Stream Restoration<br />Greg Jennings, PhD, PE<br />Professor, Biological & Agricultural Engineering<br />North Carolina S...
What is a Stream?<br />… a body of water with a current, confined within a bed and streambanks<br />Synonyms:  bayou, beck...
Streams are Ecosystems<br /><ul><li>Communities of organisms and their physical, chemical, and biological environments</li...
Sediment transport balance
In-stream habitat & flow diversity
Bank stability (native plant roots)
Riparian buffer (streamside forest)
Active floodplain</li></li></ul><li>Bed Stability & Diversity<br /><ul><li>Appropriate size sediments to resist shear stress
Riffle/Pool sequences in alluvial streams
Step/Pool sequences in high-gradient streams</li></ul>Photo Credit: Eve Brantley, Auburn University<br />
Sediment Transport Balance<br /><ul><li>Minor erosion & deposition
Alluvial bars and benches
Sufficient stream power to avoid aggradation
No net change in sediment over long time</li></li></ul><li>In-stream Habitat & Flow Diversity<br />Overhanging Bank<br />R...
Bank Stability<br /><ul><li>Dense native plant roots
Low banks with low stress</li></li></ul><li>Riparian Buffer (Streamside Forest)<br /><ul><li>Diverse native plants
Food and shade</li></li></ul><li>Active Floodplain<br /><ul><li>Regular (every year) flooding to relieve stress
Riparian wetlands
Stormwater retention & treatment</li></li></ul><li>Why Restoration?<br /><ul><li>Water quality impairments
Habitat loss
Ecosystem degradation
Land loss
Safety concerns
Infrastructure damage
Flooding
Aesthetics</li></li></ul><li>Stream Insults<br /><ul><li>Straightening & dredging
Floodplain filling
Watershed manipulation
Sedimentation & stormwater
Pollution discharges
Utilities & culverts
Buffer removal
Disdain & neglect</li></li></ul><li>Ecosystem Restoration<br /><ul><li>Activities that initiate or accelerate the recovery...
Outcomes of Ecosystem Restoration<br /><ul><li>Habitats
Water quality
Natural flow regimes
Recreation & aesthetics
Public acceptance</li></li></ul><li>Restoration Components<br />Channel morphology & floodplain connection<br />In-stream ...
Healthy “reference” streams serve as design templates<br />
Natural Stream Channel Stability<br />(from Leopold)<br />River has a stable dimension, pattern and profile<br />Maintains...
1. Channel Morphology & Floodplain Connection<br /><ul><li>Dimension (bankfull & flood flow)
Pattern (meander)
Profile (bed profile)
Floodplain connection</li></ul>2005NCSU Rocky Branch2006<br />
2008NCSU Rocky Branch<br />
Bankfull Stage:  Water fills the active channel and begins to spread onto the floodplain<br />Stream Corridor Restoration:...
Priority 1:Raise channel to existing valley and construct new meandering channel<br />Rain will come during and immediatel...
2008		          Town Creek Tributary<br />
Priority 1:Raise channel to existing valley and construct new meandering channel<br />2008Purlear Creek 	        2009<br />
2009Purlear Creek<br />
Priority 1<br />Priority 2<br />
Priority 2:Excavate lower floodplain and construct new meandering channel<br />2008Trib to Saugatchee Creek              2...
Entrenchment Ratio = Wfpa / Wbkf = 75/15 = 5 <br />Wfpa<br />Wbkf<br />
Priority 2:Excavate lower floodplain and construct new meandering channel<br />2007		   Cary Walnut Creek Tributary  	    ...
2008		   Cary Walnut Creek Tributary<br />
Priority 3:Excavate narrow floodplain benches in confined systems<br />2009Little Shades Creek              	      2010<br />
Entrenchment Ratio = Wfpa / Wbkf = 60/38 = 1.6 <br />Wfpa<br />Wbkf<br />
Before<br />Seoul, Korea<br />Cheonggye<br />“Extreme Restoration”<br />After<br />Fac. of Environment & Life Sciences, Se...
Fac. of Environment & Life Sciences, Seoul Women's University <br />After<br />Before<br />
Fac. of Environment & Life Sciences, Seoul Women's University <br />Restoration process of Cheonggye stream<br />
Fac. of Environment & Life Sciences, Seoul Women's University<br />Fac. of Environment & Life Sciences, Seoul Women's Univ...
