Have our beaches changed dramatically?

I look at many historical photos of the Coastside, including the beautiful beaches. After awhile I can’t help but notice that the beaches have changed dramatically. Most of us have no idea how much bigger the beach at El Granada was in the 1920s, or how many rock arches and caves were once part of the scenery at Moss Beach. Sand dunes covered Miramar Beach and there were nice little beaches at Princeton, too.

When did the change begin? The photos seem to say it began in the late 1920s, 1930s. That made me wonder about the Golden Gate Bridge. The bridge was built in the late 1930s. Could it have had something to do with the loss of sand on the San Mateo coastline?

John Vonderlin spends a lot of time exploring the remote South Coast beaches, many of them inaccessible, taking photographs, revering and studying the beauty that he finds.

I asked John, could construction of the Golden Gate Bridge have affected the San Mateo County beaches?

John said: I’m no expert, but here’s what I think is going on with the sand disappearing from our local beaches. First, I don’t think the Golden Gate Bridge has had a significant effect on our beaches. The tower foundations aren’t big enough to interfere seriously with the transport of sediment out of the Bay and possibly into the littoral cell south of the Golden Gate Channel.

This is from a USGS site, click here

Whatever part of that sediment that gets swept up in the Longshore current, along with the sand brought down by our local creeks or eroded from the many local wave-battered sandstone cliffs, ends up feeding and sustaining our beaches.

Dams were probably the biggest factor in the disappearance of beaches, perhaps not here so much as other places. The impoundment of sediment behind the dam on the bottoms of gradually growing more shallow lakes and ponds, surely has had an effect hereabouts. But I don’t think they are the main factor. After all, I don’t know of any new local ones being built in a long time, yet the beaches have seriously diminished using the 1972 California Coastal Records Project’s photos as a comparison. In fact, the general trend has been to remove dams in the various coastal watersheds to re-open ther streams for fish migration. Likewise, the friable, easily eroded, sandstone cliffs that contribute so much raw material to our beaches haven’t significantly changed in that timespan.

There is one plausible reason the sediment load carried to the sea from our local watersheds has greatly diminished. And that is environmentalism. Logging has greatly diminished and been forcefully required to improve the watershed protection techniques they employ. Farming is in a similar position as logging is, both as a shrinking business and one that has learned or been required to practice better land stewardship. Based on some of the pictures I’ve taken of turbid runoff entering the ocean from irrigated coastal fields, there is still more that needs to be done.

All in all, erosion control has greatly expanded in almost every aspect of land use in the county, from road building, home construction, and land clearing, to runoff management protocols and wetland restoration or protection projects.

We’re being skewered by our own success. If we prevent sediment from getting in the water flowing to the ocean we can’t expect much in the way of beaches. Unfortunately, I think it is a classic Hobbesian choice situation( i.e. your money or your life) where the Golden Age of San Mateo beaches has come and gone and there’s not much we should do about bringing it back. Enjoy. John

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About June Morrall

1947 - 2010
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