INFLOWS OUTFLOWS AT THE TRANSITION BETWEEN A COASTAL-PLAIN ESTUARY AND THE COASTAL OCEAN/

A series of numerical experiments were performed to study the dynamics at the transition region between a wide (Kelvin number between 2 and 3.6) coastal plain estuary and the adjacent coastal ocean. In particul ar, the separate effects of modifying the seaward discharge within the estuary, the coastal ambient how, the coastal ocean bottom slope, and the initial salinity gradient were investigated. The numerical experi ments were carried out in a flat-bottom estuary with a N-S orientation that is connected to the ocean in the E-W direction. Results show tha t increased seaward discharge at the estuary upstream boundary reduces volume inflow and increases volume outflow through a cross-section at the estuary mouth. A southward coastal ambient flow is responsible fo r increased volume inflow, for keeping estuarine outflow within a few kilometers from the coast, for increasing surface flow divergence at t he estuary mouth, and for hindering inflow that originates to the sout h of the estuary. When the coastal ambient flow is suppressed, the bot tom slope of the coastal ocean causes negligible effects to volume tra nsports, to the dynamical balances, and to the shape and extent of inf lows/outflows compared to results over a flat bottom. These effects of the bottom slope become non-negligible but are still minor when the c oastal ambient flow is active. A pulse of buoyant water at the estuary upstream boundary causes, after the discharge stops, increased volume inflow with respect to other experiments. Increased salinity gradient s produce enlargements to the deformation radii, the volumes exchanged , and the regions directly influenced by inflows and outflows. Copyrig ht (C) 1996 Elsevier Science Ltd.