Re-inventing Government Creek: Lessons from a successful ...€¦ · Estuary Design. Estuary Design...
Transcript of Re-inventing Government Creek: Lessons from a successful ...€¦ · Estuary Design. Estuary Design...
![Page 1: Re-inventing Government Creek: Lessons from a successful ...€¦ · Estuary Design. Estuary Design •Created by excavating & re-grading upland forest to encourage tidal inundation](https://reader034.fdocuments.in/reader034/viewer/2022051814/6038a559a1ebad106070dc9c/html5/thumbnails/1.jpg)
Re-inventing Government Creek: Lessons from a
successful stream relocationKetchikan, AK
February 5, 2015
Michelle Havey, MS and Jon Houghton, PhDFunded by Alaska Dept. of Transportation
Contact: [email protected]
![Page 2: Re-inventing Government Creek: Lessons from a successful ...€¦ · Estuary Design. Estuary Design •Created by excavating & re-grading upland forest to encourage tidal inundation](https://reader034.fdocuments.in/reader034/viewer/2022051814/6038a559a1ebad106070dc9c/html5/thumbnails/2.jpg)
Project Background
Tongass Narrows
Ketchikan
Government Creek
Boulder Creek
Airport Creek
FAA: Need to expand RSA by 1000 ft on either end
![Page 3: Re-inventing Government Creek: Lessons from a successful ...€¦ · Estuary Design. Estuary Design •Created by excavating & re-grading upland forest to encourage tidal inundation](https://reader034.fdocuments.in/reader034/viewer/2022051814/6038a559a1ebad106070dc9c/html5/thumbnails/3.jpg)
Decision
• Re-route Government Creek into Boulder Creek channel near mouth
• Create new estuary
• Alternative option: very long culvert
![Page 4: Re-inventing Government Creek: Lessons from a successful ...€¦ · Estuary Design. Estuary Design •Created by excavating & re-grading upland forest to encourage tidal inundation](https://reader034.fdocuments.in/reader034/viewer/2022051814/6038a559a1ebad106070dc9c/html5/thumbnails/4.jpg)
Project Elements• Mainstem
• 3 Side Channels
• Expanded estuary
• North Tributary
Reference
![Page 5: Re-inventing Government Creek: Lessons from a successful ...€¦ · Estuary Design. Estuary Design •Created by excavating & re-grading upland forest to encourage tidal inundation](https://reader034.fdocuments.in/reader034/viewer/2022051814/6038a559a1ebad106070dc9c/html5/thumbnails/5.jpg)
Construction Statistics• Constructed 2006 – 2007
• Stripped and saved portion of overburden soil/vegetation
• Blasted and moved 380,000 cy of rock and till
• Maximum depth of cut ~80 feet
• Excavated to flat floodplain, in dry, without ‘technical’ oversight
![Page 6: Re-inventing Government Creek: Lessons from a successful ...€¦ · Estuary Design. Estuary Design •Created by excavating & re-grading upland forest to encourage tidal inundation](https://reader034.fdocuments.in/reader034/viewer/2022051814/6038a559a1ebad106070dc9c/html5/thumbnails/6.jpg)
Typical Cross Section
• 30 to 80-foot cut to floodplain (~150 foot wide)
• Then…
Main thalweg
Side channel
![Page 7: Re-inventing Government Creek: Lessons from a successful ...€¦ · Estuary Design. Estuary Design •Created by excavating & re-grading upland forest to encourage tidal inundation](https://reader034.fdocuments.in/reader034/viewer/2022051814/6038a559a1ebad106070dc9c/html5/thumbnails/7.jpg)
With Bio/Geomorphologist oversight (!):
![Page 8: Re-inventing Government Creek: Lessons from a successful ...€¦ · Estuary Design. Estuary Design •Created by excavating & re-grading upland forest to encourage tidal inundation](https://reader034.fdocuments.in/reader034/viewer/2022051814/6038a559a1ebad106070dc9c/html5/thumbnails/8.jpg)
With Bio/Geomorphologist oversight (!):
• Excavated main channel (~2,050 lineal feet ); 3 side channels (~800 lf)
• Installed habitat features (in dry)
– Stream bed “gravel”
– ~100 boulders (2 – 12 feet in diam.)
