At quarter to three this morning I got out of bed, opened the back door for the dog. Becky woke me again at 5:45. “I think Zeke got skunked.” I roused, smelled a faint odor of Mephitis. I called Zeke to the bed. No skunk spray: just the regular disgusting smell. We went down to the park.
It had rained during the night, and the creek was up again. It filled a third of its channel. The New Year’s flood brought it out of its banks, into the yards of stream-side homes. When it receded the water left a wrack of change. Tree trunks lay up against the train trestle in an upstream stack six feet high. When we moved here there was one small drop on this section of creek, a ledge of about two inches near a prominent tree halfway to the bay. I called it “Buckeye Falls” and imagined brave rafters the size of pocket mice. After January’s flood a cascade of small riffles ran from San Pablo Avenue to tidewater. The creek had scoured the Corps of Engineers channel, sculpted carefully by backhoe and dozer to control floods, banks reclining just below the angle of repose. Instead, the flood controlled the channel. From order came a different order. Bends in the stream remained, bars and cut-banks, back-channels and rolling, v-shaped tongues for the mallards to ride.
Today the water tore at the landscape it had built. What was for the last two months a flat gravel bar at the top of the park now bore a knife-edge ridge four inches high above the waterline.
There is a spot across the bay where people decided to breach the dikes, to let the bay reclaim former hay farms as salt marsh. It was a legacy of our last transportation regime. Chinese laborers stood hip-deep in water for years piling mud to build levees. Farmers filled the marshes behind them to grow fuel for horses. Peak Hay came and went but a few farms still remained, unconverted to cities, when public sentiment turned from reviling worthless swamps to cherishing our irreplaceable wetland heritage. The engineers opened up channels into the farm a little at a time. They worried that too broad a breach would fill the bay with wave-eroded silt. The channels were twenty feet across, and long, to blunt the energy of wind-blown waves. A few seasons, they said, and gentle tides would carry silt into the lowland farms. Cordgrass marsh would replace the hay in rich, productive marshes a few inches deep. They dumped dredge spoils from the Port of Oakland to start things off.
I visited six years later. Tides had carved the breaches into deep channels, carried the dredge spoils back into the bay. Cormorants dove headlong for fish in the old hayfields. The engineers scratched their heads. It was the narrowness of the channel, some said. The lack of meanders, said others. Look at natural marshes: is there a straight slough in any of them? Still others noted the diving ducks, said they had restored a wetland, and changed the subject.
A thousand feet west the Port Sonoma Marina, a series of pools connected to the bay by a small channel, is silting up quick. It is dredged once a year, at great expense. Palo Alto’s yacht harbor grows cordgrass. Alviso was once the South Bay’s busiest port. From the Bay you might be able to kayak to Alviso now, at flood tide, in a wet year. Water does what it will.
That flat gravel bar in Pinole Creek may be gone by tomorrow. The hills will renew it soon enough. Dredged up out of the earth as one tectonic plate scrapes along another, the hills are growing faster than erosion can level them. Green serpentine from the earth’s mantle, sand laid down on the bed of a Miocene sea, shale made of silt washed down from the Sierra, diatomite from a deep trench off Monterey: all mix as pebbles in the bed of Pinole Creek. All of them will wash out to the bay, eventually. A gravel delta runs fifty yards out from the creek mouth now. It was not there last year. At quarter to three tomorrow morning the tide will wash over it again.
Wow! Thanks!
I studied Nuclear Engineering in college. I can’t explain why, except for the fact that was the field that just seemed so easy and natural and answers just came so very intuitively.
By the time I got that degree, I knew I didn’t want to do that for a living, so I ended up doing Civil Engineering for a while instead. As someone who got his bachelors trying to understand models of power gradients across a nuclear reactor, Civil engineers always amazed me by their very simple and very assumption filled models.
I look out with my eyes, and I see an extraordinarily complex and chaotic system. To me, to try to model the water flows and effects in the system you so wondefully describe in this post would be a very complex and difficult task. But then I look and I see civil engineers using what seem to me to be very simplistic models to try to model it. The whole time I worked with Hydrology, there was a voice in the back of my head thinking ... you gotta be kidding. They calc it useing THIS model! :)
I guess that’s the difference between a field that if you got it wrong you get Chernobyl, versus a field where if you get it wrong you just “scratch your head”.
