|If you build it will they come? The very popular
river restoration motive of rehabilitating spawning habitat for salmonids
poses a range of interesting technical and scientific problems. Using
the Lower Mokelumne River in California as a test bed, several experimental
rehabilitation projects have been carried out and others are planned
through 2009. This research was the focus of my Masters under the
supervision of Dr. Greg Pasternack from U.C. Davis
and in collaboration with Joseph Merz at East Bay
Municipal Utility District (EBMUD). I am actively working on the extensive
data sets we produced from the Mokelumne River.
|The decline of salmonids in regulated
rivers has been linked to many perturbations including over-harvest
and the deterioration, inaccessibility and reduction of spawning habitat
for these fish. Spawning habitat rehabilitation efforts have been
underway since the late 1970s to attempt to replenish spawning gravels
in gravel starved spawning reaches downstream of dams. In an inventory
of gravel injection projects within California's Central Valley alone
from 1976 to 1999, Lutrick and Kondolf (p. comm.) identified 73 spawning
habitat rehabilitation projects, on 19 different rivers, totaling
over US$ 45 million, and involving the addition of over 1.2 million
cubic meters ( 1.8 million metric tons) of gravel. Spawning habitat
rehabilitation can be segregated into three categories:
|Contrast between regulated and unregulated river basins
and context for spawning habitat rehabilitation activities. (Figure
from Wheaton (2003)
and Wheaton et al. (2004);
©2004 Wheaton; See Figure Copyright
Disclaimer before downloading).
Types of Spawning Habitat Rehabilitation
1) Gravel Augmentation
Photo of Keswick Dam on Sacramento River by Kondolf ©1997 Elseiver
Science (See Photo Copyright Disclaimer
|Gravel augmentation (also known as gravel injection
or gravel replenishment) seeks to replenish some portion of a regulated
river’s sediment budget deficit with imported sediment. This is typically
achieved by dumping clean spawning gravels into piles along the edges
of a river at locations upstream of degraded spawning habitat reaches
(usually just downstream of a dam). It is assumed that augmented gravels
will be entrained during high flows with the competence to transport
them downstream. Designs are rarely necessary for gravel augmentation,
but a sediment budget and a monitoring program to enable adaptive
management are appropriate.
2) Hydraulic Structure Placement
|The most common type of SHR is hydraulic structure
placement (often called habitat enhancement or instream structures).
Physical structures (e.g. large woody debris (LWD), boulder clusters,
v-dams, half-log covers, deflectors) are placed in the channel to
alter hydrodynamics in such a way that spawning gravels are deposited
in the vicinity of the structures. The technique relies on an adequate
supply of gravel from upstream and an active bedload transport regime
to deliver it. Such structures may also be intended to provide refugia,
cover and add habitat heterogeneity. In other instances, hydraulic
structures are intended to promote pool scour. The implementation
of hydraulic structure placement is typically prescriptive and usually
lacks adequate process considerations.
Clusters on the lower Mokelumne River, CA.(©2004 Wheaton; See
Photo Copyright Disclaimer before downloading).
3) Spawning Bed Enhancement
on the lower Mokelumne River, CA.(©2004 Wheaton; See Photo Copyright
Disclaimer before downloading).
| Spawning bed enhancement includes direct modifications
to the bed (e.g. riffle construction, bed ripping and riffle cleansing).
Spawning bed enhancement that involves placement of gravel differs
from gravel augmentation in that the augmented gravels are placed
as specific bed features (typically riffles or bars), potentially
providing immediate spawning habitat. Spawning bed enhancement can
be used to improve the fluvial complexity of channels detrimentally
simplified for flood control or mining purposes. Placed gravels are
intended to decrease local depth and increase velocity to better match
observed spawning preferences. Although bed enhancement may quickly
provide usable spawning habitat, limited project lifespans may result
without adequate consideration of geomorphic processes.
