Mixing and Turbulence in a Flooding Coastal River

An experimental study of turbulence and vertical mixing was carried out in the lower east Pearl River (Mississippi and Louisiana) during a high-discharge period in February and March of 2010. Direct estimates were made of the time-varying profile of turbulent Reynolds stresses (tau(x)/rho = -(u'w') over bar) through the water column. From this, both the vertical eddy viscosity (Km) and mean vertical mixing time were calculated, and the water column was shown to be vertically well mixed at all times. Segmenting the stresses into stresses due to river discharge and stresses due to tidal flows shows the coequal nature of each component and highlights the ways they vary in importance during different flow regimes. Two simple turbulence models are examined and compared to the measured mixing parameters. (C) 2013 American Society of Civil Engineers.