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Jennings tdec stream small
- 1. Understanding and RestoringStreams Greg Jennings, PhD, PE Professor, Biological & Agricultural Engineering North Carolina State University jennings@ncsu.edu
- 2. What is aStream? … 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 studyof 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: AlluvialForms Riffle Point Bar (deposition) Glide Run Pool
- 6.
- 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 Urbanizationon 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 toHydrologic Cycle University of Central Florida
- 17. Hydrograph Changes Dueto 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 aStream 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 TransportBalance • Minor erosion & deposition • Alluvial bars and benches • Sufficient stream power to avoid aggradation
- 25. Problems: Sediment TransportBalance • Excess stream power – eroding bed • Insufficient stream power – aggradation
- 26. Streams convey waterand 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 thatinitiate or accelerate the recovery of ecosystem health, integrity, and sustainability” (SER, 2004)
- 38. Planning a StreamProject: • Goals? Stability, Habitat, Recreation? • Constraints? Access, Land Availability, Utilities? • Feasibility? Will it Work? • Constructability? Equipment, Materials, Time/$?
- 39. Case Study: LongCreek (1995-2005) • Dairy Farm: Fencing, Bank Stabilization, Planting 10 years later
- 40. Roaring River, StoneMt State Park (2000-10) • Trout Stream: Channel Realignment, Structures, Planting 10 years later
- 41. Rocky Branch, NCSUCampus • 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.
- 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 ClassificationSystems • 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 ofNatural Rivers • Based on physical characteristics (empirical) • Requires field measurements • Requires bankfull dimensions www.wildlandhydrology.com
- 50.
- 51.
- 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: Raisechannel 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: Excavatelower 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: Excavatelower floodplain and construct new meandering channel 2004 NCSU Rocky Branch 2005
- 62. Rocky Branch PhaseII 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: Excavatenarrow floodplain benches in confined systems ER = 2.2; W/d = 12 2005 NCSU Rocky Branch 2006
- 64. Rocky Branch PhaseII Reach 1: Priority 3 (floodplain excavation, Bc channel) Entrenchment Ratio = Wfpa / Wbkf = 40/20 = 2
- 65. 2008 NCSU Rocky Branch
- 66. Priority 3: Excavatenarrow 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.
- 72.
- 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.
- 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.
- 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.
- 85. Cross Vane • Directflow in new channel alignment • Grade control and scour pool • Footer boulders & geotextile
- 86. Cross Vane (logsembedded) • Undercut bed 2 ft and backfill with gravel, cobble, boulders, wood • Cut thalweg 0.5 ft deep
- 87. Double-Drop Boulder CrossVane Photo Credit: Darrell Westmoreland, North State Environmental, Inc.
- 88.
- 89. Offset Boulder CrossVane at a Bridge
- 90.
- 91. Boulder Double WingDeflector
- 92.
- 93. 1st Order StreambedTransplant • Substrate transfer from old channel to new channel
- 95. Constructed Riffle • Undercutbed 2 ft and backfill with gravel, cobble, boulders, wood • Cut thalweg 0.5 ft deep
- 96. Constructed Riffle • Undercutbed 2 ft and backfill with gravel, cobble, boulders, wood • Cut thalweg 0.5 ft deep
- 97.
- 98. Wood • Food sources • Cover • Scour pools • Flow diversity
- 99. Brush Toe • Layersof logs and brush under water in pools • Live cuttings above water (silky dogwood, elderberry) • Matting, seed, transplanted alders on top
- 100. Brush Toe • Layersof logs and brush under water in pools • Live cuttings above water (silky dogwood, elderberry) • Matting, seed, transplanted alders on top
- 101. Summary: Plan forSuccess 1. Plan for floods -- immediately & often 2. Plan for dry weather 3. Plan for vegetation maintenance 4. Understand constraints 5. Expect the Unexpected