All port cities are vulnerable to storm surges and flooding from a violent sea. Long before Global Warming was even on the horizon, London got a flood barrier (see image above). Work to build it started in 1974 and had been ordered and paid for by the Greater London Council. It was finally finished in 1984, and opened by the Queen - the works didn't just consist of the flood barrier but strengthening flood protection for 11 miles down the river. It cost £534 million (about £3 billion or $4.8 billion in todays prices).
In the 1980's it was closed just four times - some snarky people would have thought the expense was just not worth it.
But as global sea levels continued to rise, it was closed 35 times in the 90's and a staggering 75 times in the noughties. It's undoubtedly saved London billions in flood damage over the years. London is not just a very old town (it was founded by the Romans and called Londinium over 2000 years ago), it has some very old infrastructure including the London Underground, the deepest subway system in the world. It is also home to some 7 million people. It was cheaper to have a barrier than to repair damage. In 1953 a North Sea storm surge killed 307 people - when a similar surge occurred in 2007, the barriers shut twice and no one was killed, indeed the storm didn't even make the news.
New York has seen terrible flooding due to storm surges caused by Hurricane Sandy. Nature is always going to do stuff like this, global warming or not. Why not spend some money on creating a barrier if you have valuable port cities? Would the damage have been as much if a barrier had been in place?