1/9/06
Elkhorn Slough Tidal Wetland Plan
Elkhorn Slough National Estuarine Research Reserve
JOINT Science Panel and Strategic Planning Team
September 28, 2005 Meeting Summary
Meeting Date and Time: September 28, 2005, 11:00 a.m. – 5:00 p.m.
Meeting Location: Elkhorn Slough National Estuarine Research Reserve
Prepared by: Jan Shriner, Kerstin Wasson, and Barb Peichel
Attendees: David Cannon, Trish Chapman, Becky Christensen, Ross Clark, Josh Collins, Bob Curry, Lesley
Ewing, Kaitilin Gaffney, Will Glamore, Jeff Haltiner, Scott Hennessy, Tisha Hutchins, Ken Johnson, Mike
Josselyn, Judy Kildow, Jessie Lacy, Bryan Largay, Chris Malzone, Cheryl McGovern, Julie Niceswanger,
Nick Nidzieko, Barb Peichel, Jill Rooth, Larry Serpa, Jan Shriner, Mark Silberstein, Eric Van Dyke, Kerstin
Wasson, Andrea Woolfolk
Purpose of Meeting:
Discuss and narrow down the list of potential alternatives based on technical evaluations and items needed to
further evaluate combinations.
Outcomes:
Revised list of combinations of potential alternatives; Identification of priority items needed to evaluate
selected combinations
Next meeting date:
 The next joint (Strategic Planning Team and Science Panel) meeting will be on February 22, 2006 from
9:00 a.m. - 5:00 p.m. at the Elkhorn Slough Reserve. The main purpose of the meeting will be to
discuss restoration and conservation alternatives for tidal habitats behind water control structures
(culverts, flap gates, etc.).
Action items:
 Obtain funding for priority next step items (pages 6-9).
A. Review water quality information from last ESTWP meeting, evaluations of potential alternatives,
summary to date
Review of August 9, 2005 meeting of likely water quality and biological trends under different potential
management alternative

Find detailed meeting notes and presentations at http://www.elkhornslough.org/tidalwetland/science.htm.

Proposed restoration/enhancement activities at Parsons Slough (the example discussed includes a water
control structure and sediment additions to raise the elevation for marsh) might decrease dissolved
oxygen, nitrate and ammonium, and turbidity (depending on the timing) levels. These same activities
might increase chlorophyll A and the variance of dissolved oxygen and salinity levels. There may also
be trends towards benthic invertebrates and fish that are more of an estuarine assemblage and marsh
plants and birds.

Proposed restoration/conservation/enhancement activities at the mouth of Elkhorn Slough (the example
discussed includes a dam under the highway 1 bridge and a new channel to Monterey Bay that could
seasonally close) might decrease nitrate and ammonium inputs and turbidity (from sediments). These
activities might increase nitrate and ammonium concentrations, chlorophyll A (but unknown), and the
variance of salinity and dissolved oxygen levels (but unknown). The benthic invertebrates, fish, and bird
assemblages may shift to more estuarine species.
Joint Science Panel and Strategic Planning Team (September 28, 2005) Meeting Summary,
Elkhorn Slough Tidal Wetland Plan
1
Evaluations of potential alternatives by experts

One of the restoration/conservation goals is to reduce the tidal prism of Elkhorn Slough so that tidal
erosion is less. It is currently thought that unless the tidal prism is reduced by a project at least the size
of Parsons Slough, there may not be any significant system-wide benefit. It is unknown whether a
project at Parsons would provide benefits to the Upper Slough based on the hydrodynamics of the system
(so this should be modeled if possible).

All of the suggested combinations of potential alternatives require both tidal flow management and
sediment addition to address tidal erosion of the channel and creeks and marsh loss.
Possible Next Steps (proposed by Barb Peichel for discussion)

We still need to explore the feasibility of potential projects at large, medium, and small scales.

