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Applied Habitat ManagementApplied Habitat Managementat Dam Removalsat Dam Removals
Dam Removal DemystifiedDam Removal Demystified
North CarolinaNorth Carolina
June 14, 2011June 14, 2011
Brian GraberBrian Graber
American RiversAmerican Rivers
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Outline:
Healthy RiverCharacteristics
Design with Habitatin Mind
Active HabitatAdditions?
86
88
90
92
94
96
98
0 20 40 60 80 100 120 140
distance (feet)
e
le
v
a
tio
n
(fe
e
t)
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Characteristics of River Habitat
ComplexityComplexityContinuityContinuity
Flow RegimeFlow Regime Water QualityWater Quality
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River species need different habitats:
Seasonally
Through life history
Refuge from events
Genetic diversity
Rivers are long, linear ecosystems
River Health: Connectivity
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Different species need connectivity in waterand along bed, banks, and floodplain
River Health: Connectivity
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Habitat Structure: Complexity
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**Good habitat is messy**
In-channel
On banks
On bed
Complexity(habitat) isprovided by:
Vegetation
Substrate
Dead wood(LWD)
Bed features
Dynamicplanform
River Health: Complexity
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Bed Feature Complexity
Slope 0% to 1% -
meandering
with pools and riffles
Slope 1% to 2% -
transitional
Slope > 2% -
step-pools
Recent research is finding thatpre-settlement rivers had even
more complexity than currenttheory (Abbe and Montgomery2003; Walter and Merritts2008)
River Health: Complexity
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Designing with Habitat in Mind
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Restoration: return to self-sustaining processes within the
current (and future) land use
Defining restoration
Return to a pre-disturbance
state?
Recent research has been highlycritical of river restoration
Dam removals turn rivers backinto rivers and let them do theirown work
Restoration Theory
Restoration Theory
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Concept Checklist for Successful Restoration
Think long-term
Pursue self-sustaining approaches First, eliminate stressors Simulate nature
Restoration Theory
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Forget about short-term benefits
and impacts
Use a 50-year rule in project planning
Think about what the river will be like in 50years and what you're doing or not doing tocontribute to that
Restoration Theory: Think Long-Term
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Anything that requires maintenance is notreally a long-term solution
Natural river processes provide habitat that is
Long-term, self-sustaining
Broad in spatial scale instead of localized
Beneficial to multiple species and life stages
Don't depend on human intervention long-term
Budgets change
Programs change
Institutional knowledge disappears
Restoration Theory: Self-Sustainability
d d ll
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Rivers are dynamic and will repairthemselves if given the opportunity
Restoration Theory: Eliminate Stressors
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The majority of the habitat restoration
comes from removing the damWater quality, flow regime, connectivity, complexity
Restored fish passage
Restored connectivity along bed, banks, riparian area
Temperature regime improvement (and associateddissolved oxygen)
Restored riverine flow characteristics
Restored sediment dynamics
Cleaned substrate
Restored vegetative cover long-term
Restored riverine bed features long-term
Dam removal sets river on a trajectory to restorelong-term habitat if given freedom to do its ownwork
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Simple Design Features for Habitat
1) Remove full vertical extent of the dam
Get any channel spanning structure outHabitat Design Features
2) C t i i id t
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2) Connect riparian corridor upstreamand downstream of dam
Turn retaining walls intoriver banks if possible
Consider more than justswimming species
Habitat Design Features
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3) Remove enough dam width for floodplain
Floodplains
Deposit sediment and nutrients
Increase riparian corridor connectivity
Increase roughness
Decrease stream power
Habitat Design Features
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= Qswhere
is stream power
is the specific weight of the flowing fluid
Q is the discharge
s is the energy slope of the channel
Stream Power
Stream Power
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Rivers are Dynamic:
Erode and DepositAdjustment is a natural process
and it creates habitat(Florsheim, et al. 2008)
Bed features pools, riffles, step-pools
Side channels Cut-off channels (ox bows)
Wood recruitment
Retains connectivity betweenriver and floodplain improves riparian vegetationdynamics
Source: Mount, 1995Stream Power
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Drained Impoundments Can BeExtremely Dynamic
Stream Power
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Aspect ratio:
Ratio of impoundmentwidth to river width
Low aspect ratio results
in less potential forlateral migration
Potential for verticalerosion remains
Impoundment
Aspect Ratio
Stream Power
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High aspect ratio
impoundment
Has high potentialfor lateral migrationfollowing dam
removal
Stream Power
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Active Habitat Additions?
