1. Understanding and Restoring Streams
Greg Jennings, PhD, PE
Professor, Biological & Agricultural Engineering
North Carolina State University
jennings@ncsu.edu

2. What is a Stream?
… a body of water with a current,
confined within a bed and
streambanks
Synonyms: bayou, beck, branch,
brook, burn, creek, crick, kill, lick,
rill, river, rivulet, run, slough, syke
A stream is:
• conduit in the water cycle
• critical habitat
• connected to a watershed

3. Fluvial Geomorphology:
The study of landforms and fluvial processes
Fluvial processes are associated with flowing
water, including sediment
erosion, transport, deposition

4. Fluvial Forms
• Bar
• Channel
• Confluence
• Cutoff channel
• Delta
• Floodplain
• Gorge
• Gully
• Meander
• Oxbow lake
• Pool
• Riffle
• Stream
• Valley
• Waterfall
• Watershed

5. Meandering Stream: Alluvial Forms
Riffle Point Bar
(deposition)
Glide Run
Pool

6. Bankfull

7. Bankfull Stage
“corresponds to the discharge at which channel maintenance
is the most effective, that is, the discharge at which moving
sediment, forming or removing bars, forming or changing
bends and meanders, and generally doing work results in the
average morphologic characteristics” (Dunne and Leopold,1978)
Stream Corridor Restoration: Principles, Processes, and Practices. 1998. Federal Interagency Stream Restoration Working Group.

9. Stream Ecosystems
• Channel (bed & banks)
• Floodplain
• Water & Sediment
• Plants & Animals
Photo Credit: Eve Brantley, Auburn University

10. Stream Functions & Services
1. Transport water
2. Transport sediment
3. Habitat (aquatic & terrestrial)
4. Recreation & aesthetics
5. Safe Water Supply

11. Effects of Urbanization on Streams (US EPA)

12. Urban Stream Syndrome (USS)
• Response to watershed changes
• Loss of natural functions & values
• Causes problems locally & downstream
• Requires systematic assessment & treatment

13. Symptoms of USS
• Erosion & incision
• Water quality decline
• Habitat loss
• Ecosystem degradation
• Flooding
• Land loss
• Infrastructure damage
• Recreation impaired
• Aesthetics impaired
• Economic loss

14. Urban Stream: Incision & bank erosion

15. Causes of USS
• Watershed impervious
• Channelization
• Impoundments
• Diversions
• Floodplain filling
• Pollution discharges
• Sedimentation
• Stormwater runoff
• Utilities & culverts
• Buffer loss
• Neglect & Ignorance

16. Urban Disturbances to Hydrologic Cycle
University of Central Florida

17. Hydrograph Changes Due to Urbanization
Higher Peak Flow
Urban More Runoff Volume
Flashier Response
Lower Baseflow
Rural

18. Runoff: more
Infiltration: less
Flooding: more
Baseflow: less

19. Constraints: Utilities, Road, Bridges, Culverts

20. What Makes a Stream Healthy?
1. Bed stability & diversity
2. Sediment transport balance
3. In-stream habitat & flow diversity
4. Bank stability (native plant roots)
5. Riparian buffer (streamside forest)
6. Active floodplain
7. Healthy watershed

21. 1. Bed Stability & Diversity
• Appropriate size sediments to
resist shear stress
• Riffle/Pool sequences in
alluvial streams
• Step/Pool sequences in high-
gradient streams
Photo Credit: Eve Brantley, Auburn University

22. Riffles
• Steep slope
• High velocity & shear stress
• Large substrate
• High porosity & groundwater
exchange
Pools
• Flat slope
• Low velocity & shear stress
• Small substrate
• Scour during high flow

23. Problems: Bed Stability & Diversity
• Headcut and excess scour
• Plane bed – filling of pools
• Armoring

24. 2. Sediment Transport Balance
• Minor erosion & deposition
• Alluvial bars and benches
• Sufficient stream power to avoid aggradation

25. Problems: Sediment Transport Balance
• Excess stream power – eroding bed
• Insufficient stream power – aggradation

26. Streams convey water and sediment
Lane’s Balance (Lane, 1955)
Channel Evolution Model (Schumm, 1984)

27. 3. In-stream Habitat
& Flow Diversity
Macrohabitats: riffles,
runs, pools, glides,
steps, side channels,
scour holes
Microhabitats: roots, leaf
packs, wood, rocks,
plants, hyporheic zone

