That "Up the Hudson" scenario is called "The NY Bight (sp)" scenario.
It's nasty - NYC knows about it - but I'd hate to say it, NYC is woefully unprepared. They were supposed to do a Hurricane drill in the early spring - it got called off due to the flooding from the rains in May - then they were called off for the Power emergency - They keep postponing and or downsizing their drills because "something else is going on"
Heck - post 9/11, you know where NYC put it's OEM? 5 feet above sea level - they KNOW it'll flood in a Cat 1!! Guess what, so will the backup. Of course, they either just have, or are just about to move into the NEW OEM - which is about 100ft above sea level, so.. But they took that risk for almost 5 YEARS.
Why? Because they wanted to be "near city hall" - politics. They had pleanty of good spots, but then they wouild not be near the center of political power
Like it or not, NYC, which is 5 counties, has a problem - that being that some are more equal than others - or to use a phrase there is Manhattan and "the outer boroughs" - and trust me, the outers get the short end
Remember too, that except for The Bronx, all the rest of NYC is on 3 Islands, and if it's bad, they are NOT going to be able to get help from Nassau or Suffolk, or most of NJ or Rockland/Westchester, who will have their own problems.
You think the NO evacuation was big? Hah - Cat IV, NYC has to move 1.25 Million people out of the flood zone. When I bought my house (in Queens - on Long Island), I made SURE I was not in a flood zone - I think of it this way - we get a 110 ft storm surge, there are bigger problems than I can deal with