Large-scale alternatives: Unless we have some sort of fix at the mouth of the estuary, we will not stop or
reverse tidal erosion and marsh loss in the next 50 years. We may not eventually choose this action, but
it is definitely worth pursuing. Our first step could be to obtain funding to support quantitative
hydrogeomorphic designs and modeling to monitor sediment dynamics and tidal inundation to predict
the possible outcomes of different large-scale restoration alternatives.

Medium-scale alternatives: These may slow the rate of tidal erosion and marsh loss/conversion (but will
not reverse these trends). The alternative needs to be at least the size of the Parsons Slough complex for
a system-wide benefit. The next step could be to obtain funding for designs, permitting, and modeling.

Small-scale alternatives: These activities could be implemented in a shorter time frame in combination of
all possible alternatives. For example, we could reduce tidal erosion and marsh loss at Bennett Slough
and enhance Struve Slough by reducing the tidal flow through the culverts under jetty road. We could
also build up sediments in subsided marsh habitats such as Estrada/North Marsh (then if a large-scale
alternative at the mouth of Elkhorn is implemented down the road, we could consider removing this
water control structure).

Monitoring/Adaptive Management: We need to set up an integrated monitoring system with measurable
objectives before restoration activities are implemented.

I assume that a project could move forward at Parsons/South Marsh even before a decision is made
whether or not to proceed with a large-scale project at the mouth of Elkhorn Slough. I also assume you
would have to first put in a water control structure at Parsons/South Marsh before attempting to add
sediment to raise marsh elevations because current levees are breaching.
Comments

It would be helpful to consider what effect only muting tides would be on salt marsh vegetation (not
restoring the elevation) because we shouldn’t assume marsh would just improve under that scenario and
it might just be faced with different hydrological threats.

The vision statement includes the word ‘natural’. Is the definition of natural the time prior to major
human alterations? Yes.

We should all spend time today reading through the goals and planning principles before moving on to
the afternoon discussion (the group did this after lunch).

We might also have to raise the subtidal elevation of the mouth of Parsons and channels as a grade
control.

Evaluation of statement “Without a fix at the mouth – won’t stop or reverse tidal erosion and marsh loss
in next 50 years”. Disagree with the statement because we don’t have a good picture yet about what the
new system equilibrium would look like. For example, would you lose all or most of the marsh along
the main channel of Elkhorn due to channel and creek widening in 50 years? There might need to be
some modeling of equilibrium to shed light on this. But we have 50-year projections based on last 50
years that strongly suggest we may have linear trends of marsh loss and tidal creek widening for some
time to come, enough that we would want to stop it.

We need to better evaluate the role of nutrient pollution in causing marsh loss.

We need to decouple the causes of marsh plain processes from subtidal processes.

It is difficult to make robust predictions over a long time period because there could be earthquakes
changing wetland elevations, major floods bringing sediments (need to account for episodic events), and
sea level rise.
Joint Science Panel and Strategic Planning Team (September 28, 2005) Meeting Summary,
Elkhorn Slough Tidal Wetland Plan
2



We shouldn’t just consider tidal prism effects. We need to separate them from base level lowering by
creating the mouth of the harbor. There could be less dramatic fixes at Hwy 1 that act as a grade control
structure even without decreasing tidal prism. But this would help with marsh loss along the banks, but
would not correct the marsh loss in the interiors which is likely due to longer periods of inundation.
The head of the Monterey Canyon could eventually join the mouth of Elkhorn Slough and cause new
changes. The head-cutting of the canyon is not something we can stop and could be under the Hwy 1
Bridge within 100 years. This fact combined with sea level rise means that we may have to focus on
protecting habitat patches of historical precedence from these factors. (As far as evidence to date, there
isn’t conclusive evidence that the canyon has moved relative to harbor since 1850, but there is ongoing
research studying the movement of the canyon head.)
We never resolved the discussion about the assumption that without fixing the mouth we can’t meet our
goals so we will need to return to this.
Project Summary document (available at http://www.elkhornslough.org/tidalwetlandplan.htm)

The predictions for tidal habitats for the next 50 years if no actions are taken include the continued
dramatic loss of marsh habitat and erosion of the main channel and tidal creeks of Elkhorn Slough.