28. Problems: In-stream Habitats
• Uniform flow – lack of diversity
• Lack of wood, leaves, roots
• Water quality – DO, nutrients, toxics

29. 4. Bank Stability
• Dense native
plant roots
• Low banks with
low stress

30. Problems: Bank Stability
• Loss of vegetation
• High, steep banks – channelization

31. 5. Riparian Buffer (Streamside Forest)
• Diverse native plants
• Food and shade

32. Problems: Riparian Buffer
• Mowers and moo’ers
• Invasive plants
• Armoring and impervious surfaces

33. 6. Active Floodplain
• Regular (every year) flooding to relieve stress
• Riparian wetlands
• Stormwater retention & treatment

34. Problems: Active Floodplain
• Channel incision
• Floodplain fill and encroachment

35. 7. Healthy Watershed
• Stormwater management
• Wastewater management
• Upstream sediment control

36. Problems: Healthy Watershed
• Stormwater energy and volume
• Point and nonpoint source pollution
• Erosion and sediment

37. Ecosystem Restoration:
“activities that initiate or accelerate the recovery of
ecosystem health, integrity, and sustainability”
(SER, 2004)

38. Planning a Stream Project:
• Goals? Stability, Habitat, Recreation?
• Constraints? Access, Land Availability, Utilities?
• Feasibility? Will it Work?
• Constructability? Equipment, Materials, Time/$?

39. Case Study: Long Creek (1995-2005)
• Dairy Farm: Fencing, Bank Stabilization, Planting
10 years later

40. Roaring River, Stone Mt State Park (2000-10)
• Trout Stream: Channel Realignment, Structures, Planting
10 years later

41. Rocky Branch, NCSU Campus
• Urban Stream: Channel Realignment, Structures, Planting

42. Restoration Components
1. Channel morphology
2. Floodplain structure
3. Hydrologic & hydraulic
analysis
4. In-stream structures
5. Habitats & vegetation
6. Site & watershed conditions
7. Monitoring, maintenance, educ
ation

43. 1. Channel Morphology
• Dimension (baseflow, bankfull, flood flows)
• Pattern (meandering, straight, braided)
• Profile (bedform – riffle, run, pool, glide, step)
Photo Credits: Darrell Westmoreland, North State Environmental, Inc.
2005 South Fork Mitchell River 2006

44. 2011 South Fork Mitchell River

45. 2011 South Fork Mitchell River

46. High-quality
“reference”
streams serve as
design templates

47. Bankfull Width, Wbkf = 9.3 ft; Bankfull Area, Abkf = 13.9 ft2
Mean Depth, dbkf = Abkf / Wbkf = 13.9 / 9.3 = 1.5 ft
Width to Depth Ratio, W/d = Wbkf / dbkf = 9.3 / 1.5 = 6.2

48. Morphologic Stream Classification Systems
• Schumm (1977)
– Alluvial channels
– Meandering, straight, braided
– Type related to channel stability & sediment transport
• Montgomery & Buffington (1993)
– Alluvial, colluvial, bedrock channels
– Channel response related to sediment inputs
– 6 classes of alluvial channels: cascade, step-
pool, plane-bed, riffle-pool, regime, and braided
• Rosgen (1994)
www.wildlandhydrology.com

49. Rosgen Classification of Natural Rivers
• Based on physical
characteristics (empirical)
• Requires field
measurements
• Requires bankfull
dimensions
www.wildlandhydrology.com

50. www.wildlandhydrology.com

51. G4 Eastern NC

52. 2000 2001
2003 2003

54. 2. Floodplain Structure
• Regular (every year) flooding to relieve stress
• Floodwater retention & riparian wetlands
• Stormwater discharge retention & treatment

55. Entrenchment Ratio
ER = Wfpa / Wbkf
Wfpa = Width of Flood Prone Area measured at the
elevation twice bankfull max depth above thalweg
Wbkf = Width of Bankfull Channel
Wfpa
Bankfull
2 x dmbkf
dmbkf
above thalweg
Wbkf

56. Priority 1: Raise channel to existing valley
and construct new meandering channel
ER = 15; W/d = 12
Rain will come during and
immediately following construction!
2006 Town Creek Tributary 2007

57. 2008 Town Creek Tributary

58. Priority 1:
lift channel
Incised
Stream
Priority 2 & 3:
lower floodplain
Stream Corridor Restoration: Principles, Processes, and Practices.
1998. Federal Interagency Stream Restoration Working Group.

