There are poorer sections of NYC that were inundated during Superstorm Sandy. These are or were modest homes, some dating back a century. The solution to repeated flooding that happens in those areas is to buy out the property and create greenscapes where no homes exist, except the isolated few who refused to sell.
Then there are areas where parks have trees being cut down to build flood walls to hold back the sea.
Lastly, more walls to protect Manhattan and the high price real estate that is what we typically think of when we think downtown New York. The challenge is that not everyone is in agreement on which tactic to use where. Thus there are lawsuits and delays, and billions in project funding getting unspent while the courts and public opinion clash.