Downstream changes in river reaches from the catchment to the sea in the East Alligator River basin, northern Australia (10631)
The East Alligator River drains a 7000 km2 catchment in northern Australia comprised largely of Aboriginal land and has a very low average population density. River reaches were classified according to geomorphic features on the East Alligator River and its major tributarys, Magela Creek, Tin Camp Creek and Cooper Creek.
Magela Creek has the Ranger uranium mine located on its left bank, upstream of the Ramsar-listed Magela Creek wetlands and Cooper Creek contains the rehabilitated Nabarlek uranium mine in its upper catchment. Tin Camp Creek does not have a mine within its catchmet however there has been exploration for uranium for the last two decades.
Sixteen reaches were described for the 242 km of the East Alligator River, ten reaches were described for the 119 km of Magela Creek, nine reaches for 114 km of Cooper Creek and seven reaches for 68 km of Tin Camp Creek. The dominant river types on the East Alligator River were various types of anabranching rivers, sandstone gorges and cuspate tidal meanders. On Magela Creek the dominant river types were wetlands and channel billabongs, island anabranching and sandstone gorges. On Cooper Creek, the dominant river types were island anabranching and cuspate tidal meanders. On Tin Camp Creek, anabranching rivers and gorges dominated. It is unusual for anabranching rivers and gorges to be so dominant, especially for rivers so close to the sea.
Current river classification schemes could not accommodate all the various river types and need to be modified so that tidal channels are covered in more detail and so that the classification of anabranching rivers recognises that sand-bed varieties occur in partly confined valley settings.