1. Aquatic Habitat Guidelines - Stream Restoration Guidelines
Spawning Gravel
Placement, nourishment, stabilization, and cleaning of spawning gravel
Kozmo Ken Bates –
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2. What makes spawning habitat?
Aquatic Habitat Guidelines - Stream Restoration Guidelines
What makes spawning habitat?
Size distribution of substrate
Permeability, compaction
Hydraulics
Depth, velocity, intergravel flow, upwell
Water quality; dissolved oxygen
Proximity to cover
Self-sustaining
Upwell figure
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4. Impacts to Spawning Habitat
Loss of substrate
Hydraulics of channel incision, straightening, armoring
Scour from floods or splash dams
Removal or blockage of wood
Recruitment blocked
Blockage at dams
Loss of source by bank armoring
Intrusion of fines
Single event or chronic
Instability during spawning

5. Spawning Gravel – Other Impacts
Loss of upwell flow when gravel bars lacking
Loss of invertebrate productivity in compacted bed ll

6. Spawning Gravel Restoration Methods
Direct placement - spawning pads
Nourishment
Trapping
Stabilization
Side channels (other technique)
Cleaning

7. Geomorphic Context

8. Spawning Gravel Placement
Aquatic Habitat Guidelines - Stream Restoration Guidelines
Spawning Gravel Placement
Direct placement - Pads
Appropriate where gravel sources are lost
Temporary fix unless hydraulics are appropriate. Tailout of drop structure or constriction with specific headloss
Spring channel enhancement
“Lost” implies there was gravel there naturally
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9. Spawning Gravel Pads

10. Spawning Pads - Risks Displaces and affects other habitats
“Attractive nuisance”
Gravel is not hydraulically sorted or place and therefore unstable for spawning
Gravel is not persistent in high energy areas
Gravel may not be persistent over hard bed
Potential low depth passage barrier

11. Spawning Gravel Nourishment
Create gravel bluff or bar
High flows distribute material “naturally”
Applies downstream of gravel traps (dams)
Restocking of bar or bluff is based on monitoring of bar (for quantity) or gravel downstream (for habitat)
Can be appropriate above high energy channels to create pocket gravel

12. Washington Spawning Nourishment Sites
Mitigation below dams
Cedar River
Green River
Cowlitz River
Spokane River

13. Cedar River Gravel Nourishment
Downstream of Landsburg Dam
About 1,000 cy to placed except 2002
Material specified; generally 5 to 50 mm
Placed as “gravel bar” to be washed downstream

14. Cedar River gravel nourishment plan
2 Downstream cross-sections
Placement berm
1 Control cross-section
2002 Channel work
City of Renton, Golder Associates drawing

15. City of Renton, Golder Associates photo

17. Cedar River Gravel Monitoring
Care of fish
Timing
Snorkel surveys
Erosion and sediment control
Turbidity monitoring
Gravel supplementation
Sieve analysis of placed material
Channel cross-sections at site and control
Pebble counts at transects downstream and control

18. Results Cross-Section 3; 2001-2006 (my trend lines by eye)
“Spawning gravel” mm
City of Renton, Golder Associates data

19. Results Cross-Section 4 2001-2006 (my trend lines)
“Spawning gravel” mm
City of Renton, Golder Associates data

20. Aquatic Habitat Guidelines - Stream Restoration Guidelines
Keswick Dam, Sacramento R
Feeder bluff supplementation
100,000 cy gravel added at 8 sites
Resulting Chinook redd
Keswick Dam - During 1990 and 1991, the California Department of Water Resources placed 100,000 cubic yards of spawning gravel at eight locations in the 12 mile reach between Keswick Dam and Clear Creek. Anadromous fisheries in the Sacramento River Basin have suffered significant declines in the years since Shasta and Keswick Dam were completed in the 1940s. The reduction in fish populations are attributed to many causes including loss of spawning gravel habitat below Keswick Dam. One million cubic yards of spawning gravel are estimated to be needed to replace the loss, and the 1990's placements represented only the first phase of a larger spawning habitat restoration project.
Feeder bluff
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21. Green River Gravel Nourishment
Corps 1125 project
Now part of Howard Hanson Dam Bi-op for Chinook and bull trout
Objectives
Increase spawning for coho, Chinook, steelhead
Reconnect side channels and floodplain
Reverse bed armoring
Restore natural gravel transport

22. Aquatic Habitat Guidelines - Stream Restoration Guidelines
Other Project Parts
Gravel Nourishment
Loose wood
Log jams
Loose wood: 50% of large debris that accumulates in reservoir plus 50 to 70 tons of small debris
2 log jams associated with gravel placement. See aerial.
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23. Debris jams
Nourishment bars
Nourishment bars
USACE photo

