I feel for the folks on the East Coast who have had their lives disrupted by the storm. I hope that they get their power back in time to keep them from freezing , and I have nothing but sympathy for them. Their way of life has been seriously disrupted, and some folks have lost everything. I can only imagine what these folks are experiencing right now.
Looking at the areas that flooded, and the very little sandbagging that was done to protect things, it occurs to me that many of the issues with flooding (and a significant amount of damage) in New York/New Jersey could have been avoided if proper sandbagging/barricading had been done (and assuming that they had materials available to do so).
Don't just pile sandbags haphazardly....this gives no strength to your wall... Stack them in layers with one layer overlapping the next much like bricks...if you go more than three high, then you need a second layer behind the first, interlock those too... You have to sandbag all around the areas that need protection, not just part of them. A semicircle of sandbags does no good if the water can run around behind the sandbag wall. Covering the sandbags with plastic sheeting helps too.
While now isn't the time to criticize the folks in the east coast for their storm preparations, it does appear that many of the flooded buildings and tunnels and subways could have been saved (or at least damaged/flooded less) if doors and other areas of water infiltration had been sandbagged or barricaded properly to prevent flooding into these areas. There was very little evidence of any storm water prevention/blockage in any of the pictures or video I have seen. Perhaps I missed them, but I don't think so. It seems as if someone had used closely stacked K-rails or even sandbags and visquene to barricade the entrances to the tunnels and subways and air vents that the stormwater flooding could have been greatly reduced. Such preparations would have prevented or greatly reduced things like this. Such barricades might not have been watertight, but they would have reduced the flooding greatly. I'm not talking individual homes here, but rather larger infrastructure.
It does appear that there were very few portable generators in the urban areas, and fewer pumps, and nearly zero sandbagging. I realize that most of the time, they don't need such items, but nature has a way of finding your vulnerabilities. Preparation is the key. And it appears that there was little of that.
Perhaps they will learn for next time. Folks in the South and the Midwest learn how to deal with floods and other examples of nature's wrath, apparently the east coasters don't. Sometimes, thinking about the New Yorkers and especially the citizens of New Jersey, I expect that they were thinking "this won't be so bad... we are the chosen folks, it never gets bad here...". Either way, it does seem that preparations that could have been taken, weren't. And that led to significantly more damage that didn't need to have happened.
Others have similar opinions.
Perhaps they will be better prepared next time.