graber - applied habitat management at dam removals

8/6/2019 Graber - Applied Habitat Management at Dam Removals

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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?

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0 20 40 60 80 100 120 140

distance (feet)

e

le

v

a

tio

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(fe

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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



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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



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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



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What provides habitat in natural rivers?



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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

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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.

graber - applied habitat management at dam removals

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