🟪 SECTION 5: THE MATURE STAGE

What are the main characteristics of the mature stage?

The mature stage is characterised by:

• A U-shaped valley or a valley with a wide floor.

• A relatively narrow floodplain.

• Gentle slopes.

• Horizontal erosion.

• Meanders.

• Generally slower-flowing water than in the youth stage.

Main idea: The river widens its valley.

What is a meander?

A meander is a bend or curve in a river channel.

Meanders become prominent in the mature and old-age stages.

How do meanders develop?

Differences in the speed of flowing water and erosion along the channel cause the river to develop bends.

The faster-flowing water generally erodes the outer bank, while slower-flowing water allows more sediment to be deposited along the inner bank.

Over time, the bends become more pronounced.

What happens on the outer bank of a meander?

Water generally flows faster along the outer bank and causes greater erosion.

The bank may become steeper as material is removed.

What happens on the inner bank of a meander?

Water generally flows more slowly along the inner bank, allowing sediment to be deposited.

This creates an area of accumulated material.

What is a floodplain?

A floodplain is a generally flat area of land next to a river or stream. It stretches from the riverbanks to the outer edges of the valley.

Floodplains can be covered by water when a river floods.

What is the difference between a river channel and a floodplain?

River channel: The section of the landscape through which the river normally flows.

Floodplain: The generally flat land beside the river that may become covered by water during flooding.

What is a narrow floodplain?

A narrow floodplain is a relatively limited area of flat land beside a river.

It is associated with the mature stage in the Geography material.

What is the difference between vertical erosion and horizontal erosion?

Vertical erosion cuts downwards into the riverbed, deepening the channel.

Horizontal erosion wears away the riverbanks, widening the channel and valley.

Memory tip:

• Vertical = downwards.

• Horizontal = sideways.

A river has gentle slopes, meanders and a relatively narrow floodplain. Which stage is it in?

The mature stage.

These features are characteristic of the middle course.