Diving Deeper into Searsville

The story of a California dam calls for a rethinking of the hows and the whens of restoration.
Author:
Publish date:

Young women, ebullient and dripping, stand in a line along the concrete walkway above Searsville Dam. Beneath their naked feet, a sheet of water rushes under the platform and arches briefly into open space. The sheet breaks up, falls flickering against the face of the dam, and tumbles toward a shallow pool 60 feet below. Above the women's capped heads, cottony clouds reflect down on the surface of the reservoir.

Downstream, San Francisquito Creek winds its way unseen through thick oak trees and city streets to San Francisco Bay some 5 miles below. Upstream, tens of miles of tributaries cut their way like veins through green hills, converging here to create a reservoir skirted by wetlands and sandy beaches. Throughout the reservoir, the cries of songbirds and the carefree laughs of college students punctuate the murmur of falling water on this spring day, 1922.

Walking trails trace the shore from the dam to a beach on the east side of the lake where young men lounge around a barbecue and grapple in the water. The boys steal glances at the girls and take in the heat and comfort of the afternoon. The girls, members of the Stanford University diving team, shuffle along the edge of the dam, joking amongst themselves and calling toward the boys, who pretend not to notice but stand a little taller and wrestle a little rougher in the shallows of the beach. A girl at the front of the line climbs 20 feet up to the third tier of the diving platform before her. She leaps into the air and arcs over the water of the reservoir, her teammates cheering her on as she slips seamlessly into the water.

Half a century later, a fresh-faced young boy spends his days catching rainbow trout on Corte Madera Creek, one of the tributaries that feed Searsville Lake. One day he walks along an overgrown trail, stopping when his toes reach a strip of mud that frames the pool at the base of Searsville Dam. A silver torpedo bursts through the rippling sheet in front of him and collides with the hard face of the dam. The torpedo, a steelhead trout, bounces back, splashes into the water and sends small ripples expanding toward the young man's feet. The trout leaps once more, collides with a meaty thump, and falls back in defeat.

Fast forward 20 more years, and Matt Stoecker — now an adult, tall and brown-bearded — fights to remove the same structure he watched a steelhead trout struggle against more than two decades earlier. With a degree in stream ecology from the University of California, Santa Barbara, Stoecker directs an environmental consulting business and manages Beyond Searsville Dam, a nonprofit alliance that pushes to remove the structure.

Stoecker tells a story of an idyllic past long before humans could lounge on the edges of Searsville Lake. He describes the natural ecosystem that existed before the Spring Valley Water Company built Searsville Dam and tells how six tributaries once converged to squeeze through the canyon that now holds the reservoir. Stoecker claims this confluence formed a network of wetlands and riparian habitat that gave refuge to native waterfowl and songbirds. This habitat framed the natural migrating and spawning corridors of native steelhead trout, which in turn supported the ecosystem by dispersing nutrients throughout the entire watershed as they arrived each season from the ocean and left nutrients locked up in eggs, juveniles and the bodies of the previous generation.

"There's no other species like the steelhead that connects the mountaintops to the faraway oceans like they do," notes Stoecker.

That critical connection was severed in October 1891, when the Spring Valley Water Company, hungry for business and thirsty for water for the rapidly expanding city of San Francisco, flooded the once thriving wetlands and blocked the tight canyon at its base with an impenetrable concrete wall. The reservoir behind this wall, Stoecker says, has become an "artificial and unsustainable ecosystem" in which exotic large-mouth bass and bullfrogs prey voraciously on native species. He understands now that the trout he caught as a child were the tattered ancestors of those fish that once swam free in the ocean and spawned in the creeks above Searsville Dam — stranded now for more than 100 years. Fueled by such painful truths, Stoecker tells a story in which Searsville Dam plays the part of a villain who must be toppled in order to mend the bonds that have been broken.

Philippe Cohen stands gripping a handrail, its age shown in the multicolored splotches of lichen that mark its surface. Standing stout beneath his feet is the structure that both physically and figuratively divides this region.

"When I first started working here, my immediate reaction to [Searsville] was, 'Let's get rid of it.' ... I thought dams: lousy investments, they do a lot of damage, just get rid of it. And I've done a complete turnaround. Because the more I learn about it, the more I get a sense of what's going on here, the less I'm convinced — and you can't imagine how painful it is for me it is to say something nice about a dam."

Cohen, whose glasses glint below wind-slicked salt-and-pepper hair, directs Stanford University's Jasper Ridge Biological Preserve, a natural laboratory and nature preserve that encompasses nearly 1,200 acres in the foothills above Stanford campus. Today the title to Searsville Dam rests in the hands of Stanford University, and the structure itself sits in the heart of the nature preserve.

