When the time has come that the police are expected to make special perparations for rioting because of the past history of the event, and an event nonetheless that is supposed to celebrate the University, perhaps that event has outgrown it's usefulness.
To be frank, the only way VIESHEA is going to survive going forward is for everybody to admit that the biggest draw for the majority of those who "attend" the event are the big alcohol bashes that surround the on-campus events. It's been that way for nearly 30 years. Yes, people work hard on floats and displays, and I really feel sorry for those who put that kind of work in. But IMO all that has taken a back seat to the partying. As others have posted, look at the pre-riot posts here on CF. How many were celebrating the partying, and how many were celebrating the parade and other on-campus events?
It's no big revelation that riots break out in large conglomerations of overly drunk people. Would there have been a riot in Ames last night if VIESHEA was not in progress?