Water On Land Flashcards
What are levees?
Natural embankments along the edges of a river channel
What conditions is needed for deposition?
The volume of water in a river falls. The amount of eroded material increases (heavier load). The water is shallower (inside of a bend). The water reaches it’s mouth.
How are levees formed?
During a flood eroded material is deposited over the flood plain. The heaviest material first when the river slows down. Deposited material builds up over time to create levees
Which course of the river are levees and flood plains found?
Lower course
What course of the river are meanders found?
The middle and lower course
How are ox bow lakes formed?
Erosion causes the outside bends of a meander to get closer together making the neck become thinner. The river then. Breaks through land so there is no longer a neck, the river flows through the shortest route. Deposition occurs cutting off the meander and forming an ox bow lake.
How are river cliffs formed?
The current on the outside bend is faster because the river is deeper. This means more erosion can take place to form a river cliff
How is a slip off slop formed?
The current is slower on the inside of the bend because the river is shallower. This causes the river to deposit its load here. As more deposition occurs it builds up a slip off slope
What conditions are needed for deposition?
Deposition happens when a river slows down this can happen because. The volume of water in a river drops. The load gets heavier. The water becomes shallower (inside of a bend). The river reaches it’s mouth
What are the 4 types of erosion?
Hydraulic action- the force of the water breaks rock particles away from the river channel.
Abrasion- eroded rocks carried by the river bang against the channel wearing it away.
Attrition- eroded rocks carried by the river bang against each other and break into smaller pieces.
Solution- so rocks are dissolved in the river e.g chalk
What are the four stages of transportation?
- Traction- large boulders are rolled down the river bed by the force of the water.
- Saltation- smaller pebble sized rocks are bounced along the river bed by the force of the water.
- Suspension- smaller particles like slit and clay are carried along by the river
- Rocks dissolve in the water and are carried by it
How are flood plains formed?
The wide valley floor on either side of the river will get flooded. The river floods and the river slows down depositing it’s load on the flood plain building it up. Meanders move across the flood plain making it wider. Deposition on the slip off slope builds up the flood plain.
How are waterfalls formed?
Water flows over and area of hard rock on top of soft rock. Over time the soft rock is eroded creating a steep step. The hard rick is undercut by by the soft rock causing it to collapse. The collapsed rocks are swirled around below the waterfall creating a plunge pool through erosion.
How are gorges formed?
Over time lots of undercutting and collapsing of waterfalls causes them to retreat back upstream. This leaves behind a steep sided gorge.
What is peak discharge?
The highest discharge in the river within the tme period
