The river from source to mouth

Over the period of the next few lessons you will understand how a river changes from source to mouth and include this information on the diagram.

Predict…

How do you think the river will change as it flows from source to mouth?

The upper course of a river

Aim: To understand what the upper course of a river is like

A River's Upper Course A River's Upper Course (Youth)(Youth)

Aim: To understand what the upper course of a river is like

Processes of river erosion

Hydraulic action

Attrition

Corrosion

Abrasion

Definitions

Hydraulic ActionThis process involves the force of water against the bed and banks.

Abrasion/CorrasionThis is the process by which the bed and banks are worn down by the river’s load. The river throws these particles against the bed and banks, sometimes at high velocity.

AttritionMaterial (the load) carried by the river bump into each other and so are smoothed and broken down into smaller particles.

CorrosionThis is the chemical action of river water. The acids in the water slowly dissolve the bed and the banks.

Do you know your processes of erosion?

Watch the video of the upper course of a river….

When complete you will be undertaking the following activities:

1. Describe the upper course of the river?

2. What makes the upper course of the river an ideal place for the source?

3. Complete paragraph and fill in missing gaps.

What are the main processes that operate in the upper course?What landforms occur in the upper course of a river?How are the landforms created?

Lea

rnin

g o

bje

ctiv

es

river disappears from view hidden by this spur of land

River Conwy

(near Mignant Moor)

Landforms in the upper course

V-shaped valleys and interlocking spurs

Rapids

Waterfalls

Why do V-shaped valleys occur?

Interlocking spursIn the upper course the river does not have a huge amount of energy to erode as it does not have a high discharge and it has to transport large pieces of sediment.

When the river meets areas of harder rock that are difficult to erode it winds around them. A series of hills form on either side of the river called spurs. As the river flows around these hills they become interlocked. So, a series of interlocking spurs are often found in the upper course of a river valley.

Techniques! – 1. Fieldsketching….

Produce an annotated fieldsketch to show that this is part of an upland river valley.

Waterfalls!

Seljalandsfoss, SW Iceland

Waterfall formation

Waterfalls

How does a waterfall form?

Rearrange the stages of formation into the correct order:

Draw and annotate a diagram to explain the formation of a waterfall. Suggested labels:

1. More resistant rock

2. Less resistant rock

3. Plunge Pool

4. Unsupported rock

5. Fallen rocks

6. Gorge

Your labels should contain detailed explanations!

Waterfalls

PLUNGE POOLUNDERCUTTING

OF SOFT ROCK

OVERHANG

WATERFALL RETREATS . .

UPSTREAM . .

21

River load in upper course

Why are they rounded?

22

River 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?

Finished questions?

Start your diagram completing the features for the upper course of the river.