Parades are potential dangerous events.
Our local uses many safety people to monitor all aspects of it's parades from unloading to final loading of vehicles exiting the area.
If you have ever been involved in parades or as a participant whose insurance for such event dictates safety requirements for insurability given prior stated loss events (injury or death) then you would know what you stated as "normal" is a reality of a statistic or actuaraly event that is trying to be minimized or elemenated.
That New Orleans has average number of deaths per year shows lack of their part to monitor every part of their parades by safety officials.
Cite your source to support your claim that three deaths per year is par.