[ggm]

Probably all three, if you include sand pumping. (I guess that's beach reconstruction said another way)

Hawaii might be different to the continental shelf abutting changes i see here in Oz. Its driven here by a northward sand flow, combined with erosion. Sea walls and groynes and channel guides and dredging for river access are a dastardly trio which wreck the natural beach as does building on sand dunes.