– ~ 50 trees (roots/limbs)
• Flow initiated in early August 2007
![Page 9: Re-inventing Government Creek: Lessons from a successful ...€¦ · Estuary Design. Estuary Design •Created by excavating & re-grading upland forest to encourage tidal inundation](https://reader034.fdocuments.in/reader034/viewer/2022051814/6038a559a1ebad106070dc9c/html5/thumbnails/9.jpg)
Monitoring Plan
• Estuary
– Saltmarsh area
– Eelgrass
– Fry rearing (coho)
• Schedule
– Pre- and Years 0, 1, 3, 5 (added Year 2, full monitoring)
• Stream
– Channel topography
– Physical habitat measures (retention of LWD)
– Bed grain size (pebble counts)
– Riparian vegetation
– Salmon spawning
– Fry rearing (coho)
![Page 10: Re-inventing Government Creek: Lessons from a successful ...€¦ · Estuary Design. Estuary Design •Created by excavating & re-grading upland forest to encourage tidal inundation](https://reader034.fdocuments.in/reader034/viewer/2022051814/6038a559a1ebad106070dc9c/html5/thumbnails/10.jpg)
Stream Success Criteria
![Page 11: Re-inventing Government Creek: Lessons from a successful ...€¦ · Estuary Design. Estuary Design •Created by excavating & re-grading upland forest to encourage tidal inundation](https://reader034.fdocuments.in/reader034/viewer/2022051814/6038a559a1ebad106070dc9c/html5/thumbnails/11.jpg)
Stream Success Criteria
• No barriers to upstream passage of juveniles at normal flows (tough!)
• Pink and chum spawning
• Instream structures retained (60% through Year 5)
• Coho rearing
• Native trees (4 spp.) by Year 5
• No excessive erosion on cut side slopes
• Side channel water quality ok for fry
![Page 12: Re-inventing Government Creek: Lessons from a successful ...€¦ · Estuary Design. Estuary Design •Created by excavating & re-grading upland forest to encourage tidal inundation](https://reader034.fdocuments.in/reader034/viewer/2022051814/6038a559a1ebad106070dc9c/html5/thumbnails/12.jpg)
Stream EvolutionYear 0
![Page 13: Re-inventing Government Creek: Lessons from a successful ...€¦ · Estuary Design. Estuary Design •Created by excavating & re-grading upland forest to encourage tidal inundation](https://reader034.fdocuments.in/reader034/viewer/2022051814/6038a559a1ebad106070dc9c/html5/thumbnails/13.jpg)
Stream EvolutionYear 3
![Page 14: Re-inventing Government Creek: Lessons from a successful ...€¦ · Estuary Design. Estuary Design •Created by excavating & re-grading upland forest to encourage tidal inundation](https://reader034.fdocuments.in/reader034/viewer/2022051814/6038a559a1ebad106070dc9c/html5/thumbnails/14.jpg)
Stream Evolution
![Page 15: Re-inventing Government Creek: Lessons from a successful ...€¦ · Estuary Design. Estuary Design •Created by excavating & re-grading upland forest to encourage tidal inundation](https://reader034.fdocuments.in/reader034/viewer/2022051814/6038a559a1ebad106070dc9c/html5/thumbnails/15.jpg)
Abundant Salmon Use• Pinks spawned within 2 weeks of flow initiation
• 2007 and 2008 cohorts returned in 2009 and 2010
• ~8,000 pink salmon observed in the constructed reaches!
• Also:
– Abundant juvenile coho
– Some Dolly Varden
– Trout fry
– Likely chum spawning
– One lonely Chinook in 2 of 3 years!
