Lawrence Peter Hughes

Water Circulation in the Coomera River Estuary

Abstract This paper describes development of a numerical tidal model and a data collection program for the Coomera River estuary on the Gold Coast. The primary objective of this project was to provide a detailed picture of the tidal characteristics within the study area; to investigate the degree and importance of tidal asymmetry at the Coomera River; to calculate the tidal prism; and also to enable the simulation of water circulation within the study area. A comprehensive data set was collected as part of this study to understand the local dynamics, and to calibrate and validate the model. The collected data include current, water level and meteorological forces in the study area. Calibration and validation were achieved through: comparison of computed tidal harmonics against those derived from harmonic analyses of the measured water level variations; and comparison between the measured discharges across four cross-sections at critical locations within the study area with the discharges predicted through modelling. As part of this study, harmonic analyses of the collected data were conducted to identify the major tidal constituents of the tidal signal within the study area. Calculations show that tide becomes mixed, and is mainly semi-diurnal in the estuary.