The Rod and Boat Club on Wharf Road in Bolinas began
its life as an ark, a type of houseboat, but was long ago raised on
pilings. Inside, below the shallow vault of the ceiling, hangs an old
photograph of a tall-masted schooner moored where the clubhouse today
sits, suspended over a mudflat at low-tide. Now it is only at the highest
of tides that even a small boat can make it out the channel.
The Bolinas Lagoon has been filling with sand for
at least the last century. To many observers, it is a parable of human
excess and an opportunity for redemption through environmental intervention.
But a new report predicting the future evolution of the lagoon breaks
from previous assumptions and is likely to dash the hopes of a quick-fix
dredging of the lagoon.
The report does not, however, deny that the lagoon
is becoming increasingly shallow and is increasingly at risk of closure,
according to Bolinas Lagoon Restoration Project Manager, Dr. Bill Carmen.
No action so far
"When I look out over the lagoon I see some definite
changes," said Ralph Camiccia, a resident of Bolinas for 30 years.
He notes the rising mudflats, the expanding delta of Pine Gulch Creek,
and the appearance, on Kent Island, of a stand of trees where there
once were none.
"Us humans have a large impact on this lagoon. We’ve
created a beach subdivision in the lagoon; we've made roads... I don’t
think you can roll back what we’ve done." But that is exactly
what many local residents have been asking Camiccia, as Chair of the
Bolinas Lagoon Technical Advisory Committee, to do.
"No matter what happens, it's going to be in small
increments," said Camiccia, who nonetheless seems anxious to get
to work. "Taking no action all of the time could come back to haunt
us in the future."
It was demonstrated in 1968 that the tidal prism, or the
amount of water exchanged by the tide in the lagoon, was decreasing.
Regular surveys confirmed the trend, and by the late 90s the Marin County
Open Space District had partnered with the Army Corps of Engineers to
produce a 2002 report proposing an extensive dredging project to prevent
the predicted closure of the lagoon by 2035.
The ACOE report was widely criticized for both its
science and its conclusions. The Open Space District entered a "reformulation
phase," and commissioned the current study to predict the result
of taking no action.
Skip Schwartz, executive director of Audubon Canyon
Ranch, which borders the lagoon, said the new study represented better
science than previous efforts. Unlike previous reports, the new study
was peer reviewed.
Sediment from bluff, not watershed
The new reports from Philip Williams and Associates
and Professor Byrne of UC Berkeley present a revised understanding of
how the lagoon functions. Previously it was believed that the added
sediment had come from watershed runoff. But according to Don Danmeier,
project manager for the Philip Williams report, "watershed only explains
for a fraction of the sediment."
Core samples revealed that most sediment had been
swept in by the tide from outside the inlet. The Bolinas bluff, to the
north of the inlet, as well as the beach itself, are the primary culprits.
Both provide an inexhaustible supply of sediment.
Danmeier said that dredging would only result in a
temporary fix.
The influx of sediment is expected to taper off as
the strength of tidal currents decreases, but it is still predicted
that the tidal prism will fall from today’s 3.5 million cubic yards
(MCY) to 2.5 MCY in 2050. High mudflats could increase by one-third.
Unnaturally deep since 1906 earthquake
The report also states that the lagoon has been unnaturally
deep since the 1906 earthquake dropped the lagoon floor by nearly a
foot. The lagoon is now beginning to seek a "long-term equilibrium
form," with a tidal prism of around 2 MCY.
The report found no evidence of previous lagoon closure,
but this projected equilibrium form could result in a once-a-decade
closure of the inlet, if an El Niño-type event coincided with
a weak neap tide. "Diversity could decline since fewer plants and
animals are tolerant to large and sudden modifications."
Missing is reference to how the lagoon would reopen
itself. According to Danmeier, "it wouldn't naturally reopen easily.
It might require mechanical intervention."
Bill Carmen, the Open Space District’s project
manager, said that it was now time to ask people, given the scenario
painted by the report, whether intervention should be considered or
not. If the public determines that there is purpose and need for intervention,
future studies will be required to determined what form it will take.
No Bugaboo
Gordon Bennett, chair of the Sierra Club Marin Group,
was happy that the new report "gets rid of the bugaboo of the big
dredging project." But he said that even environmental groups opposed
to dredging are going to want to see a range of smaller alternatives
for intervention. Key to future efforts is the concept of adaptive management,
which proposes a broader range of try-and-see empirical solutions. "You
really want to make sure you’re doing the right thing."
Scott Tye, chair of the Surfrider Foundation in Marin
County, and resident of Stinson Beach, is concerned that the report
underestimates the risks facing the lagoon. "It shouldn't just be left
in the hands of special interest groups of either persuasion."
The report is available for download at www.marinopenspace.org,
and will also be in circulation at West Marin public libraries. Public
comment will be accepted until March 31 and should be mailed to Bill
Carmen at the Open Space District, or emailed to scrubjay@sbcglobal.net.