![Page 16: Re-inventing Government Creek: Lessons from a successful ...€¦ · Estuary Design. Estuary Design •Created by excavating & re-grading upland forest to encourage tidal inundation](https://reader034.fdocuments.in/reader034/viewer/2022051814/6038a559a1ebad106070dc9c/html5/thumbnails/16.jpg)
![Page 17: Re-inventing Government Creek: Lessons from a successful ...€¦ · Estuary Design. Estuary Design •Created by excavating & re-grading upland forest to encourage tidal inundation](https://reader034.fdocuments.in/reader034/viewer/2022051814/6038a559a1ebad106070dc9c/html5/thumbnails/17.jpg)
• Potential fish barrier
• Observed adult fish struggling to get upstream even during typical flows
Upper Cascade
![Page 18: Re-inventing Government Creek: Lessons from a successful ...€¦ · Estuary Design. Estuary Design •Created by excavating & re-grading upland forest to encourage tidal inundation](https://reader034.fdocuments.in/reader034/viewer/2022051814/6038a559a1ebad106070dc9c/html5/thumbnails/18.jpg)
• Pools/steps in bedrock
• Boulders
Upper Cascade Fix
![Page 19: Re-inventing Government Creek: Lessons from a successful ...€¦ · Estuary Design. Estuary Design •Created by excavating & re-grading upland forest to encourage tidal inundation](https://reader034.fdocuments.in/reader034/viewer/2022051814/6038a559a1ebad106070dc9c/html5/thumbnails/19.jpg)
Floodplain Erosion
![Page 20: Re-inventing Government Creek: Lessons from a successful ...€¦ · Estuary Design. Estuary Design •Created by excavating & re-grading upland forest to encourage tidal inundation](https://reader034.fdocuments.in/reader034/viewer/2022051814/6038a559a1ebad106070dc9c/html5/thumbnails/20.jpg)
Floodplain Erosion
• Routine overbank flow causes regular inundation and scouring of floodplain
• Recruits spawning gravel to channel
• Inhibited establishment of floodplain vegetation
![Page 21: Re-inventing Government Creek: Lessons from a successful ...€¦ · Estuary Design. Estuary Design •Created by excavating & re-grading upland forest to encourage tidal inundation](https://reader034.fdocuments.in/reader034/viewer/2022051814/6038a559a1ebad106070dc9c/html5/thumbnails/21.jpg)
Vegetation Establishment
• “Vegetation Islands” of armored sod from nearby forested uplands created as part of 2008 Adaptive Management
![Page 22: Re-inventing Government Creek: Lessons from a successful ...€¦ · Estuary Design. Estuary Design •Created by excavating & re-grading upland forest to encourage tidal inundation](https://reader034.fdocuments.in/reader034/viewer/2022051814/6038a559a1ebad106070dc9c/html5/thumbnails/22.jpg)
Vegetation Establishment
![Page 23: Re-inventing Government Creek: Lessons from a successful ...€¦ · Estuary Design. Estuary Design •Created by excavating & re-grading upland forest to encourage tidal inundation](https://reader034.fdocuments.in/reader034/viewer/2022051814/6038a559a1ebad106070dc9c/html5/thumbnails/23.jpg)
Stream Success Criteria
No barriers to upstream passage of juveniles at normal flows (tough!)
Pink and chum spawning
Instream structures retained (60% through Year 5)
Coho rearing
Native trees (4 spp.) by Year 5
No excessive erosion on cut side slopes
Side channel water quality ok for fry
![Page 24: Re-inventing Government Creek: Lessons from a successful ...€¦ · Estuary Design. Estuary Design •Created by excavating & re-grading upland forest to encourage tidal inundation](https://reader034.fdocuments.in/reader034/viewer/2022051814/6038a559a1ebad106070dc9c/html5/thumbnails/24.jpg)
Estuary Success Criteria
• Saltmarsh area requirements (Years 3 & 5) - % and sf
• No “excessive” channel or beach erosion
• Coho rearing
![Page 25: Re-inventing Government Creek: Lessons from a successful ...€¦ · Estuary Design. Estuary Design •Created by excavating & re-grading upland forest to encourage tidal inundation](https://reader034.fdocuments.in/reader034/viewer/2022051814/6038a559a1ebad106070dc9c/html5/thumbnails/25.jpg)
Estuary Design
![Page 26: Re-inventing Government Creek: Lessons from a successful ...€¦ · Estuary Design. Estuary Design •Created by excavating & re-grading upland forest to encourage tidal inundation](https://reader034.fdocuments.in/reader034/viewer/2022051814/6038a559a1ebad106070dc9c/html5/thumbnails/26.jpg)
Estuary Design• Created by
excavating & re-grading upland forest to encourage tidal inundation
• Bed rock encountered in excavation
• Saltmarsh vegetation salvaged during construction
Original tree/HWL
![Page 27: Re-inventing Government Creek: Lessons from a successful ...€¦ · Estuary Design. Estuary Design •Created by excavating & re-grading upland forest to encourage tidal inundation](https://reader034.fdocuments.in/reader034/viewer/2022051814/6038a559a1ebad106070dc9c/html5/thumbnails/27.jpg)
Saltmarsh vegetation
• Sod transplants doing well and spreading
• Distinct lack of saline inundation on upper portions of beach – tracking by line of alder dominance
![Page 28: Re-inventing Government Creek: Lessons from a successful ...€¦ · Estuary Design. Estuary Design •Created by excavating & re-grading upland forest to encourage tidal inundation](https://reader034.fdocuments.in/reader034/viewer/2022051814/6038a559a1ebad106070dc9c/html5/thumbnails/28.jpg)
Saltmarsh vegetation
• Year 4: more salt-tolerant sp.
