A closer look at the sand on Manhattan Beach
When George Reppucci was walking his dog on The Strand one spring evening last year, watching the wind blow the sand over the walking path, he had a thought.
The retired aerospace engineer recalled pictures of Manhattan Beach he’d seen in historical books, showing the beach as a narrow strip of sand leading to the bountiful ocean.
Currently, the sand area is much wider – boasting 40 acres over 2.1 miles – and is equipped to host volleyball tournaments, surf competitions, summer camps and more than 6 million visitors a year.
“It struck me; like why is the beach wider than it was in the past? It should be eroding,” he said. “Erosion of the California coastline is a big problem.”
And so he went to work. He scoured through research papers and books and interviewed experts about the California coastline, looking for answers – why was Manhattan Beach widening when other beaches were eroding? Last month, Reppucci presented his findings to community members at the Manhattan Beach Historical Society.
He discovered that human intervention – or manmade structures like the Hyperion Wastewater Treatment Plant, Scattergood power plant, breakwaters and groins – has had a large impact on how much sand there is on the beach of Manhattan Beach.
Currently, the beach is about 420 feet wide, measuring from The Strand to the wet sand line. The beach was at its narrowest, at about 100 feet, in the late 1930s, when the some of the structures were originally developed, and has been gradually widening since. A major width increase occurred between 1947 and 1963, Reppucci said. Prior to that, the beach width was pretty consistent, albeit narrow.
The sand that was deposited on Venice and Dockweiler beaches during this time due to the manmade structures – experts estimate about 30 million cubic yards, or 2 million truck loads – has kept Manhattan Beach stable, reducing the littoral sediment drift, or the flow of sand depending on wind, swash and backwash, through the Santa Monica Bay into the Redondo Submarine Canyon, Reppucci said. The sand deposited into the canyon is not retrievable, he said.
“Numerous coastal structures have effectively compartmentalized the shoreline, reducing both the rate of alongshore transport and the loss of sediment down a major submarine canyon,” according to the research report, “Human Intervention with the Beaches of Santa Monica Bay, California,” by Craig Leidersdorf, Ricky Hollar and Gregory Woodell.
That Redondo’s littoral drift goes in the opposite direction and sinks into the canyon explains Redondo’s severe coastal erosion, Reppucci said. This spring, a dredging project will bring about 75,000 cubic yards of sand to Redondo Beach.
Understanding society’s impact on the Santa Monica Bay beaches has implications for the future and the economics of the area. “If the beach was a narrow beach, you wouldn’t be having $20 million homes, you wouldn’t be having volleyball tournaments on the beach,” Reppucci said.
Where beaches in Southern California are wide, they are usually artificially nourished, according to the Coastal Morphology Group of University of California, San Diego.
“As long as we’re nourishing the beach and have coastal structures keeping sediment flow down from washing away from the beaches, then we’re in good shape,” Reppucci said.
But, that’s a temporary fix, he said.
“Eventually, Mother Nature’s going to win out and the beaches are going to narrow — but I won’t be here to see that,” Reppucci said, with a laugh.
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