Beaches form when waves and currents deposit loose sediment like sand, gravel, and shell fragments along a shoreline. They erode when strong wave action or rising water strips that material away. Beaches erode; it’s what they do. For them not to disappear entirely, there needs to be a continuing supply of sediment. Rivers carry sediment and sand from inland areas down to the coast. Ocean waves contribute by breaking down offshore reefs and coastal cliffs into small particles.
Beaches have problems caused by the things people do around them. And those problems are big in California’s beaches. Malibu’s Surfrider Beach is iconic, inspiring films like Gidget and Endless Summer and many songs by the Beach Boys.
But now, the beach is disappearing. A century of dams, seawalls, and paved-over rivers have starved the Malibu coastline of the sediment that builds its beaches. The first dam across Malibu Creek was built in 1926. Since then, the amount of sand that the creek delivers to the coast has dropped by a factor of three.
With a massive El Niño underway, coastal residents need protection from encroaching water normally provided by beaches that have been shrinking away. In order to protect residents, more and more seawalls keep going up. Seawalls stop movement at the back of the beach and as the ocean continues to rise, the beach is eventually squeezed out.
California is the not only place where human intervention is eliminating beaches. Australians face many of the same problems. Beaches are another place where the impact of humans can be dramatic. It may not be surf’s up much longer.
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References:
A Century of Sand Debt Comes Due in Malibu
