River Processes

• Hydraulic action

• The water that sashes against the river banks

• Air becomes trapped in the cracks of the banks and bed 

• This causes the rock to break apart 

• Abrasion

• Pebbles grind along the river bank and bed 

• Sand papering effect 

• Attrition

• When the rocks that are going downstream knock against each other

• They break apart and become smaller and rounder

• Solution 

• Water dissolves certain types of rocks 

• eg . limestone 

• Traction 

• Large heavy pebbles roll along the riverbed

• Common near the source of river as load is larger 

• Salutation 

• Pebbles bounce along the riverbed 

• Common near source 

• Suspension 

• Lighter sediment is suspended within the current 

• Common near mouth

• Solution

• Movement of dissolved chemicals 

• Varies along the river

• Depends on the presence of soluble rocks 

Deposition

• When the river loses its energy 

• It drops any material it has been carrying 

  • In shallow waters 

  • At the end of the rivers journey, The mouth

  • When the volume of water decreases

Drainage Basins

• River’s water can fluctuate over time

• It's the hydrological cycle that explains why the amount of water in the river fluctuates 

• A drainage basin is the land around the river is drained by the river and its tributaries

• Tributaries

• A small river that joins the main river channelWatershed 

• Watershed 

• The area of high land forming at the edge of a river basin

• Source 

• The river begins

• Mouth

• The river meets the sea 

• Confluence 

• The point at which two rivers meet 

• Channel

• This is where the river flows

• Long profile 

• Is a line representing the river from its source to its mouth.

• How the river changes over its course

• Can show Upper course to lower course 

  • Upper course 

    • Where the river starts 

    • Often upland area 

    • River load is larger as it hasn’t eroded yet

  • Lower course

    • Flatter land 

    • Rivers load is fine sediment as erosion has broken down the rocks  

• Cross profile 

• Shows the cross section of a rivers channel and valley at a certain point along the rivers course 

• Shows the different features of the river

• So you can see the difference between upper, middle and lower course 

  • Upper course

    • Vertical erosion 

    • Shallow and narrow channel

  • Middle course

    • Some vertical erosion but mostly lateral erosion 

    • Channel is wider and deeper 

  • Lower course 

    • Less erosion but only lateral erosion 

    • Channel is at its widest and deepest