The Elkhorn Slough National Estuarine Research Reserve is working with a wide variety of partners to
conserve, enhance, and restore tidal habitats in the Elkhorn Slough watershed by developing strategies to
address marsh loss and tidal erosion issues. Theses restoration and conservation strategies will be
written in an Elkhorn Slough Tidal Wetland Plan that will likely be completed by June 2007.
Comments

Overall, very helpful document, it is simple yet encompasses the complexities.

There will be challenges with permitting medium and large-scale alternatives.
B. Revise the list of potential alternatives and assemble combinations that have the highest likelihood
of meeting the goals
Reviewing potential alternatives

Two additional alternatives were proposed for the mouth of Elkhorn Slough.
o The first option would change the harbor entrance to the south, close the current opening to
Monterey Bay, and change the Elkhorn Slough entrance to the north. Preliminary comments
include the need to find out how dredging costs might change (because there might be a
larger influence of littoral drift of sediments) and there are also surfing zones that would
have to be considered depending on the location of these new entrances.
o The second option would be to build a diagonal dam west of the Highway 1 Bridge, so that
boats can get from the harbor to the bay, but would change the Elkhorn Slough entrance to
the north. Preliminary comments include the need for designs to consider how boats could
enter Elkhorn from the North Harbor.
o A third option could be to block the existing mouth and have both the harbor and Elkhorn
Slough entrance north of the current opening.
o A fourth option would be to build a water control structure east of the Highway 1 Bridge.
Preliminary comments include the increased cost because there is not an existing structure,
but the process might be faster.

All of these additional potential alternatives would also need to consider not only reducing the tidal
prism, but also some sort of grade control in the channel to reduce the downcutting and also sediment
additions to raise the elevations of marsh plains to reduce inundation times.

Would increasing roughness of the main channel by itself be enough? From preliminary evaluations of
potential alternatives, “Increasing the roughness would tend to reduce the tidal prism.” It is unknown if
adding roughness would decrease tidal erosion.

Would increasing sinuosity of the main channel by itself be enough? From preliminary evaluations of
potential alternatives, “This would have to be very dramatic, and I can’t see it having much of a
beneficial effect. If the sinuosity is made too great, meander cutoffs will occur (I have observed this in
Marisma de Nacion in San Diego Bay. This alternative is very suitable for hydrodynamic modeling.”
Joint Science Panel and Strategic Planning Team (September 28, 2005) Meeting Summary,
Elkhorn Slough Tidal Wetland Plan
3
and “Increasing the sinuosity would increase friction, which would tend to reduce the tidal prism but it
would also increase the amount of channel thereby increasing the tidal prism. Analyses would be
required to determine the net effect.” No, we would still have a deep mouth opening to Elkhorn Slough
that the whole system would be adjusting to.
Project at Parsons Slough (medium-scale restoration)

One option is to add a water control structure and then sediment to raise the elevation of some areas for
marsh. Another option is that you could add a water control structure (such as tide gates) there and
manage it with a lower tidal frame (similar to how North Marsh is managed).

This could be a sequential project, where you could start with tide gates/culverts to cut the tidal prism by
1/10 (or some percentage) and bring back marsh at lower tidal frame and then over time, slowly raise the
elevation with sediment additions to different “sediment containment cells” in Parsons and then
eventually, you could change the water control structure to allow more flow.

What are ecological differences between marshes and tidal creeks managed at a lower tidal frame?
Muting flow results in more filamentous algae and less clapper rails.

A water control structure might involve six large culverts, two of which allow inflow and all size allow
outflow because it is a lot more difficult to get water out than in and this could maximize water quality
components. This could also allow fish passage.

The water control structure could also be made adjustable with nekton gates too which is better than a sill
for adaptive management of fish and tidal flow because you can adjust it as needed.

