River Flow

Question 1

What is the velocity + energy of a stream controlled by?

Answer 1

• gradient of channel bed
• volume of water in channel (controlled largely by pptn in drainage basin)
• shape of channel
• channel roughness, inc. friction

Question 2

What are the 3 main types of flow?

Answer 2

• laminar
• turbulent
• helicoidal

Question 3

What are the features of a laminar flow?

Answer 3

• requires smooth, straight channel w low velocity
• top + bottom layers slower due to friction
• occurs on efficient rivers

Question 4

What are the features of a turbulent flow?

Answer 4

• requires high velocities + complex channel (meandering w pools + riffles)
• causes vertical + horizontal eddies from obstructions in river + pressure imbalances
• vertical turbulence creates hollows

Question 5

What are the features of a helicoidal flow?

Answer 5

• ‘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