From the video description: "Six Flags New Orleans was destroyed by Hurricane Katrina in 2005. It has been abandoned ever since. This film was made in October 2010. The park is scheduled to be demolished in January 2011."
It's like that scene from 28 Days Later (or The Walking Dead) where a man wakes up and realizes all the trappings of civilization have been robbed of any sign of humanity. Only this isn't a fictional movie.
Update: The creator of this video has removed it "for reasons [he] would not rather have made public."