Hi @paulie!
Brisbane city council ang may brisbane flood maps. I think it is based on the 2011 flood. Can't really comment how bad it was, I wasn't here just yet. They also announce every so often if they are expecting floods in particular suburbs. Places na malapit sa Brisbane river higher tendency to flood syempre. Milton yata, got flooded in 2011 really bad. Harap lang kasi yan ng Brisbane river talaga.
Ironically, every summer lang yata may bad storms and floods. Actually, nung dumating ako nung january, storm and flood daw yun. Ang nakita ko heavy rains but no flood. Baka yung bad sa kanila normal lang sa akin. 😃
Check mo nalang po realestate.com.au for good houses. I myself am in south bank na hindi flood-prone (sana, hehe). Toowong is also a nice suburb, I think. Mga other areas you might wanna check greenslopes, holland park.
Goodluck on your move and welcome to Brissy. 🙂