Where might one relocate 12,000 prisoners, many of them quite dangerous? Here is a fairly sensible look from within the comments:

“I just checked the topographical data for Rikers and the National Hurricane Center’s storm surge risk profile, and it seems that in the worst-case scenario (if NYC took a direct hit from a category 3 hurricane), parts of Rikers island would flood, but the vast majority of structures would not be at risk. The bulk of the island is about 25′ above sea level, with the eastern part reaching heights of >60′. In a direct hit under a category 3 storm, the island would be at risk of 22′-24′ surges. While that’s not a great safety buffer, both the track of the storm taking it directly over the east river, and the strength of the storm maintaining cat. 3 winds that far up the coast are highly unlikely. That said, it’s very disturbing that the city does not have an island-wide evacuation plan as the unthinkable is (remotely) possible.”