And to whatever degree they do look different it is due to a combination of sand mining for incorporation into concrete, and a reduction in sand repopulating beaches due to more dams and other river management projects that keep new silt away from beaches.
California cracks down on last beachfront sand-mining operation in U.S.They KNOW what causes shore erosion. And it ain't global warming / cooling.
San Jose Mercury News, May 16, 2017Moving in on the last coastal sand mining operation in the United States, California regulators are ordering a Mexican-based company to obtain permits and pay state royalties for its Monterey County plant or shut down — amid a chorus of complaints that it’s causing significant erosion of beaches along Monterey Bay.
The facility, known as the CEMEX Lapis plant, has been in operation since 1906 and is located between Marina and Moss Landing. With smokestacks, conveyor belts and dredges, it produces an estimated 200,000 to 300,000 cubic yards of sand a year — enough to fill up to 30,000 dump trucks — that sells for about $4.70 a bag for a variety of uses from sand blasting to golf course sand traps to lining utility trenches.
Scientists and environmental groups, however, say the facility is causing significant erosion of beaches along Monterey Bay, from Marina south to Del Monte Beach in Monterey.
“If you take that much sand directly off the beach every year, the waves keep breaking,” said Gary Griggs, director of the Institute of Marine Sciences at UC-Santa Cruz. “The southern end of the bay is eroding at a much faster rate than it would naturally.”
Griggs, who has studied coastal erosion for more than 40 years, said that areas south of the sand plant, along the site of the former Fort Ord military base and down to the Monterey Tides Hotel in Monterey, are eroding at roughly 3 to 6 feet a year. Stilwell Hall, the former World War II-era officer’s club at Fort Ord, had to be demolished in 2003 when cliff erosion threatened to send it crashing into the ocean.
Without the sand plant, Griggs said, the coast in that area would erode by roughly 1-2 feet a year, if not less.
In decades past, there were six major sand mining plants along the shores of Monterey Bay. They used a technique called “drag lining,” in which they scraped and dragged sand with massive metal scoops from the surf line. The companies were closed by the U.S. Army Corps of Engineers between 1986 and 1990, however, after the agency enforced prohibitions on sand mining below the tide line.
The Lapis mine remained open, however, because it had shifted to a method in which it pumps sand from a lagoon on the back of the beach in an area where it owns several hundred acres. Meanwhile, last year the California Coastal Commission said it will require permits, a case that is still open, but CEMEX contends that its operations predate the 1976 Coastal Act.