We could look at the example of Anaheim as a test case because they had an accidental sill project when
dredging ran into concrete bunker subtidally.

The water wouldn’t drain with a sill because about 40 percent of Parsons Slough is below MLW (mean
lower water).

You might be able to dredge some areas in Parsons to use that for higher elevation areas (similar to what
was done for South Marsh, but with a muted tidal regime).

Our assumption is that it would take at least 10-20 years to implement a project at the mouth of Elkhorn
Slough so it would be worth it to pursue a project at Parsons Slough to slow the tidal erosion process in
the main channel. We would also have the advantage of having control over one large area of the Slough
for restoration of marsh and tidal creeks. This might be especially important in light of sea level rise,
canyon mouth migration, etc.

Muting flow increases the residence time which increases the possibility of hypoxia. There is probably a
huge nutrient reservoir in the sediments. If we add sediment to raise the marsh elevations, we actually
increase tidal flushing at Parsons and decrease residence time, so nutrients might not actually be worse if
a Parsons project is pursued.

Can we model how much we would have to mute flow at Parsons Slough to have a significant effect on
tidal erosion in the whole system? Yes. The goal would be for restoring Parson Slough itself and there
would be secondary benefits for the system. For about every ten acres of marsh restored, you could get
one acre of tidal prism reduction. So if you could reduce the tidal prism by 30 percent and gain a lot of
marsh that would be mutually beneficial.
Project at the mouth of Elkhorn Slough (large-scale restoration)

There are different water control structure options for Highway 1 that should be explored, but we should
still consider a low sill just 10 feet off of the bottom as a grade control structure. We could maybe have
several of these which could probably be much better for fish, ecology, etc. Make water control
structure(s) plural in listing of this option. We need to remember that there would be sediment added
behind it, so need to raise the elevation of the channel past the sill, not just a sill.

There is a lot more littoral drift north of current mouth than south so we should keep this in mind as pros
and cons are developed for various options.

Concerned about the uncertainty of a sill at the mouth fixing tidal erosion problems. In rudimentary
modeling, it seemed that tidal erosion could be stopped by building a sill that comes out above MHW
(mean higher water). But this could be difficult for boating access so we need to explore this option now
with better models.
Joint Science Panel and Strategic Planning Team (September 28, 2005) Meeting Summary,
Elkhorn Slough Tidal Wetland Plan
4







Also interested in possibility of diverting water from the Old Salinas River Channel to reduce the
anticipated pollution/hypoxia problems if Elkhorn Slough has a muted tidal regime. This might require
pumping because the water is lower.
We need to model what the “no action” at the mouth of Elkhorn Slough would look like. We might want
to pursue some sediment actions without a fix at the mouth.
Taking into account sea level rise, we probably need to consider adding sediment no matter what. It
appears that the major options we have for dealing with tidal erosion also would be helpful for dealing
with sea level rise increases and Monterey Canyon migration.
We need to remember that permitting will mean decades for any large-scale project.
We have to ensure that sediment sources are there to restore marshes so we shouldn’t focus so much on
reducing tidal velocities unless we can provide more sediment. Historic sediment load is a wide-open
question, guesses range from 50,000 to 2 millon tons annually. The Elkhorn Slough watershed itself
didn’t have much of a sediment load, but there are questions about whether there was transport of
sediment from the Salinas River to Elkhorn Slough. The options for sediment from the Pajaro River
project are rapidly disappearing.
Usually, an unmanaged tidal system is preferable, but managed tidal wetlands buy us time. Eventually,
we need to deal with the tidal system at its source (mouth). Tidal marsh plain only partly depends on
inorganic sediment supply, but a lot is from internal primary production. We have toyed with the idea
that maybe they subsided due to some previous problems, muted flow in the 1930s, in which case we
could just raise up the level beyond some threshold. But no matter what, it seems like we can’t manage
in the long-term all the pieces as separate managed wetlands so we need to have a whole-system fix.
Until we better understand the exact mechanisms of marsh degradation, maybe we should do
experiments with primary production and sediment so we really know why subsidence has occurred.
C. For selected combinations, discuss critical next steps needed to continue evaluating options before
implementation
How can we make biological predictions based on physical estimates? What do we need to know to see if a
structure would even work?

