How do rivers transport material?
Fluvial transport is the process by which a river carries its load. Load varies in size from large angular boulders in the upper course to fine, suspended sediment in the lower course. Load mainly comes from weathered material that has rolled down the hillside into the river bed. However, it also comes from the eroded bed and banks of the river.
Rivers transport material in four ways:
- Solution – minerals are dissolved in the water and carried along in solution. This typically occurs in areas where the underlying bedrock is limestone or chalk;
- Suspension – fine, light material such as alluvium is carried along in the water. This is known as suspended load. The load bounces in line with the rise and fall in the velocity of the river;
- Saltation – small pebbles and stones are bounced along the river bed;
- Traction – large boulders and rocks are rolled along the river bed. The load carried this way is called bed load.
Processes of transportation by a river