Provenance of sediments within the Port of Gladstone dredged channels: Feasibility and application

Maintenance dredging is required to maintain navigational channels and berths for transportation activities and safe and efficient port operations. Natural and anthropogenic sources of sediment enter the Port of Gladstone via alluvial transport of eroded materials from upstream and adjacent catchments, and from longshore drift. Identifying the quantity and provenance of annual sediment infilling navigational channels would allow Port managers to better manage and perhaps mitigate infilling (e.g. through catchment management, riparian restoration, vegetating mud banks, beneficial reuse of sediment options). This may lead to reduced dredging requirements and costs, as well as improved management, reuse or disposal of dredged sediments. The ability to identify sediment provenance using multiple lines of evidence was assessed for the Port of Gladstone: analysis of Rare Earth Element composition; Stable Isotope analysis; and, Beryllium-7 isotope analysis. Grab samples were collected at accumulation locations within the navigational channels. Potential source sediment was sampled from sites representative of longshore drift to the south of the Port of Gladstone, and intertidal “source” locations. Alluvial sediment samples were collected from dry and flood conditions, from the three main local catchments the Fitzroy, Calliope and Boyne rivers. Source sediment samples showed potential for differentiation using rare earth elements and Beryllium-7 isotope analysis indicated recent deposition of sediments from mudflats or catchment within the channels. A multiple lines of evidence approach provided greater detail on the source of recently deposited sediment to inform management decisions. Results are discussed in terms of identifying management options for maintenance sediments within the Port of Gladstone and the application of the approach at a wider scale. © Australasian Coasts and Ports 2019 Conference. All rights reserved.