CIVL316
Hydrology and Open
Channel Flow
Dr. Ali Habibzadeh, P.Eng., Ph.D.
Lecture Note #1
3
Open Channel Flow – Specific Energy
Natural
Artificial
Streams, rivers, estuaries, floodplains
(Jumping Pound Creek, Kananaskis, Alberta)
Flumes, spillways, canals, weirs, culverts
(Manitoba Flood, Portage La Prairie Spillway ‐ April 14, 2011)
http://www.manitobaphotos.com
Difference between open channel flow and pipe flow
Pipe Flow
fluid
driving force
conduit
Open Channel Flow
BC Floods, November 2021 (BC MOTI)
BC Floods, November 2021 (BC MOTI)
Flood waters cover Highway 1 in Abbotsford
BC Floods, November 2021 (BC MOTI)
Newtonian / Non‐Newtonian Fluid
Viscosity
Fluid Mechanics, Hibbeler
© UBC
Ali Habibzadeh, PhD, PEng, PMP
13
Viscosity
• Dilatants
• quicksand, slurries, corn starch
• Pseudoplastics
• paint and ketchup
• Ideal plastics (or Bingham fluids)
• Clay suspensions and toothpaste
© UBC
Ali Habibzadeh, PhD, PEng, PMP
14
Newtonian / Non‐Newtonian Fluid
Tailings Slurry Lab Testing
Bernoulli Equation (B.E.) ‐ Review
Bernoulli Equation (B.E.) ‐ Review
Secondary Currents in OCF
25
Open Channel Flow – Specific Energy

Classification of Open Channel Flows
Propagation of disturbance (wave)
 Propagation
= spread out and grow
← ‐c
c→
Depth y
Flow velocity V = 0 (still water)
Propagation speed of a surface wave in shallow water = c 
gy
g = gravitational acceleration = 9.81 m/s2
Open Channel Flow – Classification 1
Subsonic
Subcritical
Sonic
critical
Supersonic
Supercritical
27
Open Channel Flow – Specific Energy

Propagation of disturbance (wave)
 Propagation
= spread out and grow
← ‐c
c→
Depth y
Flow velocity V ≠ 0
Three possibilities:
I.
V < c → V / c < 1 → Subcri cal
II.
V = c → V / c = 1 → Cri cal
III. V > c → V / c > 1 → Supercri cal
Froude Number F  V  V
(dimensionless)
c
gy
(Open‐Channel Hydraulics, Akan, A.O., 2006)
28
Open Channel Flow – Specific Energy
(serc.carleton.edu)
Open Channel Flow – Classification 2
Open Channel Flow (OCF)
“Steady”
“Unsteady”
(v = const. with time)
(v varies with time)
“Uniform”
“Non‐uniform”
Gradually Varying
(v = const. with space)
(v varies with space)
(Quasi‐steady)
Gradually
Varying
Rapidly Varying
CIVL 316
Rapidly Varying
Open Channel Flow – Classification 2
Open Channel Flow (OCF)
CIVL 316
“Steady”
“Unsteady”
(v = const. with time)
(v varies with time)
“Uniform”
“Non‐uniform”
Gradually Varying
(v = const. with space)
(v varies with space)
(Quasi‐steady)
Gradually
Varying
Rapidly Varying
Rapidly Varying
Hydrostatic Pressure in OCF?
• Static water
• For example, in ponds and lakes
• Near‐zero acceleration
• Uniform and steady flows
• Streamlines are approximately straight and parallel
• Gradually varied flow (non‐uniform).
• We can apply the B.E. if we can assume pressure
distribution is hydrostatic.
Hydrostatic Pressure in OCF?
Hydrostatic Pressure in OCF?
• Where pressure distribution in is NOT
hydrostatic:
• “rapidly varied flow”
• Steep channels
• Curvilinear streamlines
• Steep Channels
Open Channel Hydraulics by Chow
• Pressure needs to be corrected for slope
𝟐
Can we use hydrostatic pressure in
OCF?
• Curvilinear Streamlines
• Pressure in not hydrostatic
convex
concave
Open Channel Hydraulics by Chow