We need to use a data-based model and run scenarios to calibrate it. The movement of sediment is based
on sill levels and hydraulics. So then once you have sediments, then you can link up with ecologists and
other groups to predict the results.

Predictions of biological systems can be done roughly with a habitat map and rate predictions for loss or
change. Information on tidal elevations and bathymetry for the next 10-50 years could be predicted.
Climate (precipitation and runoff) can also be predicted.

We need to use a model for predictions, but need to understand there will be error ranges with any
model. But if we use the same error ranges to compare different potential actions, then that could work.
You can run models to see what factors might be more sensitive to different forcing conditions (sediment
load, etc.).

Biologists may have an even more difficult time estimating parameters.

The type of predictive modeling use will be determined depending on your funding source (Army Corps
versus Coastal Conservancy).

Incremental cost analysis can also be plotted to find the most “cost-effective” alternative.

There are different types of models. Right now there is the 3-D hydrodynamic model. There needs to be
sediment transport information added to that model. There are also geomorphic change models. The
first step for any model is to see if it can predict the 1945 conditions before opening and then after the
new harbor to see if it can predict today’s bathymetry. Then, we can use that model for future
predictions. It needs to be a physical model of the system to predict geomorphic change under different
potential alternatives (and include marshes).

Geomorphic modeling has not been done extensively and is not trivial.

We need to model what the no action alternative would look like.

We might be able to use our goals and objectives to get an understanding of the alternatives before they
are modeled. For example, could we define the appropriate marsh elevations and tidal prism and then
model that scenario to see what the mouth and equilibrium might look like? Instead of what will
Joint Science Panel and Strategic Planning Team (September 28, 2005) Meeting Summary,
Elkhorn Slough Tidal Wetland Plan
5

equilibrium be but what needs to be done to get where we want to be? Pretend we are at the end point
and figure out what would need to be done.
We could try that. In this system, if I had a controlled mouth entrance and could bring in all sediment I
want, then I could order how the channels should be designed and the shape of the railroad bridge
entrances.
D. From the list of next steps, identify priority items that require additional funding
What do we need to know to assess the feasibility of adding sediments?

To add sediment, we need to know the volume, particle size, sediment composition, chemistry, method
and cost of transport, permeability of sediment, and subsidence of area (quantity needed).

We need to see if Union Pacific is a willing partner for a water control structure under their bridge and
also if they could help transport sediment.

We need to understand the natural sources of sediment so that we know how the marsh elevations could
be sustained over time.

We need to enumerate the sources, including dredged sediments from harbors and rivers and check on
the dredge permit records from Army Corps to see what would be available over a 10-year period.

There is not a lot of regulatory guidelines about cover versus non-cover sediment and the rooting zone is
about three feet so “dirtier” sediments can be below three feet from the surface.

An understanding of what role wind would play for stirring up sediment.

We could use something like rice straw to jump start the organic composition of the soil. Packing plant
wastes are common around here and could be used too.

The Delta has done some work on the addition of organics. They are considering how to inject water
below the peat to make it float up (as a more rapid way to create marsh in subsided areas).

We haven’t seen much difference between sand and silt but we it is slower to grow pickleweed on
gravel.

Dredge spoils are now a hot commodity now for wetland restoration so sediment sources can be thought
of more broadly than traditionally. Moss Landing and Santa Cruz harbor has dredge sediments. You can
add sediment (dredge) to marshes using a spray or broadcast method.

You would want to add the sediment in phases with multiple cells for realistic funding, permitting, and
sediment source quantities. You could see if the permit process could somehow be streamlined so you
could add sediments opportunistically.
Could any of the options be tested through pilot projects and/or implemented through phased steps?

