An experimental study of salt wedges

The objective of the estuary studies being conducted at this Institution is to attempt an understanding of tidal flushing.Two theories have been developed, that of Ketchum employing an extension of the tidal prism technique, and that of Arons andStommel who treat the flushing problem through the diffusion theory. An experimental program has been established to determine the validity of these theories so that model laws may be established for tidal flushing.At the beginning of this program, the phenomenon of the saltwater wedge was observed in the experimental apparatus over a widerange of flow conditions. To produce salinity distributions otherthan this, it was necessary to stimulate diffusion of the saltwater with turbulence created by added roughness.In view of the apparent importance of the salt wedge, it wasdecided that an investigation of the factors that influence itsshape and length would be of particular value to the future work.An empirical equation has been developed which describes thesalt water wedges formed in the laboratory. This equation, however, does not describe well the salt wedge as found in the Mississippi River. It is of particular interest that the equationappears to describe the mean horizontal distribution of salinityin estuaries where the fresh and salt water are well mixed and notstratified as in the wedge.

Office of Naval Researchunder Contract No. N6onr-27701 (NR-083-OO4)

Originally issued as Reference No. 51-99, series later renamed WHOI-.