rc401 construction jennings intro
DESCRIPTION
TRANSCRIPT
Stream Restoration Project Implementation
Greg Jennings, PhD, PEProfessor & Extension SpecialistBiological & Agricultural EngineeringNorth Carolina State [email protected]
Body of water with a current, confined within a bed and streambanks
Synonyms: brook, beck, burn, creek, crick, kill, lick, rill, river, syke, bayou, rivulet, run
Streams are conduits in the water cycle and also important habitats
What is a Stream?
Photo Credit: Eve Brantley, Auburn University
• Channel (bed & banks)• Floodplain• Water• Sediment• Plants & animals
A Stream is a System:
Photo Credit: Eve Brantley, Auburn University
Stream Functions1. Transport water
2. Transport sediment
3. Habitat (aquatic & terrestrial)
4. Recreation & aesthetics
5. Safe Water Supply
What Makes a Stream Healthy?• Bed stability & diversity
• Sediment transport balance
• In-stream habitat & flow diversity
• Bank stability (native plant roots)
• Riparian buffer (streamside forest)
• Active floodplain
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
Sediment Transport Balance• Minor erosion & deposition
• Alluvial bars and benches
• Sufficient stream power to avoid aggradation
PoolRoots Wood
Leaf Pack
RiffleRocks
In-stream Habitat & Flow Diversity
Plants
Overhanging Bank
Bank Stability• Dense native
plant roots
• Low banks with low stress
Riparian Buffer (Streamside Forest)• Diverse native plants
• Food and shade
Active Floodplain• Regular (every year) flooding to relieve stress
• Riparian wetlands
• Stormwater retention & treatment
Why Restoration?
• Water quality impairments
• Habitat loss
• Ecosystem degradation
• Land loss
• Safety concerns
• Infrastructure damage
• Flooding
• Aesthetics
Why are Streams NOT Healthy?• Straightening
• Dredging
• Floodplain filling
• Sedimentation
• Stormwater
• Utilities
• Culverts & bridges
• Buffer removal
• Disdain & neglect
“activities that initiate or accelerate the recovery of ecosystem health, integrity, and sustainability” (SER, 2004)
Ecosystem Restoration
1. design of an ecological river restoration project should be based on a specified guiding image of a more dynamic, healthy river that could exist at the site
2. river’s ecological condition must be measurably improved
3. river system must be more self-sustaining and resilient to external perturbations so that only minimal follow-up maintenance is needed
4. during the construction phase, no lasting harm should be inflicted on the ecosystem
5. both pre- and post-assessment must be completed and data made publicly available
Standards for ecologically successful river restorationPalmer et al., Journal of Applied Ecology, 2005, 42, 208–217
Habitats
Water quality
Natural flow regimes
Recreation & aesthetics
Outcomes of Ecosystem Restoration
High-quality “reference” streams serve as design templates
Natural Stream Channel Stability(from Leopold)
• River has a stable dimension, pattern and profile• Maintains channel features (riffles, pools, steps)• Does not aggrade (fills) or degrade (erodes)
Restoration Components
1. Channel morphology & floodplain connection
2. In-stream structures
3. Streambank stabilization
4. Riparian buffers
5. Stream crossings
6. Stormwater/watershed management
7. Monitoring & maintenance
8. Public access & education
• Dimension (bankfull & flood flow)• Pattern (meander)• Profile (bed profile)• Floodplain connection
1. Channel Morphology & Floodplain Connection
2005 NCSU Rocky Branch 2006
2008 NCSU Rocky Branch
Bankfull Stage: Water fills the active channel and begins to spread onto the floodplain
Stream Corridor Restoration: Principles, Processes, and Practices. 1998. Federal Interagency Stream Restoration Working Group.
Priority 1
Priority 2
2006 Town Creek Tributary 2007
Priority 1: Raise channel to existing valley and construct new meandering channel
Rain will come during and immediately following construction!
2008 Town Creek Tributary
Priority 1: Raise channel to existing valley and construct new meandering channel
2008 Purlear Creek 2009
2009 Purlear Creek
Priority 1: Raise channel to existing valley and construct new meandering channel
2005 South Fork Mitchell River 2006Photo Credits: Darrell Westmoreland, North State Environmental, Inc.
2008 South Fork Mitchell River
2007 Cary Walnut Creek Tributary 2008
Priority 2: Excavate lower floodplain and construct new meandering channel
Photo Credit: David Bidelspach, Stantec, Inc.