You put it very well ...“Water does what water will”, or something close to that. If there are civil engineers who can get it right, then its more of an art and an appreciation of nature than it is anyone trying to calc anything by any method I ever saw. Maybe there are some PhD’s at some school of engineering who have a model that works, but I never saw it in the real world.
“Water does what water will”. Any civil engineer that doesn’t accept that has their head buried in some of that Port of Oakland sludge. Maybe you can nudge it, but you’d better expect a lot of unexpected effects, usually somewhere else. Most of the time you just try to be conservative and see if you can avoid flooding someone out of their home.
Personally, I wouldn’t trust any civil engineer that’s trying to play with systems like the one you describe that doesn’t understand chaotic systems and lots of unexpected effects. And I don’t ever remember meeting a civil engineer who was curious about chaotic systems. :)
Thanks for the wonderful description. Its a beautiful thing to read.
No, the Sonoma Baylands project didn’t really work as intended. But, some do:
http://www.swampthing.org/wwr_projects_highlight.html#petaluma
What was different: An integrated monitoring, modeling and adaptive approach, using real-time data, high-precision time-series change detection and geomorphic insight into the controlling processes. This is my friend Stuart’s baby, his PhD work, and the beginning of integrated interdisciplnary tidal marsh restoration in SF Bay. Lots of lessons learned from the failure of more-or-less purely engineering solutions to complex hydrobiogeomorphic problems.
Great link, Fred! Fascinating stuff.
Maybe someday, when someday’s ever come, the various dams across the frontline of the Sierra foothills will be so filled with the silts they have been collecting now for half a century, that the Corps and PG&E (and SMUD) will simply have to let out a large gianormous release (much like they did with Glen Canyon and the Colorado). Literal mountains of silt will again flow out to the ocean, much stopping along the delta’s thousand islands, and large moraines of the rest will gob up the North Bay’s various wetlands and water courses. As i said, someday, one of these somedays; soon maybe, i hope.
There was already a field-test of the “release big gobs of sediment from the Sierra into the Delta and SF Bay” experiment. It was called “hydraulic mining”, and between about 1852 and 1884, did wash literal mountains of silt and coarser sediments out of the Sierra into the large tributary rivers of the Delta and the Bay. The Supreme Court case “Edwards Woodruff v. North Bloomfield Gravel Mining Company” declared the practice “a public and private nuisanceâ€? and put an end to the practice. This decision is frequently cited as one of the first environmental court decisions, although the interests of farmers vs. miners was what was predominantly in dispute (http://www.learncalifornia.org/doc.asp?id=526). The immediate and lasting consequences of sedimentation hydraulicking were enormous - aggradation of river channels increased flooding and made the rivers un-navigable, and about 25% of the Bay filled in. The town where I live, Oroville, is built entirely on coarse hydraulic spoils, and Oroville Dam, the Damoclean monstrosity that sits astride the Feather River just upstream is made almost entirely of mining debris. It’s a mile long, a mile wide at the base, 730 feet tall, and is supposed to contain enough material to build a road all the way around the world.
A reservoir release, a la the Glen Canyon Dam flushing flow experiment, would not supply much sediment to the system. Flows over spillways are poor in sediment - it’s all at the bottom of the reservoir. If the dams were to fail that’s a different story. In the 1982 El Nino, Glen Canyon came much closer than most people know. The spillway pipes through the Navajo Sandstone began to cavitate, a hydraulic phenomenon that was still unknown at the time. They’ve since been concrete-lined to prevent that, but an uncontrolled spill might still wreak havoc there. Not that that’s likely anytime soon.
The most likely scenario for massive readjustment of the Delta wetlands is the levee failure that’s been discussed a lot recently. Marc Reisner’s posthumously published description of the effects of a great earthquake on the Hayward Fault (A Dangerous Place) goes into this in detail. The greatest consequence would be the influx of salt water out of the Bay back up into the Delta, flooding the below-sea level Delta islands, and effectively completely destroying the water transport system form North to South.