Rivers Flashcards
What is the river bed and bank
River bed is the bottom of the channel but the river bank is the sides
What is erosion
The wearing away of rock
What is transportation
When material is moved downstream. The sediment gets smaller and rounder
What is deposition
When the river loses energy and drops the material it was carrying
What is Hydraulic action
Where the river banks have cracks where water and air are compressed so the cracks widen and break off
What is abrasion
When the rocks scrape the river bank and bed, eroding it, making the rocks smoother
What is attrition
When the rocks collide and break away
What is a solution
When the water is slightly acidic due to absorption of carbon dioxide and the rocks dissolve
What is a source
Where a river begins
What is a tributary
A small stream that joins a larger one
What is it called when 2 rivers meet
Confluence
What is the mouth
Where the river joins the sea
What is the watershed
The border surrounding a river basin
What is vertical erosion
It erodes downwards and can create V shapes
What is lateral erosion
Where the outside bend gets eroded
What is the valley shape
Describes the shape of a river where it could be steep or flat, wide or narrow
What is traction
Where the river banks roll along the river bed
What is saltation
The small rocks bounce across the river
What is suspension
Where light material is carried without touching the river bank and bed
What is gradient
The angle of a river
What is discharge
The volume of water moving downstream
What is velocity
The speed
Describe the upper course
It will be shallow and narrow moving at a slow speed with big angular rocks with a steep shape
Describe the middle course
It is deeper and moving at a moderate speed where it is carrying medium sized, sub angular rocks along a shallow gradient
Describe the lower course
It is deep carrying small, smooth rocks in fast water on a flat gradient
Describe the stages of a waterfall forming
- River flows over hard rocks and soft rock
- The soft rocks erodes quicker forming a step in the river bed
- The water undercuts the hard rocks making a plunge pool
- There is an overhang and it repeatedly cracks because it is not supported
- The rocks swirl in the plunge pool causing erosion
- The waterfall repeats this process and recedes
What are meanders
Bends in a river
How are meanders formed
- It starts as a slight bend and the discharge is high on the outside bend
- The erosion is on the outside bend but deposition is happening in the inside bend
- It turns in a meander
- It forms a light loop over years
- The water level is really high and can go straight through the loop not around
- This is called a meander cutoff
- The river uses the new channel so the deposition builds up and the loop is left as an oxbow lake
- The lake dries up and grows plants
Give an example of flooding defences
York embankments which is a permanent raised bank of earth which can have items built on it