Start with restoring Parsons while you look at the data for an option at the mouth of Elkhorn Slough.
Does anyone strongly disagree with that? No.

Is there a better way to do restoration so it is more adaptable? Yes, if we have enough culverts with flap
gates that we could open wide at Parsons, then we could manage the system across a spectrum of
alternatives.

Could you do a pilot at a place like Azevedo? How about only doing one arm of Parsons Slough/Five
Fingers area with a water control structure and sediment addition? But we already have a few pilots –
there are a number of wetland sites around Elkhorn that are receive different levels of tidal influence.

Why do we even need a pilot project? It might be helpful to demonstrate a success in order to request
large amounts of funding. But the large-scale options will still require modeling and we might as well do
the modeling to see what options are on or off the table.

We could think of Parsons being a Phase 1 project and the mouth of Elkhorn Slough as a Phase 2 project.

We already have an abundance of pilot projects in California that demonstrate muted systems and filling
with dredge sediments to raise the elevations to create marsh.
Project at Parsons Slough (medium-scale restoration)
1. What critical information is needed to make a decision?

We need to run a simple hydrodynamics model to get the size of the water control structure right.

It might also be helpful to understand the ecological functions of North Marsh to see if it would be
reasonable to manage this area at a lower tidal frame.
Joint Science Panel and Strategic Planning Team (September 28, 2005) Meeting Summary,
Elkhorn Slough Tidal Wetland Plan
6

We would need to demonstrate the outcome of a no action alternative for comparison.
2. What is the estimated time/cost of implementation activities (including EIR, survey for endangered species,
engineering design, then constructions)?

Water control structure only: 5 to 7 years, $5 to 7 million

Sediment additions: 10 to 50 years (depending on the project size and sediment availability), $6.7 to 50
million
Project at the mouth of Elkhorn Slough (large-scale restoration)
1. What critical information is needed to make a decision?

Models to predict changes to velocities, tidal prism, and sediment erosion/deposition patterns (and then
possible ecological trends) under different restoration alternatives (including no action).
o 3-D hydrodynamic model (Trim) should be up and running in about a month. This model
could predict areas of erosion and deposition within a range of errors and cubic velocity for
the main channel of Elkhorn under different options. But it would be difficult to use this to
model partial flow such a tide gates versus completely blocking off an area. This model
does not include the marsh plain.
o We need an intermediate step for modeling to get from the hydrodynamic model to sheer
stress erosion and deposition to geomorphic predictions of the channel and marsh plain.
o The Trim model will give shear stress, but there are models that will take that and
extrapolate the bed changes. We do that with the Delph model for South San Francisco Bay
from shear stress to geomorphic change which is a cutting-edge estuarine model.
o Then we need to figure out how to do come up with ecological predictions based on the
physical predictions of sediment elevations. This could be very expensive too because it
would have to go through CEQA/NEPA permitting. It might be better to have a range of
acceptable habitat conditions that we are aiming for, say between 10-30 percent gain of high
quality salt marsh so we can maximize flexibility in management. We would have to
evaluate the options with a limited number of key species otherwise it would be unrealistic.
We need to focus on the habitats, not on species (most species will come if we build the
habitat right). We need to develop success criteria.
o But how do models incorporate the fact that approximately 90 percent of sediment comes
from episodic events? Do we have data on sediment inputs? No, we don’t know what came
into Elkhorn from the Pajaro River flood.
o Modeling would take 1-1.5 years can could cost around $500K.
o We could also use the outputs of the model to link to a biogeochemical box model.

Measurements of sediment grain size and cohesion in order for the models to more accurately predict
changes to the erosion and deposition of sediments (and sheer stress).