2008 Cary Walnut Creek Tributary
Priority 2: Excavate lower floodplain and construct new meandering channel
2004 NCSU Rocky Branch 2005
2006
NCSU Rocky Branch
2006
2008 NCSU Rocky Branch
Priority 2: Excavate lower floodplain and construct new meandering channel
2008 Trib to Saugatchee Creek 2008
Wfpa
Wbkf
Entrenchment Ratio = Wfpa / Wbkf = 75/15 = 5
Priority 3. Excavate floodplain benches and add structures to maintain straight channel
2000 NCSU Rocky Branch 2001
NCSU Rocky Branch
2008
Priority 3: Excavate narrow floodplain benches in confined systems
2009 Little Shades Creek 2010
Wfpa
Wbkf
Entrenchment Ratio = Wfpa / Wbkf = 60/38 = 1.6
2. In-Stream Structures (Logs & Rocks)• Streambank protection• Habitat enhancement (pools, aeration, cover)• Grade control• Sediment transport
Boulder Vane (single-arm)
Runaway Truck Ramp
J-Hook Boulder Vane
J-Hook
Boulder Vane
J-Hook Boulder Vane
J-Hook Boulder Vane
J-Hook
Log Vane
J-Hook Log Vane
J-Hook Log Vane
Double Drop J-Hook Log Vane
Multiple Log Vanes
Saugahatchee Creek
2007
2008
Multiple Log Vanes
Saugahatchee Creek
2009 January
2009 JulyPhoto Credit: Dan Ballard, Town of Auburn
Boulder Cross Vane
Double-Drop Boulder Cross Vane
Photo Credit: Darrell Westmoreland, North State Environmental, Inc.
Photo Credit: Darrell Westmoreland, North State Environmental, Inc.
Double-Drop Boulder Cross Vane
Double-Drop Boulder Cross Vane
Double-Drop Offset Boulder Cross Vane
Photo Credit: CAWACO RC&D
Double-Drop Offset Boulder Cross Vane
Offset Boulder Cross Vane at a Bridge
Boulder W-Vane
Boulder Double Wing Deflector
Boulder Double Wing Deflector
Boulder Single Wing Deflector
Constructed Riffle
Z - Vane
Constructed Step-Pool
Constructed Step-Pool
Constructed Step-Pool + Cross Vane
Habitat Enhancements
• Food sources• Cover• Scour pools• Flow diversity
Pool Maintenance
Successful Structures
• Properly designed and located• Low profile• Constructed to withstand stress• Excellent vegetation
• Temporary matting• Root wads• Bioengineering (living brush mattress)• Armoring
3. Streambank Stabilization
• Biodegradable (coir, jute, excelsior)• Seed and straw UNDER mat• Keep matting relaxed• Key in at top• Stakes: wood or biodegradable plastic
Temporary Matting
Root Wads
10-15 ft tree trunk attached
Streambank Bioengineering:
2007 NCSU Rocky Branch 2008
Integrating living woody and herbaceous materials to increase strength and structure of the soil (i.e. increase critical shear stress)
Brush Mattress
live cuttings of silky willow in dormant season
2007 October
2009 August
Newland Kentucky Creek
bioengineering with black willow cuttings
4. Riparian Buffer (Streamside Forest)• Temporary ground covers• Permanent grasses• Wetland plants• Shrubs and trees
Grasses: temporary & permanent ground covers (wheat, rye, millet, switchgrass)
Wetland plants: transplants, containers, seed (rushes, sedges, flowering plants)
Live Stakes(willows, dogwoods,
elderberry, birch, ninebark, etc)
Transplants, Bare roots, & Containers
5. Stormwater Management
• Energy dissipation• Floodplain retention• Channel protection• Water quality treatment
Floodplain stormwater retention and treatment
6. Stream Crossings
• Aquatic organism passage• Minimize geomorphic impacts• Pass flood flows
7. Monitoring & Maintenance• Projects are most vulnerable early• Natural adjustments to hydrologic &
habitat conditions
8. Public Access & Education• Greenways & paths• Signs• Tours
Why do Projects Fail?
1. Faulty design
2. Faulty construction
3. Poor vegetation
4. Constraints in valley
5. Watershed conditions