The Development of Wave Wake Criteria for the Noosa and Brisbane Rivers in South East Queensland

Several rivers in Queensland, Australia, are experiencing bank erosion problems. Public concern compelled the relevant authorities to commission a series of inter-related studies to determine the extent of the erosion, its probable causes and a means of quantifying the erosion potential of vessel wash. Sections of the Noosa River are in pristine condition, suffering little or no anthropogenic impact. However, one reach of the river is used by recreational and small commercial vessels as a transit route between two large lakes and is often traversed at high speed. The Brisbane River is also used for recreational boating, but the river has undergone significant change since European settlement almost 200 years ago. The Australian Maritime College (AMC) conducted field tests to measure the wave wakes of a variety of craft that frequent these rivers. The wakes were analysed for certain maximum values such as wave height, wave period and wave energy, as well as total wake trace energy. Previous experiments attempting to correlate erosion thresholds against wake parameters were re-analysed and applied to the Noosa and Brisbane Rivers. Vessel operating criteria were developed for each river in terms of the energy of the maximum wave, maximum permitted waterline length (which can characterise wave period) and vessel speed. It is proposed that multiple criteria provides a better indicator of erosion potential than traditional single indicators such as wave height.