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River features?River features?

Are facial features the same thing for rivers?

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River FeaturesRiver FeaturesRivers 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.

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River StructureRiver Structure

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Upper valley characteristicsUpper valley characteristics

“V”shape valley, mostly vertical erosion

Interlocking spurs

Narrow, shallow channel, low velocity and discharge

Large rocks that come from upstream and from valley sides

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Interlocking spurs, Interlocking spurs, Robinson, Lake DistrictRobinson, Lake District

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

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River load in upper courseRiver load in upper course

Why are they rounded?

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River load in upper courseRiver load in upper course

Boulders are large and semi-rounded, due to attrition within the load and abrasion with the stream bed and banks

Why are they rounded?

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Waterfall formationWaterfall formationLook at the diagram, How is a waterfall formed?

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Waterfall and Gorge 1

(OBLIQUE AERIAL VIEW)EROSION

TYPE: Vertical and Headward

Upper Course: Waterfalls & Upper Course: Waterfalls & GorgesGorges

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High Force waterfall, R. TeesHigh Force waterfall, R. Tees

Plunge pool

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

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Potholes

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.

EROSION TYPE: Vertical

(by EDDY CURRENTS)

Upper Course: PotholesUpper Course: Potholes

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Potholes, human scale!!Potholes, human scale!!

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Middle course, R. TeesMiddle course, R. TeesMiddle course, R. TeesMiddle course, R. TeesHOW DOES THIS DIFFER FROM THE UPPER SECTION?HOW DOES THIS DIFFER FROM THE UPPER SECTION?

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Middle course, R. TeesMiddle course, R. Tees

Valley opens out, more gentle slopes, wider valley bottom

First signs of meanders

River channel wider, deeper, greater velocity and discharge

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Meandering RiversMeandering Rivers

WHAT IS A MEANDER?

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

Meanders 1

(Aerial View)

Middle Course: MeandersMiddle Course: Meanders

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.

Middle Course: Meanders Middle Course: Meanders 22

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Meander, R. Lavant, Meander, R. Lavant, ChichesterChichester

Floodplain

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

River Cliff Slip-Off Slope

WHICH WAY IS THIS MEANDER MOVING?WHICH WAY IS THIS MEANDER MOVING?

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River Cliff

Slip-off slope

}Meander loop

WHERE IS EROSION TAKING PLACE?WHERE IS EROSION TAKING PLACE?

WHERE IS DEPOSTION TAKING PLACE?WHERE IS DEPOSTION TAKING PLACE?

A

B

C

D

E

F

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What happens to the river when What happens to the river when it moves to the middle courseit moves to the middle courseGradient becomes less steepRiver continues to erode vertically a bit but more LATERAL erosion now occurs in MEANDERSThe meanders MIGRATE. What do you think that means?Name three effects it have on the valley.

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Lower Course: Severn ValleyLower Course: Severn Valley

HOW DOES IT DIFFER FROM THE MIDDLE COURSE?

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Lower Severn ValleyLower Severn Valley

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

Very gentle valley side gradients

Very wide floodplain

Ox-Bow Lake 1

(Aerial View)

EROSION TYPE: Lateral

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.

Lower Course: Ox-bow Lower Course: Ox-bow lakelake

Ox-Bow Lake 2 (Aerial View)

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

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Ox Bow lake on MississippiOx Bow lake on Mississippi

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The Nile Delta from spaceThe Nile Delta from space

River NileRiver Nile

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Estuary FormationEstuary FormationHOW DOES THIS DIFFER FROM A DELTA?HOW DOES THIS DIFFER FROM A DELTA?

RAISED VALLEY SIDESRAISED VALLEY SIDES

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