The Clarence River catchment is defined by the Macpherson Ranges in the north and by Baldblair, the Doughboy Ranges and the Dorrigo Plateau in the south. The Great Dividing Range, from Stanthorpe to Glen Innes defines the western rim of the catchment. The Richmond Ranges north of Iluka, and the coastal ranges from Coffs Harbour to Yamba form the north eastern and south eastern boundaries, respectively. The mouth of the river is between the towns of Yamba and Iluka, with its estuarine reaches extending approximately 108 kilometres upstream to Copmanhurst.