Rivers Flashcards
What is discharge?
The amount of water in the river.
What is the width of a river?
The number of meters perpendicular to the line of river flow from one side of the river to the other.
What is the depth of the river?
How many meters the river is from the surface to the base.
What is the gradient of the river?
How steep the river is.
What is the velocity of the river?
How fast the river is moving.
What is the sediment size in a river?
How large particles in the river are.
What is the friction of a river?
The surface to volume ratio.
What is the carrying capacity of a river?
How much sediment it can carry.
What is the carrying competence of the river.
The mass of sediment the river can carry.
What are the 4 processes of erosion.
Hydraulic actionAttritionCorrasionAbrasion
What is Hydraulic action?
Waves breaking at the foot of a cliff force air in cracks to be compressed. Loose rocks are dislodged and removed. When the wave retreats the compressed air rushes out of the crack and can further weaken faults in the cliff face.
What is attrition?
Attrition is when rocks carried by seawater collide – gradually making them smaller and smoother.
What is Corrasion?
Corrasion is when rock caught up in surging waves are hurled at a cliff face – causing it to be chipped and gauged.
What is Abrasion?
Abrasion is the sandpaper effect of loose rocks being scraped along bare rock. It often smooth’s and polishes the rock.
What is transportation?
Transportation is movement of sediment by the action of waves.
What are the 4 processes of transportation?
Traction, Saltation, Solution, Deposition
What is traction?
Traction involves the rolling of large and heavy rocks along the seabed.
What is a Saltation?
Saltation involves smaller material being bounced along the seabed.
What is Solution?
Sediment that has dissolved completely will be transported in solution.
What is suspension?
Suspension is when lighter sediment is suspended within the water. This often discolours the water close to the shore.
What is deposition?
Deposition occurs when energy levels decrease in environments such as bays and estuaries. Where deposition occurs on the inside of a spit a salt marsh can form.
Describe a river delta.
This is a ‘D’ shaped area of sandy/ muddy sediment built up into the open water where the river meets the sea.
Where is the line of fastest flow in a river?
The thalweg.
What is a Levee?
If a river floods, material is deposited on the banks, the material that is dropped first is the coarsest, and creates a natural embankment
What happens to levee when the water in the river is low.
When the amount of water in the river is low deposition takes place, the bed of the river rises and flooding is again likely. In some countries, artificial levees are put in place to reduce the flood risk.
What defines the amount of energy available for fluvial processes such as erosion and transport.
The vertical distance to the sea at any given point in a rivers course - Potential energy.The discharge, volume of flow per second.
Where is the rivers energy used?
The rivers energy is primarily used in overcoming friction.95% is used for friction, any surplus available will cause erosion and sedimentation.
When do streams and rivers achieve peak energy?
At bank full discharge which is when the river is the most efficient, moving the most water and sediment for the lest amount of energy expended.
What is base flow?
Rate of discharge in a stream where only the throughflow and groundwater flow from subsurface aquifers contribute to the overall flow.
What does a river need to be in equilibrium?
Friction and energy must be in balance.
What could cause an increase in discharge?
A change in the weather.
How would a river respond to an increase in discharge.
By eroding more.
What returns a river back to equilibrium?
Negative feedback.
How would you describe a v-shaped valley?
This is a valley whose typical cross section is shaped like a ‘v’.(a cross section is the shape that you would walk if you walked down one side of a valley and up the opposite side).(the long profile is the shape that you would walk if you walked from the river’s source to its mouth).
Explain a V-shaped valley.
explanation - As the river cuts down into the landscape in an upland area, gravity and mass movements roll material down the valley sides to give the valley a typical ‘v’ shape.
Describe a floodplain.
- This is an area of flat land found on either side of a river. This usually becomes wider as the river nears its mouth.
Explain a flood plain.
The flood plain is the area of land which is flooded when a river overflows its banks. In this area layers of alluvium are laid down. The soils are thus thick and fertile and the land is flat.
Describe a levee.
- These are mounds of alluvium piled up along the river’s edge.
Explain a levee.
explanation - These are formed by the river depositing the coarsest part of its load (pebbles, gravel and sand) close to the river channel when the river floods. This happens because usually when the water overflows the river bank its speed (and therefore its ability to transport alluvium) is greatly reduced.Sometimes these are built by people in an attempt to prevent the river flooding.
Describe a meander.
description - These are bends (loops) in the river. explanation - Lateral (sideways) erosion of the river channel results in the river forming a winding pattern. (tip! if a river or stream has an absolutely straight pattern then it is probably artificial i.e. a canal).
Explain a meander.
- As the water flows down a river, its speed is faster on the outside of the meander causing erosion and slower on the inside of the meander resulting in deposition.
