Yeah, sounds like between the basement apartment deaths in NY, and those in cars in flooding, everything happened VERY FAST. Not just a trickle of water slowing rising, but a surge of fresh water just flowing into homes and roads.
In the moments it happens, I imagine you just freak out and panic and its hard to think straight when thats happening. I can't even imagine what those people went through during their last moments.
You can scream until you're blue in the face about the threat, but if people are in cars not listening to a news station that would give them that information, how will they know?
Push EAS alerts, send out mass texts, I honestly do not know how you communicate that threat to make sure everyone hears it. I imagine that is almost impossible to do. But I'm not an EM person, obviously, so I don't know the logistics of it all.