Canonical Parameters for Estuary Classification

The dispersion coefficient of a one-dimensional dispersion equation governing the dispersion of salt in a shallow two-dimensional estuary is used to derive a canonical three-parameter set. From this set many of the existing parameters used for estuary classification based on the Hansen and Rattray (1966) estuary classification diagram may be derived and it is shown that implicit in these empirical results are parametrizations of longitudinal ʹdiffusionʹ and of vertical mixing. In addition, Hansen and Rattrayʹs concept of a diffusive fraction of the upstream salt flux is extended to include ʹbuoyancyʹ, ʹinteractiveʹ and ʹdischargeʹ fractions. However, the interactive and discharge fractions lie outside the domain of validity of the classical theory.