A map of the San Francisquito Watershed. (Courtesy Oakland Museum of California). Click to enlarge)

A map of the San Francisquito Watershed. (Courtesy Oakland Museum of California). Click to enlarge)

While Cohen admits that the reservoir behind Searsville houses many invasive species, he stresses that — ironically enough — the dam has also spawned the expansion of some natural habitats that are quite attractive and valuable in their own right. Tens of acres of wetland have formed in the alluvial fan above Searsville Dam, and with more than 95 percent of freshwater wetlands replaced by heavy development in the Bay Area, this habitat now provides rare support for an incredible array of native birds, bats, invertebrates and bottom-dwelling creatures.

Stoecker maintains that by removing the dam and allowing the area to return to its natural state the area could gain wetland habitat far more valuable than the few acres Cohen espouses. "Philippe will keep talking about how it's a great bird habitat, but he won't acknowledge what was destroyed and what could be restored," Stoecker argues. The environmentalist paints a particular story of the San Francisquito watershed's past, supporting his vision with a hand-drawn map he claims depicts that natural state of the Searsville site, portraying a valley cut by confluence of streams and framed by lush wetlands.

Not only that, Stoecker believes that by restoring the natural system we can gain improved protection against flooding - a concern that has grown in importance to local residents in recent years. The heavy El Niño rains of 1998 caused flooding in the heavily developed areas of Palo Alto, Menlo Park and East Palo Alto downstream of Searsville Dam, creating tens of millions of dollars of damage. Stoecker believes we can avoid such catastrophes in the future by creating wetlands that will "act like a big sponge to soak up high flows."

Some people are not so sure, however, that the story is as simple as Stoecker suggests, or that the benefits he promises from removing the dam - new wetland habitat, flood mitigation and steelhead trout spawning grounds — will actually materialize. Cohen raises his eyebrows at Stoecker's "handmade" map, saying he doesn't think the natural habitat in the place of the reservoir "looked anything like" what Stoecker draws.

"I'd like to see the data he drew that on," Cohen challenges. As for the flood mitigation these alleged wetlands would offer, Cohen counters that whatever flood mitigation is provided by removing the dam is flood mitigation that already exists without dam removal.

Similarly, it's not clear to Cohen that San Francisquito Creek has ever had particularly suitable spawning conditions for steelhead trout. "Everything I've read about spawning by steelhead makes it really clear that very turbid, sediment-heavy systems tend to be really problematic for spawning," he says.

A comparison of the sediment loads of the water entering and leaving Searsville Lake during the flood events of the 1997-98 El Niño season. (Courtesy Gary Kittleson and Jasper Ridge Biological Preserve)

A comparison of the sediment loads of the water entering and leaving Searsville Lake during the flood events of the 1997-98 El Niño season. (Courtesy Gary Kittleson and Jasper Ridge Biological Preserve)

Although a population of trout has persisted above Searsville Dam ever since the dam's construction, Cohen is not convinced that the creek can maintain good habitat for steelhead spawning while the remarkably high sediment flows he and his colleagues have measured continue to flush through the creek. Removing Searsville Dam will increase the sediment load in the creek downstream, and as an additional complication, it is entirely possible that this increased load would damage steelhead spawning and wintering habitat by plugging up gravel beds and cold deepwater pools in the creek.

Even if Stoecker is right about the past state of the San Francisquito watershed, some people question whether returning to such a past is even possible.

Professor David Freyberg, a Stanford hydrologist and sedimentologist whose attire of choice includes a fly-fishing hat and a bolo tie, has studied sediment transport at Searsville extensively. Freyberg points out that rivers don't just move water, but engage in a continual reshaping of the Earth's surface. They are the conduits by which sediment, or small fragments of organic or inorganic material, reaches the ocean. When the natural flow of a river is altered with a dam, so too is the natural flow of sediment — often in unexpected ways.

Every dam in the world is filling up with sediment to some degree, and this is an especially imminent problem for those dams - like Searsville - that collect water from the highly erosive faces of the mountains of the Pacific Coast Range.

Sediment enters Searsville Lake primarily during extreme flooding events, and the rate at which it does so at any one time can be astoundingly high. During the 1997-98 El Niño rains that caused flooding in Palo Alto, East Palo Alto and Menlo Park, scientists at Jasper Ridge monitored the sediment load of Corte Madera Creek, the tributary that contributes most to the sediment problem at Searsville. "We were measuring in terms of suspended loads something on the order of 22,000 milligrams per liter of suspended sediment. You could go to McDonald's and get milkshakes thinner than that," Cohen recalls.

