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River features?. Are facial features the same thing for rivers?. River Features. Rivers are eroding, transporting and depositing constantly. The river can be divided into 3 sections – Upper Course at the Source, Middle Course and Lower Course at the Mouth of the river.

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River features
River features?

Are facial features the same thing for rivers?


River features1
River Features

  • Rivers are eroding, transporting and depositing constantly.

  • The river can be divided into 3 sections – Upper Course at the Source, Middle Course and Lower Course at the Mouth of the river.

  • The river displays different characteristics at each section.



Upper valley characteristics
Upper valley characteristics

“V”shape valley, mostly vertical erosion

Narrow, shallow channel, low velocity and discharge

Interlocking spurs

Large rocksthat come from upstream and from valley sides


Interlocking spurs robinson lake district
Interlocking spurs, Robinson, Lake District

An upper course valley often has interlocking spurs, and steep valley sides


River load in upper course
River load in upper course

Why are they rounded?


River load in upper course1
River load in upper course

Why are they rounded?

Boulders are large and semi-rounded, due to attritionwithin the loadand abrasion with the stream bed and banks


Waterfall formation
Waterfall formation

Look at the diagram, How is a waterfall formed?


Upper course waterfalls gorges
Upper Course: Waterfalls & Gorges

Waterfall and Gorge 1

(OBLIQUE AERIAL VIEW)

EROSION TYPE: Vertical and Headward


High force waterfall r tees
High Force waterfall, R. Tees

Waterfall creates gorge as it recedes upstream by eroding the base and neck

Plunge pool


Upper course potholes
Upper Course: Potholes

Potholes

EROSION TYPE: Vertical

(by EDDY CURRENTS)

Boulders broken off by erosion that sit on the river bed create swirling eddy currents as the water flows past as the river is not strong enough yet to move the boulders by TRACTION. These eddies swirl the boulder round and erode a pothole in the river bed by ABRASION.



Middle course r tees
Middle course, R. Tees

HOW DOES THIS DIFFER FROM THE UPPER SECTION?


Middle course r tees1
Middle course, R. Tees

Valley opens out, more gentle slopes, wider valley bottom

First signs of meanders

River channel wider, deeper, greater velocity and discharge


Meandering rivers
Meandering Rivers

WHAT IS A MEANDER?


Middle course meanders
Middle Course: Meanders

Meanders 1

(Aerial View)

Meanders are formed because the current swings to the outside of a bend and concentrates the erosion there. Deposition occurs on the inside of the bed where there is not enough energy to carry load.

EROSION TYPE: Lateral


Middle course meanders 2
Middle Course: Meanders 2

Meanders 2

(Profile View / Cross Section X - Y)

EROSION TYPE: Lateral

This cross section clearly shows the eddy current (near ’X’) formed by the velocity of the river being concentrated on the outside of the bend. These UNDERCUT the bank causing the formation of a RIVER CLIFF. On the inside (NEAR ‘Y’), a SLIP-OFF-SLOPE is formed where current is too slow to carry any load.


Meander r lavant chichester
Meander, R. Lavant, Chichester

WHICH WAY IS THIS MEANDER MOVING?

Floodplain

Slip-Off Slope

River Cliff

Pebble deposits on the inner meander bend where there is low energy


WHERE IS EROSION TAKING PLACE?

River Cliff

F

A

E

B

Slip-off slope

}

Meander loop

C

D

WHERE IS DEPOSTION TAKING PLACE?


What happens to the river when it moves to the middle course
What happens to the river when it moves to the middle course

  • Gradient becomes less steep

  • River continues to erode vertically a bit but more LATERAL erosion now occurs in MEANDERS

  • The meanders MIGRATE. What do you think that means?

  • Name three effects it have on the valley.


Lower course severn valley
Lower Course: Severn Valley

HOW DOES IT DIFFER FROM THE MIDDLE COURSE?


Lower severn valley
Lower Severn Valley

Very wide floodplain

Well developed meanders with bars in the channel indicating high sediment load

Very gentle valley side gradients


Lower course ox bow lake
Lower Course: Ox-bow lake

Ox-Bow Lake 1

(Aerial View)

Ox-bow lakes are formed when two meander RIVER CLIFFS are being eroded towards each other. These will eventually meet, causing the river to then flow across the bottom of the diagram.

EROSION TYPE: Lateral


Lower course ox bow lake 2
Lower Course: Ox-bow lake 2

Ox-Bow Lake 2(Aerial View)




Estuary formation
Estuary Formation

HOW DOES THIS DIFFER FROM A DELTA?

RAISED VALLEY SIDES


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