CMS-Flow Coordinate System
Before presenting the depth-integrated and wave-averaged governing equations, it is useful to define the coordinate system and basic variables. Variables are defined spatially in a Cartesian coordinate system , where x and y are the horizontal coordinates, and z is the vertical coordinate (positive is upwards). A schematic of several of the main variables in the vertical direction is provided in Figure 2-1. The vertical coordinate datum is usually the Still Water Level (SWL). The bed elevation (zb) is measured from the vertical datum (i.e., negative downwards).
Vertical conventions used for the bed and mean water surface elevation.