The result: More than 10% of the state's coastline — and about one-third of Southern California — is protected with man-made barriers.
Although sea walls effectively protect property in the short term, they can intensify the effect of waves and alter surf patterns, leaving beaches stripped of sand until they narrow or even vanish altogether.
Environmental and surfing groups strongly oppose the barriers, and coastal regulators have increasingly asked property owners to find other ways to cope with the ocean.
There are some signs San Francisco is moving in that direction.
Last month the Coastal Commission granted the city an emergency permit to drop large sandbags on a length of the beach in preparation for this winter's storms, a softer approach on the city's part that even drew praise from a member of the local chapter of the Surfrider Foundation, an opponent of sea walls.