Spatial patterns of bulk stratification in Long Island and western Block Island sounds observed near the fall equionx of 1978 show a strong correlation (r = 0.79) with contours of the h/U3 stratification index derived from tidal stream and depth charts. The index delineates stratified, transitional, and mixed regions with apparent good accuracy, with the martinally stratified frontal zones being charcterized by log 10h/U3~1.5 m-2 s3. These results and theoretical considerations suggest that the index may be a useful parameter in corroborating and prediciting frontal boundaries in other moderately stratified estuaries where local buoyancy fluxes are derived from fresh water sources.