[distinctive landscapes] river formations & management

[ BBC Bitesize 'Distinctive Landscapes ⇢ River Processes' page 1 ]

Traction

Type of Transportation → large, heavy pebbles are rolled along the river bed. This is most common near the source of a river, as here the load is larger.

Saltation

Type of Transportation → pebbles are bounced along the river bed, most commonly near the source.

Suspension

Type of Transportation → lighter sediment is suspended (carried) within the water, most commonly near the mouth of the river.

Solution

Type of Transportation → the transport of dissolved chemicals. This varies along the river depending on the presence of soluble rocks.

Deposition

When material is dropped due to a decrease of energy.

Factors Leading to Deposition:

• shallow water

• slower velocity at the end of the river's journey, at the river's mouth and on the inside bends of meanders

• when the volume of the water decreases

Drainage Basin

The area of land around the river that is drained by the river and its tributaries.

Watershed

The area of high land forming the edge of a river drainage basin.

Source

Where a river begins.

Mouth

Where a river meets the sea.

Estuary

A tidal mouth of the river.

Confluence

The point at which two rivers meet.

Tributary

A small river or stream that joins a larger river.

Channel

This is where the river flows.

Causes of Flooding:

• prolonged rainfall

• heavy rainfall

• relief

• geology

• vegetation

• urban land use

Prolonged Rainfall

If it rains for a long time, the land around a river can become saturated (it's holding as much water or moisture as can be absorbed). If there is more rainfall it cannot be soaked up, so it runs along the surface. This is known as surface run-off.

Heavy Rainfall

Relief

Geology

Vegetation

Urban Land Use

Stage 1 of V Shaped Valley Formation

Upper course of river has fast currents so vertical erosion occurs due to hydraulic action, abrasion and solution.

Stage 2 of V Shaped Valley Formation

River bed erodes vertically and the steep gorges are now exposed freeze-thaw. weathering which loosens the rock , causing the rocks to continue eroding

Stage 3 of V Shaped Valley Formation

The steep sides have rocks falls and collapse into the river, transporting them downstream. This creates a deeper V shaped valley and interlocking spurs.