Thanks (from a dedicated lurker) for all of your hard work on this thread.
A couple of questions that come to mind, reading your damage report --
1)Is "pier-and-beam" construction used much in this part of the state(s)?
2) If so, how stable are "pier-and-beam" houses that have had the piers underwashed by flooding?
I guess what I'm wondering is if the "still-standing" structures are as untouched as they might appear from a distance?
I didn't see any evidence of post and beam construction from the overheads, but you can set such a structure on a foundation that would appear rectangular from the air. Any ground with a high water table requires extra steps to put concrete or concrete and steel standards in below that depth, so a more or less standard foundation may have been used.
In either case, the key to stability is lateral bracing. You get some from buried standards, a cantilever effect that increases with depth, but which is wholly dependenent on the ratio of depth to the visible section.
The deeper you go, the more you resist the scouring that comes from moving water as well, but once you hit water, you have to use a special equipment to keep the sides of the excavation from caving in. Once such is boring equipment with a two part screw, which augers in and then is withdrawn, leaving an auger shaped sheet metal shell in place and which can be filled with concrete.
These would be expected to leave a visible footprint from the air, a pattern of dots, but what shows up on the photographs are simple rectangles.
If going that route, the pier bases need to be firmly fixed to the concrete, and any lateral stability is derived from diagonal bracing. For wind resistence only, I like timbers with plate steel, angled plate if possible, since it resists both tensile and compressive forces. Even so, I still prefer having the braces in opposition since even angle steel will fail under considerably less compressive force than it will to tensile stresses.
With any chance of moving water in the equation, wood simply cannot be trusted to hold fasteners of any kind under the potential loads involved. On a coastal area, I'd insist on all steel for any columns used to raise the structure, with resistance to oxidation in a salt environment being a primary concern.