Rivers KQ1 Flashcards
(35 cards)
Name all the inputs in a slope system?
Gravity
Precipitation
Frost
Human activity - building
Name all the factors in a slope system?
Type of surface and vegetation
Soil depth and type
Geology
Vegetation
Name the erosional processes?
Abrasion Attrition Hydraulic action Solution Cavitation
What is critical erosion velocity?
Removal of the bed and bank and the flow increases until there is a point of balance between the moving and resisting forces.
Where does deposition occur?
Anywhere where the river does not have enough energy to transport material.
What is deposition within a channel called?
Agridation
What is deposition after floods called?
Overbank deposits
What does a rivers energy depend on?
Vertical distance to the sea at any point - potential energy
Discharge
Kinetic energy
Where does most of the rivers kinetic energy go?
It is lost through heat due to friction 95%
What does a greater velocity mean?
Greater energy meaning a faster flowing river that transports lots of material.
What is a denunciation slope?
There is a net loss of material because the transporting processes are too fast for any material to accumulate.
What is a transportation slope?
There is an equilibrium there is no loss or gain of material as the transport and accumulation levels are similar.
What is an accumulation slope?
There is a net gain of material as weathered material accumulates quicker than it can be removed by the transportation processes.
What factors affect weathering in river valleys?
Climate - chemical weathering increases by 2-3x and fluctuating temps = freeze thaw or heating and coooling.
Geological structure - joints, bedding planes and pores increase the surface area susceptible to weathering
Rock type - minerals composition affects the susceptibility to weathering by increasing or decreasing.
Vegetation - the more vegetation the more susceptible to weathering - organic matter decomposing into pH levels and roots breaking rock up.
Name rocks that are likely to have joints/bedding planes within?
Limestones
Sandstones
No bedding planes but joints = granite
Name the inputs of a river system?
Water - from run off, precipitation and ground water
Load - particulate (grains/gravel) and solute (calcium carbonate)
Human activity
What is the store of a river?
The channel
What are the outputs in a river system?
Water
Material
Define “discharge”?
The amount if water flowing in the stream expressed as a volume of water flowing down a channel.
Measure in cubic metres per second / cumecs
What processes occur in channels?
Erosion = vertical (deepens the channel - corrasion), lateral (increases the width - hydraulic action) and headward erosion (increases the length Transport = carrying material this does however have a stream capacity (total volume) Deposition = which can shallow the gradient decreasing the velocity, decrease in the volume, an increase in the friction, or human obstructions such as a dam.
What is the Hjulstrom curve?
It shows the velocity needed to erode, transport and deposit different sizes of grains of material
Define channel flow?
The flow of water in a river channel is the result of a balance between force (i.e gravity - steam energy, it is potential energy converted into kinetic energy by the water movement) and friction (i.e energy lost as noise or thermal energy - can be 95% of the energy)
What is the remaining energy in a river used for?
After 95% of energy is lost through heat or noise the remaining 5% is used for erosion on the banks and bed.
What are the similarities and differences between laminar and turbulent flow?
Both velocities decrease the close to the bed
Laminar velocity reduces after the maximum near the top
Turbulent is in swirls
Laminar is in horizontal lines
