Sharon Astyk wrote from her home in NY: 

"So yesterday I reminded people we are ALL facing regular #flooding events, & of course, a lot of people responded with why that doesn't mean them personally.  I get it - I live up on a hill too, quite intentionally.  The odds of my personal space flooding ARE lower than my neighbors down the hill.  However, that's not really the point.
Having lived through a massive flooding event (Hurricane Irene) up above the worst areas, let's talk about what it is like EVEN for people whose houses don't flood - & why even people on hillsides can have problems.
1. First, being high above sea level does not necessarily mean water will not cause flooding.  Sewer backups, can happen even on hills - the water will go where it is most convenient to flow, & it may be more convenient to back into your basement than anywhere else.
2. If the water comes down fast enough, even places that are quite elevated can still have flooding. Also places above YOU may send water in your direction....