1. An Assessment of Hydrologic Variability on
R. boylii Habitat Hydraulics using 2-Dimensional Hydrodynamic Modeling
Sarah Yarnell1
Sarah Kupferberg2
Amy Lind3
Jeff Mount1
1Center for Watershed Sciences, University of California, Davis, CA
2Questa Engineering, Point
Richmond, CA
3USDA Forest Service, Sierra Nevada Research Center, Davis, CA
Acknowledgments
* PIER program - CA Energy Commission
and SWRCB
* Pulsed Flow Program, Center for Aquatic
Biology and Aquaculture, UC Davis

2. Research Questions Addressed with 2D Hydrodynamic Modeling
How does R. boylii habitat suitability change throughout a river reach during a simulated pulsed flow event?
Spring pulsed flow event - egg habitat suitability
Aseasonal pulsed flow event - tadpole habitat suitability
Potential loss due to scour
Why are some suitable habitats unoccupied?
Buffering Capacity; Habitat connectivity
Primary Question – pulsed flows; Secondary questions – habitat availability across all modeled flows, occupied suitable habitat

3. Overview of Modeling Process
Survey 3D topography in field
Create bed topography file suitable for modeling
Create and refine calculation mesh
Run model (River2D) and calibrate to surveyed data – iterative process
Prediction

4. Modeling Study Sites

5. Modeling Study Sites South Fork Eel River North Fork Feather River
SFER: Coastal River System, Mean Annual Q = 5 cms, unregulated, rain-dominated hydrograph
survey area = ~4000 m2; Survey resolution: 0.1 boulders to 0.25m2 near-shore to 1.5m2 mid-channel; avg density = 1.3 pts/m2
Calibrated flows : 5 – 88 cfs; simulated 15 – 350 cfs
NFFR: Sierran system, Mean Annual Q = 26 cms, regulated, snow-melt dominated hydrograph
Survey area = ~12500m2; survey resolution 0.25m2 near-shore to 2.0m2 mid-channel; avg density = 0.6 pts/m2
calibrated flows: 155 – 555 cfs; simulated 250 – 2000 cfs
South Fork Eel River
North Fork Feather River

6. SF Eel River Calibration – 1.45 cms
Depth - reach
Velocity - reach
Depth – egg locations
Velocity – egg locations
When calibrate a 2d model – really checking on quality of topography and water surface elevation data. If topography accurate, and water surface elevation correct for a given flow, then model does well. Errors largely result from inaccurate topography – missing boulders, etc. See that in general model predicts well, but less precision in near-shore environment. Tendency to overpredict velocity and underpredict depth due to large substrate sizes.

7. Mean Error – Surveyed vs. Modeled Values
Depth (m)
Velocity (m/s)
Mean +/- 2 SE
• Mid-channel
• Near-shore
• Egg locations
SF Eel
2.5 cms
1.45 cms
NF Feather
4.4 cms
15.7 cms
SF Eel
2.5 cms
1.45 cms
NF Feather
4.4 cms
15.7 cms

8. Simulated Pulsed Flow Events
3 simulations each site using River2D* - various low flows to a high spring or ‘boatable’ flow:
SF Eel River - NF Feather River
1.0 to 7.0 cms to 30.0 cms
1.45 to to 30.0
2.0 to to 30.0
Evaluate each for potential loss
Potential for scour of eggs in spring
Potential for swept tadpoles in summer (aseasonal)
*River2D (Steffler and Blackburn, 2002)

9. Habitat Suitability Criteria
Suitable Egg Habitat =
depth = m, velocity = m/s
** Field Observations 2006
Suitable Tadpole Habitat =
depth = m,
velocity = m/s
‘Tolerable’ Tadpole Habitat =
depth = m, velocity = m/s
At 0.1m/s tads have sub-lethal negative effects (limited growth/development, higher predation risk). Precludes ‘normal’ foraging behavior, but low enough to seek refuge in substrate. 25% of tads “lost” downstream in Brett-chamber experiment.
** Experimental Results – Kupferberg et al 2007

