A friend of mine bought an old home about 20 feet from the water on the Manokin River. (about 1/2" above the estuary) He had to elevate it to 75% of the height of the 100 year flood line in order to get insurance he could afford. At 75% it was "reasonable," though at the 100 yr flood line, it would have been cheaper.

I'm not sure at what minimum height, he would qualified for insurance.

During Isabel, he got water under the house within an inch of his first floor boards, but it did not penetrate into the house. So, he felt he had made a good choice.

If you notice, the homes in the slide show are all on stilts. So, they probably all had flood insurance. Of course, the fact that they are built on a spit of constantly moving and shifting sand, doesn't appear to have any impact on them.