 decks)

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