Pieces of river sediment become smaller and more rounded as they move downstream. Carbon dioxide dissolves in the river to form a weak acid.
This dissolves rock by chemical processes. This process is common where carbonate rocks such as limestone and chalk are evident in a channel. Transportation of material in a river begins when friction is overcome. Material that has been loosened by erosion may be then transported along the river. There are four main processes of transportation. Suspension is when material made up of very fine particles such as clay and silt is lifted as the result of turbulence and transported by the river.
Faster-flowing, turbulent rivers carry more suspended material. This is why river appear muddy as they are approaching bankfull discharge and towards the mouth of the river where velocity is greater as is the occurrence of finer sediment. Solution is when dissolved material is carried by a river. This often happens in areas where the geology is limestone and is dissolved in slightly acidic water.
Saltation is when material such as pebbles and gravel that is too heavy to be carried in suspension is bounced along the river by the force of the water.
Traction is when large materials such as boulders are rolled and pushed along the river bed by the force of the river. The video below shows transportation in a river in the form of traction, saltation and suspension. The capacity of a river is the total load a river can transport at a given point. Deposition is the process of the eroded material being dropped. This happens when a river loses energy. A river can lose its energy when rainfall reduces, evaporation increases, friction close to river banks and shallow areas which leads to the speed of the river reducing and therefore the energy reduces, when a river has to slow down it reduces its speed and ability to transport material and when a river meets the sea.
When discussing transportation you need to know the difference between the competence and capacity of a river.
C - in the lower course there is a lot less erosion, with only some lateral erosion. The channel is at its widest and deepest. River profiles - cross profiles and long profiles Long profile A long profile shows how the river changes over its course from its source where it starts to its mouth where it meets the sea. When there is a very high discharge usually during a flood , the river cuts across the neck, taking a new, straighter and shorter route. Deposition will occur to cut off the original meander, leaving a horseshoe-shaped oxbow lake.
Erosional and depositional landforms Meanders As the river makes its way to the middle course , it gains more water and therefore more energy. Solution or corrosion is when acidic water dissolves rocks such as chalk or limestone. What is lateral and vertical erosion? Lateral and vertical erosion. Related Topics Use the images below to explore related GeoTopics.
Weathering and mass movement in river valleys. Topic Home. How do rivers transport material? Please Support Internet Geography If you've found the resources on this site useful please consider making a secure donation via PayPal to support the development of the site.
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