Y10 Geography - River profiles + fluvial processes

What is a river profile?

How a river’s gradient, channel shape and processes change from source to mouth.

What is a long profile?

A side view showing how a river’s height changes from source to mouth.

Why does a river’s gradient generally decrease downstream?

Erosion cuts the bed upstream and deposition builds it up downstream, forming a graded profile.

What is a cross profile?

The shape of a river valley and channel when viewed across the river.

Describe the upper course valley and channel.

channel is small and shallow. (V shaped)

What type of erosion dominates the upper course?

Vertical erosion (downcutting), which deepens the valley.

Describe the middle course valley and channel.

channel becomes wider and deeper.

What happens to erosion in the middle course?

Vertical erosion decreases while lateral (sideways) erosion increases.

Describe the lower course valley and channel

Channel is widest and deepest

What is the dominant process in the lower course?

Deposition, as more sediment is dropped.

What are the three main fluvial processes?

Erosion, transportation and deposition.

What is erosion?

The wearing away of a river’s bed and banks.

What is hydraulic action?

The force of water hits the bed/banks. Air is compressed in cracks, breaking rock apart

What is abrasion (corrasion)?

Sediment carried by the river scrapes and grinds the bed and banks.

What is attrition?

Rocks collide during transport, becoming smaller, smoother and rounder.

What is solution (corrosion)?

Soluble rocks such as limestone or chalk dissolve in the water.

Name four factors that increase river erosion.

Steeper gradient, higher discharge, faster velocity and more/larger load.

What is transportation?

The movement of a river’s load downstream.

What is traction?

Large rocks and boulders roll along the river bed.

What is saltation?

Small pebbles bounce or hop along the river bed.

What is suspension?

Fine particles such as silt and clay are carried within the water.

What is solution as a transport process?

Dissolved minerals are carried within the water.

How does river load usually change downstream?

It becomes smaller, smoother and rounder, mainly due to attrition.

Why can rivers usually carry more material downstream?

Discharge generally increases downstream, allowing more load to be transported.

What is deposition?

The dropping of sediment when a river loses energy and cannot carry as much load.

Give five reasons why river energy may decrease.

Lower velocity, lower discharge, gentler gradient, entering still water, or increased friction.

Which material is deposited first?

The largest and heaviest material, because it needs the most energy to transport.

Which sediment can travel furthest downstream?

Fine sediment, because it requires less energy to remain transported.

Why is vertical erosion important in the upper course?

The steep gradient gives the river lots of energy to erode downwards.

Which erosion processes are important in the upper course?

Hydraulic action and abrasion.

How do river processes change in the middle course?

Vertical erosion decreases, lateral erosion increases, while transportation remains strong.

Why can deposition increase in the lower course?

The gentler gradient and greater friction can reduce river energy, encouraging deposition.

What is vertical erosion?

Erosion that cuts down into the river bed, deepening the valley.

What is lateral erosion?

Erosion that acts sideways, widening the river valley or channel.

What is discharge?

The volume of water passing a point per second, measured in m³/s.

What is velocity?

The speed at which river water flows