The co-op weather observer just happens to be right next door to the house in the video that has rushing water running through it. Here is the rainfall recorded at their station from 9/1/09-9/27/09. They had a whopping 19.22" of rain. When the flood happened they got roughly 14.50" in 3 days. The radar estimates from the 21st show areas west and northwest of Atlanta(in white) receiving 20"+ in a single day.
It was just crazy! Here's a pic I took with my cell while sandbagging the garage.