Landforms in middle course Flashcards
What are meanders in a river?
Bends in a river
Meanders are formed due to lateral erosion and deposition.
What conditions lead to a river starting to meander?
i) A tree may fall into the river
ii) Water flowing over shallow areas and through deeper areas creates a helicoidal flow
These factors induce a corkscrew motion that contributes to meandering.
What is Thalweg in the context of rivers?
Fast flowing water on the outside bank
The Thalweg is where the fastest water flows, leading to significant erosion.
What causes lateral erosion on the outside bank of a river?
Abrasion and hydraulic action
This erosion undercuts the bank and forms a river cliff.
How does faster flow affect the river bed?
Causes vertical erosion, deepening the river bed
This results in an asymmetrical cross-profile of the river.
What happens on the inside bend of a meander?
The river is slower, and material is deposited
This deposition forms a gentle slip-off slope.
What process occurs due to erosion on the outside of a bend and deposition on the inside?
The shape of a meander changes over time
Erosion narrows the neck of the land within the meander.
What occurs during a very high discharge, such as during a flood?
The river cuts across the neck, taking a new, straighter route
This leads to the formation of a horseshoe-shaped oxbow lake.
What is a floodplain?
The area around a river that is covered in times of flood
Floodplains are fertile due to rich alluvium deposited by floodwaters.
How are levees formed along a river?
Through the deposition of heavy sediment when a river bursts its banks
The size of the sediment decreases with increased distance from the river.
What is the effect of meandering on a floodplain over time?
The floodplain is widened
This process occurs over thousands of years.
Fill in the blank: A build-up of alluvium can create _______.
Levees
Levees raise the river bank and help control flooding.
True or False: The sediment size deposited by a river is uniform regardless of distance from the river.
False
Sediment size decreases with distance from the river.
