Hydrodynamics and longitudinal dispersion in the Red Cedar River (Michigan)

A one-dimensional hydrodynamic model for the Red Cedar River based on the EPA version of DYNHYD5 is presented herein for simulating the unsteady flow conditions. The model framework was built using bathymetric data from flood insurance studies. Channel geometry of the model network was kept sufficiently simple so as to yield characteristic results in a single spatial dimension. The objective was to accurately predict the hydrodynamic parameters for use in simulating contaminant transport through the river reach. A series of dye dispersion studies conducted for different flow conditions offer a characterization of the river reach with regards to longitudinal dispersion, which is an essential component in contaminant transport. The results of dye dispersion studies confirm the variability of dispersion with space and time. The model itself and the empirical equation developed for predicting the dispersion coefficient at any point within the reach bounds can be used as a base for simulating contaminant transport by the water quality model.