River Processes Flashcards
River Processes
Erosion and Transportation
Erosion: The primary process in the upper part of the river where the river bed is steepest and roughest.
There are four main erosional processes in a river.
Transportation: Describes how a river moves material (the river's load). This typically occurs in the middle part of the river.
Types of Transportation
Traction:
Involves large stones being moved along the river bed by the river current.
Saltation:
Refers to sand-sized particles being bounced along the river bed in a leap-frog movement.
Suspension:
Occurs when very small particles are carried within the water flow.
Solution:
Involves minerals being dissolved in the water.
River Energy and its Impact
During periods like summer or winter, river characteristics change over time and from place to place.
Increased river energy:
Allows the river to erode more.
Enables the river to transport larger pieces of rock.
Some rocks only move during river floods when velocity dramatically increases.
Deposition
As the river reaches flatter land, it loses energy.
This leads to deposition, where the river drops or leaves behind its load.
The deposited material is called sediment.
The order of deposition is based on size and weight:
The biggest and heaviest stones and pebbles are deposited first.
Then smaller ones.
The smallest particles are deposited last.
Dissolved material remains in the water, eventually ending up in a lake or sea.
The River's Long Profile
Upper Course:
Erosion is the main process.
Results in a V-shaped valley due to downward erosion.
Middle Course:
Both erosion and deposition occur.
The river channel widens as the banks are eroded.
A floodplain begins to form due to repeated flooding.
Lower Course:
Deposition dominates as the river loses energy.
The channel is wider and deeper, holding more water.
The floodplain becomes wider.
Erosion and Transportation
Erosion: The primary process in the upper part of the river where the river bed is steepest and roughest.
There are four main erosional processes in a river.
Hydraulic action: The sheer force of the water hitting the banks.
Abrasion: When the load carried by the river repeatedly hits the bed or banks, wearing them away.
Attrition: When the rocks being carried by the river smash together and break into smaller, smoother particles.
- Solution: The dissolving of soluble chemicals in rocks.
Transportation: Describes how a river moves material (the river's load). This typically occurs in the middle part of the river.
Types of Transportation
Traction:
Involves large stones being moved along the river bed by the river current.
Saltation:
Refers to sand-sized particles being bounced along the river bed in a leap-frog movement.
Suspension:
Occurs when very small particles are carried within the water flow.
Solution:
Involves minerals being dissolved in the water.
River Energy and its Impact
During periods like summer or winter, river characteristics change over time and from place to place.
Increased river energy:
Allows the river to erode more.
Enables the river to transport larger pieces of rock.
Some rocks only move during river floods when velocity dramatically increases.
Deposition
As the river reaches flatter land, it loses energy.
This leads to deposition, where the river drops or leaves behind its load.
The deposited material is called sediment.
The order of deposition is based on size and weight:
The biggest and heaviest stones and pebbles are deposited first.
Then smaller ones.
The smallest particles are deposited last.
Dissolved material remains in the water, eventually ending up in a lake or sea.
The River's Long Profile
Upper Course:
Erosion is the main process.
Results in a V-shaped valley due to downward erosion.
Middle Course:
Both erosion and deposition occur.
The river channel widens as the banks are eroded.
A floodplain begins to form due to repeated flooding.
Lower Course:
Deposition dominates as the river loses energy.
The channel is wider and deeper, holding more water.
The floodplain becomes wider.