Jennings tdec stream small

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Jennings tdec stream small

  1. 1. Understanding and Restoring StreamsGreg Jennings, PhD, PEProfessor, Biological & Agricultural EngineeringNorth Carolina State Universityjennings@ncsu.edu
  2. 2. What is a Stream?… a body of water with a current,confined within a bed andstreambanksSynonyms: bayou, beck, branch,brook, burn, creek, crick, kill, lick,rill, river, rivulet, run, slough, sykeA stream is:• conduit in the water cycle• critical habitat• connected to a watershed
  3. 3. Fluvial Geomorphology:The study of landforms and fluvial processesFluvial processes are associated with flowing water, including sediment erosion, transport, deposition
  4. 4. Fluvial Forms• Bar• Channel• Confluence• Cutoff channel• Delta• Floodplain• Gorge• Gully• Meander• Oxbow lake• Pool• Riffle• Stream• Valley• Waterfall• Watershed
  5. 5. Meandering Stream: Alluvial FormsRiffle Point Bar (deposition)Glide Run Pool
  6. 6. Bankfull
  7. 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.
  8. 8. Stream Ecosystems• Channel (bed & banks)• Floodplain• Water & Sediment• Plants & Animals Photo Credit: Eve Brantley, Auburn University
  9. 9. Stream Functions & Services1. Transport water2. Transport sediment3. Habitat (aquatic & terrestrial)4. Recreation & aesthetics5. Safe Water Supply
  10. 10. Effects of Urbanization on Streams (US EPA)
  11. 11. Urban Stream Syndrome (USS)• Response to watershed changes• Loss of natural functions & values• Causes problems locally & downstream• Requires systematic assessment & treatment
  12. 12. Symptoms of USS• Erosion & incision• Water quality decline• Habitat loss• Ecosystem degradation• Flooding• Land loss• Infrastructure damage• Recreation impaired• Aesthetics impaired• Economic loss
  13. 13. Urban Stream: Incision & bank erosion
  14. 14. Causes of USS• Watershed impervious• Channelization• Impoundments• Diversions• Floodplain filling• Pollution discharges• Sedimentation• Stormwater runoff• Utilities & culverts• Buffer loss• Neglect & Ignorance
  15. 15. Urban Disturbances to Hydrologic Cycle University of Central Florida
  16. 16. Hydrograph Changes Due to Urbanization Higher Peak Flow Urban More Runoff Volume Flashier Response Lower Baseflow Rural
  17. 17. Runoff: moreInfiltration: lessFlooding: moreBaseflow: less
  18. 18. Constraints: Utilities, Road, Bridges, Culverts
  19. 19. What Makes a Stream Healthy?1. Bed stability & diversity2. Sediment transport balance3. In-stream habitat & flow diversity4. Bank stability (native plant roots)5. Riparian buffer (streamside forest)6. Active floodplain7. Healthy watershed
  20. 20. 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
  21. 21. Riffles• Steep slope• High velocity & shear stress• Large substrate• High porosity & groundwater exchangePools• Flat slope• Low velocity & shear stress• Small substrate• Scour during high flow
  22. 22. Problems: Bed Stability & Diversity• Headcut and excess scour• Plane bed – filling of pools• Armoring
  23. 23. 2. Sediment Transport Balance• Minor erosion & deposition• Alluvial bars and benches• Sufficient stream power to avoid aggradation
  24. 24. Problems: Sediment Transport Balance• Excess stream power – eroding bed• Insufficient stream power – aggradation
  25. 25. Streams convey water and sedimentLane’s Balance (Lane, 1955) Channel Evolution Model (Schumm, 1984)
