Monitoring of Tweed River Entrance Dredging and Nourishment Activities

The entrance navigation channel of the Tweed River in northern NSW, Australia has been maintained by dredging since April 1996. To May 2001, 3,640,000 cubic metres of sand from the entrance had been used to nourish the southern Gold Coast Beaches in Queensland. The dredge activities have been monitored to ensure dredge navigation safety, maintenance of the design channel, achievement of the desired beach nearshore profiles, monitoring compliance with relevant approvals and for payment purposes. The first three objectives have been achieved by Hydrographic survey, monitoring of the dredge depth sounders and tracking dredge position. Sand volumes for payment could not be accurately ascertained from survey due to the high rate of natural sand drift. Therefore, sand volumes were obtained using dredge hopper dippings and ullage tables, and by mass flow rate metering on the dredge pipe where available. The tracking program involved logging dredge coordinate details.