Estimates of sediment supply in order for restored marshes to be sustainable.
o We need to model various scenarios to see how it would littoral drift in the lower part of
system might change. A closure might be permanent or scour 25 ft. deep, 250 foot wide so
understanding sediment source is important.
o Can we better understand sedimentation rates on the marsh plain? Sediment elevation tables
will be going in that measure sediment accretion rates and elevation changes. It might be
better to start with addition of sediment to marsh areas since they are in such horrible
disrepair already since this would take time.
o Are there any old benchmarks or transects of elevation changes over time? Yes, there are
benchmarks and there was a survey in 1980 that suggest that we are losing elevation in the
vicinity of tidal creeks (tens of centimeters).
o Is there evidence of sedimentation in upper slough when the Pajaro River flooded in 1995?
Yes, but anecdotal. Could we reintroduce the old flow of Pajaro River or at least capture
these sediments in overflow years?
o What about sediments from the old Salinas River channel (Tembladero watershed)? There
are a lot of fines seen by turbidity but I don’t know how much is actually settling.
Joint Science Panel and Strategic Planning Team (September 28, 2005) Meeting Summary,
Elkhorn Slough Tidal Wetland Plan
7
o
o
o





We need some minerals in the system to increase the productivity of plants.
We should look at the turbidity data from the LOBO water quality buoys.
The water in the Slough looks like chocolate milk for 3-4 months of the year but it is
flushing more rapidly (the load seems higher than in the recent past).
o Charlie Paull from MBARI has done some work on analyzing sediments in the Monterey
Canyon. There are a lot of places where sediment cores demonstrate accelerated erosion
from cattle on the landscape. Now we have very little sediment input compared to then.
Detailed descriptions of each potential alternative (not just a flow chart of options). For example, we
need to develop the sill and backfill options more clearly before modeling these options.
Designs of potential alternatives that detail what the water control structures look like and what they
would do.
Estimates of timing and cost-benefits compared with the goals and objectives and principles.
Literature review of similar projects so that we can learn from the successes and failures of similar
estuarine restoration project around the world.
Measurements of tidal range and inundation duration and frequencies, estimates of sediment inputs and
elevation, estimates of tidal prism, and studies of ecological functions comparing wetland sites with
different levels tidal influence to guide the development of small-scale restoration actions and help
provide guidance for designs for Parsons Slough.
o We could start with measurements at each site for three days during a normal tidal cycle to
compare it with the ecological data. Is three days enough? Yes, in open tidal areas, it is
easy to extrapolate to a model for different tidal ranges. It would be better to study the tidal
ranges in a longer time period to capture the freshwater inflow seasonally.
o We need to get estimates of tidal inundation frequency and duration on the marsh plain
(undiked areas) and compare that with our elevation data.
2. What is the estimated time/cost of implementation activities (including EIR, survey for endangered species,
engineering design, then constructions)?

Water control structure(s) (dam, sill, etc.): 10-20 years, $15 million

Backfill in subtidal channel: $8-20 million

Construction of a new channel mouth: $50-75 million?

Sediment additions to marshes along channel: $5 to 50 million
Additional Comments

We need to implement a small to mid-scale project now that, in fifteen years, would work with a largescale alternative at the mouth of Elkhorn Slough.

We need to get elevations and feasibility analysis for projects that first reduce the tidal prism and then
add sediments.

We don’t need much research because a lot of marsh has already been lost and we need to move on and
start with Parsons Slough.

We need one more year more to collect elevation and velocity data.

While we are starting permit legwork for Parsons, we could get a better understanding of small-scale
projects to see if any of those water control structures or marshes could be enhanced.

Reality check – research money is hard to get. Smaller projects will be at least four years so they won’t
be much less complicated than Parsons.

We should better understand the mechanisms of marsh loss and get tidal range readings.

We need to define measurable objectives for all of the restoration projects.

We need cost benefit and hydrodynamic modeling to better define the options.

Parsons is the best option; we can get bathymetry at Parsons and look at what it would take to restore it
under a muted tidal regime or what it would cost to add sediment even to a portion of it.

There is a lot of research going on about these same issues around the world so you might want to work
with others to figure out how far we are from a natural state.

