relationships between flow fluctuations and redd dewatering and ...

juvenile stranding, the results of the redd dewatering analysis indicate that, as expected, greater
drops in flow result in a greater percentage of salmon and steelhead/rainbow trout redds being
dewatered. However, the redd dewatering analysis did not show flow threshold patterns, as
were observed for juvenile stranding.
A basic assumption of all instream flow studies is that a stream is in dynamic equilibrium. When
a channel is in dynamic equilibrium, there is an approximate balance between sediment supply
and transport, so that the channel pattern and cross-sectional profile of the entire stream is
consistent (Bovee 1996). For a stream in dynamic equilibrium, it would be expected that large
flow events would not result in a significant change in flow-habitat relationships. Recent high
flows on the Yuba River (Figure 13) have resulted in significant channel changes. While we do
not have direct evidence that the Yuba River is in dynamic equilibrium, our findings on the
American River that the January 1997 flood did not result in a substantial change in Chinook
salmon or steelhead spawning flow-habitat relationships (US Fish and Wildlife Service 2000)
offer support that the results of this study are still applicable to the Yuba River.
USFWS, SFWO, Energy Planning and Instream Flow Branch
Yuba River Redd Dewatering and Juvenile Stranding Report
September 15, 2010
CONCLUSION
The model developed in this study is predictive for flows ranging from 400 cfs to 4,500 cfs for
redd dewatering and juvenile stranding upstream of Daguerre Point Dam, and for flows ranging
from 150 cfs to 4,500 cfs downstream of Daguerre Point Dam. This study supported and
achieved the objective of modeling the effects of flow decreases on Chinook salmon and
steelhead/rainbow trout spawning habitat and maximum potential juvenile entrapment in the
Yuba River between Englebright Dam and the Feather River.
REFERENCES
Becker, C.D., D.A. Neitzel and D.H. Fickeisen. 1982. Effects of dewatering on Chinook salmon
redds: tolerance of four developmental phases to daily dewaterings. Transactions of the
American Fisheries Society 111: 624-637.
Bovee, K.D., editor. 1996. The Complete IFIM: A Coursebook for IF 250. U.S. Geological
Survey, Fort Collins, CO.
Bradford, M.J., G.C. Taylor, J.A. Allen and P.S. Higgins. 1995. An experimental study of the
stranding of juvenile coho salmon and rainbow trout during rapid flow decreases under
winter conditions. North American Journal of Fisheries Management 15: 473-379.
California Department of Fish and Game. 2001. Evaluation of effects of flow fluctuations on
the anadromous fish populations in the Lower American River. Sacramento, CA:
California Department of Fish and Game, Stream Evaluation Program, Technical Report
No. 01-2.
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