River Land Forms Flashcards
What is a meander?
Large bends usually found in the middle and lower courses of rivers
How is a meander formed?
Current is faster on outside because channel is deeper (less friction)
So more erosion takes place on outside bend forming river cliffs
Current is slower on inside bend because it’s shallower
More eroded material deposited on inside bend forming slip off slopes
How is an oxbow lake formed?
Erosion caused outside bend to get closer until neck between bends is narrow
River breaks through the neck usually during a flood and the river flows along the shortest course
Deposition eventually cuts off meander forming an oxbow lake
May dry up and form meander scar
How is a waterfall formed?
Hard rock overlies soft rock
Soft rock eroded quicker due to hydraulic action and abrasion
The hard rock is undercut forming an overhang as the erosion of soft rock continues
Eventually the hard rock collapsed into the plunge pool when it can’t support itself
The waterfall retreats upstream forming a steep sided gorge
The process repeats
What is a floodplain?
The wide valley floor on either side of the river which occasionally flood
How is a floodplain made higher?
River floods onto flood plain, water slows down and deposits the eroded material which builds up
Meanders migrate across floodplain making it wider
Deposition of slip off slopes also builds up on floodplain
What is a levee?
Natural embankments (raised bits) along the edges of a river channel
How are levees formed?
Eroded material is deposited on floodplain
Heaviest material is deposited closest to channel
Deposited material builds up creating levees
