You are looking for a small, magnetic cache that would have been safe even in the 1946 floods.
The important message for travellers and locals alike, is to be aware of extreme weather conditions. Be aware of the threat of floods in Winter and Spring and never, ever drive through flowing flood water. In Summer and Autumn be on the lookout for smoke and fire. Know the day's Fire Danger Rating and avoid high risk areas (long, dry grass and bushland) on Severe, Extreme and Code Red days.