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.