1. “the great sculptor of the landscape”
Fluvial Processes
“the great sculptor of the landscape”

2. I. The River Channel
A. Basic Mechanics
1. Laminar Flow
2. Turbulent Flow

3. I. The River Channel
B. Flow Equations and Resisting Forces
Discharge = velocity * depth * width
Q = V*A
1. Manning Equation

4. 1.Manning Equation
v = R 2/3 S ½ n
Where
v = average flow velocity
r = hydraulic radius
s = channel slope (unitless)
n = Manning roughness coefficient
R = A/P
A = Area
P = Wetted Perimeter

6. Q = A R 2/3 S ½ N
Where
Q = average flow discharge
A = area of channel
R = hydraulic radius
S = channel slope (unitless)
n = Manning roughness coefficient
R = A/P
A = Area
P = Wetted Perimeter

7. II. The Erosion Process

8. II. The Erosion Process
D. Water
Sheet Wash

10. A. Erosion

11. Rill Erosion

12. Gully Erosion

13. II. Sediment in Channels
A. Transportation
1. Suspended load
2. Bedload
B. Entrainment and Erosion

16. II. Sediment in Channels
A. Transportation
1. Suspended load
2. Bedload
3. Washload
B. Entrainment and Erosion
C. Deposition

17. II. Sediment in Channels
A. Transportation
1. Suspended load
2. Bedload
3. Washload
B. Entrainment and Erosion
C. Deposition
“ a battle between velocity and gravity”

18. III. The Quasi-Equilibrium Condition

19. III. The Quasi-Equilibrium Condition
A. Hydraulic Geometry

20. III. The Quasi-Equilibrium Condition
A. Hydraulic Geometry
Q = V*A

21. III. The Quasi-Equilibrium Condition
A. Hydraulic Geometry
Q = V*A
Q = V * w * d

22. III. The Quasi-Equilibrium Condition
A. Hydraulic Geometry
Q = V*A
Q = V * w * d
w = aQb
d = cQ f
v = kQ m

23. M = 0.26
A. Hydraulic Geometry
M = 0.4
“at a station trends”
M = 0.34

24. M = 0.5
A. Hydraulic Geometry
M = 0.4
“distance downstream trends”
M = 0.1

25. Distance Downstream

28. B. The Influence of Slope
(ft/mi)

29. B. The Influence of Slope

30. III. The Quasi-Equilibrium Condition
C. Channel Shape

31. III. The Quasi-Equilibrium Condition C. Channel Shape
….in cross section:
F = 255M-1.08
Where F = width to depth ratio (W/D)
M = % silt and clay in channel

32. IV. Channel Patterns
….in plan view (bird’s eye)
Straight
Meandering
Braided
Transition between Straight
And Meandering is when
Sinuosity is 1.5

33. IV. Channel Patterns
From: Montgomery and
Buffington, 1997

34. High Gradient, Confined Channels
Cascades

35. High Gradient, Confined Channels
Step-Pool

36. Moderate to Low Gradient, Unconfined Channels
Plane Bed

37. Plane-Bed Channels

38. Moderate to Low Gradient, Unconfined Channels
Pool Riffle

39. Sebaskachu R (Labrador) - tortuous meandering river developed on marine silt and fine sand.
Copyright © Norm Catto 2002

41. Extremely Low Gradient, Unconfined Channels
Dune Ripple

42. (pools and riffles)

43. (pools and riffles)
Riffles are spaced ~ 5-7 times
the channel width

44. (pools and riffles)

45. (pools and riffles) `

46. IV. Channel Patterns
Meanders…….

47. IV. Channel Patterns
Meanders…….

48. IV. Channel Patterns
Meanders…….

49. IV. Channel Patterns
Meanders…….

50. Meanders…….

51. A few final words on stream form….
Anastomosing channels
braided

52. A few final words on stream form….
The factors responsible are……

53. A few final words on stream form….
Why do channels take on a certain pattern?????

54. A few final words on stream form….

55. A few final words on stream form….
Why do channels take on a certain pattern?????
It’s primarily due to the relationship between slope and discharge
(or velocity)

56. A few final words on stream form….
Why do channels take on a certain pattern?????
It’s primarily due to the relationship between slope and discharge
(or velocity)
The ole’ Chezy Equ:
V = C *(RS)1/2 or
V = C *(DS)1/2

57. V = C *(DS)1/2 A few final words on stream form….
It’s primarily due to the relationship between slope and discharge (or velocity)
The ole Chezy Equ:
V = C *(DS)1/2
V = velocity
C = roughness
D = depth of flow
S = slope of channel

58. V = C *(DS)1/2 V = velocity C = roughness D = depth of flow
S = slope of channel
The change in slope is a RESPONSE to changes in channel shape,
NOT a cause of braiding
Increasing the slope of a stream DOES NOT cause it to braid.

59. V. Rivers, Equilibrium, and Time
“the profile of streams”

60. knickpoints

61. V. Rivers, Equilibrium, and Time
the graded river: (page 227)

62. V. Rivers, Equilibrium, and Time
the graded river: (page 227)
“one in which, over a period of years, slope is delicately
adjusted to provide, with available discharge and with prevailing
channel characteristics, just the velocity required for the transportation
of the load supplied from the drainage basin. The graded stream is a
system in equilibrium; its diagnostic characteristic is that any change
in any of the controlling factors will cause a displacement of the
equilibrium in a direction that will tend to absorb the effect of the
change.” Mackin, 1948

63. Factors affecting stream morphology • Width • Depth • Slope • Velocity
Lane Diagram
the graded river:
Factors affecting
stream morphology
• Width
• Depth
• Slope
• Velocity
• Discharge
• Flow resistance
• Sediment size
• Sediment load
Leopold et al (1964)

64. V. Rivers, Equilibrium, and Time
Responses from adjusting load and discharge…
Mass in = Mass out + change in storage
and…
Energy in = Energy out

65. V. Rivers, Equilibrium, and Time
Responses from adjusting load and discharge…
ACTIVITY Local Stream Gradient Response
Increase in load Aggradation
Decrease in load Degradation
Increase in discharge Degradation
Decrease in discharge Aggradation

66. V. Rivers, Equilibrium, and Time
The reservoir problem…..

67. V. Rivers, Equilibrium, and Time
The reservoir problem…..
Chris Greene Lake
Charlottesville

68. V. Rivers, Equilibrium, and Time
The reservoir problem…..