Search Geography Rivers 11-14 Key Stage 3

Stages in a river - youth

A river which rises in mountain or upland areas is formed by a number of small streams joining to form a fast flowing watercourse with an irregular gradient. As more small tributaries join the main stream, the river forms a narrow but steep sided valley with a cross section in the shape of a V. This valley cuts both downwards and towards the head of the river.

In this youthful stage of the river, such features as small lakes, waterfalls, rapids and interlocking spurs are frequently found. All these will be described on later pages.

Youthful Features

A 'young' river.

Stages in a river - maturity

As the gradient of the river becomes less steep, erosion takes place outwards as well as downwards. The outward erosion broadens the river valley, and bends or meanders cut away at the spurs truncating them. Sediments collect on the floor of the valley which becomes less jagged. Unlike the youthful stage, the mature valley has few large boulders but is still an upland river. Tributaries in this stage are usually small and fast flowing.

Mature Features

A 'mature' river.

Stages in a river - old age 1

In this stage of the river valley there are several quite noticeable differences from the other two. It is no longer a distinct, narrow valley within hills and crosses a flat plain, known as the flood plain. The actual valley of the river is no longer just its course but the whole of this flood plain across which it meanders. This is normally the most fertile part of the valley although it is sometimes liable to damaging floods. Features common to this stage are large meanders, oxbow lakes and the landforms associated with estuaries.

A river valley with a flood plain.

Stages in a river - old age 2

The estuary is the place where the river meets the sea. This is the final part of the third (old age) stage in a river valley. The sediment carried (transported) by the flow of the river is usually either dispersed by tides or deposited as sand bars or spits at the river mouth. If the sea cannot disperse the sediment, it is dropped in the estuary and can form a delta. The best known examples of these are at the mouths of the Nile and Mississippi. In the British Isles, small deltas in the form of an alluvial fan may be seen in some lakes but they are not found in British estuaries.

Old Age Features

A River Estuary

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