Miami Herald Says Chertoff had power to help but didn't

I just read in today's Miami Herald that Chertoff had the power to help, and was in fact in charge of the response to Katrina before and after it hit.

Not to excuse "Brownie", but according to the Herald, Chertoff, not
Brown was in charge of managing the national response to a catastrophic event according to the National Response Plan, the federal gov't's blueprint for how agencies deal with natural disasters or terrorist attacks.

They go on to say that Brown had only limited authority until 36 hrs after the storm hit. They said that Chertoff may have been confused about his role.