Palo Alto Weekly

Spectrum - March 18, 2011

On Deadline: Could a quake/tsunami hit Palo Alto, East Palo Alto, Menlo Park? You bet

by Jay Thorwaldson

In the shadow of the double-whammy disaster in Japan (assuming nuclear meltdown doesn't make it a triple) the inevitable question is: Can it happen here?

Well, sure.

It doesn't take much of a stretch of the imagination to envision (1) a big shake on the Hayward Fault, deemed at highest risk for a big shakeout, just ahead of the infamous San Andreas; (2) a surge of water moving down the bay; (3) a wind pushing the surge; (4) a high-tide — they happen twice daily; (5) a rainstorm that has filled local creeks; and (6) a power outage that stops Palo Alto's pumps (remember the El Nino storm of February 1998?).

One hopes, of course, that those conditions never line up. But there's always Murphy's Law: "Anything that can go wrong, will. ..."

The possibility of really really bad things happening right here at home is "old news" in many ways. There are scores of people, perhaps hundreds, involved in one way or another in trying to get Palo Alto and surrounding communities better prepared for earthquakes, floods and other natural or man-made disasters — the big kind that impact the entire city or region.

Advances have been made, such as improved communication systems between agencies and a fast telephone dial-up warning or alert system. Yet citizens and officials involved are the first to admit that the community is far from being truly prepared.

Neither neighborhoods nor families nor individuals are ready in terms of having adequate emergency drinking water and food set aside, adequate emergency First Aid kits, enough training, "Go Boxes" for their most precious possessions and papers, or a neighborhood or family emergency plan.

The news that the bay may pose a disaster threat also is pretty old.

In 1975 I wrote a piece for the former Palo Alto Times reporting a study that cited an urgent need to rebuild the levees surrounding the South Bay, most from the building of salt ponds over the decades. Pumping out groundwater for the fast-growing Santa Clara Valley was causing the land to subside, and that included a drop in levee height of up to 5 or 6 feet. (Subsidence has since been halted by percolation ponds that maintain the underground water table.)

But sea level stayed the same, putting the entire South Bay at greater risk of serious high-tide flooding.

The 1975 estimate to rebuild the levees was $95 million, a paltry sum today but real money a third of a century ago.

Then engineers came up with a better idea: Rather than rebuilding the twisting, in-and-out levees on the bay side of the wetlands and salt ponds they proposed building a concrete wall on the landward side, much shorter. This idea horrified those who loved the view of the wetlands and the bay, and the idea was stomped to death.

To my knowledge, there has never since been a region-wide repair of the levees, although work has been done here and there.

And a new concern has arisen: a possible rise in sea level due to global warming — now accepted as real by most independent climate scientists around the world. A conservative estimate is that within 50 years there would be about a 2 foot 2 inch rise in sea level, which also means "bay level." Some projections are worse, including up to a 55-inch rise.

Two feet doesn't sound like much, but it would be equivalent to the feared "100-year flood," the common standard used for flood preparations (meaning a flood with a 1 percent chance of occurring in any given year). A 2-foot sea level rise would be equivalent to a fairly typical high tide of today — then would come the tide.

Should the bay overtop the levees, or if the levees fail under storm battering, large areas of Palo Alto, Menlo Park and East Palo Alto would be subject to flooding. People pretty much know where the water would go in Palo Alto based on the 1998 flood, when the storm-swollen San Francisquito Creek overflowed. In addition to the main overtopping at the Chaucer Street Bridge there were 17 other spots reported on both sides of the creek, where water slopped over into all three communities.

The Bay Conservation and Development Commission (BCDC) has issued a flood-risk map, and the Pacific Institute also recently issued such a map showing both the 100-year flood zone with a 55-inch rise in sea level added in dark blue. Both maps show immense areas of the cities being submerged, clear to Louis Road and beyond in Palo Alto.

How deep? There were deep waters in parts of Palo Alto in 1998, as firefighters rescued people from homes. Yet mostly the water was wading level, and rose slowly, not in a big surge.

The worst local threat is to East Palo Alto's low-lying Gardens neighborhood, where several hundred homes could be inundated by up to a potentially deadly 8 to 10 feet of water. The Weekly called it a potential "mini-New Orleans" in an editorial following Hurricane Katrina — helping free up stalled federal funding for continuing a study of flood threats from the creek.

For many years the battle over how to make the creek safer has churned between the communities, until the San Francisco Creek Joint Powers Authority brought the three cities and two counties together more than a decade ago.

The threat from the bay has mostly been ignored, however.

No longer. Len Materman, the executive director of the creek JPA, has repeatedly called attention to the possible "other source" of flooding. And things are moving at last.

A major study of the flood potential and what might be done to protect the communities is due out by June 1, sponsored by the Army Corps, the Santa Clara Valley Water District and the Coastal Commission. But Palo Alto's bayfront won't be part of that, the Corps and water district decided March 8. They shifted the study's priority to more vulnerable areas <0x0214> such as Alviso.

