The California Delta - earthquakes

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El and Bill

New member
The US Geological Survey has just released a report from a study concerning the 1,000 plus miles of levees in the California Delta - this is a favorite cruising area for many C-Dory owners. The USGS says many of the levees are very old, they are in an active fault zone area, and the possibility of quake-induced failure is probably much highly than previously thought.

Forewarned is forearmed - good to know risks so they don't come as a possible debilitating surprise.

I am especially concerned as a geologist who has experienced a 7+ quake, less than two miles from the epicenter, and watched waves (through dry ground) over ten feet high roll toward me - had to stand at right angles to the long period waves with my feet spread wide apart to maintain balance. Like standing in a dinghy as high waves from a wake rolled past.

The power of a large quake is truly awesome.

In a boat, on the delta, I'd power straight to shore and ground the boat. The 'islands' there are below water level, so a failed levee might pull your boat into a waterfall of very fast and violent water.

To understand an island below water level, click on:

http://www.cruisingamerica-halcyondays. ... unique.htm
 
Having lived there and fish there I can tell you this is a long known problem. Its been talked about for as long as my family has lived there and my great grandfather built many of the levee's as did not grandfather.

in the 95 flood the army corps rushed out to rebuild a lone neglected section of the levee on the feather. It was going to break if not fixed. In the end a far newer and supposed "safe" area of the levee broke. Truth is any part can go at anytime of high water. remember that Sacramento is the native word for "valley of death"

In the 50's or early 60's the upper valley flooded from the sacramento river to the feather. Gridley, my home town , was a island for a week. much of the delta was under water at this time. My grand mother had photos of it.
 
The worry and concern, though I can't disagree with the tremendously horrific results when the big one occurs, are in my opinion, overblown and simply a fact of life on earth. Truth is, no place is immune from natural disasters, it is just what you are comfortable with. While in Detroit, my wife worked on the orthopeadic ward. Every winter, she was beyond busy treating fractures, many severe and often hips and pelvises, from slips on the ice. I have shoveled sand out of my living room in Florida after a hurricane, my father had to replace a roof and wall in Florida after a hurricane, my Grandfather's neighbor had to rebuild after a tornado, and my father's cars were all totaled by hail in Colorado (the crops were devastated). My wife grew up in Northern California near a fault and we spent 10 years in California in the Coast Guard and college, no damage, no injuries. In college she did "surf" in the shower during the Coalinga quake in 1983 pondering whether to run outside naked (I just got motion sick during that one) and I was in the Stanford pool during the Morgan Hill quake of 1984 (both in the 6s). I know it is anecdotal, but still, in all places nature will wreak havoc in one way or another, and as I said earlier, it is a matter of what your psyche can tolerate and deal with. I personally would rather deal with hurricanes over ice and shakers but quakes are better than ice. My wife prefers the quakes over the hurricanes and ice, and my best friend from high school can't fathom dealing with hurricanes or quakes and still lives in Michigan. We have actually had this conversation with all three of us and marveled at how people are afraid or uncomfortable with different kinds of natural disasters, often times depending on where you grew up. If we were all the same, we would all crowd into one tiny corner of the globe. (Can a globe have a corner?)
 
You know what they say "no one gets out alive". I like storms and twister. Lighting and thunder are great. I have been in 4 god size quakes and hundreds of after shocks. Lived thru one hurricane ( Hugo) and did not like it. I have never been flooded out but have seen it and deal with it a lot. I'm very picky about where I live.
 
I agree that some of the levees are vulnerable, fear of earthquakes in Calif by non-Californians can be very significant, not really justified by experience. Having lived in Calif almost 50 years, endured 3 big earthquakes. When looked at over the long run, the annual death rate from Calif earthquakes (less than 10 per year) is much smaller than the annual death rate from being struck by lightening (20-30/yr).

Was in SF for the '89 earthquake, worked at UCSF Medical Center. We discharged almost 200 patients instantly for the flood of expected patients, we got 6. If you were under the freeway that collapsed, healthcare didn't matter, but other than that, very few deaths or injuries. Probably more deaths from road rage after the quake from disabled freeways. Same for the LA quake of '71, I lived 4 miles from center, lasted 90 sec, scary as shit for this Jr in High School. But again, very few deaths and serious injuries. The Van Norman Lakes (reservoir) north of LA was a concern, but no water loss. I walked around the area, some pretty big cracks.

I did get to watch a huge aftershock from the 3rd story of a building, saw that "wave" coming, and no exaggeration, the earth rose and sunk a good ten feet. I will never forget it, or the sound.

Always good to be prepared and aware of one's surroundings (preaching to the choir on this site as that's rule #1 in boating for me), but not let fear drive us.

Interesting question of what to do if on a boat in SF bay or Delta?? Most of us who have discussed it (+/- alcohol) came up with getting into open water ASAP, away from levees and land. Most felt that shoreline was most vulnerable spot.

We live in Sacramento, fairly low risk for earthquakes, but not zero. The levees are a concern
 
Good responses.

Perhaps a little clarification - We were not trying to generate fear with my post on the delta - there are natural hazards in virtually every corner (hmm - yes, Tivo, where is the corner on a globe?) of the earth. Some hazards may be foretold - hurricanes, floods, heavy rain, blizzards - and some can only be foretold by past occurrences and playing probabilities of future events - many geologic hazards, and certainly most earthquakes, fit in this category.

But, I do know from experience working with Civil Defense on real and potential geological disasters that being forewarned is the best defense. It has amazed me how often individuals are 'caught be surprise' and are unaware of the potential hazards of the area where they live or travel. The harm in a natural disaster often comes from panic or not being mentally (and physically) prepared. Our biggest potential earthquake 'hazard' for Civil Defense (playing the geological odds) in southern Nevada was thought to be a zillion panicked southern Californians fleeing by car from the aftermath of a major CA quake and overloading relief services in southern Nevada.

Certainly, choose to live wherever you wish and where you can be comfortable with the natural disaster risk (usually slight if a geological hazard, on the human time scale). But, be forearmed what the risks are and how to respond should it be necessary. Even more important as we travel - cruising on our boats (or for work or vacation).

My post was only to forearm folks that the USGeological Survey has recently increased the level of risk from a quake in the delta region. Of course, it has been known for many years that there was risk for flooding or quake - simply that new geological studies have indicated that the risk is considerably higher than previously thought by geologists.

Certainly, getting to a big open water area is a good idea if caught in a quake on the delta. Potential large waves could render shoreline dangerous. This would be true near a coastal shore or any lakeshore in a big quake - however, as delta boaters know, there are many areas in the delta where that is not easily possible - if in one of the narrow channels, bounded by levees, there may not be time to get to open water - then we would suggest ground that boat on the nearest intact shore to prevent being swooshed through a levee break into the lowlands on the other side of the levee.
 
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