Floating Cities or reclaimed land cities to house refugees
It is entirely possible today to build floating cities or reclaimed land cities. Holland is using this as their strategy as their dams will need replacing and Dubai has shown the world what can be done using land reclamation.
I propose that instead of housing refugees using current methods that new cities are built for temporary or permanent occupation and self governed. In preparation for disasters whether man made or natural.
If they were built beyond any countries territorial limit it would require a new nation and government to be formed.