I don't know about Californian beaches, but I know in Australia there's been a significant attempt to replant native grasses in erosion zones and maintain the d

I don't know about Californian beaches, but I know in Australia there's been a significant attempt to replant native grasses in erosion zones and maintain the dunes. The article describes this. What do you mean by "solutions that would work"? The solutions to coastal erosion are many, but one that sometimes works is having dunes held together by plants with sturdy root systems.