This reminded me — I drove to South Philly Saturday night to pick up a friend and parts of Delaware Avenue (or Columbus Boulevard, as you transplants call it).
I’ve been driving that road for almost 40 years and never, ever saw or heard of flooding there — this was flooding from high tide, not a storm. This is not good.
It’s an ongoing process. The Chesapeake Bay was formed by melting glaciers. It used to be the Susquehanna River valley, which was drowned by rising sea levels. Check it out: http://en.wikipedia.org/wiki/Chesapeake_Bay#Geology