Materman says the JPA may be able to pick up the Palo Alto portion, which would cover from San Francisquito Creek to the Charleston Slough just south of Palo Alto. The creek and tides are tightly connected. Menlo Park and East Palo Alto shorelines are already being studied and some work has been done in Palo Alto.

Meanwhile, a major emergency-preparedness "fair" is being planned in Palo Alto for Sunday, May 1. Check www.paneighborhoods.org/ep.

An e-mail announcement says it all: "It can happen here. This is another wake-up call."

At least we have no nuclear plant.

Former Weekly Editor Jay Thorwaldson can be e-mailed at jthorwaldson@paweekly.com.

Comments

Posted by Sethro, a resident of another community
on Mar 18, 2011 at 3:09 pm

It's a point well taken to take earthquake planning seriously and have appropriate supplies (including cash on hand). I'm glad I did when Loma Prieta struck. Earthquakes aren't just a possibility here, they are a matter of inevitability.
On the topic of a tsunami being generated inside the bay itself, there is a very, very slim chance. Tsunamis are a result of a land mass displacing water. They can be generated by an earthquake from a subduction fault but not from the slip/strike faults in the bay area. It's the wrong type of movement to generate large waves. The only way a tsunami could be generated inside the bay would be from a large landslide into the bay (as had happened at Lake Tahoe).
A tsunami could enter the Bay through the Golden Gate but the direction of travel would be towards the East Bay, not the South Bay. It would take a very large wave (30 feet or more) to have any significant flooding impact in the Palo Alto area.
Or so I've been told by USGS earthquake scientists based in Menlo Park.


Posted by Anon., a resident of Crescent Park
on Mar 20, 2011 at 1:11 pm

We can never rule anything out, but in terms of a surge pushing all the way down to the bay due to a tsunami ... I'm a little skeptical.

The reason I am skeptical is that if said giant tsunami is not high enough to go over the mountains that protect us the only surge that will be able to push a volume of water into the bay would be the golden gate.

Assuming it is a pulse of water ... a wave that surges in and then washes out ... only a certain amount of water would be able to pass through the golden gate ... even if it was 30 or 40 or even more feet high, how much actual volume of water would make it into the bay, and as it levels out how much would it fill the bay as far south.

I think a reasonable calculation could be made if one had the numbers of how high the wave is for how long and has fast it washes out. I question if the results would be anything like a 55 inch rise in sea level ... because that would be a steady state phenomenon, where a tidal wave would be wash of water in and out depending on the volume and frequency of the wave it is questionably whether that wave would push significantly all the way to the end of the bay.

Obviously if the tidal wave was big enough and lasted long enough it would fill the whole bay. I'd love to see if someone has done a simulation using values of the maximum measured rise and fall of sea level over the maximum time of the wave and apply that to a rush of water through the golden gate.

All things being equal I would much rather be here than in say New Your City/Manhattan which is the exact opposite of our configuration. Of course we could get the huge earthquake we CA is supposed to fall into the ocean like Atlantis, and we can never plan for something like that.


Posted by Anon, a resident of Another Palo Alto neighborhood
on Mar 20, 2011 at 6:03 pm

Anon from Crescent Park:

Remember that the wavelength of a tsunami is much, much longer than a wind driven wave, and, the amount of energy involved is vastly larger. A 30-foot wind-driven wave has enough energy to kill someone (e.g. at Maverick's recently), but, if you look at the videos of the recent tsunami in Japan, you will realize that a 30-foot tsunami has many orders of magnitude more energy.


Posted by Anon., a resident of Crescent Park
on Mar 20, 2011 at 6:55 pm

> Anon, a resident of Another Palo Alto neighborhood

I realize a tidal wave has a lot of energy, but only a relatively small segment of that wave can get into the bay, so it gets dispersed, like radiation in the air from Fukushima such that it will spread out in all directions. I'd like to know if anyone can simulate this?

For instance integrate the surge of water to get a volume and then distribute that around the bay and see if evenly distributed how high the tide would be? It would be ugly to see the ballpark floating down to the south bay but maybe we could float it over and ground it on the PA airport! ;-)

For sure heaven help anyone on Alcatraz.


Posted by Orwell, a resident of another community
on Mar 21, 2011 at 9:55 am

Think and worry EARTHQUAKE before you get shingles talking tsunami.
IF a tusnami hits Palo Alto, it would most certainly come after an iron meteor being on target on the Stanford admissions office.


Posted by WilliamR, a resident of Fairmeadow
on Mar 22, 2011 at 9:48 pm

The Army Corps of Engineers has a large-scale model of San Francisco Bay at their facility in Sausalito. They use it for studying tidal movements and currents, so they are probably researching how a tsunami surge through the Golden Gate would affect the rest of the Bay. (Google 'San Francisco Bay Model' for more information and the times it is open to the public.)


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