If you are planning to attend the event be prepared to keep a note/photo of any specific alcohol-related incidences.
Inform event organisers and/or attending Police or security of any alcohol-related issues you observe.
A lot of alcohol-related problems go unreported. It is then difficult for anyone to address these in the future. Your reporting of alcohol-related problems can assist authorities in making informed decisions about future events/licences.
If you are not attending the event but the event is impacting on you (e.g. you live near the venue) keep a log of the incidents associated with it. Then report these incidences to the Police and/or local Council.