Rivers Flashcards
(25 cards)
What is a tributary?
A smaller river which joins a larger river
What is a river basin?
An area of land drained by one main river
What is a confluence?
The point where a tributary meets a river
Name 4 features of the upper course
1) Interlocking Spurs
2) V-shaped valleys
3) Waterfalls
4) Gorges
Name 3 features of the middle course
1) Meanders
2) Oxbow Lakes
3) Floodplains
Name 3 features of the lower course
1) Delta
2) Mouth
3) Levees
Name the 5 processes for precipitation to go into a river
Surface runoff Infiltration Percolation Through flow Ground-water flow
Describe infiltration
When water is absorbed into the soil
Describe percolation
The downward movement of water through soil
Describe through flow
The lateral movement of water through the soil
Describe ground-water flow
The lateral movement when water hits layer of impermeable rock
Describe surface runoff
When water travels along the surface of the ground due to saturation
What are the inputs, outputs and stores in the water cycle?
Inputs - precipitation
Outputs - transpiration
Stores - trees, soil, lakes
What are the 3 types of weathering and give an example of each
1) Biological - burrowing animals/roots
2) Chemical - acid rain
3) Physical - freeze thaw
What are the 4 types of erosion?
1) Hydraulic Action - force of water
2) Abrasion - rocks beat on bed/banks
3) Attrition - rocks beat together
4) Corrosion - chemicals wear rock
What are the 4 types of transportation in rivers?
1) traction - rolling
2) saltation - bouncing
3) suspension - suspended in water
4) solution - dissolved/chemical
What increases deposition?
Shallow water, low gradient on banks, too much sediment, and human activity
How are V-shaped valleys formed?
Lateral and vertical erosion works on the banks and bed.
Valley sides become saturated and slump.
Precipitation and weathering erode banks.
How are interlocking spurs formed?
When a river meets areas of hard rock it erodes around it, forming hills either side.
How are waterfalls and gorges formed?
As the river reaches softer rock or the rivers gradient slows down so it cuts downwards. The water forms a plunge pool at the bottom which erodes the softer rock underneath until the hard rock on top forms an overhang and falls. This way the river moves upstream leaving a gorge
How are meanders formed?
On the outside of a meander, the current is faster and can carry more material eroding the banks forming river cliffs.
On the inside, the current is slower and material is deposited forming a slip-off slope.
Causing the bend to increase
How are ox-bow lakes formed?
Continued erosion on the neck of the meander will cause the river to break through. Deposition will block off the old meander leaving an oxbow lake
How are deltas formed?
At the point where the river meets the sea, if the rate of deposition is greater than the rate of sediment removal by the sea; a delta is formed
What physical factors cause flooding
- Heavy rainfall
- Saturated ground
- High silt levels/undredged
- Land shape
- Impermeable rock
- Snow melt