  26. 26. 3. In-stream Habitat & Flow DiversityMacrohabitats: riffles, runs, pools, glides, steps, side channels, scour holesMicrohabitats: roots, leaf packs, wood, rocks, plants, hyporheic zone
  27. 27. Problems: In-stream Habitats• Uniform flow – lack of diversity• Lack of wood, leaves, roots• Water quality – DO, nutrients, toxics
  28. 28. 4. Bank Stability• Dense native plant roots• Low banks with low stress
  29. 29. Problems: Bank Stability• Loss of vegetation• High, steep banks – channelization
  30. 30. 5. Riparian Buffer (Streamside Forest)• Diverse native plants• Food and shade
  31. 31. Problems: Riparian Buffer• Mowers and moo’ers• Invasive plants• Armoring and impervious surfaces
  32. 32. 6. Active Floodplain• Regular (every year) flooding to relieve stress• Riparian wetlands• Stormwater retention & treatment
  33. 33. Problems: Active Floodplain• Channel incision• Floodplain fill and encroachment
  34. 34. 7. Healthy Watershed• Stormwater management• Wastewater management• Upstream sediment control
  35. 35. Problems: Healthy Watershed• Stormwater energy and volume• Point and nonpoint source pollution• Erosion and sediment
  36. 36. Ecosystem Restoration:“activities that initiate or accelerate the recovery ofecosystem health, integrity, and sustainability”(SER, 2004)
  37. 37. Planning a Stream Project:• Goals? Stability, Habitat, Recreation?• Constraints? Access, Land Availability, Utilities?• Feasibility? Will it Work?• Constructability? Equipment, Materials, Time/$?
  38. 38. Case Study: Long Creek (1995-2005)• Dairy Farm: Fencing, Bank Stabilization, Planting 10 years later
  39. 39. Roaring River, Stone Mt State Park (2000-10)• Trout Stream: Channel Realignment, Structures, Planting 10 years later
  40. 40. Rocky Branch, NCSU Campus• Urban Stream: Channel Realignment, Structures, Planting
  41. 41. 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
  42. 42. 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
  43. 43. 2011 South Fork Mitchell River
  44. 44. 2011 South Fork Mitchell River
  45. 45. High-quality“reference”streams serve asdesign templates
  46. 46. Bankfull Width, Wbkf = 9.3 ft; Bankfull Area, Abkf = 13.9 ft2Mean Depth, dbkf = Abkf / Wbkf = 13.9 / 9.3 = 1.5 ftWidth to Depth Ratio, W/d = Wbkf / dbkf = 9.3 / 1.5 = 6.2
  47. 47. 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
  48. 48. Rosgen Classification of Natural Rivers• Based on physical characteristics (empirical)• Requires field measurements• Requires bankfull dimensions www.wildlandhydrology.com
  49. 49. www.wildlandhydrology.com
  50. 50. G4 Eastern NC
  51. 51. 2000 2001 2003 2003
  52. 52. 2. Floodplain Structure• Regular (every year) flooding to relieve stress• Floodwater retention & riparian wetlands• Stormwater discharge retention & treatment
  53. 53. 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 dmbkfabove thalweg Wbkf
  54. 54. Priority 1: Raise channel to existing valley and construct new meandering channel ER = 15; W/d = 12Rain will come during andimmediately following construction!2006 Town Creek Tributary 2007
  55. 55. 2008 Town Creek Tributary
  56. 56. Priority 1: lift channel Incised Stream Priority 2 & 3:lower floodplainStream Corridor Restoration: Principles, Processes, and Practices.1998. Federal Interagency Stream Restoration Working Group.
