The Fitzroy River is one of Australia's largest river systems, with an estuarine section extending 60 km from its mouth to a tidal limiting barrage. The Fitzroy River, whose catchment is 142450 km2 experiences annual short-lived flooding as a result of intermittent heavy summer rainfall events. This study revealed that the Fitzroy River estuary behaves as an enclosed bay as it does not experience a freshwater inflow after the cessation of a flood event. There was a need to develop a predictive estuarine recovery graph as typical formulas, (such as the fraction of freshwater) did not apply. Implications of this simplistic (salinity recovery) graph will lead to a better understanding and knowledge base for both the independent and commercial fisheries. The reason for this being that a during a flood event, the majority of freshwater species (upstream of the barrage) and estuarine-dependant (downstream) species are washed into the adjacent Pacific Ocean. The re-migration of both the fresh and estuarine-dependant species after the flood event is closely related to the rate of salinity recovery.