To qualify for flood insurance, your floor has to be at the elevation in effect when it was built. That's why my floor is at 10' above sea level. If you don't meet those standards, you can't get the subsidized federal flood insurance and without flood insurance here, you can't get a mortgage.
Homes built prior to the regulations are grandfathered, but anything built since then must meet the regulations.
When I moved here back in 1973, homes were built at 2 feet above the crown of the road. If this house were built by that measure, I would have been flooded out on numerous occasions.