Channel Processes

Channel Processes

1. Transportation

   • Types
     • Traction
       • Only operates in times of high discharge
       • Large stones/boulders are rolled along the river bed by water moving downstream
     • Suspension
       • Contributes to a large amount of the river flows
       • Small particles, are carried along by the flow of the river
     • Saltation
       • Assoited with high energy conditions
       • Small stones bound/leap frog along the river bed
     • Solution
       • Dissolved minerals being transported within the mass of the water
   • The river obtains it's load through in two main ways
     • Material being washed/fallen into the river
     • Material being eroded from the river bed/banks
   • The capcity of the river is the amaont of material in a river
   • The competence of a river is the diameter of the largest particle it can carry

2. Erosion

   • Types
     • Attrition
       • The reduction in the size of fragments, in the river
       • Sediment strike each other, becoming smaller, smoother and more rounded
     • Corosion
       • The most active rocks contain carbonates
       • The minerals in the rock are dissolved by acids and carried away
     • Abrasion
       • Wear's away the river bed/banks
       • The scraping, scouring, and rubbing action of materials along by the river
     • Hydraulic Action
       • The movement of loose material due to frictional drag
       • Caused by the sheer power of water movement
   • Lateral erosion
     • This energy is used laterally (against the river banks mostly)
     • River processes a lot of energy
     • Usually occurs in the middle/lower course of the river
   • River's erode because they process the energy too
     • The total energy of a river depends on;
       • Steepness of the Channel
       • The weight of the water
       • The height of the river above base level
   • Vertical erosion
     • Often produces steep sided valleys
     • Mainly caused by abrasion and Hydraulic Action
     • River is attempting to erode down towards base level
     • Dominates when rover is high above base level

3. Deposition

   • Usually occurs when;
     • There is a reduction in the gradient
     • The discharge is reduced
     • There is shallow waters
     • There is an increase in the size of the load
     • The river overflows, its banks
   • A river deposit's its load when there has been a decrease in the rivers energy
   • The largest fragments generally get deposited first, followed by smaller particles. Although the finest particles may never be deposited