There is a council map of the flood zones on their website if you are looking at buying. We are rarely properly flooded in and if so its only for a short period usually ie few hours. BOM has river height data frequently updated so you dont get stuck and also Kombu wholefoods have a live web cam showing Lavenders Bridge. Its not a big deal at all.
If you are cut off it's only ever for a very short time. The media do love to make a big deal about Bellingen flooding. It floods in Bellingen most years but it was never much of a problem. We got to miss some school because the kids in outlying areas like Kalang or Thora were cut off. It's certainly not a reason to avoid living there.
Waterfall Way and Hydes Creek Road are normally accessible. It is only the bridge over the Bellinger that generally gets flooded. The press make such a fuss about the bridge going under that the whole world rings to see if we are OK. Cheers