Only a very small section of Inala is flood prone. Overall, it is one of the flood safest suburbs in the area. Simply check Brisbane City Council flood awareness map for the property you are interested in and you will be well informed. https://www.brisbane.qld.gov.au/community-and-safety/community-safety/disasters-and-emergencies/be-prepared/flooding-in-brisbane/flood-awareness-map
Some parts of Inala can flood. The affected areas are close to local creeks, but luckily most of those areas are parks, which means few houses are affected. However, the nicest part of Inala (Inala Heights) with Buddleia Street right on the top of the ridge and the nearby streets never flood.