It seems that the “old town” – the main street of the historic district of Ellicott City got the worst of it although there was also flooding in other areas including in north Baltimore City along the Jones Falls.
http://www.nbcnews.com/news/weather/severe-damage-after-flooding-maryland-n620416
I’ve been to and have enjoyed going to the old town Ellicott City district many times over the years.
It is a great place to visit and hang out for the day. Lots of small specialty shops of all kinds - unique clothing, jewelry, crafts and arts and gift stores, and many antiques shops; all small independently owned small businesses and also some really good places to eat, to meet friends for a good meal and some brew. And many of the building go back to the 1700’s in what was once a very prosperous and inportant mill town. There is also the B&O Railroad Museum's Ellicott City Station.
http://www.destinationmainstreets.com/maryland/ellicott-city.php
But it is also in an area because of its topography and being in a river basin, that has been very prone to flooding the in past.
FWIW Ellicott City got more than 6” of rain over a very short period of time.