🟥 SECTION 6: THE OLD-AGE STAGE

What are the main characteristics of the old-age stage?

The old-age stage is characterised by:

• A very flat landscape.

• A broad and shallow river.

• Slow-flowing water.

• Wide floodplains.

• Meanders.

• Deposition.

• Oxbow lakes.

• Islands.

• Deltas.

Main idea: Deposition becomes particularly important in the lower course.

Why is the landscape generally flat in the old-age stage?

The river flows through a region with a relatively gentle gradient.

The surrounding landscape is flatter than the mountainous terrain associated with the youth stage

Why is the river broad and shallow in the old-age stage?

The river flows over a gentler gradient, and its channel and valley have widened over time.

The old-age stage is associated with a broad and shallow river and a wide floodplain.

What is an oxbow lake?

An oxbow lake is a curved body of water formed when a bend in a meandering river becomes cut off from the main river channel.

It is associated with the old-age stage.

How does an oxbow lake form?

1. A meander develops in a river.

2. Erosion along the outer banks causes the bend to become more pronounced.

3. The neck of the meander becomes narrower.

4. During high flow or flooding, the river may cut through the narrow neck.

5. Deposition can seal off the ends of the former bend.

6. The isolated bend remains as an oxbow lake.

Memory tip: Meander → narrow neck → river cuts through → ends seal off → oxbow lake.

What is a river island?

A river island is an area of land surrounded by water within a river or its channels.

Islands can form where sediment accumulates within the river system.

What is a delta?

delta is a landform created when a river deposits sediment near its mouth, often producing a branching network of channels.

Deltas are associated with the old-age stage in the Geography material.

How does a delta form?

1. A river transports sediment downstream.

2. The river enters a larger body of water.

3. The river loses energy and deposits sediment.

4. The deposited material accumulates.

5. The river may divide into smaller channels.

6. Continued deposition builds up the delta.

Why is deposition important near a river's mouth?

As the river enters a larger body of water, it may lose energy and deposit sediment.

Over time, this sediment can accumulate and contribute to the formation of a delta.

What is the difference between an oxbow lake and a delta?

Oxbow lake: A curved body of water separated from the main river after a meander is cut off.

Delta: A landform built from sediment deposited near a river's mouth.

Both are associated with the old-age stage, but they form through different processes.

river flows slowly across a flat landscape and has wide floodplains and oxbow lakes. Which stage is it in?

The old-age stage.

Slow-flowing water, wide floodplains, meanders and oxbow lakes are characteristic features of this stage.

What is the difference between the upper and lower courses of a river?

Upper course	Lower course
Steep gradient	Gentle gradient
Fast-flowing water	Slow-flowing water
Vertical erosion	Deposition is particularly important
V-shaped valley	Wide floodplain
Waterfalls and rapids	Oxbow lakes and deltas

The upper and lower courses differ in their gradient, valley shape, dominant processes and landforms.