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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
Outline
Background & challenges in Columbia R. Estuary
Purpose
Methods & scope
Tidal wetland restoration - 2 case studies
Take-home considerations
Lower Columbia River Estuary
75% loss of tidal off-channelhabitat1
Development
Agriculture
Hydropower
Many others
1 Bottom et. Al 2005
Challenges
Photo courtesy of NPS
Science• Physical/ecological• Limited monitoring
funding• Still evolving
Legal• Pressures on
agencies• Deadlines• Site scarcity
Purpose
Inform the state of the art
Applicability of passive & active approaches
Improve project evaluation (identification, ranking)
Improve project implementation (design, construction)
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
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
Fort Columbia Tidal ReconnectionFar Term Evolution
20-50+ YearsNear Term Evolution
2-10 Years
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)
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
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
Fort Clatsop
National HistoricPark
Varied wetlandhabitat quality
South Slough - 45acres of dikedpasture on dredgefill
Elevations ‘high’ andearth compacted
South Slough
New bridge in 2007 -improved connectivity
Experimental passiveapproach - no pilotchannel
4 years of monitoring
Positive veg/fishresponses in north
South – somewhatreduced response
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
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
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%)
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?
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
QUESTIONS?
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.