There is much more funding available for implementation instead of research for tidal wetlands so we
need to start pilot projects. Potential projects could include: 1) research on the mechanisms of marsh loss
on the north side of the Slough, 2) implementing small projects such as at Azevedo ponds, 3) pursuing
Joint Science Panel and Strategic Planning Team (September 28, 2005) Meeting Summary,
Elkhorn Slough Tidal Wetland Plan
8







Parsons Slough restoration at some level, 4) trying test cases at the Five Fingers area of sediment
additions, and 5) demonstrating what no action would possibly look like.
Start with Parsons Slough, but if needed we could start smaller for implementation. We need to show the
differences in ecological function for funding.
The Louisiana experience is that they spent millions of dollars and twenty years on small projects, but
didn’t achieve their overall goal so we could learn from their example and consider the big project that is
really needed for Elkhorn Slough.
We need to think big and start with Parsons as the first phase of a larger project.
There is a sense of urgency since the dramatic marsh loss we are seeing is ongoing. There already is
very good data available, so the more we talk the more we lose. We need to know if the big fixes are on
or off the table. We waffle between small-medium scale projects but need to know what we “should” be
doing for the whole system.
Start with designs and the regulatory compliance and biological research for a project Parsons Slough as
the first phase of restoration in Elkhorn.
Parsons Slough is a good focus and time dependent
We need to set measurable goals and a timeline. How many acres of tidal marsh, self-sustaining or not
will define our success?
E. Set the next meeting date and discuss possible meeting topics

The next joint (Strategic Planning Team and Science Panel) meeting will be on February 22, 2006 from
9:00 a.m. - 5:00 p.m. at the Elkhorn Slough Reserve. The main purpose of the meeting will be to
discuss restoration and conservation alternatives for tidal habitats behind water control structures
(culverts, flap gates, etc.).
F. Proposed Outcome for Field Portion (8:30 - 11:00 a.m.): Become acquainted with the physical
locations of potential alternatives (Moss Landing Wildlife Management Area, Parsons Slough, Estrada/North
Marsh)

It is important to look at marshes that are not degrading (some of the “good” sites in Elkhorn Slough are
still degrading).

There are two basic processes are contributing to marsh loss – (1) the headcut of subtidal channel cutting
into tributaries and erosion of marshes along creek and channel banks, and (2) the loss of marsh
vegetation from the interior of the marsh plain. Therefore, there needs to be two steps to any restoration,
the fix of the subtidal channel and addition of sediment to the marsh plain.

Are we all in agreement that we can’t restore the system without a subtidal fix? It might be better to start
with marsh restoration while we study the possible subtidal options.

We need to better model the no action scenario. We could do this while we start with a restoration
project at Parsons Slough. We could start with separate cells to add sediment to different pieces either
by barge or train.

Would we have to keep adding sediment every 50 years or so to keep the marsh elevation up? This is an
important question to answer.

Parsons is a good study system for mouth because it is both manageable and degraded. Can we scale up
from Parsons to the mouth? We can probably scale up in terms of marsh response to muting and
sediment additions, but the hydraulics and marine fish communities, etc. might not scale up. It is a broad
test though of our ability to reduce potential tidal exchange in a large area

San Diego Verner Pond is comparable to North Marsh – great for birds. We could lower culverts to have
it drain completely with true intertidal, but not let in high tides so that marsh is sustained despite being
subsided. Are there natural analogues to North Marsh type habitats? The Salinas has large salt ponds
with hypersaline areas and freshwater depressional wetlands at margins of the estuary. If this area is
functioning pretty well, maybe we don’t want to mess with it right now, but rather work on Parsons that
doesn’t seem as ecologically. For North Marsh, you could raise the elevation and then increase the
mouth size to allow more of a natural tidal amplitude.
Joint Science Panel and Strategic Planning Team (September 28, 2005) Meeting Summary,
Elkhorn Slough Tidal Wetland Plan
9