The SHIRA Approach
We developed SHIRA for use on salmonid spawning
habitat rehabilitation projects in regulated rivers. The approach
is driven by a mix of field data, conceptual models, and numerical
algorithms to provide predictive and explanatory insight into
the design and planning process. At the heart of SHIRA is a conceptual
spawning model that explicitly identifies the assumptions behind
the approach (see figure below). Although, this approach was developed
specifically for spawning habitat restoration, many of its components
are directly transferable to other forms of river restoration.
Jump to References
| Conceptual spawning habitat model.
The arrows indicate influences, the circles represent processes and
characteristics, and the boxes are the results. A combination of hydrogeomorphic
processes spanning a range of scales combine to create physical habitat.
Physical habitat is chosen by females for redd construction based
on the ecologic functions provided by physical habitat and ecologic
factors including habitat heterogeneity, run size, timing, social
factors and physiology. The survival of alevins and ultimate emergence
of fry is then primarily controlled by the substrate and local flow
conditions during the incubation period. Figure 3 from Wheaton (2003):
Conceptual Spawning Model.©2003
| SHIRA flowchart. The two primary
components are phases and modes. Projects progress sequentially through
specific project phases, ranging from the initial problem identification
to long-term monitoring and adaptive management. During each of seven
phases, four primary modes are used to collect and analyze data on
which informed decisions can be based. Figure 2 from Wheaton (2003)
website is the official repository for all SHIRA related publications
and developments. In addition, the website includes examples of the
application of SHIRA in different case studies on different rivers.
Below, I only list the publications that I was directly involved with.
For a detailed summary of the approach, check out the first paper below in the International Journal of River Basin Management.
The second companion paper illustrates with a case study how design hypothesis testing
under SHIRA is carried out. For further, less concise details, my
is provided. Please note that all PDFs are provided as courtesy copies
only, and all copyrights are retained by the respective publishers).
- A SHIRA website is maintained by Dr. Pasternack.
- Wheaton, J. M., Pasternack,
G. B., & Merz, J. E. 2004. Spawning Habitat Rehabilitation - I. Conceptual Approach and Methods,
International Journal of River Basin Management, 2(1): 3-20.
- Wheaton, J. M., Pasternack,
G. B., & Merz, J. E. 2004. Spawning Habitat Rehabilitation - II. Using Hypothesis Testing and Development in Design, Mokelumne River, California, U.S.A.,
International Journal of River Basin Management, 2(1): 21-37.
- Wheaton, J. M. (2003).
Spwaning Habitat Rehabilitation, M.S. Thesis, University
of California at Davis, Davis, CA.
- Pasternack, G.B., Gilbert,
A.T., Wheaton, J.M. and Buckland, E.M., 2006. Error Propagation for Velocity and Shear Stress Prediction: Using 2D Models For Environmental Management. Journal of Hydrology.
328 (1-2): 227-241.
- Wheaton, J.M., Pasternack,
G.B. and Merz, J.E., 2004. Use of habitat heterogeneity in salmonid spawning habitat rehabilitation design. In: D. Garcia and P.V. Martinez (Editors), Fifth International
Symposium on Ecohydraulics: Aquatic Habitats: Analysis and Restoration.
IAHR-AIRH, Madrid, Spain, pp. 791-796.
- Merz JE, Setka JD, Pasternack
GB and Wheaton JM. 2004. Predicting benefits of spawning-habitat rehabilitation to salmonid (Oncorhynchus spp.) fry production in a regulated California river. Canadian
Journal of Fisheries and Aquatic Sciences. 61(8): 1433-1446.
- Merz, J.E., Pasternack,
G.B. and Wheaton, J.M. 2006. Sediment budget for salmonid spawning habitat rehabilitation in a regulated river. Geomorphology, 76 (1): 207-228.
documents from the Cosumnes-Mokelumne Paired Basin Project: Linked
hydrogeomorphic ecosystem models to support adaptive management
| Since Dr. Gregory.
B Pasternack, Dr. Joe Merz and I first developed SHIRA, Eve Elkins
and Rocko Brown have completed their masters at UC Davis extending
and improving elements of SHIRA on the Mokelumne and Trinity Rivers.
Additionally, Dr. Merz continues to implement and test SHIRA with
EBUMD on the Mokelumne River. Check out Greg's research
pages for more information.|