re-inventing government creek -- lessons from a successful...

-- Lessons from a successful

salmon stream and estuary relocation on Gravina Island

Jon Houghton, Ph.D. and Derek Ormerod, M.S., P.E. -

Pentec Environmental/Hart Crowser, Inc.

D. Shane Cherry, M.S. - Cherry Creek Environmental

Lance Mearig, P.E. - USKH Corporation

February 2, 2010

contact: jon@pentecenv.com

Re-inventing Government Creek

FAA: Need to expand RSA by 1000 ft on either end

Alternative: long culvert

Project Background

Airport Cr.

Government Cr.

Boulder Cr.

Tongass Narrows

Adaptive Management by IDT

- Interdisciplinary Team (IDT=ADOT&PF, ADF&G, NMFS, FWS, USACOEand consultant team)

- Reviewed and Approved:> Approach

> Design> Monitoring Plan

- Review Monitoring Reports

- Review and approve AM actions

Decision:

Re-route Government Cr. into Boulder Cr. channel near mouth; and create new estuary

(alternative option: very long culvert)

Project Elements

Mainstem; 3 Side Channels; Expanded Estuary; North Tributary

Constructed 2006 – 2007

Stripped and saved portion of overburden soil/vegetation

Blasted, ripped, and moved 380,000 cy of rock and till

Maximum depth of cut approximately 80 feet

Excavated to flat flood plain, in dry, w/o „technical‟ oversight

Statistics:

Typical cross section

30 to 80-foot cut to flood plain(~150 foot wide)

Then…

Excavated main channel and 3 side channels

Built ~2,050 lineal feet of new channel, plus ~800 feet of side channels

Installed habitat features (in dry)

- Stream bed “gravel”

- Approx. 100 boulders 2 – 12 ft in diam.

- Approx. 50 trees w. roots/limbs

Flow initiated August 2007

With Bio-/Geomorpho-logist oversight (!):

contact: jon@pentecenv.com

Monitoring PlanSchedule Pre- and Years 0, 1, 3, 5

In Stream - Channel topography Standard habitat measures (retention of LWD) Bed grain size (pebble counts) Riparian vegetation Salmon spawning Fry rearing (coho)

In Estuary Saltmarsh area Eelgrass Fry rearing (coho)

Stream Evolution

Spawning Gravel Original bed material did not meet spec

Too much sand and not enough gravel – washed away

Good gravel recruitment from eroding floodplain and glacial till

Have far exceeded performance goal (1,200 sf) each year, and continues to stabilize and expand

Abundant Salmon Use

Pinks spawned within 2 wks of flow initiation

2009 return of that cohort

3000+ Pink salmon observed in the constructed reaches!

Also, abundant juv coho, some DV, trout fry, likely chum spawning, and one lonely female Chinook!

Upper Cascade Fix

Potential cascade fish barrier – observed adult fish struggling to get upstream even during typical flows

With AMT/IDT ok, created pools/steps in bedrock and added boulders to break up flow

Estuary Design New estuary created by excavating and re-grading upland forest to encourage tidal inundation

Bed rock encountered in excavation

Salt-marsh vegetation salvaged during construction

Original tree/HWL

Salt-marsh vegetation

Sod transplants doing well and spreading

Year 2: first observed seedlings

Distinct lack of saline inundation on upper portions of beach – tracking by line of alder dominance

Estuary Erosion

Significant intertidal erosion

due to increased stream power

Delta growth and braided channel

Pilings not observed during construction!

Estuary Evolution

Areas of Change:

Low-tide channel erosion

Delta formation

Eelgrass loss in delta

Clam resources affected

Salt-marsh vegetation mixed with riparian vegetation

Estuary Step Work

Part of Adaptive Management Work

Potential bedrock ledge fish barrier

Created pools/steps in bedrock ledge

Before

During

After

Floodplain Erosion

Routine overbank flow causes regular inundation and scouring of floodplain

Recruits spawning gravel to channel

Has created additional side channels and pools that isolate fish as water recedes

Inhibits establishment of floodplain vegetation

Vegetation Establishment

Overbank flow scouring floodplain has allowed minimal natural recruitment of veg

“Vegetation Islands” of armored sod from nearby forested uplands created as part of

2008 Adaptive Management

Side Channels Created to provide juvenile coho rearing habitat

Have had concerns with in-flow rates and sediment deposition clogging lower side channel

Varying levels of effectiveness based on amount of flow

Do support juvenile coho

North Tributary Created to provide juvenile coho rearing habitat

Varying levels of habitat quality based on amount of flow

Very dense pink spawning in 2009

Success Criteria

Stream Channel No barriers to upstream passage of juv at normal flows (tough!) Pink and chum shall spawn Instream structures shall remain (60% thru Year 5) Coho shall rear Native trees (2 spp.) by Year 3 No excessive erosion on cut side slopes Side channel water quality ok for fry

Estuary Saltmarsh area (Year 3 and 5) No “excessive” channel or beach erosion Coho shall rear

Conclusions Rate of change, high in Year 1, has slowed in Year 2

Successful salmon spawning and rearing habitat

Appear to be meeting all fish-related criteria

Vegetation of flood plain uncertain

Estuary erosion still a concern, but stabilizing

Adaptive management can work!

contact: jon@pentecenv.com

Questions?

(Upstream reference reach)