EMPIRICAL RELATIONSHIPS BETWEEN INLET CROSS-SECTION AND TIDAL PRISM: A REVIEW

The well-known empirical relationship between the equilibrium cross-sectional area of tidal inlet entrances (A) and the tidal prism (P), first developed by O'Brien (1931), has been extensively reviewed. A theoretical investigation indicates that a unique A-P relationship should only be expected for clusters of inlets that are phenomenologically similar (i.e. fairly similar hydrodynamic and morphological conditions), and that the exponent q in the A-P relation should be larger than 1. However, the relevant published data available to date do not clearly support this theoretical finding. A re-analysis of the available data sets indicates that they may not be sufficiently reliable to verify our theoretical finding with regard to q>1 due to the violation of the condition of phenomenological similarity, and possibly also due to violating the initial definitions given by O'Brien (1931) in estimating the tidal prism. The resolution of this issue is important because slightly different values of q result in significantly variable values for the equilibrium cross-sectional area of the tidal entrance. This may have significant implications in determining the true stable equilibrium entrance cross-sectional area. We advocate a careful re-scrutiny of the datasets available as a necessary first step in evaluating the robustness of the theoretical considerations presented herein.