Modelling and observation of tropical river inflow to the coastal ocean

River inflow brings freshwater, silt and nutrients to the coastal ocean. When there are valuable economic resources such as coral reefs adjacent to the river mouth the fate of the freshwater and the nutrients contained therein are of considerable interest. Field experiments and numerical simulations were carried out to study the plume from the Herbert River, Queensland, Australia which flows through the Hinchinbrook estuary into the Great Barrier Reef Lagoon. Ground measurements were made through spring and neap tide conditions and flood and normal river flows in 1986 and 2002. Additionally airborne remote sensing by a Scanning Low-Frequency Microwave Radiometer (SLFMR) was conducted together with the ground measurement in 2002. A numerical model of the Hinchinbrook estuary and the region 15 km offshore has also been constructed, which was used to predict the stratified flow within the estuary during periods of river flood for the 1986 and the 2002 ground truth periods. The model shows that the freshwater plume follows the coast under typical flood conditions in agreement with the Salinity Mapping flights.