Assume you were to rebuild somewhere further inland, above sea level, how do you determine who owns what??
Actually an excellent question. Those that have clear title on record would be all set.
Do you want a Democratically controlled state government to come in and pull the "eminent domain" deal they just got in New England? Won't that be exciting!
Buy the land at the new site. Give an equal number of sq feet to all property owners at the old site, or the equivalent in cash. Lots of details, but in essence they would be no different than laying out a new city, such as Brasilia, which was created in the 1950s out the Amazon jungle.