A numerical study of storm surges and tides, with application to the North Queensland coast

A two-dimensional numerical model of the shallow-water equations, with a modified Orlanski-type radiation boundary condition, is applied to study storm surges and tides on the North Queensland coast. The numerical simulations show that with the tides included in the storm surge model the sea level elevation is generally lower than if we simply add the astronomical tides to the surge. This has been previously observed and has been commonly explained as a nonlinear interaction between the storm surge and the tides. The authors demonstrate that this effect is due to the quadratic bottom friction law. Analysis of the important dynamical processes yields a simple rule to estimate the total sea level due to the combined effects of a storm surge and tide.