Stress and Tidal Current in a Well-Mixed Estuary

A procedure for calculating the vertical shear stress distribution in tidal channels of well-mixed estuaries from current profile measurements is formulated. A linearized boundary layer form of the Navier-Stokes equation and an eddy viscosity representation of Reynolds shear stress are used to determine the depth and time dependence of current velocity and stress. A lower (near bottom) boundary condition on stress is employed rather than the usual no-slip condition on velocity. A verification experiment is described in which the theoretical model is used to calculate stress from current profile data taken in a tidal channel over a half tidal cycle. The predicted stress is then compared with a direct independent measurement of Reynolds shear stress. It is shown that for a one-layer estuary model best results are obtained using an eddy viscosity having a quadratic depth dependence.