Marmot Dam Marmot Dam RemovalRemoval

Predictions and Predictions and ObservationsObservations

Yantao Cui1, Bruce Orr1, Andrew Wilcox2,

Jen Vick3, Charles Podolak4, and Peter Wilcock4

1. Stillwater Sciences, 2855 Telegraph Ave., Berkeley, California

2. Department of Geosciences, U of Montana, Missoula, MT

3. Consultant, 416 Perry Avenue, Pacifica, CA 94044

4. Dept. of Geography & Environmental Engineering, Johns Hopkins University, Baltimore, MD

2008 AGU Fall Meeting, San Francisco, CA

2

Courtesy of Portland General

Electric (PGE)

3

$

$

$

$

$

#

#

# #

SANDYMARMOT

TROUTDALE

BRIGHTWOOD

Marmot Diversion Dam

Little Sandy Diversion Dam BRIGHTWOOD

TROUTDALE

MARMOTSANDY

Sandy R

Bull Run Dam 2

Bull Run Dam 1

Bull Run Powerhouse

0 5 Miles

Stillwater Sciences. 5/24/2000N

StreamsFlume

# Cities

Drainage Area: 680 km2 at Marmot Dam 1,120 km2 at Bull Run River confluence 1,305 km2 at Columbia River confluence

Mt. Hood

50 km to Portland, Oregon

4

0

50

100

150

200

250

300

-5 0 5 10 15 20 25 30 35 40 45 50

Distance from Marmot Dam (km)

Ele

vati

on

(m

)

Reach 5Reach 4Reach 3Reach 2Reach 1

Marmot Dam

Dodge Park

Oxbow ParkDabney Park

Revenue Bridge

Rea

ch 0

(re

serv

oir

area

)

5

Key Issues Necessitate Key Issues Necessitate Sediment Transport Sediment Transport

ModelingModeling Fish habitatFish habitat

Spawning habitat;Spawning habitat; Rearing habitat;Rearing habitat; Passage. Passage.

Home owner – Home owner – flooding risks.flooding risks.

Piles ~ 600 ft high in a football field!

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Modeling ChallengesModeling Challenges

Coupled modeling of up- and Coupled modeling of up- and downstream reaches;downstream reaches;

Large size range (0.5 – 250 mm);Large size range (0.5 – 250 mm); Stratified sediment deposit;Stratified sediment deposit; Large temporal scale (~ 10 years);Large temporal scale (~ 10 years); Large spatial scale (~50 km).Large spatial scale (~50 km).

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Model Model FoundationFoundation

Sediment pulse work (Gary Parker, Tom Lisle, Sediment pulse work (Gary Parker, Tom Lisle, Jim Pizzuto, Yantao Cui and colleagues);Jim Pizzuto, Yantao Cui and colleagues);

Reservoir deposit = sediment pulse,Reservoir deposit = sediment pulse,

Sediment pulse model should work for Sediment pulse model should work for dam removal simulation with some dam removal simulation with some adaptations.adaptations.

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Simulated Dam Removal Simulated Dam Removal AlternativesAlternatives

Blow-and-go;Blow-and-go; Two season staged removal;Two season staged removal; Dredging prior to dam removal.Dredging prior to dam removal.

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Results of Sediment Results of Sediment Transport ModelingTransport Modeling

Staged two-season removal provides Staged two-season removal provides absolutely no benefitabsolutely no benefit;;

Dredging 15% of sediment (the max Dredging 15% of sediment (the max can be dredged in one year) provides can be dredged in one year) provides minimal benefitminimal benefit in terms of minimizing in terms of minimizing downstream sediment deposition; downstream sediment deposition;

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Selection of Dam Removal Selection of Dam Removal OptionOption

Because multiple-year dredging is Because multiple-year dredging is technically unreliable (a winter technically unreliable (a winter storm may completely fill in the storm may completely fill in the previous dredging slot) and previous dredging slot) and economically unacceptable, the only economically unacceptable, the only sensible dam removal alternative is sensible dam removal alternative is blow-and-go, blow-and-go, provided that modeling provided that modeling results indicated no serious impactsresults indicated no serious impacts..

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Key ResultsKey Results

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Modeling Modeling ResultsResults

Reservoir Reservoir erosion starts erosion starts fast but fast but slowdown slowdown after year one;after year one;

Not depositing Not depositing everywhere;everywhere;

Need a few Need a few years.years.

Reach 3 Reach 4 Reach 5

Rea

ch 1

1st year

2nd year

3rd year

4th year

5th year

6th year

7th year

10th year

8th year

9th year

Vertical Scale: each grid = 1 m

Horizontal Scale: 10 km

1st year

Rea

ch 0

Initial

Rea

ch 2

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Modeling Modeling ResultsResults

Annual Annual change is change is small except small except during the during the first couple first couple of years at of years at selected selected locations.locations.

Reach 2 Reach 3 Reach 4 Reach 5

Reach 1

1st year

2nd year

3rd year

4th year

5th year

6th year

7th year

10th year

8th year

9th year

Vertical Scale: each grid = 0.3 m/yr

Horizontal Scale: 10 km

1st year

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Modeling ResultsModeling Results

Sand pass through the river quickly to the Sand pass through the river quickly to the Columbia River;Columbia River;

Sand deposition is minor and near mouth.Sand deposition is minor and near mouth.