Assess riskAssess risk Simulate natureSimulate natureGrade control,Grade control,
bank stabilizationbank stabilization
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Will short-term erosioncause long-term damage?
Species of concern
Particle sizes
2) Sediment Transport
Active Habitat: Assess Risk
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Is the river free to createhabitat?
Urban settings
Give the river as muchspace as possible
Stream Power:Baseflow dominatedspring creeks take
longer to form habitatthan powerful rivers
3) Habitat Formation
Active Habitat: Assess Risk
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Failure risk of active habitat management
Consider potential for lateral and vertical
migration
Look at aspect ratio and stream power
4) Failure potential of habitat work
Active Habitat: Assess Risk
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Simulate Nature
Consider naturalanalogs to guide
restoration
Consider historicalchanges to reference
conditions
Consider limitations
to simulating nature
Active Habitat: Simulate Nature
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Benefits of Simulating Nature
Only way to really restore multiple native
species and multiple life stages
**Over time, the river will win**
Work with the rivers natural tendency Consider 50-year timeframe
Active Habitat: Simulate Nature
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What provides habitat in natural rivers?
Active Habitat: Simulate Nature
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Woody habitatprovides:
Habitat cover
Bed complexity Creates and maintains pools
Habitat stability:
Decreased erosive power
wood only 2% of streambedarea, but accounted for 50%of the total flow resistance(Manga and Kirchner 2000)
Active Habitat: Wood
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Consider jump starting the riparian
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Consider jump-starting the ripariansuccession
plant trees
It takes 80 to 150 years of tree growth before wood is
sustainably recruited into river
Active Habitat: Wood
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How Long-Term Riparian Growth Helps Rivers
Allows succession
Provides cover
Equilibrium channel
stability
Increases infiltration
Reduces temperature
Increases DO Reduces sediment
Recruits woody habitat
Photo by Tim WattsActive Habitat: Wood
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Some Thoughts on Bank
Stabilization
What provides bank stability
in natural rivers?
Channel cross section dimensions
more important to bank stability than
what is on the banks
Appropriate channel dimensionsallow use of vegetation for stability
rather than heavy rock
(assess infrastructure risk)
Riffle X-Section at 83 on long profileDist FS HI elevation
-3.4 4.27 100 95.73 2 feet up to top of slope, top of bank is ferns and rush-2.7 4.45 100 95.55
5 10.96 100 89.04
7.6 12.5 100 87.5
9 13.7 100 86.3 bankfull-top of mini-point bar
12.6 14.31 100 85.69 on point bar15 14.94 100 85.06 LEW
18 15.52 100 84.48
20.8 15.96 100 84.04 deepest point
25.5 15.88 100 84.12
30.3 15.73 100 84.27
35.5 15.47 100 84.53
40 14.99 100 85.01 REW
42.3 13.71 100 86.29 grassy
45.3 12.28 100 87.72 trees overhang
47 11.51 100 88.49
49.7 10.31 100 89.69
56.3 9.02 100 90.98 slopes gently up to steep forested valley after 40 ft.
North Fish Creek
82
84
86
88
90
92
94
96
-10 0 10 20 30 40 50 60
distance (ft.)
elevation(
ft.)
