Many of California's beaches have been steadily eroding for decades. With rising sea levels and many of the streams that once carried sediment to the ocean now dry, the beaches cannot withstand the steady wave action of the Pacific.
Homes in Malibu (and other oceanfront communities a stone's throw from high tide) will eventually lose their beaches. Those homes close to the high tide mark now will probably vanish as their undersides are washed away.
The solution is to build sufficiently far from the coast and not to spend so much money and effort to prevent Mother Nature from doing the inevitable. Sand bags and rock walls are only temporary measures.