GowanusLounge has some interesting maps up, showing the vulnerable areas of Williamsburg and Greenpoint. Not surprisingly, an understanding of historical geography helps to make sense of it all. Obviously, the coastal blocks are all inundated in a Cat1 storm or higher. But upland, the effects are different block by block. The area immediately around the Bushwick Inlet, as far inland as Berry, would also be flooded in a Cat1 storm. Further inland, a Cat2 storm out past McCarren Park to Withers Street, and south along Union to Grand. Its not coincidental that that pattern corresponds exactly to the footprint of the old Bushwick Inlet that we noted earlier.
Elsewhere, much of Greenpoint would be underwater in a Cat2 storm, but most of Williamsburg to either side of Grand Street would not be effected until Cat4 or Cat5, if at all. This makes sense if you know that Williamsburg once had a bluff running along the line of what is today Bedford Avenue, and that Greenpoint was mostly uninhabitable (and inaccessible) swampland until developer Neziah Bliss came along.