River Processes

Hydraulic action

where the sheer force of the water erodes the stones, bed and banks of the river. Most effective when the water is moving fast.

Abrasion

where stones in transport are thrown into the bed and the banks dislodges particles into the flow of the river.

Solution(erosion process)

where weak acids within the water react with the rocks and bed and bank of the river. Happens when the river flows over limestone and the rock is slowly dissolved.

Attrition

Where stones are carried by the river are thrown into one another gradually making the stones smaller and more rounded.

Erosion

the wearing away of land by moving forces.

Lateral erosion

sideways - widening river valleys & channel banks

Vertical erosion

downwards - erode down into the bed creating deeper parts of the channel.

transportation

the movement of material by river water. (2 types of material - bedload & suspended load)

Bedload

large heavy stones that are generally found on the river bed.

Suspended load

smaller sediments that are carried/suspended in the water itself.

Solution(transportation process)

where material is dissolved within the water.

Suspension

where small particles are held up or suspended in the water

Saltation

the bouncing motion of larger particles along the river bed

Traction

the rolling motion of sediment along the bed - normally much larger sediment.

Deposition

 laying down of sediment in the river channel or on floodplains. occurs when river river velocities slow within the channel/floodplains/when river enters sea or lake.

larger sediments(deposition)

tend to be deposited in the upper course of the river. They are only transported for very short distances, mostly by TRACTION, during periods of very high flow.(heavier + harder to carry)

Lighter(finer, smaller) sediment

 carried further downstream, mostly held in suspension. This material will be deposited on the river bed or banks where velocity is slowed down by friction.