The determination of estuarine diffusion coefficients using a fluorimetric dye tracing technique

An improved dye-injection technique has been used to collect new field data to study the transverse and vertical mixing in a section of the Conwy estuary. These results define the full three-dimensional spatial concentration distribution of the dye plume. Estimates of the diffusion coefficients are given and were found to be strongly influenced by the transverse shear induced density variations and bed topography. The results suggest that an analogy with Fickian diffusion appears inappropriate on flood tides because of the importance of secondary circulations during this tidal phase. © 1988.