I find that the signal to noise ratio can be considerably reduced by simply following (relatively) trusted sources, in your case the journalism professor seems a good bet.
Recently I found myself in a similar situation where my local town was the scene of a "protest" by some particularly obnoxious far-right types and naturally violence and unrest was expected. Like you I found twitter to be the best source of information, about problem areas etc. After the initial search I found it possible to determine and follow enough authoritative sources (including the local police force) to supply me with enough quality information with far less noise.
Undoubtedly there would have been information that I had missed but I felt it was a good compromise. The other advantage of this approach seemed to be that the sources deemed higher quality that engaged in re-tweeting acted as filters against the garbage re-tweets and spam.