• Year 6: met the 50% coverage criteria by saltmarsh species
![Page 29: Re-inventing Government Creek: Lessons from a successful ...€¦ · Estuary Design. Estuary Design •Created by excavating & re-grading upland forest to encourage tidal inundation](https://reader034.fdocuments.in/reader034/viewer/2022051814/6038a559a1ebad106070dc9c/html5/thumbnails/29.jpg)
Estuary Erosion
Looking downstreamLooking upstream
![Page 30: Re-inventing Government Creek: Lessons from a successful ...€¦ · Estuary Design. Estuary Design •Created by excavating & re-grading upland forest to encourage tidal inundation](https://reader034.fdocuments.in/reader034/viewer/2022051814/6038a559a1ebad106070dc9c/html5/thumbnails/30.jpg)
Estuary Erosion
• Significant intertidal erosion due to increased stream power
• Delta growth & braided channel
• Pilings not observed during construction!
![Page 31: Re-inventing Government Creek: Lessons from a successful ...€¦ · Estuary Design. Estuary Design •Created by excavating & re-grading upland forest to encourage tidal inundation](https://reader034.fdocuments.in/reader034/viewer/2022051814/6038a559a1ebad106070dc9c/html5/thumbnails/31.jpg)
Areas of Change:
• Eelgrass loss in delta
• Clam resources affected
• Low-tide channel erosion
• Delta formation
![Page 32: Re-inventing Government Creek: Lessons from a successful ...€¦ · Estuary Design. Estuary Design •Created by excavating & re-grading upland forest to encourage tidal inundation](https://reader034.fdocuments.in/reader034/viewer/2022051814/6038a559a1ebad106070dc9c/html5/thumbnails/32.jpg)
Estuary Step Work
• Part of Adaptive Management
• Potential bedrock ledge fish barrier
• Created pools/steps in bedrock ledge
After
Before
During
![Page 33: Re-inventing Government Creek: Lessons from a successful ...€¦ · Estuary Design. Estuary Design •Created by excavating & re-grading upland forest to encourage tidal inundation](https://reader034.fdocuments.in/reader034/viewer/2022051814/6038a559a1ebad106070dc9c/html5/thumbnails/33.jpg)
Estuary Success Criteria
Saltmarsh area requirements (Years 3 & 5) - % and sf
No “excessive” channel or beach erosion
Coho rearing
![Page 34: Re-inventing Government Creek: Lessons from a successful ...€¦ · Estuary Design. Estuary Design •Created by excavating & re-grading upland forest to encourage tidal inundation](https://reader034.fdocuments.in/reader034/viewer/2022051814/6038a559a1ebad106070dc9c/html5/thumbnails/34.jpg)
Conclusion• Rate of change, high in Year 1,
slowed in Years 2-6
• Successful salmon spawning and rearing habitat
• Appear to be meeting all fish-related criteria
• Vegetation in floodplain and saltmarsh met criteria
• Estuary erosion greater than expected, but stabilized
• Adaptive management can work!
![Page 35: Re-inventing Government Creek: Lessons from a successful ...€¦ · Estuary Design. Estuary Design •Created by excavating & re-grading upland forest to encourage tidal inundation](https://reader034.fdocuments.in/reader034/viewer/2022051814/6038a559a1ebad106070dc9c/html5/thumbnails/35.jpg)
Questions?