1. 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 A. Basic Mechanics 1. Laminar Flow 2. Turbulent Flow 3. Reynolds Number Re = driving forces = V D p = (velocity * depth * fluid density) resisting forces u (fluid viscosity) laminar < 500 700 < turbulent \

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

5. 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

7. 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

8. I. The River Channel B. Flow Equations and Resisting Forces 1. Manning Equation 2. Chezy Equation V = C *(RS) 1/2

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

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

13. 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”

14. III. The Quasi-Equilibrium Condition

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

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

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

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

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

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

21. Distance Downstream

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

25. B. The Influence of Slope

26. 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

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

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

30. (pools and riffles)

31. Riffles are spaced ~ 5-7 times the channel width

32. (pools and riffles)

33. `

34. IV. Channel Patterns Meanders…….

35. IV. Channel Patterns Meanders…….

36. IV. Channel Patterns Meanders…….

37. IV. Channel Patterns Meanders…….

39. A few final words on stream form…. braided

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

41. A few final words on stream form….

42. The factors responsible are……

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

44. A few final words on stream form….

45. Why do channels take on a certain pattern????? It’s primarily due to the relationship between slope and discharge (or velocity)

46. 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 V = C *(DS) 1/2 or

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

48. 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.

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

50. knickpoints

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

52. 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

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

54. V. Rivers, Equilibrium, and Time Responses from adjusting load and discharge…

55. V. Rivers, Equilibrium, and Time Responses from adjusting load and discharge… ACTIVITYRESPONSESLOPE

56. V. Rivers, Equilibrium, and Time Responses from adjusting load and discharge… ACTIVITYRESPONSESLOPE Increase in load?????? Decrease in load?????? Increase in discharge?????? Decrease in discharge??????

57. V. Rivers, Equilibrium, and Time Responses from adjusting load and discharge… ACTIVITYRESPONSESLOPE Increase in loadAggradationincrease Decrease in load Increase in discharge Decrease in discharge

58. V. Rivers, Equilibrium, and Time Responses from adjusting load and discharge… ACTIVITYRESPONSESLOPE Increase in loadAggradationincrease Decrease in loadDegradationdecrease Increase in discharge Decrease in discharge

59. V. Rivers, Equilibrium, and Time Responses from adjusting load and discharge… ACTIVITYRESPONSESLOPE Increase in loadAggradationincrease Decrease in loadDegradationdecrease Increase in dischargeDegradationdecrease Decrease in discharge

60. V. Rivers, Equilibrium, and Time Responses from adjusting load and discharge… ACTIVITYRESPONSESLOPE Increase in loadAggradationincrease Decrease in loadDegradationdecrease Increase in dischargeDegradationdecrease Decrease in dischargeAggradationincrease

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

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

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