River Flow Flashcards
1
Q
What is the velocity + energy of a stream controlled by?
A
- gradient of channel bed
- volume of water in channel (controlled largely by pptn in drainage basin)
- shape of channel
- channel roughness, inc. friction
2
Q
What are the 3 main types of flow?
A
- laminar
- turbulent
- helicoidal
3
Q
What are the features of a laminar flow?
A
- requires smooth, straight channel w low velocity
- top + bottom layers slower due to friction
- occurs on efficient rivers
4
Q
What are the features of a turbulent flow?
A
- requires high velocities + complex channel (meandering w pools + riffles)
- causes vertical + horizontal eddies from obstructions in river + pressure imbalances
- vertical turbulence creates hollows
5
Q
What are the features of a helicoidal flow?
A
- ‘corkscrew’ motion due to pressure differences on a meander
- from high to low pressure: eroding outer banks + depositing sediment to inner bank (creating meander)
- starts at thalweg: line/flow of max. velocity