channel morphology

Question 1

Discharge

Answer 1

Volume of water flowing through a cross-section @ any point in time (in a channel)

Question 2

Stream gradient

Answer 2

Inclination of water surface to the horizontal distance covered
- decreases downstream
- represented by a long profile graph

Question 3

Long profile graph

Answer 3

Illustration of stream gradient ⇒ shows channel height in relation to the base level
- shows amount of potential energy potential for vertical erosion to take place

Question 4

Cross-sectional area

Answer 4

Area of a vertical slice along any point of the channel
- channel depth x bankfull width

Question 5

Hydraulic radius

Answer 5

Proportion of water in constant contact with the stream channel
- higher ratio = lower friction & turbulence

Question 6

Wetted perimeter

Answer 6

Length of a channel the cross-section in contact with the water in a channel

Question 7

Velocity

Answer 7

Rate of water flow in a channel
- controlled by driving & resisting forces

Question 8

Driving forces of velocity:

Answer 8

• Channel gradient ⇒ steeper gradient = higher velocity
• volume of water in the channel ⇒ higher volume = higher impact of local factors

Question 9

Resisting forces of velocity

Answer 9

• Amount of friction ⇒finer bed material = higher velocity
• channel shape ⇒ wider channel = lower RH = higher friction = lower velocity energy

Question 10

Channel width & bankfull

Answer 10

Width = shortest distance from 1 edge of the channel to the other

Bankfull ⇒ immediate channel state before a flood
- bankfull width ⇒ width measurement airing the bankfull stage

Question 11

W/d ratio of a channel

Answer 11

Ratio of bankfull width against the channel depth