Channel characteristics

Question 1

What happens to discharge and velocity as it goes downstream?

Answer 1

Discharge increases downstream as tributaries and more surface runoff join the main channel
Velocity increases due to gradient, discharge and channel characteristics

Question 2

What is the hydraulic radius?

Answer 2

channel’s cross-section area divided by the length of its wetted perimeter

Question 3

What is the wetted perimeter?

Answer 3

the total length of the banks and bed that are in contact with the water.

Question 4

What does a larger hydraulic radius result in?

Answer 4

Smaller proportion of water is in contact with wetted perimeter
Friction is lower and energy loss is reduced
Increasing velocity and discharge

Question 5

Which types of channels have a large hydraulic radius?

Answer 5

Smooth, narrow deep channels have a larger hydraulic than shallow, broader channels

Question 6

Features of channel roughness and what this does

Answer 6

Protruding banks
Large, angular boulders
Increase the wetted perimeter and causes more friction
Reduces efficiency, velocity and discharge