tidal marsh restoration - rrnw.org€¦ · tidal marsh restoration do more or do less? a discussion...
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TIDAL MARSH RESTORATIONDO MORE OR DO LESS?
A DISCUSSION OF RESTORATION TECHNIQUES FORRECENTLY CONSTRUCTED TIDAL RECONNECTION PROJECTS
Curtis LoebMerri MartzTetra Tech Portland, OR
Matt Van EssColumbia River Estuary Study Taskforce(CREST) Astoria, OR
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Outline
Background & challenges in Columbia R. Estuary
Purpose
Methods & scope
Tidal wetland restoration - 2 case studies
Take-home considerations
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Lower Columbia River Estuary
75% loss of tidal off-channelhabitat1
Development
Agriculture
Hydropower
Many others
1 Bottom et. Al 2005
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Challenges
Photo courtesy of NPS
Science• Physical/ecological• Limited monitoring
funding• Still evolving
Legal• Pressures on
agencies• Deadlines• Site scarcity
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Purpose
Inform the state of the art
Applicability of passive & active approaches
Improve project evaluation (identification, ranking)
Improve project implementation (design, construction)
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Fort ClatsopSouth SloughWetland
FortColumbiaWetland
Lewis & ClarkRiver
ChinookRiver
A TALE OF TWO FORTS
Ft ColumbiaState Park
BAKERBAY
OREGON
WASHINGTON
Ft ClatsopNat’l Park
Contrast two recently constructedprojects
Tidal, off-channel salmonidhabitat
Passive and active habitatcreation methods
Focus on “perched” wetlands
Not relevant to subsidedwetlands
Town ofChinook
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Existing “Perched”Culvert, 24” RCP
New 12’ x 12’Culvert
ConstructedLimits ofWetland
Fort Columbia Tidal Reconnection
Wetland cutoff by Hwy 101
Fish passage culvert, wetland, LWD, reveg.
Completed Spring 2011
Pilot channel excavated
Passive restoration
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Fort Columbia Tidal ReconnectionFar Term Evolution
20-50+ YearsNear Term Evolution
2-10 Years
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Fort Columbia Tidal Reconnection
Immediate & significant fish use
Immediate channel response
0
20
40
60
80
100
120
140
March April May June
Nu
mb
er
2011 Salmonid AbundanceWithin Wetland
Chum
Coho
Chin
(Over 800Trapped
Outside ofCulvert in April)
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Fort Columbia Tidal Reconnection
Looking West Near Endof Wetland Channel
Looking East Near End ofWetland Channel
Looking North atUpstream End of Channel
Looking D/S from Upper Endof Wetland Chanel
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Channel Profile Adjustment
2.0
3.0
4.0
5.0
6.0
7.0
8.0
9.0
10.0
11.0
3+50 4+00 4+50 5+00 5+50 6+00
Eleva
tion
(FeetN
AV
D88)
Profile of Wetland Channel Thalweg (Feet)
2/15/2011 2/21/2011 3/25/2011 5/11/2011 12/15/2011
MTL EL +4.5
THA
LWEG
New TidalPrism &Habitat
FLOW
MHHW
EL +8.6
Approx. Limit of
ConstructionNew
Culvert
THA
LWEG
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Fort Clatsop
National HistoricPark
Varied wetlandhabitat quality
South Slough - 45acres of dikedpasture on dredgefill
Elevations ‘high’ andearth compacted
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South Slough
New bridge in 2007 -improved connectivity
Experimental passiveapproach - no pilotchannel
4 years of monitoring
Positive veg/fishresponses in north
South – somewhatreduced response
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0.0
2.0
4.0
6.0
8.0
10.0
12.0
0 5 10 15 20 25 30 35 40 45 50
Eleva
tion
(FeetN
AV
D88)
Downstream - Cross Section 2
2009
2010
2011
Deepeningof Channel
Slough Morphology XS1
XS5XS2
XS4XS3
0.0
2.0
4.0
6.0
8.0
10.0
12.0
0 5 10 15 20 25 30 35 40 45
Eleva
tion
(FeetN
AV
D88)
Station (Feet)
Upstream - Cross Section 5
2009
2010
2011
SlightWidening
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South Slough Wetland Response
Increase in tidal prism & in-channel habitat
General transport out of wetland
Erosion up to 2 feet near mouth in first year
Profile adjusting, coming into new equilibrium
Rate of change may be slowing
Limited new prism, particularly mid-, high tidalmarsh range & overbanks
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A Tale of Two Forts - Comparison
Characteristic Fort ColumbiaFort Clatsop(S. Slough)
Channel Study Length 400 feet (new, growing) 700 – 900 feet (pre-exist.)
Channel Top Width 10 - 25 feet 10 - 40 feet
Wetland Elevations (Overbank)+5 to +8’ NAVD88
(Mid- to Upper-Intertidal)+8 to +10’ NAVD88
(Supratidal)
Thalweg Slope (+ = downstream) +0.04% to +0.60% -0.4% (adverse) to +0.5%
Hydrology Qbase ~ 1 - 5 cfs Q2yr ~ 50 cfs
Predominant Soils Medium Sands (~0.6mm, #30) Fine Sands (~0.2 mm, #80)
Predominant Vegetation Dense sedges, scrub-shrub Pasture grasses
Ave. Annual Change in Prism(% Change from Initial)
+1,100 CY/Year(First Year, +28%)
+300 CY(+5%)
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It is the Best of Times, and the Best of Times
Passive restoration has a chance …
Sufficient hydrology
Topography is within intertidal range
Difficult to estimate vegetation impacts
Active restoration
Not an either/or question
Used in combination to kick-start
Questions are… how much, how & where, when?
A Tale of Two Forts... what does the next chapter hold?
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Special Thanks
Staff at CREST - Micah Russell, Matt Van Ess,Madeline Dalton, Sam Giese, April Silva
Lower Columbia River Estuary Partnership (LCREP)
Bonneville Power Administration
Dave Bellinger & Rob Mistic, WSDOT – SW RegionMS 5, Kelso, WA
Amy Ammer, Cowlitz County Public Works Dept.
National Park Service – Fort Clatsop staff
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QUESTIONS?
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Citations
Bottom, D.L., C.A. Simenstad, J. Burke, A.M Baptista, D.A. Jay, K.K. Jones, E. Casillas,and M.H. Schiewe. 2005. Salmon at River’s End: The Role of the Estuary in Declineand Recovery of Columbia River Salmon. US Dept. Commerce, NOAA technicalmemorandum. NMFS-NWFSC-68.
Zedler, J.B. ed. The Handbook for Restoring Tidal Wetlands, CRC Press LLC, 2001.