Two field investigations, under low river flow regime, were conducted in the Isonzo River mouth, Gulf of Trieste, to examine effluent dynamics and suspended sediment characteristics through the water column. The well-marked stratification influences particle size distribution. Multivariate statistical analysis was successfully utilized to define the characteristics and mutual relationships of the water masses in the estuarine zone. The results allow the Isonzo River mouth to be identified as a microtidal, low-energy, fine-grained deltaic system. The highly stratified water column and related hypopycnal flux prevail in the dynamic regime within the lower reach of the distributary mouth. This type of circulation is interrupted during extreme river floods, when the salt-wedge is pushed out of the river mouth.
