Rising sea levels threaten San Mateo County

Posted by on Mon, March 16, 2009

Area in blue at currently at risk Area in purple shows 1.4 meter sea level rise.

Rising sea levels are a major threat to California, according to a state-funded report from the Pacific Institute, an environmental think tank. And San Mateo County could be particularly hard-hit—on the Bayside as well as the Coastside.

But some of the aesthetic beauty and recreational values associated with the California shore, one of the state’s prime natural assets, are at risk, including the famed central coastal cliffs of Big Sur. In all, 41 square miles (66 km) of coast will be lost to erosion, according to the study.

"Changes to California coasts are inevitable," Cooley said. "We need to evaluate and assess what our values are and which qualities of the coast we want to maintain."

Flood damage envisioned by the study would result from storm surges occurring with greater frequency and intensity in low-lying areas once a safe distance from the shore. Areas that already lie within an existing coastal flood plain would face even greater risk.

About 260,000 people live in flood-prone areas around San Francisco Bay and other low-lying coastal communities up and down the state. That number would grow to 480,000 if sea levels were to rise 1.4 meters (1.4 yards) without any mitigating actions being taken, the report found.

However, most of the low-lying development is on the Bayside. There are more maps on the Institute’s website.

The LA TImes writes: "The group floated several radical proposals: limit coastal development in areas at risk from sea rise; consider phased abandonment of certain areas; halt federally subsidized insurance for property likely to be inundated; and require coastal structures to be built to adapt to climate change."

and what is the chance of sea-levels rising 1.4 meters? I just did a quick bit of research and found this on the NOAA site (with data specific to San Francisco)

“The mean sea level trend is 2.01 millimeters/year with a 95% confidence
interval of +/- 0.21 mm/yr based on monthly mean sea level data from
1897 to 2006 which is equivalent to a change of 0.66 feet in 100 years.”

looks to me like it will likely be several hundred years before we have to be concerned with a rise of 1.4 meters.

I’m not going to address the validity of either NOAA’s or the Pacific Institute’s forecast. I don’t have the information or background to call that one.

However, I’m skeptical of a trend based on about 100 years of historical data. We’re clearly off the map, with multiple non-linear relationships and positive feedback loops.  Historical trends can contribute only so much to modeling the future under those circumstances.

I just found some more intriguing information via this site http://sealevel.colorado.edu/maps.php

It appears to me that from 1993 - 2008 the eastern Pacific sea levels have dropped while the western Pacific has risen. Data was gathered via satellite measurements.

I believe that the 1.4 meter number is the result of very recent data showing that polar ice is melting faster than earlier anticipated.

Not only is Big Wave in the inundation zone along with the Pillar Ridge mobile home park but so is the SAM plant. SAM operations are of interest to ALL coastsiders.

So, for example, should any new water purification plant be located at the SAM plant?
Should SAM be setting aside reserves for future possible re-location? If so, where would that re-location site be?

It also looks like the Strawflower shopping center might be at risk. I have trouble believing that it is only 6 feet above the current high water mark, but maybe so.

At least I live outside the ‘purple’ zone. But then, I won’t be around then. The big issues are really on the bay side. For instance, portions of Hwys 101 and 92 might be under water well before the year 2100.

Say goodbye to our beautiful beaches.

We’re going to be guarding our homes and highways with riprap, so the beach can’t move inland in its historical fashion.

It’s not the most important loss due to global warming, but it’s going to leave an empty spot in all of us.

pardon my ignorance but what exactly is the SAM plant?

Huh ?

“Say goodbye to our beautiful beaches. “

Barry, Don’t you think you are over reacting a bit ?

Don’t you think that you should get a little bit of evidence that the sea level change is changing more rapidly that normal before you go there ?

I just read the other day that some polar ice cap scientists were saying that all the polar use would be melted next summer. They got called out on their data. Turns out that the instruments they were using to collect the data were broken and pointing in the wrong direction.

I am not saying that Climate change / Global warming isn’t happening but do you really think we will see a 1.4 meter increase in our life time ?

SAM is the Sewer Authority Midcoastside, and operates our sewer plant. 

They’re located near Pilarcitos Creek at the end of Sewer Plant Road on this map:


This area is shown as inundated on the map above. The finger reaching toward Hwy 92 in the map appears to follow the streambed, creating a sort of estuary on the map.

Regarding the beaches, I don’t see how they can survive much of an increase in sea level, even one far short of 1.4m. And I don’t believe the report indicates a 1.4m change in our lifetimes.

I’m simply contemplating the fact that our grandchildren will live in a world with no polar bears and few, if any, sandy beaches.  Trivial concerns in the larger scheme of global warming, but something that’s in the back of my mind when I play in the surf with my daughter.

I don’t see how our beaches survive the change.  Maybe not in my lifetime, but probably in hers.

Ok maybe I was jumping to conclusions. My bad.

The SAM plant (Sewer Authority Midcoastside) is our coastside sewer treatment plant. It is located west of Hwy 1 near the Pilarcitos Creek bridge on the Coastal Trail. It is well within the inundation zone.

If the plant has to move, where will it go?

Scratching my head at the map of inundation zone—Pillar Ridge is in the current tsunami zone which I understand is set at 30 feet.  Our lowest point is around 19 feet.  I don’t see how the predicted sea level rise puts that under water. 

Re the beaches—the more bluffs we preserve now, the more beaches would survive in this scenario.  As preserves they’ll be able to crumble and form new beaches naturally.

when I think of how the world is changing I also think about the world of my grandmother and how it changed from her childhood to her death. She grew up playing in the bicycle shop of the Wright Brothers and lived to see man land on the moon. I wonder now what marvels will be invented that my great nieces and nephews will consider normal. The world around us is always changing and we as a species have survived in part due to our inventive abilities and facility at adapting to new circumstances. Beaches have come and gone, moved inland and outward for millenia. They may not be in the same places but they will be somewhere for future generations to enjoy.

There’s difference now. There will be no place for most of our beaches to move.

We’re going to be protecting homes and roads with riprap and armoring. We will have some beaches in much less accessible areas, but we’re going to lose a lot of great beaches on the Coastside.

Hi Lisa,

The ocean level changes due to storm surge as well as tides. Last year we had a surge that swept waves many feet higher than the high tide mark. These are relatively rare events that don’t necessarily happen every year. The beach dunes at south Venice beach swept away last year have not returned this year and may never return because they are crested by high tides every winter now.

Scientists seem to be learning that the effects of global warming are more severe than anticipated. Each year, the predictions are that sea level will rise faster than thought. What do we, as intelligent citizens, do now to keep future generations from having to cope with poor decisions made in our time?