Solution refers to the breaking down of rock through chemical reaction. Rocks such as limestone and chalk are dissolved by weak acid in the river water before being carried away in solution.
Transportation
A river transports its load downstream through solution, suspension, saltation and traction.
SUSPENSION: Fine, light material is carried along by the river
TRACTION: Large boulders and rocks are rolled along the river bed
SOLUTION: Minerals are dissolved in the water. This is a chemical change
SALTATION: Small pebbles and stones are bounced along the river bed
River bed Solution
Solution occurs when soluble rocks such as limestone and chalk are dissolved and carried away in solution. Solution accounts for only a small percentage of the river’s load transported downstream. Transport by solution needs very little energy, unlike the other processes of transportation.
GEO DICTIONARY Suspension
Clay and silt particles are lifted off the river bed by hydraulic action and carried in suspension. A large percentage of the river’s load is carried in suspension which gives rivers a brown or muddy appearance, especially in times of flood.
Saltation
Saltation occurs when small pebbles that are too heavy to be carried in suspension for a long time are bounced along the bed of the river. Hydraulic action lifts the pebbles off the river bed and the turbulent water carries them a short distance before dropping them again.
Traction
Traction occurs when large stones that are too heavy to be transported by suspension or saltation are dragged along the river bed. This process of transportation requires large amounts of energy and only occurs during times of flood or at certain times of year. Most traction occurs during winter as the volume and velocity of rivers are greater.
Suspension: eroded particles are carried by the river
Saltation: heavier pebbles are bounced along the river bed
Traction: larger rocks are dragged along the river bed during times of flood
: Fig. 10.5 The processes of river transportation
PATTERNS AND PROCESSES IN THE PHYSICAL ENVIRONMENT 179