59. Priority 2: Excavate lower floodplain and
construct new meandering channel
ER = 6; W/d = 11
2008 White Slough 2010

60. Entrenchment Ratio = Wfpa / Wbkf = 90/15 = 6
White Slough 2010

61. Priority 2: Excavate lower floodplain and
construct new meandering channel
2004 NCSU Rocky Branch 2005

62. Rocky Branch Phase II Reach 2:
Priority 2 (floodplain excavation, C channel)
Entrenchment Ratio = Wfpa / Wbkf = 90/20 = 4.5
Flood water flows onto floodplain
several times each year

63. Priority 3: Excavate narrow floodplain
benches in confined systems
ER = 2.2; W/d = 12
2005 NCSU Rocky Branch 2006

64. Rocky Branch Phase II Reach 1:
Priority 3 (floodplain excavation, Bc channel)
Entrenchment Ratio = Wfpa / Wbkf = 40/20 = 2

65. 2008 NCSU Rocky Branch

66. Priority 3: Excavate narrow floodplain
benches in confined systems
ER = 1.6; W/d = 15
2009 Little Shades Creek 2010

67. Entrenchment Ratio = Wfpa / Wbkf = 60/38 = 1.6

68. Little Shades Creek 2010

69. In-Stream Structures (Logs & Rocks)
• Streambank protection
• Habitat enhancement (pools, aeration, cover)
• Grade control
• Sediment transport

70. Structure Criteria:
• Natural materials
• Habitats & passage for aquatic organisms
• Natural sediment transport (alluvial systems)
Do you like these?

71. Boulder J-Hook Vane

72. Runaway Truck Ramp

73. Boulder J-Hook Vane
• 3-5 % arm slopes
• 20-25 degree arm angles
• Boulder footers & non-woven geotextile
• 0.5 ft drops over j-hook inverts

74. Boulder Vane
20-25 degree angles
3-5 % arm slopes
20-25 degrees
3-5 % arm slopes

75. Boulder
J-Hook Vane

76. Log Vane
• 2-4 % arm slopes
• 20 degree arm angles
• Sealed with woven geotextile & backer logs

77. Log J-Hook Vane
• Direct flow away from bank around bend
• Grade control and scour pool
• Brush toe buried under log vane
• Backer logs & geotextile

78. Log J-Hook Vane
• Hook boulders control grade
• Footer boulders and geotextile
• Boulder sills

79. Log J-Hook Vane
• Hook boulders control grade
• Footer boulders and geotextile
• Boulder sills

80. Log J-Hook Vane

81. Multiple Log
Vanes
Saugahatchee
Creek
2007
2008

82. Multiple Log
Vanes
Saugahatchee
Creek
2009 January
2009 July
Photo Credit: Dan Ballard, Town of Auburn

83. Multiple Log Vanes: Saugahatchee Creek
Photo Credit: Dan Ballard, Town of Auburn

84. Boulder Cross Vane

85. Cross Vane
• Direct flow in new channel alignment
• Grade control and scour pool
• Footer boulders & geotextile

86. Cross Vane (logs embedded)
• Undercut bed 2 ft and backfill with
gravel, cobble, boulders, wood
• Cut thalweg 0.5 ft deep

87. Double-Drop Boulder Cross Vane
Photo Credit: Darrell Westmoreland, North State Environmental, Inc.

88. Double-Drop Boulder Cross Vane

89. Offset Boulder Cross Vane at a Bridge

90. Boulder W-Vane

91. Boulder Double Wing Deflector

92. Constructed Riffle

93. 1st Order Streambed Transplant
• Substrate transfer from old channel to new channel

95. Constructed Riffle
• Undercut bed 2 ft and backfill with
gravel, cobble, boulders, wood
• Cut thalweg 0.5 ft deep

96. Constructed Riffle
• Undercut bed 2 ft and backfill with
gravel, cobble, boulders, wood
• Cut thalweg 0.5 ft deep

97. Riffles with
Bouder/Log Steps

98. Wood
• Food sources
• Cover
• Scour pools
• Flow diversity

99. Brush Toe
• Layers of logs and brush under water in pools
• Live cuttings above water (silky dogwood, elderberry)
• Matting, seed, transplanted alders on top

100. Brush Toe
• Layers of logs and brush under water in pools
• Live cuttings above water (silky dogwood, elderberry)
• Matting, seed, transplanted alders on top

101. Summary: Plan for Success
1. Plan for floods -- immediately & often
2. Plan for dry weather
3. Plan for vegetation maintenance
4. Understand constraints
5. Expect the Unexpected