24. Monitoring Intensive monitoring for five years
Background for management of 50-year project

25. Gravel Monitoring Questions
Are gravel berms effectively providing spawning gravels each year?
What is the rate of gravel transport through the reach? How does gravel size affect transport?
How is substrate composition changing downstream?
What is the effect of gravel nourishment on Chinook and steelhead spawning?
Log jam and loose wood monitoring also

26. Geomorphology Monitoring
Changes in channel morphology?
Change in water surface elevation?
Channel migration?
Localized storage of spawning gravel?
Signs of bank erosion?
Due to any or all three activities.

27. Spawning Monitoring Activities
Aquatic Habitat Guidelines - Stream Restoration Guidelines
Spawning Monitoring Activities
Low flow / spring survey of gravel berms
Post high flow / visual inspection of gravel berms
Photo points
Survey cross-sections
Pebble counts
Gravel patch mapping / aerial photo analysis
Side channel water levels (G)
Fall spawner survey
Habitat mapping (H)
Hydrology
Patch composition is estimated by eye – that’s somewhat of a problem especially as project and gravel age – now looking more at total gravel volume moving through sites – field crew has calibrated their eyes at sites upstream of gravel placement
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28. See recommendations for future monitoring

30. USACE photo

33. Photopoint 17
Looking downstream at ELJ2
Sept 2003
July, 2005

35. Aquatic Habitat Guidelines - Stream Restoration Guidelines
Before after shots
Models greatly underestimated entrainment of gravel – 50% of gravel scoured in two events lower than median flow – 90% scoured before design flow of 1.5-year event
More gravel will be needed more frequently
Will build bars higher – approaching idea of bluffs
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36. Aquatic Habitat Guidelines - Stream Restoration Guidelines
Also seeing side channel inundated more frequently
USACE photo
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37. USACE contact

38. Aquatic Habitat Guidelines - Stream Restoration Guidelines
Risks
Fish spawning on fresh gravel – Green River
Material transported at low events
Constriction of channel changes hydraulics locally 1
Green River - high flows in Sept and Oct – flow sheets across bars - pinks spawning material and then bar eroded – Solution: build higher mounds to keep flow off top of bar during spawning – compare that to bluffs
Considering placement during winter – trade-off of spawning on fresh gravel vs placement during incubation 2
Green River
gravel moving through pretty fast – more gravel will be needed more frequently – have placed 4,000 cy per year - total authorization is 3 times that. This year will put in 8,000 cy.
Changed gravel spec from 4 to 5 and now going from 4 to 6.
50% Some material was transported 2 miles in 2 years
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39. Spawning Gravel Trapping
Outlet cr

40. Cedar Cr Fish First project

41. Cedar Cr Fish First project

42. Risks
Installation of trapping structures
Backwater effects

43. Spawning Gravel Cleaning
Cleaning of in-place channel bed
Mechanical
Hydraulic
Temporary solution
Use only if one-time sediment effect or source is remedied
High cost
Not a current practice

44. Spring channels

45. Spawning Gravel Cleaning “Gravel Gertie”
Jets clean to 12” deep
Fines decreased 3 to 78%
Siltation partially confined in hoods

46. Spawning Gravel Cleaning Other Cleaning Mechanisms
Maybe drop this slide

47. Spawning Gravel Cleaning Effects
High level of disturbance
Flattens and lowers streambed
Temporary “attractive nuisance” of unstable bed
Impact is limited with smaller equipment
Removes invertebrates
Re-colonized within weeks
Water quality impacts moves some of the sediment downstream

48. Spawning Gravel Complementary Techniques
Restore channel profile, floodplain connectivity
Remedy sources of fines
Add roughness to trap gravel
Debris, boulders, drop structures
Add structure to distribute and sort gravel

49. Spawning Gravel Restoration Uncertainties
Aquatic Habitat Guidelines - Stream Restoration Guidelines
Spawning Gravel Restoration Uncertainties
Uncertainties are high for placement
Depends on flow events
Uncertainty low for supplementation
Monitoring required
K Bates
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50. Spawning Gravel Monitoring

51. Aquatic Habitat Guidelines - Stream Restoration Guidelines
Last thoughts
To be sustainable, spawning gravel is the right combination of
Gravel source
Hydrology
Hydraulics
It’s tough to improve on natural spawning habitats.
Without all 3, it’s not spawning habitat.
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