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River Processes

1.River Processes by rgamesby

Erosion - the wearing away of the land by moving forces - in this case the river.  Processes include;

Hydraulic action - where the sheer force of the water erodes the stones, bed and banks of the river

Corrasion or abrasion- where stones in transport are thrown into the bed and the banks eroding them

Corrosion - where weak acids within the water react with the rocks and bed and bank of the river

Attrition - where stones in  transport are thrown into one another

These erosion processes can erode the river's banks LATERALLY widening river valleys and the channels banks.  They can also erode VERTICALLY down into the bed creating deeper parts of the channel.

Stones are eroded gradually as they are transported downstream, meaning that stones are smaller closer to the sea.

River erosion processes

Transport - the movement of material, in this case by river water.  There are 2 types of material that we consider in rivers - the bedload and the suspended load.  Bed load is the large, heavy stones that are generally found on the river bed. Suspended load is smaller sediments that are carried or suspended in the water itself. Processes include;

Solution - 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.

Obviously the larger sediments will only be moved during periods of high river flow.

Rivertransport processes

 

Mass movement - these processes involve material on slopes moving down slope.  They range in speed from rock falls to much slower soil creep.  A land slide happened in Jesmond Dene, Newcastle, in November 2012.  I took some pictures shown below;

Deposition - this is the laying down of sediment in the river channel or on floodplains.  This occurs when river velocities slow within the channel, or when velocities slow over floodplains or when the river enters a sea or lake. Larger sediments can be deposited at quite high river velocities, as this material tends to be heavier and harder to carry.  Lighter and smaller material will be deposited at very low velocities and transported in faster flowing rivers that have more energy.
Think about it

Try the quizlet set below

Hot Potatoes matching exercise on River processes