Hi Matt, Totally agree with Roger's comment, I live in Fairfield and that was also flood affected. As Roger mentioned the most recent floods was a result of poor management causing wide spread flooding all over Brisbane. I personally think the flood issue should not hinder your decision to live or purchase in Yeronga or any other southside suburb.
I don't think you could define a once in 30yr event "flood prone" (means regular), would be a better description "previously flood affected" (the State Government has accepted responsibility for the 2011 floods which was caused by poor dam management) . Less than 10% of the homes in Yeronga were affected by the 2011 floods and in actual fact Yeronga is now looking better than ever with lots of new homes and recent renovations from the flood event (most covered by insurance). Yeronga is a river suburb like all of Brisbane's most exclusive suburbs bordering the banks of our river, riverfront is the City's most expensive real estate and follows the worldwide trend of premium suburbs border water. I don't think Brisbane is going to buck a worldwide trend. Statistically you would have a much higher chance of your home being damaged in a severe storm, bushfire or hail storm in Brisbane than river flooding, I hope this helps.