Bank Stabilization
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Erosion can occur
in two stages:(where there is a large quantity
of fine-grained sediment)
Stage 1: Initialvertical erosion(headcutting)
Stage 2: Long-term
bank erosion
Consider managing it
in two stagesBank Stabilization
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Two-Stage
Process
Slowly drainimpoundment to allow
sediment to stabilize inplace
Later, pull back banksto a more stable crosssection
May be higher cost
may need to mobilizetwice
Bank Stabilization
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Some Thoughts on Grade Control
Grade Control
Intro to
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Intro toInstream
Structures
Grade control
cross vanes, vortex
weirs, W-weirs
Instream habitatstructures
J-hook
vanes, wing deflectors,lunker structures
Instream bankstabilization
flow
deflectors
Grade Control
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Some Grade Control Considerations
Grade control can inhibit cleaning of bed material
Grade control does not inhibit lateral migration
It may take river out of context (simulate nature)
Cross vanes create step-pools
Step-pools only occur naturally at steeper slopes
Remember stream power:
Steep streams will create their own step-pools naturally
Grade Control
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Instream Structure Failures
Mooney, et al. (2007) analyzed 127 instream structures:
Found a 42% failure rate and 32% partial failure rate
Frissell and Nawa (1992) analyzed 161 instream structuresfrom 1
5 years old:
Found 18.5% failure rate and 60% damage (impairment)rate
Miller, et al. (2010) analyzed 391 instream structures in NorthCarolina:
30% of structures were damaged, with cross vanes and
double wing deflectors sustaining the most damage
**Over time, the river will win**
Grade Control
Grade Control: Think Long-Term
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Grade Control: Think Long-Term
Because of failure rate, dont count on gradecontrol alone to protect at-risk infrastructure
If grade control is critical to sediment
management, consider that it will fail over time
Consider deformable
structures
Plan for intentional failure
Design rock sizes for a smaller flood such as 10-year or25-year floodGrade Control
D i i M ki P f
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Decision-Making Process for
Applied Habitat Management
1) What will happen if we do nothing
besides remove the dam?
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consider 50-100 year timeframe
2) Assess risk (many types)
3) Simulate nature if actively managing
Summary of Habitat Management
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Summary of Habitat ManagementSteps to Consider
1) Remove full vertical extent of dam2) Remove enough width for banksand some floodplain3)
Consider letting river reconstruct itsown habitat
4)
Consider jump-starting riparian
succession (plant trees)5) If active management desired,consider using wood
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For more information:
Brian Graber, [email protected]
Thank You!
References
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ReferencesAbbe, T.B. and Montgomery, D.R. 2003. Patterns and processes of wood
debris
accumulation in the Queets River basin, Washington. Geomorphology 51:81-107.Florsheim, J.; Mount, J.; and Chin, A. 2008. Bank erosion as a desirable attribute of
rivers. BioScience 58(6):519-529.Frissell, C. and Nawa, R.K. 1992. Incidence and causes of physical failure of artificial
habitat structures in streams of Western Oregon and Washington. North AmericanJournal of Fisheries Management 12:182-197.
Manga, M. and Michael and Kirchner, J.W. 2000. Stress partitioning in
streams by largewoody debris. Water Resources Research 36(8):2373-2379.
Miller, J.C. and Kochel, R.C. 2010. Assessment of channel dynamics, in-stream structuresand post-project channel adjustments in North Carolina and its implications toeffective stream restoration. Environmental Earth Sciences 59:1681-1692.
Miller, S.W.; Budy, P.; and Schmidt, J.C. 2010. Quantifying macroinvertebrate
responses
to in-stream habitat restoration: applications of meta-analysis to river restoration.
Restoration Ecology 18(1):8-19.Mooney, D.; Holmquist-Johnson, C.; and Holburn, E. 2007. Qualitative evaluation of rock
weir field performance and failure mechanisms. U.S. Bureau of Reclamation TechnicalServices Center.
Palmer, M.A.; Menninger, H.L.; and Bernhardt, E. 2010. River restoration, habitatheterogeneity and biodiversity: a failure of theory or practice?
Freshwater Biology
55: 205-222.Thompson, D. 2002. Long-term effect of instream
habitat-improvement structures on
channel morphology along the Blackledge
and Salmon Rivers, Connecticut, USA.
Environmental Management 29(1):250-265.Stewart, et al. 2006. Does the use of in-stream structures and woody debris increase the
abundance of salmonids? Centre for Evidence-Based Conservation Systematic ReviewReport No. 12.
Thompson, D. 2006. Did the pre-1980 use of in-stream structures improve streams? Areanalysis of historical data. Ecological Applications 16(2): 784-796.