10. Simulated Pulse Flow – Habitat Suitability
Suitable Habitat =
depth = m,
velocity = m/s

11. Simulated Pulse Flow – Habitat Suitability
Suitable Habitat =
depth = m,
velocity = m/s

12. Simulated Pulse Flow – Habitat Suitability
Suitable Habitat =
depth = m,
velocity = m/s

13. Simulated Pulse Flow – Habitat Suitability
Suitable Habitat =
depth = m,
velocity = m/s

14. Simulated Pulse Flow – Habitat Suitability
Suitable Habitat =
depth = m,
velocity = m/s

15. Simulated Pulse Flow – Habitat Suitability
Suitable Habitat =
depth = m,
velocity = m/s

16. Simulated Pulse Flow – Habitat Suitability
Suitable Habitat =
depth = m,
velocity = m/s

17. Simulated Pulse Flow – Habitat Suitability
Suitable Habitat =
depth = m,
velocity = m/s

18. Simulated Pulse Flow – Habitat Suitability
Suitable Habitat =
depth = m,
velocity = m/s

19. Simulated Pulse Flow – Habitat Suitability
Suitable Habitat =
depth = m,
velocity = m/s

20. Spring Pulsed Flow Event
SF Eel Study Site
NF Feather Study Site
Assess what happens at initially suitable nodes/habitats – do they remain suitable?
Less than 30% and 5% of initially suitable habitats remain suitable
Associated Loss*:
<0.1 m/s = ~10% cumulative loss of eggs;
m/s = ~45% cumulative loss;
>0.4 m/s = ≥ 50% cumulative loss
*Spring Rivers Ecological Sciences, 2003, FYLF studies for PG&E Pit River Hydroelectric Project

21. Aseasonal Pulsed Flow Event
SF Eel Study Site
NF Feather Study Site
Greater than 30% and 75% of initially suitable habitats show high potential loss
Associated Loss*:
<0.1 m/s = ~ 25% loss of tadpoles;
m/s = ~ 50% loss;
>0.25 m/s = ~ 75% loss
*Kupferberg et al, 2007

22. Channel Morphology SF Eel Study Site NF Feather Study Site
SF Eel generally wider, shallower with asymmetrical floodplain bars; NFFR entrenched with steep-faced flood bars and perched terraces – few floodplain features

23. Why are some suitable habitats unoccupied?
Buffering Capacity (refuge from velocity increases)
Connectivity between breeding and rearing habitats
Non-flow related factors (predation, cover, food availability, etc)

24. Buffering Capacity
Areas where eggs located in buffered sites on NFFR, and moderately buffered on SFER.
Why then are some suitable habitats unoccupied
1.45 to 7.0 cms
7.1 to 30.0 cms
Egg locations on SF Eel in sites with moderate velocity increases
Egg locations on NF Feather in sites with low velocity increases

25. Habitat Suitability as Flow Decreases
Suitable Habitat =
depth = m,
velocity = m/s

26. Habitat Suitability as Flow Decreases
Suitable Habitat =
depth = m,
velocity = m/s

27. Habitat Suitability as Flow Decreases
Suitable Habitat =
depth = m,
velocity = m/s

28. Habitat Suitability as Flow Decreases
Suitable Habitat =
depth = m,
velocity = m/s

29. Non-flow related factors
Predation
Shade Tree
Shade limits water temps and algae production
Modeling can provide additional information on ecological aspects of a species of concern as well as inform flow management decisions.

30. Conclusions – Pulsed Flows
During simulated pulsed flows, small percentages of suitable breeding/rearing habitat remained suitable – “buffered” (SF Eel: 25-30%; NF Feather: <5%)
In the aseasonal pulse scenarios, large percentages of suitable rearing habitat became highly unsuitable with >75% potential tadpole loss (SF Eel: 30-45%; NF Feather: 75-90%)

31. Conclusions – Unoccupied Suitable Habitat
NF Feather - occupied breeding habitat overlapped with buffered habitats.
SF Eel - occupied breeding habitat overlapped with large areas of suitable tadpole rearing habitat
Non-flow factors (predation, food availability) important