Fac. of Environment & Life Sciences, Seoul Women's University <br />
Stream Design Approaches<br />Threshold Channel<br />Alluvial Channel<br />Regime Equations<br />Analogy (Reference Reach)...
Threshold Channels<br />Rigid boundary systems<br />Simple design approach:  select channel configuration where the stress...
Threshold Channels<br />
Shear Stress<br />
Threshold Channels – Shear Stress<br />
Shear Stress<br /> = Rs<br /> = Shear Stress (lb/ft2)<br /> = Unit Weight of Water = 62.4 lb/ft3<br />R = Hydraulic Ra...
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Rc201 day 1 jennings 10

  1. 1. Stream Restoration<br />Greg Jennings, PhD, PE<br />Professor, Biological & Agricultural Engineering<br />North Carolina State University<br />jennings@ncsu.edu<br />
  2. 2. What is a Stream?<br />… a body of water with a current, confined within a bed and streambanks<br />Synonyms:  bayou, beck, branch, brook, burn, creek, crick, kill, lick, rill, river, rivulet, run, slough, syke<br />Streams are conduits in the water cycle and also important habitats<br />Photo Credit: Eve Brantley, Auburn University<br />
  3. 3. Streams are Ecosystems<br /><ul><li>Communities of organisms and their physical, chemical, and biological environments</li></li></ul><li>What Makes a Stream Healthy?<br /><ul><li>Bed stability & diversity
  4. 4. Sediment transport balance
  5. 5. In-stream habitat & flow diversity
  6. 6. Bank stability (native plant roots)
  7. 7. Riparian buffer (streamside forest)
  8. 8. Active floodplain</li></li></ul><li>Bed Stability & Diversity<br /><ul><li>Appropriate size sediments to resist shear stress
  9. 9. Riffle/Pool sequences in alluvial streams
  10. 10. Step/Pool sequences in high-gradient streams</li></ul>Photo Credit: Eve Brantley, Auburn University<br />
  11. 11. Sediment Transport Balance<br /><ul><li>Minor erosion & deposition
  12. 12. Alluvial bars and benches
  13. 13. Sufficient stream power to avoid aggradation
  14. 14. No net change in sediment over long time</li></li></ul><li>In-stream Habitat & Flow Diversity<br />Overhanging Bank<br />Roots<br />Wood<br />Pool<br />Leaf Pack<br />Plants<br />Riffle<br />Rocks<br />
  15. 15. Bank Stability<br /><ul><li>Dense native plant roots
  16. 16. Low banks with low stress</li></li></ul><li>Riparian Buffer (Streamside Forest)<br /><ul><li>Diverse native plants
  17. 17. Food and shade</li></li></ul><li>Active Floodplain<br /><ul><li>Regular (every year) flooding to relieve stress
  18. 18. Riparian wetlands
  19. 19. Stormwater retention & treatment</li></li></ul><li>Why Restoration?<br /><ul><li>Water quality impairments
  20. 20. Habitat loss
  21. 21. Ecosystem degradation
  22. 22. Land loss
  23. 23. Safety concerns
  24. 24. Infrastructure damage
  25. 25. Flooding
  26. 26. Aesthetics</li></li></ul><li>Stream Insults<br /><ul><li>Straightening & dredging
  27. 27. Floodplain filling
  28. 28. Watershed manipulation
  29. 29. Sedimentation & stormwater
  30. 30. Pollution discharges
  31. 31. Utilities & culverts
  32. 32. Buffer removal
  33. 33. Disdain & neglect</li></li></ul><li>Ecosystem Restoration<br /><ul><li>Activities that initiate or accelerate the recovery of ecosystem health, integrity, and sustainability (SER, 2004).</li></li></ul><li>Standards for ecologically successful river restoration<br />Palmer et al., Journal of Applied Ecology, 2005, 42, 208–217<br />design of an ecological river restoration project should be based on a specified guiding image of a more dynamic, healthy river<br />river’s ecological condition must be measurably improved<br />river system must be more self-sustaining and resilient to external perturbations so that only minimal follow-up maintenance is needed <br />during the construction phase, no lasting harm should be inflicted on the ecosystem<br />pre- and post-assessment must be completed and data made publicly available<br />
  34. 34. Outcomes of Ecosystem Restoration<br /><ul><li>Habitats
