middle course Flashcards
what can cause a river to meander?
a tree falling into the river
what are meanders?
large bends in the rivers course caused by lateral(sideways) erosion and deposition
how are meanders formed? (erosion)
erosion - hydraulic action and abrasion
occurs on the outer bend where the water flows fastest
how are meanders formed? (deposition)
deposition happens on the inner bend where the water moves slower creating a slip off slope on the inside
what are oxbow lakes?
u shaped lakes formed when a meander is cut off from the main river
how are oxbow lakes formed?
- erosion narrows the neck of a meander
-during high discharge (flooding), the river cuts through the neck, taking a straighter course.
-deposition seals off the old meander, forming an oxbow lake.
what are levees?
natural embankments formed along the edges of a river
how are levees formed?
-during floods, the river deposits heavier sediments first, forming raised banks
-overtime, repeated flooding increases the height of these levees
how are levees formed?
-during floods, the river deposits heavier sediments first, forming raised banks
-overtime, repeated flooding increases the height of these levees
how are slip off slope and river cliffs formed?
river cliffs form on the outer bend of a meander due to erosion
slip off slopes form on the inner bend due to deposition
what is hydraulic action?
the force of the river against the banks
what is abrasion?
the force of the water in the river carrying stones and other materials grind the bed-load like a piece of sandpaper
what are floodplains?
wide flat areas on either side of the river formed by repeated flooding
what are floodplains?
wide flat areas on either side of the river formed by repeated flooding
how do floodplains form?
when the river overflows, it deposits the fine sediment( alluvium) gradually building up the floodplain
these areas are fertile and great for farming
