RiversChapter 7

Rivers………

Start on high,Flow down low,Creating featuresAs they flow!

River Terms

Three stages of a river

Youth Stage = Upper Course

Mature Stage = Middle Course

Old age Stage = Lower Course

Three stages of a river

The Work of Rivers

Stage Upper Course Middle Course Lower Course

Slope

Main processes

Valley shape

Main features

Stage Upper Course Middle Course Lower Course

Slope

Main processes

Valley shape

Main features

Processes of Erosion

How a river erodes

The Work of Rivers

Processes of erosion:

1. Hydraulic Action

The force of the moving water causes erosion of the river bed and the banks of the river. The greater the speed and amount of water the greater the force.

The Work of Rivers

Processes of erosion:

2. Abrasion

The rivers load is bounced and dragged along the river bed causing it to scrape and deepen the course of the river.

The Work of Rivers

Processes of erosion:

3. Attrition

The rivers load is constantly colliding in the moving river water causing the load to break down into smaller pieces.

The Work of Rivers

Processes of erosion:

4. Cavitation

As a river flows over the uneven river bed air bubbles travel up to the top of the river, pop and send ripples out towards the river banks. These ripples gently erode the rivers banks.

The Work of Rivers

Processes of erosion:

5. Solution

Chemicals in the rivers water and rocks along the river course change the river chemically which reacts with and erodes various rocks along the way.

Transport

How a river moves its load

Features

F.E.E.D

F: Feature (Name, erosion or deposition, stage it is found)

E: Explain with at least one or two processes explained

E: Three examples, one Irish

D: Clear 1/2/3 diagram/s to show how the feature is

formed.

Describing a feature

Youth Stage = Waterfalls

Mature Stage = Meanders and Oxbow Lakes

Old age Stage = Deltas

Three features we will study

Features of the Youth Stage

• V – Shaped Valleys• Interlocking Spurs • Waterfalls

A typical upper course V-Shaped valley with interlocking spurs, steep valley sides and active slope processes.

The diagram below shows the formation of interlocking spurs.

Interlocking spurs

1 2

3 4

Feature of ErosionName

Found

Processes involved

Waterfall

Youth Stage

Hydraulic ActionAbrasion

Waterfalls are features of erosion usually found in the upper course (youth stage) of a river.

They are found in areas where a river is flowing over bands of hard and soft rock. The

hard rock is slower to break down but the river can erode the soft rock much quicker. A

band of hard rock lies on an area of soft rock. The river erodes the soft rock by the

processes of hydraulic action (the force of the moving water) and abrasion (the scraping

of the rivers load against the banks and bed). This causes a small notch to be formed into

the soft rock which is eroded further into a drop over which the water falls. As the water

falls over the drop there is a greater rate of hydraulic action and the rivers load also scrapes

and deepens a hole in the bottom of the waterfall. This hole is called a Plunge Pool. The

hard rock is slowly eroded and hangs over the edge called a Overhang. This is eventually

worn down by the river and is carried away as the rivers load.

f

e

Waterfalls

Examples of waterfalls include:

1

2

3

Diagram of a waterfall being formed

e

d

Angel Falls, Venezeula

Victoria Falls, Zimbabwe

Torc Waterfall, Killarney, Kerry

Examples

1A2

1A5

Waterfall

foe/sor

(e) px2

Aoh/srsrw

neisr

rfovdpp@bow

ucipp

weu

Waterfall

foe/sor=Feature of erosion….stage of river

(e) px2=Erosion, Process are hydrualic action and abrasion

Aoh/sr srw=Areas of hard/soft rock, soft rock weaker

Neisr=Notch eroded in soft rockRfovd=

River falls over vertical drop

pp@bow=Plunge pool at base of waterfall

Ucipp=Undercut collapses into plunge pool

Weu=Waterfall erodes upstream

Can you put the labels below into the correct place on he diagram?

Feature of Erosion and Deposition

Name

Found

Processes involved

Meanders and Ox Bow Lakes

Mature and Old Age Stage

Erosion and Depositon

Ox Bow lake on Mississippi

F.E.E.D

F: Feature (Name, erosion or deposition, stage it is found)

E: Explain with at least one or two processes explained

E: Three examples, one Irish

D: Clear 1/2/3 diagram/s to show how the feature is

formed.

Describing a feature

1a2

1a5

F.E.E.D

F: Feature (Name, erosion or deposition, stage it is found)

E: Explain with at least one or two processes explained

E: Three examples, one Irish

D: Clear 1/2/3 diagram/s to show how the feature is

formed.

Describing a feature

Deltas

Pg 37

Examples of deltas include:The River Nile, EgyptThe Mississippi River in Louisiana, USAThe River Shannon in Limerick, Ireland

Humans and Rivers

New Orleans, Louisiana, USA29th August 2005

New Orleans Video

Read Page 38-39

1. Name the river and the city of this case study?2. The city is between two physical areas…what are

they?3. How is the city protected from flooding?4. What did the President do to the amount of money

available for protection of the land?5. When did the disaster strike?6. What was the name of the hurricane?7. How many poor people could not leave the area?8. How many people drowned in this disaster?

HEP: Hydro Electric Power

Electricity made by the power of moving water