In spite of its name, that part of Parramatta River downstream from the city of Parramatta is not a river at all, but an intermediate tide dominated, drowned valley estuary. As it is the main tributary of Sydney Harbour, and numerous secondary tributaries flow into it - the Lane Cove and Duck River being the most prominent of them - it is given the status of 'River'. The Parramatta River is deemed to enter Sydney Harbour at Manns Point and Yurulbin Point a short distance downstream from Cockatoo Island, some 21 kilometres from the Tasman Sea.
