A numerical, three‐layered, stationary salt wedge model

Abstract

A numerical, three‐layered, stationary salt wedge model is presented. It contains the effects of wind stress, interfacial stress, bed and wall stress, breadth variations, and mixing between the upper fresh layer and the homogeneous saline bottom layer. Because of the mixing an intermediate mixing layer develops which increases in thickness along the estuary toward the sea. The solutions obtained are compared with observations reported by Sorgard et al. (1990). Good agreement is obtained, both with regard to the thickness and position of the pycnocline, and with the velocities in each layer. The model was tested with different values for the bed and wall drag coefficient. To obtain a best fit with the observations, the modeled interfacial stress had to be decreased when the bed and wall drag coefficient was increased. The modifications to the dynamics due to the presence of the mixing layer are analyzed by comparing with the two‐layer model of Schijf and Schonfeld (1953). It turns out that the modeled interfacial stress has to be decreased because of the changed pressure field introduced by the mixing layer.