  35. 35. Water quality
  36. 36. Natural flow regimes
  37. 37. Recreation & aesthetics
  38. 38. Public acceptance</li></li></ul><li>Restoration Components<br />Channel morphology & floodplain connection<br />In-stream structures<br />Streambank bioengineering<br />Riparian buffers & habitat enhancements<br />Stream crossings<br />Stormwater/watershed management<br />Monitoring & maintenance<br />Public access & education<br />
  39. 39. Healthy “reference” streams serve as design templates<br />
  40. 40. Natural Stream Channel Stability<br />(from Leopold)<br />River has a stable dimension, pattern and profile<br />Maintains channel features (riffles, pools, steps)<br />Does not aggrade (fills) or degrade (erodes)<br />
  41. 41. 1. Channel Morphology & Floodplain Connection<br /><ul><li>Dimension (bankfull & flood flow)
  42. 42. Pattern (meander)
  43. 43. Profile (bed profile)
  44. 44. Floodplain connection</li></ul>2005NCSU Rocky Branch2006<br />
  45. 45. 2008NCSU Rocky Branch<br />
  46. 46. Bankfull Stage: Water fills the active channel and begins to spread onto the floodplain<br />Stream Corridor Restoration: Principles, Processes, and Practices. 1998. Federal Interagency Stream Restoration Working Group.<br />
  47. 47. Priority 1:Raise channel to existing valley and construct new meandering channel<br />Rain will come during and immediately following construction!<br />2006 Town Creek Tributary 2007<br />
  48. 48. 2008 Town Creek Tributary<br />
  49. 49. Priority 1:Raise channel to existing valley and construct new meandering channel<br />2008Purlear Creek 2009<br />
  50. 50. 2009Purlear Creek<br />
  51. 51. Priority 1<br />Priority 2<br />
  52. 52. Priority 2:Excavate lower floodplain and construct new meandering channel<br />2008Trib to Saugatchee Creek 2008<br />
  53. 53. Entrenchment Ratio = Wfpa / Wbkf = 75/15 = 5 <br />Wfpa<br />Wbkf<br />
  54. 54. Priority 2:Excavate lower floodplain and construct new meandering channel<br />2007 Cary Walnut Creek Tributary 2008<br />Photo Credit: David Bidelspach, Stantec, Inc.<br />
  55. 55. 2008 Cary Walnut Creek Tributary<br />
  56. 56. Priority 3:Excavate narrow floodplain benches in confined systems<br />2009Little Shades Creek 2010<br />
  57. 57. Entrenchment Ratio = Wfpa / Wbkf = 60/38 = 1.6 <br />Wfpa<br />Wbkf<br />
  58. 58. Before<br />Seoul, Korea<br />Cheonggye<br />“Extreme Restoration”<br />After<br />Fac. of Environment & Life Sciences, Seoul Women's University <br />
  59. 59. Fac. of Environment & Life Sciences, Seoul Women's University <br />After<br />Before<br />
  60. 60. Fac. of Environment & Life Sciences, Seoul Women's University <br />Restoration process of Cheonggye stream<br />
  61. 61. Fac. of Environment & Life Sciences, Seoul Women's University<br />Fac. of Environment & Life Sciences, Seoul Women's University <br />Typical cross-section of the restored stream section<br />
  62. 62. Fac. of Environment & Life Sciences, Seoul Women's University <br />
  63. 63. Stream Design Approaches<br />Threshold Channel<br />Alluvial Channel<br />Regime Equations<br />Analogy (Reference Reach)<br />Hydraulic Geometry<br />Analytical Models<br />Combination of Methods<br />
  64. 64. Threshold Channels<br />Rigid boundary systems<br />Simple design approach: select channel configuration where the stress applied during design conditions is below the allowable stress for the channel boundary<br />
  65. 65. Threshold Channels<br />
  66. 66. Shear Stress<br />
  67. 67. Threshold Channels – Shear Stress<br />
  68. 68. Shear Stress<br /> = Rs<br /> = Shear Stress (lb/ft2)<br /> = Unit Weight of Water = 62.4 lb/ft3<br />R = Hydraulic Radius (ft) = A/P<br />s = Energy Slope (water surface) (ft/ft)<br />A = Riffle Cross-Section Area (ft2)<br />P = Wetted Perimeter (ft) [P ~ Wbkf + 2 x Dbkf]<br />http://www.epa.gov/warsss/sedsource/bedload.htm<br />
  69. 69. Threshold Channels – Shear Stress<br />
  70. 70.
