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By Brian Seals
Santa Cruz Sentinel
April 30, 2005
Tourists and locals alike flock to Santa Cruz County to sun on the spacious beaches along the northern edge of the Monterey Bay.
Those beaches, however, are likely to shrink as a major source of sand that nourishes them exhausts itself, a local geologist contends.
UC Santa Cruz lecturer emeritus Gerald Weber presented that theory Friday in San Jose at a joint meeting of the American Geological Society and the American Association of Petroleum Geologists.
Northern Monterey Bay beaches have been kept unusually wide for about 200 to 300 years by a reserve of sand north of Ano Nuevo that drifts down and collects on area beaches, he said.
Weber believes that when Ano Nuevo Island separated from the mainland about 300 years ago, perhaps because of an earthquake along the San Gregorio fault, it opened a channel for sand trapped above Point Ano Nuevo to drift southward.
"The point acted like the jetty does at the yacht harbor," Weber said Friday.
That sand, an estimated 50,000 cubic yards a year, resulted in wider beaches to the south, from New Brighton State Beach to the Pajaro River he said.
But the roughly 13 to 20 million cubic yards of sand has been exhausted, resulting in less sand flowing to Santa Cruz area beaches.
Weber said shrinking is already noticeable at Point Ano Nuevo and Greyhound Rock, near the county line.
"Beaches down drift from Point Ano Nuevo have shrunk drastically over the past 25 to 30 years, and sea cliff erosion is accelerating," Weber said.
He said that could have effects in the Mid-County area where homes are built along the beach. No need for homeowners to panic, Weber said, but they should be aware.
"The slow change may be starting already," Weber said. "The full impact may take 20 years or 25 years."
There’s no one to blame, he said, because the beaches in those areas have appeared stable for centuries, a long time for humans but a tick of the clock in geological terms.
"Most people don’t think in the time frame we’re talking here," Weber said.
Weber first set forth this idea more than 20 years ago. Since then, he said he has gathered more evidence by poring over maps and decades worth of aerial photographs.
However, some of Weber’s colleagues aren’t so sure about his conclusions.
UC Santa Cruz geologist Gary Griggs said he does not doubt Weber’s observation.
"What I question is the impact of that," Griggs said Friday.
Sand from area streams and river mouths is enough to keep the area’s beaches spacious, and any impacts of the depleting sand reserve at Ano Nuevo should be noticeable by now, he said.
"The beaches of Santa Cruz are as wide as they have ever been," Griggs said.
Weber said he is accustomed to the disagreement in the marine geology community. That kind of dissension is commonplace in academia.
Weber and Griggs have been colleagues for years. In a book Griggs is updating titled, "Living with the Changing Coast of California," he and Weber wrote a chapter together on this very topic.
Griggs was also Weber’s thesis adviser 35 years ago.
Weber is pretty confident of his theory, but he may never know for sure.
"I’ll probably be dead by the time we know if I am right about this," Weber said.
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