All of the Northern Territory’s shorelines experience strong winds and seas resulting from seasonal winds and cyclonic depressions. The estuaries across the top end of the NT are predominantly macro tidal while the east facing estuaries are meso tidal. All receive freshwater flood flows from large catchments during the wet season. The NT coast supports several shipping ports supporting the LNG and minerals export industries. Darwin Harbour is the largest of the deep water harbours and is adjacent to the capital city with a population of 100,000 people. Also along the shorelines are many coastal wetlands that are significant habitats for fisheries, migratory birds and vegetation such as paperbark and mangroves. Over the past several decades changes have been noted in these wetlands being mainly saltwater intrusion and shoaling of estuaries.
The NT experiences seasonal tidal fluctuations of up to 0.3 metres about mean sea level due to the effects of the interaction of the seasonal winds across the broad shallow continental shelf and the shallow waters of the Gulf of Carpentaria. The estuaries are highly turbid and exhibit sediment trapping efficiencies resulting in the shoaling of the estuary. If climate change scenarios are realised then the Northern Territory coast may experiences more sediment discharge and resultant shoaling, greater saltwater intrusion into coastal freshwater wetlands resulting in loss of freshwater wetland habitat and increased shoreline erosion threatening infrastructure and habitat.
Data has been collected on the physical behaviour of selected estuaries and a systematic program of model development is being implemented. The models will use the newly deployed Integrated Marine Observation System (IMOS) network in the Joseph Bonaparte Gulf and Darwin Habour to further refine the models so that predictions on the consequence of a range of climatic scenarios can be made. Several examples will be shown.