  71. 71.
  72. 72. Shear Stress Around Bends <br />
  73. 73. Shear Stress Distribution<br />Flow around bends <br />creates secondary currents <br />higher shear stresses on the channel sides and bottom compared to straight reaches <br />maximum shear stress in a bend is a function of the ratio of channel curvature to bottom width <br />
  74. 74. Shear Stress Distribution<br />from Chang, 1988<br />
  75. 75. Shear Stress Distribution<br />
  76. 76. Alluvial Channels<br />Movable boundary systems<br />Complex design approach: assess sediment continuity and channel performance for a range of flows<br />Dependent variables: Width, Depth, Slope, Planform<br />Independent variables: Sediment inflow, Water inflow, Bank composition<br />Empirical & Analytical approaches should be used concurrently<br />
  77. 77. Steady State Equilibrium<br />dimension, pattern and profile of the river and its velocity have adjusted to transmit the discharge and sediment load from its catchment under the present climate and land use conditions without any systematic erosion or deposition; namely regimeconditions (Hey)<br />
  78. 78. Assumption: Stream Behavior Is Predictable<br />Streams evolve to a state of dynamic equilibrium<br />Equilibrium is a function of flow and sediment<br />Equilibrium is naturally associated with a main channel and a flood-prone area<br />The main channel is formed by the effective (“bankfull”) discharge over time<br />Alluvial stream meandering<br /> is predictable<br />
  79. 79. Design Criteria Selection<br />From Will Harman, Stream Mechanics<br />
  80. 80. Alluvial Channels – Regime Approach<br />Empirical equations<br />Use as a check<br />Hey equations:<br />
  81. 81. Alluvial Channels – Analogy Approach<br />Reference reach: Must have similar bed/bank materials, sediment inflow, slope, valley type, and hydrograph<br />Upstream/downstream of design reach is best<br />Nearby similar watershed acceptable<br />Use as a starting point or check (BE CAREFUL)<br />
  82. 82. Alluvial Channels – Hydraulic Geometry<br />
  83. 83. Alluvial Channels – Hydraulic Geometry<br />
  84. 84.
  85. 85.
  86. 86. Hydraulic Geometry<br />National Center for Earth Dynamics<br />http://www.nced.umn.edu/Stream_Restoration_Toolbox.html<br />Single-Thread Gravel-Bed Rivers Have Consistent Bankfull Geometries<br />
  87. 87. Alluvial Channels – Analytical Methods<br />Choose appropriate model<br />Assess a range of solutions<br />Use as a check<br />Analytical Design Approach, Shields, 2006<br />
  88. 88. Combination Approach to Natural Channel Design<br />Existing Conditions – valley, watershed, constraints<br />Design Goals<br />Design Criteria<br />Regime Equations<br />Analogy (Reference Reach)<br />Hydraulic Geometry (Regional Curves)<br />Other Restoration Projects<br />Analytical Models<br />
  89. 89. Natural Channel Design Approach, from Rosgen, 2006<br />
  90. 90. Design Criteria Selection<br />From Will Harman, Stream Mechanics<br />
  91. 91. Reference Reach Versus Design Reach<br />Stream restoration project immediately after construction; floodplain devoid of vegetation<br />Reference reach with mature forest<br />From Will Harman, Stream Mechanics<br />
  92. 92. Reference Reach Pattern<br />From Will Harman, Stream Mechanics<br />
  93. 93. Reference Reach:<br /><ul><li>Upstream/downstream
  94. 94. Same watershed
  95. 95. Similar watershed
  96. 96. Historical photos</li></ul>From Will Harman, Stream Mechanics<br />

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