0

0.2

0.4

0.6

0.8

1

1.2

34 36 38 40 42 44 46 48

Distance from Marmot Dam (km)

Th

ickn

ess

of

San

d D

epo

siti

on

(m

)

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Modeling ResultsModeling Results

TSS < 500 ppm;TSS < 500 ppm; Spikes associated with storm Spikes associated with storm

events;events; Fish ok!Fish ok!

10

100

1000

0 365 730

Time (days)

Su

sp

en

de

d S

ed

imen

t C

on

cen

tra

tio

n (

pp

m)

Marmot Dam (0 km)

Sandy below Bull Run River confluence (20 km)

Downstream of Dabney Park (40 km)

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MonitoringMonitoring

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NCED Field NCED Field MeasurementsMeasurements 4 years4 years

Summer 2007-Summer 2007-Summer 2010Summer 2010

Repeat SurveysRepeat Surveys Deposit VolumeDeposit Volume Deposit Deposit

LocationLocation Pebble countsPebble counts

Surface GSDSurface GSD

Reach 3 Reach 4 Reach 5

Rea

ch 1

1st year

2nd year

3rd year

4th year

5th year

6th year

7th year

10th year

8th year

9th year

Vertical Scale: each grid = 1 m

Horizontal Scale: 10 km

1st year

Rea

ch 0

Initial

Rea

ch 2

Chuck’s play ground!

PGE survey for end point analysis!LiDAR survey in 2006, 2007 and 2008.

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Comparisons with Comparisons with Observations One Year Observations One Year

After RemovalAfter RemovalThe quick initial erosion of the reservoir The quick initial erosion of the reservoir

deposit without forming a head-cut;deposit without forming a head-cut;

Low TSS except in the first few Low TSS except in the first few hours (Major et al. 2008 hours (Major et al. 2008 EOS EOS TransactionsTransactions););Deposition in Reach 1, almost Deposition in Reach 1, almost nothing further downstream.nothing further downstream.

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Reservoir AreaReservoir Area

-10

-8

-6

-4

-2

0

2

00.511.522.5

Distance Upstream from Marmot Dam (km)

Cha

nge

in A

vera

ge B

ed E

leva

tion

One

Yea

r F

ollo

win

g D

am R

emov

al (

m)

Flow direction

Dry

Average

Wet

Note: modeling results (lines) used discharge record of a wet, an average, and a dry year as model input, providing three different predictions.

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-1

0

1

2

3

4

5

0 10 20 30 40

Distance from Marmot Dam (km)

Cha

nge

in A

vera

ge B

ed E

leva

tion

One

Yea

r F

ollo

win

g D

am R

emov

al (

m)

Reach 3 Reach 4 Reach 5

Rea

ch 1

Rea

ch 2

Note: modeling results (lines) used discharge record of a wet, an average, and a dry year as model input, providing three different predictions.

Average yearWet yearDry year

-1

0

1

2

3

4

5

0 0.3 0.6 0.9 1.2 1.5 1.8

Average

Dry

Wet

PGE survey data

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NCED Field Measurements NCED Field Measurements (C. Podolak)(C. Podolak) Wedge in upper part of reach 1Wedge in upper part of reach 1 No measurable deposition in study areas in No measurable deposition in study areas in

reaches 2, 3 or 4reaches 2, 3 or 4 No measurable change in GSD in No measurable change in GSD in

downstream reachesdownstream reaches

Reach 3 Reach 4 Reach 5

Rea

ch 1

1st year

2nd year

3rd year

4th year

5th year

6th year

7th year

10th year

8th year

9th year

Vertical Scale: each grid = 1 m

Horizontal Scale: 10 km

1st year

Rea

ch 0

Initial

Rea

ch 2

(Note: simulation results are based on average hydrologic condition.)

Mar

mo

t D

am (

14.7

m t

all)

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PerspectivePerspective

0

50

100

150

200

250

-5 0 5 10 15 20 25 30 35 40 45 50Distance from Marmot Dam (km)

Ele

va

tio

n (

m)

Not much change beyond this reach. Primary concern here was fish passage.

Primary spawning habitat. The deposit was allowed to go downstream because modeling results indicated not much will occur here. All the signs to date show that modeling results will remain true in the future, but we may want to wait for a few years before we can give the prediction a final verdict.

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Nov 17, 2008 1150 cfs Nov 14, 2008 2800 cfs

Jan 26, 2008 850 cfs Jul 5, 2007 587 cfs

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Final RemarksFinal Remarks

Chapter 23Sedimentation Engineering, ASCE Manual 110, M.H. Garcia Ed.

www.stillwatersci.com

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AcknowledgementAcknowledgement

Funding from Funding from Portland General Portland General Electric (PGE)Electric (PGE);;

Helpful discussions with Helpful discussions with Tom LisleTom Lisle and and Bill DietrichBill Dietrich during modeling; during modeling;

Support and help from Support and help from PGE and PGE and Stillwater Sciences staffStillwater Sciences staff;;

Review of modeling report by Review of modeling report by Bill Bill DietrichDietrich, , Marcelo GarciaMarcelo Garcia, , Tom LisleTom Lisle, , Jim PizzutoJim Pizzuto, and , and Steve WieleSteve Wiele..