In the Netherlands we rely on beach grass, a type of grass that can root well in loose sand, to keep dunes together. This forms the main sea barrier. The grass has historically been replanted at least partially to maintain the protection. This spans back at least a few hundred years I believe.

It's interesting that Lousisana works so differently. I always kind of assumed that dunes would always be needed to keep the sea out in low lying areas, but that's not the case at all.