1.3 River Notes (changes + processes) Flashcards
(15 cards)
How does a river change along its course
- Increase in size, channel becomes wider + deeper
- Increased Discharge due to this + carries more sediment
- Channel roughness decreases - bedload become smaller more rounded
- Velocity of water increases; despite low relief due to less friction
Why does river change along its course
Volume - higher velocity, larger csa so less friction, also increases due to tributeries
Roughness - more energy more erosion
CSA - more water more erosion
Gradient - Hills, alt steepest at the top slowest due to friction, 95% of energy lost in upper course - due to angular bedload
Competency & Capacity
Competency - Size of load it can carry
Capacity - Maximum load it can carry
Abrasion
The wearing away of channel bed & banks by hard rock carried within river’s load
Hydraulic Action
The force/power into the bed & banks from water due to the river’s velocity
Cavitation
Force of air exploding; as water accelerates pressure drops and bubble from - the explosion of the bubble also causes pressure
Corrosion
Chemical Action - dissolves chamical ions in carbonate rocks e.g. limestone
Attrition
Load particles bang together and are worn away - become smaller and more rounded
What factors effect erosion?
Velocity - more energy - think along course
Sediment Load Capacity - more sediment more attrition and abrasion - course
Sediment Load Competence - larger doesn’t make too much difference
Discharge - more energy, more erosion
Traction
Larger loads rolled along bed by river current
Saltation
Hopping & bouncing of medium sized load on bed
Suspension
Lighter sediment like sands and grvaels - suspended above bed by current
Saltation
Transport of soluble materials dissolved in waterF
Factors which effect transportation
Velocity - faster movement
Discharge - increased capacity
Roughness - more friction less transportation
Hjulstrom Curve
Size of Particles
Clay - 0.001mm // Sand - 0.1mm // Cobbles 100mm
