Water On The Land Flashcards
Characteristics of the upper course of a river
- steep gradient
- v-shaped valley
- steep narrow sides
- shallow channel
Characteristics of the middle course of the river valley
- medium gradient
- gentle sloping valley sides
- wider
- deeper channel
Characteristics of the lower course of the river valley
- gentle gradient
- very wide
- almost flat valley
- deep channel
What are the four processes of erosion
- hydraulic action
- abrasion
- attrition
- solution
What is hydraulic action?
They force from the water breaks the rock away from the river channel
What is abrasion
Rocks picked up by the river scrape and rub against the channel wearing it away
What is attrition?
Rocks picked up by the river smash into each other breaking into smaller fragments
What is solution? (Erosion)
The river water dissolves some types of rocks
What is transportation?
The movement of eroded materials
- traction
- saltation
- suspension
- solution
What is traction?
Large particles are pushed along the river bed by the force of the water
What is saltation?
Pebbles sized particles bounce along the river bed by the force of the water
What is suspension?
Small particles are carried along by the water
What is solution? (Transportation)
Soluble materials dissolve in the water
What is deposition?
When a river drops eroded material due to the river losing velocity
How is a meander formed?
- The current is faster on the outside of the bend due to the deeper channel
- more erosion at the outside bend, forming river cliffs
- on the inside bend, the current is slower meaning more material is deposited there forming slip off slopes
Where is an ox bow lake formed?
From meanders
How is an oxbow lake formed?
- erosion causes the outside bends to become closers
- usually during a flood, the river breaks through this, looking for a shorter path
- deposition eventually cuts if the meander, leaving behind a ox bow lake
What is a levees?
Natural embankments along the edges of a river channel
•heaviest material is deposited closest to the river channel
•this builds up over time forming levees
Physical reasons for flooding
- prolonged rainfall
- heavy rainfall
- snowmelt
- relief
Human reasons for rainfall
- deforestation
* construction work
Hard engineering
- dams and reservoirs
* channel straightening
Sort engineering
- flood warnings
- preparation
- flood plain zoning
- do nothing
