The Hydrodynamics of an Idealized Estuarine Plume along a Straight Coast: A Numerical Study

The hydrodynamics of an idealized estuarine plume along a straight coast are studied using a three-dimensional hydrodynamical module of the Coupled Hydrodynamical Ecological Model for Regional Shelf Seas. The sensitivity of the solution with respect to river discharge, bottom roughness length, and the presence or absence of tides are studied. Assuming constant water depth and no wind forcing, modeled results for the surface layer are obtained, including: (1) variation in the horizontal shape of the plume; (2) horizontal distribution of the current vector; and (3) horizontal distribution of the salinity field within the plume over one tidal cycle. Effects of three different river discharges, four selected different bottom roughness lengths, and tides on its development are examined. Results suggest: (1) the plume length naturally increases through time under tidal forcing or as well as without tidal forcing, but its width shows approximately periodic variation; (2) both the plume width and length increase with increasing river discharge; (3) both the plume width and length decrease with increasing four selected bottom roughness lengths; and (4) both the bulge and coastal current of the plume are more evident without the presence of tidal effects. The results show their potential implications for contaminant fate and transport and novel methods of pollution prevention and control in estuarine and coastal waters.