Even though estuarine processes are inherently three dimensional, most of the previous studies have focused primarily on the axial (longitudinal and vertical) variabilities. Recent surveys in the lower Delaware Bay indicate the presence of significant transverse variability in the salinity distribution and residual circulation pattern. Conceptual models are developed to examine the mechanisms which might explain the observed transverse structure. Results indicate that both the gravitational effect and wind forcing are capable of generating substantial transverse structure in drowed river valley estuaries with triangular cross sections. ¿ American Geophysical Union 1994