Longitudinal Dispersion Coefficients in Estuary

Abstract

Field measurements of velocity and salinity on a transverse cross section of a straight reach in the upper Conwy estuary have been used to evaluate the temporal and intratidal variations of the transverse and vertical shear induced components of the longitudinal dispersion coefficient. The results yield clear temporal trends and an element of reproducibility between tides. A comparison with earlier published results for a cross section further downstream in the same estuary suggests that changes in the channel width, cross‐sectional shape, and bends probably contribute significantly to a longitudinal variation of dispersion coefficient values. A comparison of the values of the longitudinal dispersion coefficients with those obtained from a solution of governing transport equations emphasizes the need for a better understanding of the spatial and temporal variation of the values of the vertical and transverse eddy diffusion coefficients.