Chemical spill assessment carried out for the Derwent River, Tasmania

Chemical spills caused by shipping incidents can have catastrophic effects on a region's environment, population and economy. For that very reason the following paper investigates hypothetical chemical spill modelling for the Derwent River, in southern Tasmania, Australia. The modelling assessed the likely movement and fate of two chemicals (sodium hydroxide and sulphuric acid) released into the estuary under range of seasonal conditions. The modelling study was carried out in stages. Firstly, a validated ocean/coastal model (HYDROMAP) was used to generate tidal current data for the study site. Secondly, the ambient tidal and locally measured wind data were used as input into an advanced 3-dimensional chemical model, CHEMMAP, to assess the likely fate of each chemical and the toxicity to nearby marine organisms. The modelling results indicated that there would be a build up of higher concentrations along the coastline surrounding the Hobart and Risdon Ports, as a result of the sluggish tidal currents unable to readily disperse the chemicals. Consequently, with these regions predicted to be exposed to pollutant levels above the recommended guidelines for healthy waterways, there is potential for adverse effects on known protected spotted handfish and sea grass habitats.