Question

• Explain how streams become graded
• Describe the formation of stream terraces
• Describe the processes by which sediments are moved by streams and the flow velocities that are necessary to erode them from the stream bed and keep them suspended in the water

Answer 1

Answer- The stream becomes graded under the mechanism of dispersive pressure and kinetic seaving or due to normal settling. The settling of sediments during river flow due to normal settling leads to the normal grading where the finning of the sediments takes place upward. Where as the kinetic seaving and the dispersive pressure leads the reverse grading where the coarsening of the sequence takes place.

Answer- The formation the stream terraces takes place due to the lateral erosion by the river. When the unequal lateral erosion takes place it leads to the formation of the assymmetric terraces and the equal erosion leads to the formation of the symmetric terraces.

Answer- The processes by which the sediments are moved by the stream are saltation(series of jumps), rolling and traction and suspension. The flow velocity must be high enough to agitate and carry the load of the sediments which mainly depends upon the capacity and the competency of the river.