Middle Course Landforms- Meanders and Oxbow lakes Flashcards
What is a River Cliff?
A steep river bank on the outside bend of the meander
River cliffs form due to erosion caused by the fast-flowing thalweg.
Define Pool in the context of river meanders.
A deep section of the channel on the outside bend of a meander
Pools are areas where erosion has deepened the channel.
What is a Riffle?
A shallow area of channel found in the straight section of the river between meanders, dominated by deposition
Riffles occur where flow velocity decreases, causing sediment to deposit.
What is a Slip-off slope?
A gentle sloping channel found on the inside bend of the meander
Slip-off slopes are formed by sediment deposition due to lower water energy.
What is a River beach?
An area of deposition found above the inside bend of the meander
River beaches are formed from the accumulation of sediments on the inside bank.
Define Thalweg.
The shoot of fast-flowing water in the meander
The thalweg is crucial for erosion and shaping the river channel.
What is Helicoidal flow?
The corkscrew motion that describes the flow dynamics of the thalweg
This motion contributes to increased turbulence and erosion.
What is a Secondary cell?
The pattern of flow that describes how some water moves from the outside bend to the inside bend
Secondary cells help redistribute sediments along the river.
Define Meander neck.
The narrow section of floodplain separating two meander loops
The meander neck is critical in the formation of oxbow lakes.
What is an Ox-bow lake?
A section of meander cut off from the main channel
Oxbow lakes are formed when meander loops migrate and eventually isolate.
Define Meander scar.
A dried up ox-bow lake
Meander scars indicate former water bodies that have since filled in.
What causes the formation of meanders?
The river attempting to find a balance between its energy and the water and load it is transporting
Meanders represent a dynamic equilibrium in river systems.
What are the effects of velocity variation in a meander?
Erosion of the outer bend and deposition on the inside bend, creating an asymmetrical cross-profile
This dynamic leads to the characteristic shape of meanders.
Describe the process of meander migration.
Erosion on the outside bend and deposition on the inside bend occur simultaneously
This results in the gradual movement of meanders over time.
What happens when two meander loops migrate towards each other?
It is possible for oxbow lakes to form
This occurs when the neck of the meander is eroded and the river cuts through.
What are the two key factors allowing the Thalweg to erode the river cliff?
- More energy due to greater velocity
- Corkscrew motion increasing turbulence
These factors enhance the erosive power of the thalweg.
What causes deposition on the inside bend?
- Slower-moving water has lower energy and competence
- Secondary cell moves sediments from the river cliff to the slip-off slope
These processes lead to sediment accumulation on the inside bend.
True or False: Meanders only form through deposition.
False
Meanders form through both erosion and deposition processes.