It turns out that far more sediment is trapped in the reservoir than the dam's architects expected. Sediment deposits disproportionately in the alluvial fan behind the dam, and vegetation in this alluvium amplifies the process by stabilizing newly deposited sediment and allowing the alluvial fan to slowly creep up on the dam. As it stands today, the reservoir has lost nearly 90 percent of its original storage capacity of 1,000 acre-feet, and the next big erosion event could completely fill the reservoir with sediment.

If the dam were removed, Freyberg warns that it's not at all clear what will happen to the 12 decades worth of sediment that has built up behind the dam.

"When you talk about dam removal, it's not like you're suddenly allowing things to go back to being natural," argues Cohen. "This is one of those dams that has been around long enough that it has really — in some respects — integrated itself into the landscape, and the streams downstream and upstream have calibrated to its presence."

Even if one ignores the sediment currently filling the reservoir, both Cohen and Freyberg argue that what would happen to San Francisquito Creek if the dam were removed is not still as simple as Stoecker likes to suggest.

All of the sediment currently filling up the reservoir is sediment that has been robbed from what would naturally have deposited downstream and in the San Francisco Bay.

One analysis  the optimistic view — suggests that reaches of the creek might keep only a small amount and that most of the increased sediment load would end up in the bay. In the other extreme, all of the sediment gets locked up in the creek, the creek gets shallower, and risks of flooding skyrocket. The exact outcome will be somewhere between those two extremes, but exactly where it ends up is in no way clear. It is clear, however, that suddenly restoring the natural sediment flux in San Francisquito Creek does not necessarily translate to an automatic return to the "natural" state.

A panoramic photo of Searsville Dam in Jasper Ridge Biological Preserve, Portola Valley, Calif. Click to enlarge. (Courtesy Philippe Cohen, Jasper Ridge Biological Preserve, Stanford University)

A panoramic photo of Searsville Dam in Jasper Ridge Biological Preserve, Portola Valley, Calif. Click to enlarge. (Courtesy Philippe Cohen, Jasper Ridge Biological Preserve, Stanford University)

Stoecker tells a tempting story of a glorious return to a better past, yet many question the validity of his assumptions and the viability of the promises he makes. "It's a very sexy thing," notes Alan Launer, the campus biologist for Stanford University. As Launer sees it, Stoecker tells a win-win-win story: Remove the dam and we get fish, we get flood mitigation, and we get wetlands. But it's more complicated than that, Launer warns, and others like Cohen and Freyberg echo his concerns.

The question of what to do with Searsville Dam is not a new debate, and people like Philippe Cohen and Matt Stoecker have been playing opposite sides for at least the last 10 years. The most recent development unfolded on April 16, 2010, when the U.S. Fish and Wildlife Service and the National Oceanic and Atmospheric Administration released a draft Stanford Habitat Conservation Plan for a public comment period that lasted until July 15, 2010 — after which point they will write and approve the final draft. Stanford's conservation plan is an agreement that institutes conservation measures such as the establishment of creek easements and no-build zones on the university's land in order to protect several species listed under the Endangered Species Act, including the steelhead trout.

Beyond approving maintenance dredging in the reservoir and commissioning a study that looks into the feasibility of creating a fish passage at the dam, the plan in its current form calls for surprisingly few specific actions to be taken at Searsville. Catherine Palter, the associate director of Stanford's Land Use and Environmental Planning Department and the project manager for the conservation plan, argues that complications like those with sediment, flood mitigation, wetlands and steelhead, made modifying Searsville Dam too uncertain and risk-laden to be addressed with the plan.

In order to cover minor work the university already undertakes at Searsville such as scientific research and the drawing of water for irrigation, the writers of the habitat conservation plan "really took a status quo approach," says Palter.

In the face of rising sediment in the reservoir and increasingly poor rainfall in water-strapped California, many recognize that following the status quo at Searsville Dam is only a temporary solution that forestalls the truly difficult decisions.

Peter H. Gleick, the president of the Pacific Institute — an interdisciplinary research group that aims to find and implement solutions to issues of sustainable resources — warns that "California's water system was designed and is operated on the assumption that the future climate is going to look like the past — and it isn't."

Despite the relative inaction of Stanford's conservation plan in the face of urgencies like those Gleick brings up, Cohen adamantly argues that "the only option not on the table is the status quo," and all parties involved agree that we're going to have to do something relatively soon with Searsville Dam. Yet, Palter warns that decisions like these take "years and years and years."