  57. 57. Priority 2: Excavate lower floodplain and construct new meandering channel ER = 6; W/d = 112008 White Slough 2010
  58. 58. Entrenchment Ratio = Wfpa / Wbkf = 90/15 = 6 White Slough 2010
  59. 59. Priority 2: Excavate lower floodplain and construct new meandering channel2004 NCSU Rocky Branch 2005
  60. 60. Rocky Branch Phase II Reach 2: Priority 2 (floodplain excavation, C channel) Entrenchment Ratio = Wfpa / Wbkf = 90/20 = 4.5Flood water flows onto floodplainseveral times each year
  61. 61. Priority 3: Excavate narrow floodplain benches in confined systems ER = 2.2; W/d = 122005 NCSU Rocky Branch 2006
  62. 62. Rocky Branch Phase II Reach 1:Priority 3 (floodplain excavation, Bc channel)Entrenchment Ratio = Wfpa / Wbkf = 40/20 = 2
  63. 63. 2008 NCSU Rocky Branch
  64. 64. Priority 3: Excavate narrow floodplain benches in confined systems ER = 1.6; W/d = 152009 Little Shades Creek 2010
  65. 65. Entrenchment Ratio = Wfpa / Wbkf = 60/38 = 1.6
  66. 66. Little Shades Creek 2010
  67. 67. In-Stream Structures (Logs & Rocks)• Streambank protection• Habitat enhancement (pools, aeration, cover)• Grade control• Sediment transport
  68. 68. Structure Criteria:• Natural materials• Habitats & passage for aquatic organisms• Natural sediment transport (alluvial systems) Do you like these?
  69. 69. Boulder J-Hook Vane
  70. 70. Runaway Truck Ramp
  71. 71. 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
  72. 72. Boulder Vane 20-25 degree angles 3-5 % arm slopes20-25 degrees3-5 % arm slopes
  73. 73. BoulderJ-Hook Vane
  74. 74. Log Vane• 2-4 % arm slopes• 20 degree arm angles• Sealed with woven geotextile & backer logs
  75. 75. 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
  76. 76. Log J-Hook Vane• Hook boulders control grade• Footer boulders and geotextile• Boulder sills
  77. 77. Log J-Hook Vane• Hook boulders control grade• Footer boulders and geotextile• Boulder sills
  78. 78. Log J-Hook Vane
  79. 79. Multiple Log Vanes Saugahatchee Creek2007 2008
  80. 80. Multiple Log Vanes Saugahatchee Creek2009 January 2009 July Photo Credit: Dan Ballard, Town of Auburn
  81. 81. Multiple Log Vanes: Saugahatchee Creek Photo Credit: Dan Ballard, Town of Auburn
  82. 82. Boulder Cross Vane
  83. 83. Cross Vane• Direct flow in new channel alignment• Grade control and scour pool• Footer boulders & geotextile
  84. 84. Cross Vane (logs embedded)• Undercut bed 2 ft and backfill with gravel, cobble, boulders, wood• Cut thalweg 0.5 ft deep
  85. 85. Double-Drop Boulder Cross Vane Photo Credit: Darrell Westmoreland, North State Environmental, Inc.
  86. 86. Double-Drop Boulder Cross Vane
  87. 87. Offset Boulder Cross Vane at a Bridge
  88. 88. Boulder W-Vane
  89. 89. Boulder Double Wing Deflector
  90. 90. Constructed Riffle
  91. 91. 1st Order Streambed Transplant• Substrate transfer from old channel to new channel
  92. 92. Constructed Riffle• Undercut bed 2 ft and backfill with gravel, cobble, boulders, wood• Cut thalweg 0.5 ft deep
  93. 93. Constructed Riffle• Undercut bed 2 ft and backfill with gravel, cobble, boulders, wood• Cut thalweg 0.5 ft deep
  94. 94. Riffles withBouder/Log Steps
  95. 95. Wood• Food sources• Cover• Scour pools• Flow diversity
  96. 96. Brush Toe• Layers of logs and brush under water in pools• Live cuttings above water (silky dogwood, elderberry)• Matting, seed, transplanted alders on top
  97. 97. Brush Toe• Layers of logs and brush under water in pools• Live cuttings above water (silky dogwood, elderberry)• Matting, seed, transplanted alders on top
  98. 98. Summary: Plan for Success1. Plan for floods -- immediately & often2. Plan for dry weather3. Plan for vegetation maintenance4. Understand constraints5. Expect the Unexpected

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