Who cares? Who do you think owns the coastlines - the wealthy. The same people pushing for trillions in everyone else's tax dollars for global warming. Just consider it a tax on the wealthy.
1) Stop subsidizing flood insurance. You own it, you pay for insurance.
2) Offer money now, before a rise in sea levels, understanding the worth is less because of impending doom.
3) One the land is subjected to recurring floods, the value drops to almost nothing. Act or lose.
4) Make all the land public for recreational use.
Costal Flooding Solved.