Vessel traffic and river environment descriptor variables have been listed and the magnitudes of their ranges defined. Target physical variables were selected on the basis of their likelihood of having biological effects. The total number of variables is 34, not including several basic quantities like water density and viscosity, which were introduced in a discussion of dimensional analysis. Dimensional analysis was used as a rational approach to a conceptual model of the physical impacts of navigation on constructed waterways. Eight parameters characterizing the physical effects of tow passages were discussed in detail. Because of its complexity, special attention was given the effects of the propulsion system. Study approaches to determine the relationships between tow passage characteristics and typical target physical variables were treated from the perspective of hydraulic engineering. The basics of scale for physical effects were presented, but the appropriate scale for the biological aspects remains unknown. A final section presented an approach that involves three levels of model to conceptually relate tow passage to population scale effects on the biota of the riverine ecosystem.