The longitudinal dispersion coefficient is a parameter used to evaluate the effect of cross-sectional variations on substance mixing mechanisms in estuaries influenced by tide, wind and internal density variations. Considering a two dimensional approach, this study aims at evaluating a tidal area of the lower James River at approximately 19 miles upstream from the mouth at the Chesapeake Bay, in the City of Newport News, and applies an experimental procedure based on in-situ salinity concentrations to estimate the dispersion coefficient in the area where receives a discharge from the HRSD James River Wastewater Treatment Plant, and further characterizes Total Suspended Solids (TSS) mixing and transport mechanisms in the surrounding area. In-situ data collection was carried out twice a day during two consecutive days (July 21st and July 22nd, 2016) to measure salinity, turbidity, temperature and velocity. Subsequently, Control Volume (CV) approach method with Steady State Response Matrix (SSRM) was applied to characterize the transport mechanism of Total Suspended Solids among eight segments in the study area, with two of them acting as boundary conditions. Statistical General Linear Model (GLM) method was used to develop in-situ correlationship between Turbidity and Total Suspended Solids from historical HRSD James River plant data series during the years 2001 through 2015. Then measured Turbidity values were used to estimate corresponding Total Suspended Solids concentrations used in the study. The results obtained during this research suggest that in the study area of the James River, dispersive mechanisms of Flood cycles influence the transport of TSS towards the upstream, reducing the effect of advective movement from the Warwick River towards the lower reach of the James
