Free flowing rivers retain the natural hydrological, ecological and geomorphological processes associated with river flow. Free flowing rivers are likely to be more resilient to climate change impacts and by allowing biota to move to more suitable habitat may facilitate climate change adaptation. Definitions of free flowing vary but all highlight the absence of dams and other major water infrastructure that restrict the movement of aquatic biota and the transport of sediment and nutrients and the replenishment of floodplain wetlands.
We assessed the free flowing status of 3 million km of stream nationally at multiple hierarchically nested catchment scales. Preliminary results show that there are few large drainage basins that are entirely free of major infrastructure. Most of these are located in northern or arid areas of Australia. Perennial streams total less than 2% of the total length of stream in free flowing basins. Tributary streams flowing freely from source to outlet are similarly rare in many drainage basins including those targeted for future developments. Our analysis highlights the urgent need for a comprehensive national program aimed at identifying and protecting the remaining free flowing rivers.