Among rich states, none is more threatened by sea level rise than the Netherlands. Their plans are reflective of this. Following the terrible flood of 1953, they began their Delta Works scheme for protection against storms. Now, they are contemplating how to modify that system to deal with at least 200 years of rising sea levels.
As such, they are planning to deal with 0.5 to 1 metre of sea level rise by 2100, and by 2 to 4 metres by 2200. The scheme to deal with this is expected to cost 1.2 to 1.6 billion Euros a year, between now and 2050. One can only speculate about the human and material costs of extending such defences to all the areas around the world that would be affected by such climatic changes.