Such impasses and difficulties like those at Searsville are endemic to conflicts over dams and water, and it turns out we in the United States may soon face such problems with increasing regularity in circumstances of rising urgency. In many areas of the United States, conflict over water is a familiar story that has defined our history in many ways — and may well define our future.

Many water conflicts start with a river and hinge on a dam. Rivers are extraordinarily dynamic on many scales of both time and space, and many support important and diverse ecosystems. They are the most accessible - and exploitable - distributed water resource on the planet, and they are the one most profoundly affected by human activities. Rivers cross multiple types of boundaries and jurisdictional lines, posing difficult management issues where the effects of decisions in one area spread both upstream and downstream.

Dams on our rivers provide many important benefits, and, while we could certainly get by with fewer, "we literally couldn't support our population" without many of them, says Freyberg. Humans need water perennially, yet water is not naturally available in channels throughout the year, and the only way to get around that is with water storage from dams.

A graph showing dams in the United States by completion date. Click to Enlarge

A graph showing dams in the United States by completion date. Click to Enlarge

Given this dependence, a serious challenge looms. The National Inventory of Dams, a database maintained by the U.S. Army Corps of Engineers, identifies nearly 84,000 dams in the United States. The U.S. built more than one-third of these dams in the short period from 1950 to 1970, and - with the projected design life of most dams being between 25 to 50 years - many like Freyberg believe the country has reached a point where it will soon have to make many difficult decisions about what to do with its rapidly aging population of dams.

As exemplified by Searsville Dam, each of these aging structures will come with its own idiosyncrasies that complicate any vision that strives for a clean return to a better past.

Winter now, and today Philippe Cohen stands on top of Searsville Dam gripping the icy handrail. Cohen bikes to work here every day of the year from his home in the hills nearby. He breathes hard and adds his own foggy breath to mist that rises off the water and whisks past his shoulders into the void before him. The sound of water tumbling over the stepped face of the dam drowns away the quick beat of his heart.

These winter days, frost sparkles on every surface in the freezing air. Cohen puts his chilled hands into his pockets and begins to make his way back up to his bike and toward his office on the ridge above the dam. He stops briefly and ponders the aged remains of the women's diving platform; the centerpiece of that fine spring day in 1922. All that is left of those joyful days is a steel frame that juts crudely over the water surface, rusting in jagged red flakes and lined in white frost. Cohen marvels at the hardiness of those women who trekked to the dam even in winter to practice their dives in the freezing water of the reservoir. He peers past the frame into the turbid water and toward the muddy bottom 12 feet below. He would never dive from a 20-foot platform on a day like this - if not to stay warm, then to avoid a face full of mud.

And neither would anyone else. The year 1922 heralded the opening of a recreational park at Searsville Lake that served as a weekend retreat for sun-hungry college students and locals for the better part of 50 years. The operation of this park was not, however, without its disadvantages. In part to end conflicts between park-goers and the Stanford researchers and classes trying to study the ecosystem, the Stanford University Trustees closed the park in 1976. Little now remains of the old diving platform, and with the muddy bottom of the lake rising inch by inch, it is clear that even if we rebuilt the platform, there is little chance we could relive the vision of sepia-toned college days it represents. Even less likely is returning to the alluring dream of an earlier time before man's heavy hand forever changed his rivers by clogging them up with dams.

The desire to return to such a past reflects a common conception of dams and restoration. This conception points to the many dams on our rivers that have outlived their usefulness and now lie aging and crumbling on the ruins of what was once a thriving ecosystem — symbols of a time when man in his arrogance thought he could conquer and should tame wild nature. In this framework, nature and her rivers are good; man and his dams are bad.

Cohen responds to such a simplification with a surprising insight. "I don't like setting up dichotomies of what people do versus what is, quote-unquote, natural, as somehow being diametrically opposed. I think those interactions are more nuanced."

He also questions the mindset that thinks about restoration as "somehow going back to the past." The past — contrary to common intuition — may not always be the best model for what we will face in the future. Indeed — with Searsville — visions of our past cannot be the reality of our future, and the common sense of the word "restoration" requires some rethinking.

While such insights can sting in the face of loss, perhaps their message is something better rejoiced over than lamented, because the reality of the past rarely lives up to the fantasies we construct around it. After all, the only reason the ladies on the Stanford diving team stood dripping on the cold concrete of Searsville Dam was that the campus pools were, of course, only for men.

subscribe-to-mm

Related